Showing papers by "The Chinese University of Hong Kong published in 2022"

SARS-CoV-2 Omicron variant shows less efficient replication and fusion activity when compared with Delta variant in TMPRSS2-expressed cells

Abstract: The novel SARS-CoV-2 Omicron variant (B.1.1.529), first found in early November 2021, has sparked considerable global concern and it has >50 mutations, many of which are known to affect transmissibility or cause immune escape. In this study, we sought to investigate the virological characteristics of the Omicron variant and compared it with the Delta variant which has dominated the world since mid-2021. Omicron variant replicated more slowly than the Delta variant in transmembrane serine protease 2 (TMPRSS2)-overexpressing VeroE6 (VeroE6/TMPRSS2) cells. Notably, the Delta variant replicated well in Calu3 cell line which has robust TMPRSS2 expression, while the Omicron variant replicated poorly in this cell line. Competition assay showed that Delta variant outcompeted Omicron variant in VeroE6/TMPRSS2 and Calu3 cells. To confirm the difference in entry pathway between the Omicron and Delta variants, we assessed the antiviral effect of bafilomycin A1, chloroquine (inhibiting endocytic pathway), and camostat (inhibiting TMPRSS2 pathway). Camostat potently inhibited the Delta variant but not the Omicron variant, while bafilomycin A1 and chloroquine could inhibit both Omicron and Delta variants. Moreover, the Omicron variant also showed weaker cell-cell fusion activity when compared with Delta variant in VeroE6/TMPRSS2 cells. Collectively, our results suggest that Omicron variant infection is not enhanced by TMPRSS2 but is largely mediated via the endocytic pathway. The difference in entry pathway between Omicron and Delta variants may have an implication on the clinical manifestations or disease severity.

Prospects and applications of photonic neural networks

Abstract: Neural networks have enabled applications in artificial intelligence through machine learning, and neuromorphic computing. Software implementations of neural networks on conventional computers that...

Ion Migration in Perovskite Light‐Emitting Diodes: Mechanism, Characterizations, and Material and Device Engineering

Abstract: In recent years, perovskite light-emitting diodes (PeLEDs) have emerged as a promising new lighting technology with high external quantum efficiency, color purity, and wavelength tunability, as well as, low-temperature processability. However, the operational stability of PeLEDs is still insufficient for their commercialization. The generation and migration of ionic species in metal halide perovskites has been widely acknowledged as the primary factor causing the performance degradation of PeLEDs. Herein, this topic is systematically discussed by considering the fundamental and engineering aspects of ion-related issues in PeLEDs, including the material and processing origins of ion generation, the mechanisms driving ion migration, characterization approaches for probing ion distributions, the effects of ion migration on device performance and stability, and strategies for ion management in PeLEDs. Finally, perspectives on remaining challenges and future opportunities are highlighted.

Photocatalytically recovering hydrogen energy from wastewater treatment using MoS2 @TiO2 with sulfur/oxygen dual-defect

Abstract: Photocatalysis is a promising technology for energy and environment applications. Herein, a dual-defect heterojunction system of TiO2 hierarchical microspheres with oxygen vacancies modified with ultrathin MoS2−x nanosheets (MoS2−x @TiO2-OV) is designed for simultaneously degrading pollutants and evolving hydrogen. MoS2−x @TiO2-OV exhibits a dramatically enhanced photocatalytic activity with a H2 evolution rate of 2985.16 μmol g−1h−1. In treating the simulated pharmaceutical wastewater, MoS2−x @TiO2-OV is capable of purifying various refractory contaminants, with the highest H2 evolution rate of 41.59 μmol g−1h−1 during enrofloxacin degradation. While treating the simulated coking wastewater, the catalyst achieves a H2 evolution rate of 102.72 μmol g−1h−1 and a mineralization rate of 50%. Computational studies suggest that the dual-defect is superior for the adsorption of H* and producing·OH (‘dual-defect boosted dual-function’). Also, the dual-defect sites significantly boosted the charge-carrier separation and transfer efficiencies. This work highlights the crucial role of defect engineering to develop the energy-recovering wastewater treatment approaches.

Improved mechanical properties in titanium matrix composites reinforced with quasi-continuously networked graphene nanosheets and in-situ formed carbides

Abstract: In order to construct quasi-continuously networked reinforcement in titanium (Ti) matrix composites, in this study, Ti-6Al-4V spherical powders were uniformly coated with a graphene nanosheet (GNS) layer by high energy ball milling and then consolidated by spark plasma sintering. Results showed that the GNS layer on the powder surface inhibited continuous metallurgy bonding between powders during sintering, which led to the formation of quasi-networked hybrid reinforcement structure consisting of in-situ TiC and remained GNSs. The networked GNSs/Ti64 composite possessed noticeably higher tensile strength but similar ductility to the Ti64 alloy, leading to both better tensile strength and ductility than the GNSs/Ti composite with randomly dispersed GNSs and TiC. The formation mechanism and the fracture mechanism of the networked hybrid reinforcement were discussed. The results provided a method to fabricate Ti matrix composites with high strength and good ductility.

