Background:The ongoing outbreak of novel corona virus disease 2019 in Wuhan, China, is arousing international concern. This study evaluated whether and when the infected but asymptomatic cases during the incubation period could infect others. Methods:We collected data on demographic characteristics, exposure history, and symptom onset day of the confirmed cases, which had been announced by the Chinese local authorities. We evaluated the potential of transmission during the incubation period in 50 infection clusters, including 124 cases. All the secondary cases had a history of contact with their first-generation cases prior to symptom onset. Results:The estimated mean incubation period for COVID-19 was 4.9 days (95% confidence interval [CI], 4.4 to 5.4) days, ranging from 0.8 to 11.1 days (2.5th to 97.5th percentile). The observed mean and standard deviation (SD) of serial interval was 4.1±3.3 days, with the 2.5th and 97.5th percentiles at -1 and 13 days. The infectious curve showed that in 73.0% of the secondary cases, their date of getting infected was before symptom onset of the first-generation cases, particularly in the last three days of the incubation period. Conclusions:The results indicated the transmission of COVID-9 occurs among close contacts during the incubation period, which may lead to a quarantine loophole.Strong and effective countermeasures should be implemented to prevent or mitigate asymptomatic transmission during the incubation period in populations at high risk.

Solar thermal fuels offer a closed cycle and a renewable energy storage strategy by harvesting photon energy within the chemical conformations of molecules and retrieving energy by an induced release of heat. However, the majority of reports are limited to the ultraviolet light storage, which potentially interferes with the surrounding environment and reduces the material lifetime. Here, we present a novel arylazopyrazole (AAP)containing dendrimer that not only addresses the hindrance of visible light storage for solar thermal fuels but also exhibits outstanding performances of abundant energy conversion and stable storage, which are attributed to the substantial absorbance in visible wavelengths of para-thiomethyl-substituted AAP groups and the stability of cis isomers, respectively. The energy density of the dendrimer fuel after efficiently harvesting blue light (405 nm) is as high as 0.14 MJ kg −1 (67 kJ mol −1 ), and the storage half-life of the fabricated dendrimer film can reach up to 12.9 days. Moreover, the heat release of the dendrimer film can be triggered by different stimuli (light and heat). The dendrimer film displays a 6.5 °C temperature difference between trans isomers and cis isomers during green light irradiation. Our work provides a fascinating avenue to fabricate visible light storage solar thermal fuels and unlocks the possibility of developing natural sunlight storage in the future.

Dendrimers are well-defined, highly branched macromolecules that have been widely applied in the fields of catalysis, sensing, and biomedicine. Here, we present a novel multifunctional photochromic dendrimer fabricated through grafting azobenzene units onto dendrimers, which not only enables controlled switching of adhesives and effective repair of coating scratches but also realizes high-performance solar energy storage and on-demand heat release. The switchable adhesives and healable coatings of azobenzene-containing dendrimers are attributed to the reversible solid-to-liquid transitions because trans-isomers and cis-isomers have different glass transition temperatures. The adhesion strengths increase significantly with the increase in dendrimer generations, wherein the adhesion strength of fifth-generation photochromic dendrimers (G5-Azo) can reach up to 1.62 MPa, five times higher than that of pristine azobenzenes. The solar energy storage and heat release of dendrimer solar thermal fuels, the isomers of which possess different chemical energies, can be also enhanced remarkably with the amplification of azobenzene groups on dendrimers. The storage energy density of G5-Azo can reach 59 W h kg −1 , which is much higher than that of pristine azobenzenes (36 W h kg −1 ). The G5-Azo fuels exhibit a 5.2 °C temperature difference between cis-isomers and trans-isomers. These findings provide a new perspective and tremendously attractive avenue for the fabrication of photoswitchable adhesives and coatings and solar thermal fuels with dendrimer structures.

