We describe the epidemiology of a coronavirus disease (COVID-19) outbreak in a call center in South Korea. We obtained information on demographic characteristics by using standardized epidemiologic ...investigation forms. We performed descriptive analyses and reported the results as frequencies and proportions for categoric variables. Of 1,143 persons who were tested for COVID-19, a total of 97 (8.5%, 95% CI 7.0%-10.3%) had confirmed cases. Of these, 94 were working in an 11th-floor call center with 216 employees, translating to an attack rate of 43.5% (95% CI 36.9%-50.4%). The household secondary attack rate among symptomatic case-patients was 16.2% (95% CI 11.6%- 22.0%). Of the 97 persons with confirmed COVID-19, only 4 (1.9%) remained asymptomatic within 14 days of quarantine, and none of their household contacts acquired secondary infections. Extensive contact tracing, testing all contacts, and early quarantine blocked further transmission and might be effective for containing rapid outbreaks in crowded work settings.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Brain organoids derived from human pluripotent stem cells provide a highly valuable in vitro model to recapitulate human brain development and neurological diseases. However, the current systems for ...brain organoid culture require further improvement for the reliable production of high-quality organoids. Here, we demonstrate two engineering elements to improve human brain organoid culture, (1) a human brain extracellular matrix to provide brain-specific cues and (2) a microfluidic device with periodic flow to improve the survival and reduce the variability of organoids. A three-dimensional culture modified with brain extracellular matrix significantly enhanced neurogenesis in developing brain organoids from human induced pluripotent stem cells. Cortical layer development, volumetric augmentation, and electrophysiological function of human brain organoids were further improved in a reproducible manner by dynamic culture in microfluidic chamber devices. Our engineering concept of reconstituting brain-mimetic microenvironments facilitates the development of a reliable culture platform for brain organoids, enabling effective modeling and drug development for human brain diseases.
Color of Copper/Copper Oxide Kim, Su Jae; Kim, Seonghoon; Lee, Jegon ...
Advanced materials (Weinheim),
04/2021, Letnik:
33, Številka:
15
Journal Article
Recenzirano
Odprti dostop
Stochastic inhomogeneous oxidation is an inherent characteristic of copper (Cu), often hindering color tuning and bandgap engineering of oxides. Coherent control of the interface between metal and ...metal oxide remains unresolved. Coherent propagation of an oxidation front in single‐crystal Cu thin film is demonstrated to achieve a full‐color spectrum for Cu by precisely controlling its oxide‐layer thickness. Grain‐boundary‐free and atomically flat films prepared by atomic‐sputtering epitaxy allow tailoring of the oxide layer with an abrupt interface via heat treatment with a suppressed temperature gradient. Color tuning of nearly full‐color red/green/blue indices is realized by precise control of the oxide‐layer thickness; the samples cover ≈50.4% of the standard red/green/blue color space. The color of copper/copper oxide is realized by the reconstruction of the quantitative yield color from the oxide “pigment” (complex dielectric functions of Cu2O) and light‐layer interference (reflectance spectra obtained from the Fresnel equations) to produce structural color. Furthermore, laser‐oxide lithography is demonstrated with micrometer‐scale linewidth and depth through local phase transformation to oxides embedded in the metal, providing spacing necessary for semiconducting transport and optoelectronics functionality.
Atomically flat perfect single‐crystal Cu films prepared by the atomic‐sputtering epitaxy method realize the coherent propagation of an oxidation front and display full‐color by controlling the oxide‐layer thickness. More than 50% of the standard red/green/blue color space is covered. Laser‐oxide lithography forming a microscale local oxide embedded in metal is introduced.
The objective of this study is to fabricate conductive carbon fiber composites with thermal and electrical properties by degradation carbon-fiber-reinforced plastics (CFRPs) and recycled carbon ...fibers using only supercritical water without any catalyst or oxidant. We focused on a recycling method that is harmless to the human body and environment-friendly, by using supercritical fluid water rather than recycling CFRP by physical or pyrolysis methods. In particular, we recycled carbon fibers (R-CFs) in which up to 99.5% of epoxy resin was removed, by optimizing the conditions of supercritical fluid water (SCF-W) treatment, and we fabricated conductive R-CFs composites with thermal and electrical properties by combining the R-CFs with cyclic butylene terephthalate (CBT), which is a polymerizable low-viscosity thermoplastic resin. The fabricated composites had a thermal conductivity of 1.35 ± 0.05 (W/mK) and an electrical conductivity of 11.23 × 10−6 (S/cm) when the added amount of recycled carbon fibers was 5 wt%.
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Electroluminescence efficiencies of metal halide perovskite nanocrystals (PNCs) are limited by a lack of material strategies that can both suppress the formation of defects and enhance the charge ...carrier confinement. Here we report a one-dopant alloying strategy that generates smaller, monodisperse colloidal particles (confining electrons and holes, and boosting radiative recombination) with fewer surface defects (reducing non-radiative recombination). Doping of guanidinium into formamidinium lead bromide PNCs yields limited bulk solubility while creating an entropy-stabilized phase in the PNCs and leading to smaller PNCs with more carrier confinement. The extra guanidinium segregates to the surface and stabilizes the undercoordinated sites. Furthermore, a surface-stabilizing 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene was applied as a bromide vacancy healing agent. The result is highly efficient PNC-based light-emitting diodes that have current efficiency of 108 cd A−1 (external quantum efficiency of 23.4%), which rises to 205 cd A−1 (external quantum efficiency of 45.5%) with a hemispherical lens.Guanidinium doping is shown to enhance the operation of perovskite nanocrystal light-emitting diodes.