A Near‐Infrared Absorbing and Emissive Quadruple Helicene Enabled by the Scholl Reaction of Perylene

Abstract: Herein, we report the synthesis, structural analysis, optical and chiroptical properties of a novel quadruple helicene, which has two [6] and two [7]helicene moieties fused in a contorted framework of 92 sp2 carbon atoms. It was synthesized by the Scholl reaction of a perylene-containing substrate with the formation of eight carbon-carbon bonds on the perylene unit in a single synthetic operation. Chemical oxidation of the quadruple helicene with tris(4-bromophenyl)ammoniumyl hexachloroantimonate resulted in an air-stable dication, which exhibits the same helicity in its four helicene moieties as unambiguously identified by single-crystal X-ray crystallography. The quadruple helicene exhibits unusual near-infrared absorption and emission with absorption and emission maxima at 848 nm and 977 nm, respectively, and its isolated enantiomers exhibit electronic circular dichroism in the near-infrared and visible-light regions.

Cigarette smoke promotes colorectal cancer through modulation of gut microbiota and related metabolites

Abstract: Objective Cigarette smoking is a major risk factor for colorectal cancer (CRC). We aimed to investigate whether cigarette smoke promotes CRC by altering the gut microbiota and related metabolites. Design Azoxymethane-treated C57BL/6 mice were exposed to cigarette smoke or clean air 2 hours per day for 28 weeks. Shotgun metagenomic sequencing and liquid chromatography mass spectrometry were parallelly performed on mice stools to investigate alterations in microbiota and metabolites. Germ-free mice were transplanted with stools from smoke-exposed and smoke-free control mice. Results Mice exposed to cigarette smoke had significantly increased tumour incidence and cellular proliferation compared with smoke-free control mice. Gut microbial dysbiosis was observed in smoke-exposed mice with significant differential abundance of bacterial species including the enrichment of Eggerthella lenta and depletion of Parabacteroides distasonis and Lactobacillus spp. Metabolomic analysis showed increased bile acid metabolites, especially taurodeoxycholic acid (TDCA) in the colon of smoke-exposed mice. We found that E. lenta had the most positive correlation with TDCA in smoke-exposed mice. Moreover, smoke-exposed mice manifested enhanced oncogenic MAPK/ERK (mitogen-activated protein kinase/extracellular signal‑regulated protein kinase 1/2) signalling (a downstream target of TDCA) and impaired gut barrier function. Furthermore, germ-free mice transplanted with stools from smoke-exposed mice (GF-AOMS) had increased colonocyte proliferation. Similarly, GF-AOMS showed increased abundances of gut E. lenta and TDCA, activated MAPK/ERK pathway and impaired gut barrier in colonic epithelium. Conclusion The gut microbiota dysbiosis induced by cigarette smoke plays a protumourigenic role in CRC. The smoke-induced gut microbiota dysbiosis altered gut metabolites and impaired gut barrier function, which could activate oncogenic MAPK/ERK signalling in colonic epithelium.

Enhanced Catalytic Ozonation for Eliminating CH₃SH <i>via</i> Stable and Circular Electronic Metal–Support Interactions of Si–O–Mn Bonds with Low Mn Loading

Abstract: Catalytic ozonation of methyl mercaptan (CH3SH) can effectively control this unbearable odorous sulfur-containing volatile organic compound (S-VOC). The construction of an electronic metal-support interaction (EMSI) coordination structure to maximize the number of active sites and increase the intrinsic activity of active sites is an effective means to improve catalytic performance. In this work, the abundant Si-OH groups on PSBA-15 (SBA-15 before calcination) were used to anchor Mn to form a Si-O-Mn-based EMSI coordination structure. Detailed characterizations and theoretical simulations reveal that the strong EMSI effect significantly adjusts and stabilizes the electronic structure of Mn 3d states, resulting in an electron-rich center on the Si-O-Mn bond to promote the specific adsorption/activation of ozone (O3) and an electron-poor center on the (Si-O-)Mn-O bond to adsorb a large amount of CH3SH accompanied by its own oxidative degradation. In situ Raman and in situ Fourier transform infrared (FTIR) analyses identify that catalytic ozonation over 3.0Mn-PSBA generates atomic oxygen species (AOS/*O) and reactive oxygen species (ROS/•O2-) to achieve efficient decomposition of CH3SH into CO2/SO42-. Furthermore, the electrons obtained from CH3SH in electron-poor centers are transferred to maintain the redox cycle of Mn2+/3+ → Mn4+ → Mn2+/3+ through the internal bond bridge, thus accomplishing the efficient and stable degradation of CH3SH prolonged to 180 min. Therefore, the rational design of catalysts with abundant active sites and optimized inherent activity via the EMSI effect can provide significant potential to improve catalytic performance and eliminate odorous gases.