The rapid spread of infectious diseases is devastating to the healthcare systems of all countries. The dynamics of the spatial spread of epidemic have received considerable scientific attention. However, the understanding of the spatial variation of epidemic severity in the urban system is lagging. Using synchronized epidemic data and human mobility data, integrated with other multiple-sourced data, this study examines the interplay between disease spread of coronavirus disease (COVID-19) and inter-city and intra-city mobility among 319 Chinese cities. The results show a disease spreading process consisting of a major transfer (inter-city) diffusion before the Chinese New Year and a subsequent local (intra-city) diffusion after the Chinese New Year in the urban system of China. The variations in disease incidence between cities are mainly driven by inter-city mobility from Wuhan, the epidemic center of COVID-19. Cities that are closer to the epidemic center and with more population in the urban area will face higher risks of disease incidence. Warm and humid weather could help mitigate the spread of COVID-19. The extensive inter-city and intra-city travel interventions in China have reduced approximately 70% and 40% inter-city and intra-city mobility, respectively, and effectively slowed down the spread of the disease by minimizing human to human transmission together with other disease monitoring, control, and preventive measures. These findings could provide valuable insights into understanding the dynamics of disease spread in the urban system and help to respond to another new wave of pandemic in China and other parts of the world.
The self-assembly of diphenylalanine peptides (l-Phe-l-Phe) into microtubes with "turn on" bright yellow green fluorescence was described, which was achieved using an aggregation-induced emission (AIE) molecule of 9,10-bis[4-(3-sulfonatopropoxyl)-styryl] anthracene (BSPSA) sodium.
Self-assembled monolayers (SAMs) have been widely employed as etching resists in wet lithography systems to form patterns in which the ordered molecular packing of the SAM regions significantly delays the etchant attack. A generally accepted recognition is that the SAMs ability to resist etching is positively correlated to the quality of the surface-assembled structures, and a more ordered molecular packing would correspond to a better etching resistance. Such a classical belief is debated in the present work by providing an alternative SAM-assisted negative lithography where ordered SAM regions are etched more quickly than their disordered counterparts. This method features a unique photoirradiation-imprinted patterning process that simply consists of two steps: (1) UV irradiation on an OH-terminated SAM-modified gold surface through a photomask and (2) the subsequent immersion of the exposed substrate in an aqueous etching solution of N-bromosuccinimide/pyridine to develop a wet lithographic pattern. The entire experimental process reveals a finding from previous work that the etching rate on the UV-exposed regions with disordered molecular packing could be modulated to be slower than that in the unexposed well-defined SAM regions. Longer irradiation times would also revert the patterns from negative to positive. Thus, by merely using one kind of SAM-modified surface to provide both positive and negative micropatterns on gold layers, one could obtain flexible opportunities for high-resolution micro/nanofabrication resembling photolithography.
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