substitution [10] were proposed to obtain pure organic URTP materials, [11] while the stringent requirement of the formation of crystalline state and H-aggregation, the inevitable phase separation in host-guest systems, and the complicated process of deuterium substitution hindered their practical applications. [12] Owing to outstanding features of polymers, such as elasticity, flexibility, film-forming ability, and transparency, the polymer-based URTP materials are quite suitable for manufacturing and processing organic phosphorescent devices with complex shapes. [13] Zhao and coworkers developed phosphors-doped URTP polymer materials with 0.75 s phosphorescence lifetime based on poly(vinyl alcohol) matrices. [13a] Ogoshi et al. reported a nondoped URTP polymer, poly (styrene sulfonic acid), with 1.22 s phosphorescence lifetime. [13c] However, few URTP polymer materials achieved phosphorescence lifetimes longer than 2 s. [14] Moreover, the URTP polymer materials with longer phosphorescence lifetimes showed extremely low phosphorescence quantum yields (<2%), [14a] which significantly limited their practical applications. The short lifetimes and low quantum yields in polymer materials are mainly caused by the severe nonradiative decay of triplet excitons. [15] Therefore, the suppression of nonradiative decay is the key to improve phosphorescence lifetime and quantum yield. Herein we propose a novel URTP strategy for simultaneously achieving ultralong lifetimes and high quantum yields in polymer films, based on the effective suppression of nonradiative decay of organic phosphors by dense 3D network. A recordbreaking 2.28 s ultralong phosphorescence lifetime and up to 8.35% phosphorescence quantum yield are achieved simultaneously in the tetramethylbenzidine (TMB)-doped URTP polymer film. To the best of our knowledge, it is the first phosphors-doped URTP polymer with ultralong phosphorescence lifetime (>2 s) and simultaneous high phosphorescence quantum yield (>8%). The URTP polymer films were fabricated by simply doping the organic phosphors into epoxy polymer with dense 3D network. The chemical structures of the epoxy molecule diglycidyl ether of bisphenol-A (DGEBA), the curing agent ethylenediamine (EDA), and the phosphor N, N, N′, N′-tetramethylbenzidine (TMB) are shown in Figure 1a. The Ultralong room temperature phosphorescence (URTP) is an attractive phenomenon in organic photonics. Polymer-based URTP materials are superior alternatives to traditional inorganic or organometallic phosphors because of their unique transparency and flexibility. However, few URTP polymer films achieve room temperature phosphorescence lifetimes longer than 2 s and the polymer films with longer lifetimes show extremely low phosphorescence quantum yields (<2%). Herein, a reasonable strategy is proposed to simultaneously achieve ultralong room temperature phosphorescence lifetimes and high phosphorescence quantum yields in polymer films, based on the effective suppression of nonradiative decay of organic phosphors by dense 3D network...

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To explore the association between γ-glutamyl transpeptidase to high-density lipoprotein ratio (GGT/HDL), triglyceride glucose-body mass index (TYG-BMI), and metabolic associated fatty liver disease (MAFLD) in a Chinese population with type 2 diabetes (T2DM) by cross-sectional analysis. To investigate the role of GGT/HDL played in MAFLD by TYG-BMI. Patients and Methods: A total of 1434 adult patients hospitalized with T2DM at Hebei General Hospital (Shijiazhuang, China) were included in the study. Patients' demographic and clinical data were collected. Spearman correlation was used to test for an association between GGT/HDL or TYG-BMI and related risk factors of MAFLD among T2DM patients. Multiple logistic regression analyses were performed to investigate the association between GGT/HDL or TYG-BMI and MAFLD. Mediation analysis was used to explore whether TYG-BMI mediated the association between GGT/HDL and MAFLD. Results: A total of 1434 T2DM patients were enrolled, the MAFLD group showed a higher level of GGT/HDL compared to the non-MAFLD group. There was a progressive increase in the prevalence of MAFLD with increasing tertiles of GGT/HDL. After adjusting for confounding factors, multivariate logistic regression analysis revealed that high levels of GGT/HDL were independent risk factors for MAFLD in T2DM patients. BMI further grouped the patients: ≤ 23kg/m2,>23kg/m2. GGT/HDL was found to be an independent risk factor for MAFLD but only in T2DM patients with a BMI greater than 23 kg/m2. Mediation analysis indicated that GGT/HDL had a significant direct effect on MAFLD. Conclusion: GGT/HDL was positively associated with MAFLD incidence in T2DM patients with a BMI greater than 23 Kg/m2, and TYG-BMI partly mediated the association.

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Here, a novel triple-responsive graphene oxide hybrid supramolecular hydrogel based on the electrostatic self-assembly between graphene oxide and a quaternized polymer and the host−guest inclusion between α-cyclodextrins and poly(ethylene glycol) monomethyl ether (mPEG) was constructed. The quaternized polymer was synthesized by quaternization between pH-sensitive poly(N,N-dimethylaminoethyl methacrylate) and bromine end-capped poly(ethylene glycol) monomethyl ether. The supramolecular hydrogels prepared from the host−guest inclusion of poly(ethylene glycol) monomethyl ether and α-cyclodextrins would turn into a mobile sol phase when the temperature was increased above a certain temperature (Tgel−sol). Graphene oxide sheets not only acted as a core material to provide additional cross-linking but also absorbed NIR light and converted NIR light into heat to trigger the gel−sol transition. The constructed graphene oxide hybrid cyclodextrin-based supramolecular hydrogels could respond to NIR light, temperature, and pH, which could be beneficial for controlled release of cargoes and would hold great promise in the field of delivery systems.