Copper surfaces that exhibit a wide range of achromatic colors while still metallic have not been studied, despite advancements in antireflection coatings. A series of achromatic copper films grown ...with 111 preferred orientation by depositing 3D porous nanostructures is introduced via coherent/incoherent atomic sputtering epitaxy. The porous copper nanostructures self‐regulate the giant oxidation resistance by constructing a curved surface that generates a series of monoatomic steps, followed by shrinkage of the lattice spacing of one or two surface layers. First‐principles calculations confirm that these structural components cooperatively increase the energy barrier against oxygen penetration. The achromaticity of the single‐crystalline porous copper films is systematically tuned by geometrical parameters such as pore size distribution and 3D linkage. The optimized achromatic copper films with high oxidation resistance show an unusual switching effect between superhydrophilicity and superhydrophobicity. The tailored 3D porous nanostructures can be a candidate material for numerous applications, such as antireflection coatings, microfluidic devices, droplet tweezers, and reversible wettability switches.
A series of achromatic Cu films with semi‐permanent stability and switchable superhydrophobic and superhydrophilic states on rough or curved surfaces is realized by an innovative strategy. Comprehensive atomic‐resolution microscopy reveals that their surfaces are of a series of monoatomic steps and have a counterintuitive lattice contraction, which demonstrates the self‐oxidation resistance of copper.
Ion enhanced polarizationHafnium oxide is an exciting material because it has ferroelectric behavior that makes it attractive for various device applications. Kang et al. found that the ferroelectric ...properties improve by bombarding films of hafnium oxide with a beam of helium ions. The ion bombardment creates oxygen vacancies and strain changes from helium implantation that push more of the polycrystalline samples into the ferroelectric orthorhombic phase. This method may become an important tool for stabilizing the ferroelectric phase for the next generation of electronic devices. —BG
The outbreak of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in China and rapidly spread worldwide. To prevent SARS-CoV-2 ...dissemination, understanding the in vivo characteristics of SARS-CoV-2 is a high priority. We report a ferret model of SARS-CoV-2 infection and transmission that recapitulates aspects of human disease. SARS-CoV-2-infected ferrets exhibit elevated body temperatures and virus replication. Although fatalities were not observed, SARS-CoV-2-infected ferrets shed virus in nasal washes, saliva, urine, and feces up to 8 days post-infection. At 2 days post-contact, SARS-CoV-2 was detected in all naive direct contact ferrets. Furthermore, a few naive indirect contact ferrets were positive for viral RNA, suggesting airborne transmission. Viral antigens were detected in nasal turbinate, trachea, lungs, and intestine with acute bronchiolitis present in infected lungs. Thus, ferrets represent an infection and transmission animal model of COVID-19 that may facilitate development of SARS-CoV-2 therapeutics and vaccines.
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•SARS-CoV-2-infected ferrets exhibit elevated body temperature and virus replication•SARS-CoV-2 is shed in nasal washes, saliva, urine and feces•SARS-CoV-2 is effectively transmitted to naive ferrets by direct contact•SARS-CoV-2 infection leads acute bronchiolitis in infected ferrets
The outbreak of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapidly spreads, leading to a pandemic infection. Kim et al. show that ferrets are highly susceptible to SARS-CoV-2 infection and effectively transmit the virus by direct or indirect contact, recapitulating human infection and transmission.
The issues over increases in energy demand and environmental pollution attributed to excessive use of fossil fuel have been the driving forces of the exploration for eco-friendly resource. ...Lignocellulosic biomass consisting of carbohydrates and lignin can be a renewable feedstock for replacing fossil fuels in the future because it is a plentiful and carbon neutral material. Especially, lignin, cross-linked phenolic polymers, is a topic of interest owing to its abundant production from pulp/paper industries as well as lignocellulose based biorefinery. The large potential of platform chemicals and biofuels from lignin has opened up an extensive range of opportunities to develop thermal and catalytic conversion technology. Over a few decades, several lignin conversion processes including catalytic pyrolysis, catalytic depolymerization, and catalytic oxidation have been developed to improve target products yields and to suppress side reactions. More recently, lignin-first approaches which maintain carbohydrates intact by selective extraction of lignin as valuable phenolics from whole biomass has been suggested. This review introduces recent ten years progress on thermal and catalytic conversion technology in terms of process type, catalyst development, and target products. This review is expected to offer an influential information for future research into the thermal and catalytic conversion of lignin as well as lignocellulosic feedstock.
•Recent discoveries in thermal and catalytic lignin conversion are introduced.•A proper conversion process should be considered depending on the lignin type.•Catalyst plays a decisive role in product distribution and selectivity in process.•The challenges and future perspective of each process is discussed.
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