ObjectiveTransmissibility of COVID-19 by children in the household is not clear. Herein, we describe children’s role in household transmission of COVID-19.Design and settingAll paediatric COVID-19 ...index cases and their household members reported from 20 January to 6 April 2020 in South Korea were reviewed. The secondary attack rate (SAR) from child index case to household secondary case was calculated. Epidemiological and clinical findings of child index case-household secondary case pair was assessed.ResultsA total of 107 paediatric COVID-19 index cases and 248 of their household members were identified. One pair of paediatric index-secondary household case was identified, giving a household SAR of 0.5% (95% CI 0.0% to 2.6%). The index case was self-quarantined at home after international travel, stayed in her room, but shared a meal table with the secondary case.ConclusionThe SAR from children to household members was low in the setting of social distancing, underscoring the importance of rigorous contact tracing and early isolation in limiting transmission within households.
Next-generation electronics require mechanical flexibility and durability as well as electrical conductivity. In this report, few-layer graphene and polyelectrolytes were assembled into ultrathin ...films on flexible plastic substrates by a simple and cost-effective layer-by-layer technique. This technique integrated high electrical conductivity and excellent oxygen barrier property into a single film. These characteristics have been rarely reported for other types of thin films prepared by solution processing. The optical properties, film thickness, and mass of the films were precisely controlled by the number of bilayers. After a brief exposure to nitric acid (HNO3) vapor, the films exhibited much improved electrical conductivity while preserving their other properties. Raman, x-ray photoelectron, and FT-IR spectroscopy proved that the effects of the HNO3 treatment were due to the removal of polymeric components and restricted to the film surface, and not due to the chemical doping of graphene.
Display omitted
In this study, we report an effective synthesis approach for fabricating low-density polyethylene (LDPE)-based multi-functional composite through hybridization with short PE chain branched boron ...nitride nanosheet (BNNS) to be applied as a high-performance hot-melt adhesive (HMA) type thermal interface material (TIM). To enhance the thermal and mechanical properties of BNNS/LDPE, the BNNS surface was modified with short PE chain (PE–g–BNNS) via nitrene coupling reaction to improve the interfacial bonding force between the BNNS with LDPE. As a result, PE–g–BNNS/LDPE exhibited 22% increase in through-plane and 66% increase in in-plane thermal conductivity compared to the BNNS/LDPE. Its heat radiation performance was also increased by about 11% compared to the bare LDPE. In addition, the PE–g–BNNNS/LDPE shows 66% increase in tensile strength and 350% enhancement in modulus compared to the bare LDPE, suggesting that the PE–g–BNNNS/LDPE could be used as a TIM to meet the requirements for application in high-tech electronic devices.
Display omitted
•The effective synthesis way to fabrication of high-performance BNNS/LDPE composites.•Efficient heat conduction paths were constructed by linked PE-g-BNNS with LDPE.•Enhance the performance by strengthening the coupling between BNNS and LDPE matrix.•The BNNS/LDPE composites with excellent comprehensive properties can be used as TIM.
The Korea National Health and Nutrition Examination Survey (KNHANES) was initiated in 1998 to provide evidence for the development and evaluation of health policies and programs. The Korea Disease ...Control and Prevention Agency is responsible for the KNHANES and has conducted it as a series of surveys. Over the past 20 years, efforts to produce accurate, timely, and nationwide health statistics have been refined by establishing a continuous annual survey system with full-time field staff, incrementally expanding survey components, collaborating with relevant academic societies for quality control, and revising the survey methods Additionally, the utility of the collected data was increased by linking the KNHANES data with related data from other government agencies or institutions and making the overall data publicly available on the official website of KNHANES (http://knhanes.kdca.go.kr). Additional long-term plans are being developed, including plans to continue producing nationwide health indicators and invigorating the utilization of the KNHANES data.
Graphene-based carbon nanostructures with nanometer dimensions have been of great interest due to the existence of a bandgap. So far, well-ordered edge structure and uniformly synthesized graphene ...quantum dots (GQDs) with a hexagonal single-crystalline structure have not been directly observed owing to the limited precision of current synthesis approaches. Herein, we report on a novel approach not just for the synthesis of the size-controlled single-crystalline GQDs with hexagonal shape but also for a new discovery on constructing 2D and 3D graphene single crystal structures from d-glucose via catalytic solution chemistry. With size-controlled single-crystalline GQDs, we elucidated the crucial role of edge states on luminescence from the correlation between their crystalline size and exciton lifetime. Furthermore, blue-emissive single-crystalline GQDs were used as an emitter on light-emitting diodes and exhibit stable deep-blue emission regardless of the voltage and doping level.
The octadecylamine (ODA) modified graphene oxide (mGO-ODA)/maleic anhydride grafted polypropylene (MAPP) composites (mGO-ODA/MAPP) were prepared and applied successfully as gas barrier and corrosion ...protection coating materials for the first time. The hydrophobic mGO-ODA sheets showed improved solubility in non-polar solvents with molar absorptivity was found to be 36mLmg−1cm−1 in ethylcyclohexane. FTIR analysis confirmed that mGO-ODA chemically interacts with MAPP. The mGO-ODA nanosheets were well exfoliated and dispersed in the MAPP matrix as confirmed by XRD analysis. The mGO-ODA/MAPP composites were coated on modified nylon sheets by a spray coating method, and the gas transmission rates (GTRs) of H2 and O2 were tested for these coated films. Cross-sectional FESEM showed the excellent attachment of these composite with the nylon film. The 60% mGO-ODA/MAPP-coated nylon film exhibited 93% and 112% improvement in elastic modulus values than the MAPP-coated and pure nylon films, respectively. Besides, 60% mGO-ODA/MAPP exhibited 94.1% and 95.0% reduction for H2GTR and O2GTR, respectively, compared to the pure nylon film. In addition, mGO-ODA/MAPP coated steel substrate exhibited excellent anticorrosion performance. The corrosion inhibition efficiency and corrosion rate were calculated to be 99.15% and 2.26 × 10−3mm/year, respectively, for 60% mGO-ODA/MAPP.
Display omitted
•The mGO-ODA/MAPP composites were prepared for gas barrier and anti-corrosion studies.•The H2 and O2 gas barrier film was fabricated by spray coating of composite on nylon film.•The barrier film showed 95.0% reduction of O2GTR compared to the nylon film.•The lowest corrosion rate was 2.26 × 10−3mm/year for the composite.
Objectives
Human resources (HR) are essential indicators of safety and health (SH) status, and HR can be key sources of workplace safety management such as safety and health education at work (SHEW). ...This study analyzed significant HR factors associated with SHEW of small manufacturing businesses in Korea.
Methods
The secondary data of the 2012 Korea Occupational Safety and Health Trend Survey were used to achieve this research purpose. A total of 2,089 supervisors or managers employed in the small manufacturing businesses completed the interview survey. Survey businesses were selected by multiple stratified sampling method based on industry code, business size, and region in Korea. The survey included workplace characteristics of HR and SHEW.
Results
SHEW was significantly related to business size, occupational injury incidence in the previous year, foreign and elderly worker employment, presence of site supervisors, and presence of SH committees (p <.05). SHEW for office workers, non‐office workers, and newcomers was associated with business size, presence of site supervisors, and presence of SH committees in logistic regression analysis (p < .001) . Businesses with 30‐49 workers conducted SHEW 3.64 times more than did businesses with 5 to fewer than 10 workers. The companies that had occupational injuries in the previous year conducted SHEW 1.68 times more than the others. The businesses that had site supervisors and committees conducted SHEW 2.30 and 2.18 times more, respectively, than others.
Conclusions
Site supervisors and SH committees were significant HR factors that improved SHEW in small manufacturing businesses.
Display omitted
•Bio-based epoxidized chitosan-oligoaniline hydrogel coatings were developed.•Samples were examined for cyclic voltammetry, UV/Vis. and swelling ratio (SR).•SR of electroactive ...epoxidized chitosan decreased 150% compared to reference (500%).•Degradation rate was decreased by increasing oligoaniline content.
Neural electrodes have opened new horizon in neuroscience which discover the new aspect of neural and brain behavior. Neural electrodes are usually fabricated using metals. Metals cause chronic inflammation in long term due to mechanical mismatch with soft tissue. In this regards, hydrogel based coating has been proposed to regulate the modulus. Electroactive hydrogel coating because of the similar modulus with brain, proper biocompatibility and low impedance can be used as proper coating for neural interface. In this work, the electroactive epoxidized chitosan was firstly synthesized and studied for electroactivity using cyclic voltammetry and UV–vis. Cyclic voltammetry diagram exhibited two redox peak between 0.38 and 0.8 related to oxidation/reduction transient; In addition, UV–vis spectra exhibited π-π* transition and benzenoid to quinoid excitonic transition around 330 nm and 620 nm, respectively. Swelling ratio of the electroactive epoxidized chitosan was decreased 150% compared to electroactive one (500%). The hydrophobic oligoaniline decreased the swelling ratio and hindered the water molecule diffusion within the hydrogel structure. Hence, the degradation rate was decreased by enhancing the oligoaniline content. Electroactive coating showed the lower impedance compared to isolated one. Moreover, the electroactive substrate exhibited more cell proliferation because of its conductive nature which enhanced the PC12 cells activity. This study introduced the novel hydrogel based on electroactive coating, which can be potentially used as a neural electrode coating and pave a way for architecting new coating for biomedical devices.
Abstract
Plant cells have a remarkable plasticity that allows cellular reprogramming from differentiated cells and subsequent tissue regeneration. Callus formation occurs from pericycle-like cells ...through a lateral root developmental pathway, and even aerial parts can also undergo the cell fate transition. Pluripotent calli are then subjected primarily to shoot regeneration in in vitro tissue culture. Successful completion of plant regeneration from aerial explants thus entails a two-step conversion of tissue identity. Here we show that a single chromatin modifier, ARABIDOPSIS TRITHORAX 4 (ATX4)/SET DOMAIN GROUP 16, is dynamically regulated during plant regeneration to address proper callus formation and shoot regeneration. The ATX4 protein massively activates shoot identity genes by conferring H3K4me3 deposition at the loci. ATX4-deficient mutants display strong silencing of shoot identity and thus enhanced callus formation. Subsequently, de novo shoot organogenesis from calli is impaired in atx4 mutants. These results indicate that a series of epigenetic reprogramming of tissue identity underlies plant regeneration, and molecular components defining tissue identity can be used as invaluable genetic sources for improving crop transformation efficiency.
PDF
