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Governments can use social media platforms such as Twitter to disseminate health information to the public, as evidenced during the COVID-19 pandemic [Pershad (2018)]. The purpose of this study is to gain a better understanding of Canadian government and public health officials' use of Twitter as a dissemination platform during the pandemic and to explore the public's engagement with and sentiment towards these messages. We examined the account data of 93 Canadian public health and government officials during the first wave of the pandemic in Canada (December 31, 2019 August 31, 2020). Our objectives were to: 1) determine the engagement rates of the public with Canadian federal and provincial/territorial governments and public health officials' Twitter posts; 2) conduct a hashtag trend analysis to explore the Canadian public's discourse related to the pandemic during this period; 3) provide insights on the public's reaction to Canadian authorities' tweets through sentiment analysis. To address these objectives, we extracted Twitter posts, replies, and associated metadata available during the study period in both English and French. Our results show that the public demonstrated increased engagement with federal officials' Twitter accounts as compared to provincial/territorial accounts. For the hashtag trends analysis of the public discourse during the first wave of the pandemic, we observed a topic shift in the Canadian public discourse over time between the period prior to the first wave and the first wave of the pandemic. Additionally, we identified 11 sentiments expressed by the public when reacting to Canadian authorities' tweets. This study illustrates the potential to leverage social media to understand public discourse during a pandemic. We suggest that routine analyses of such data by governments can provide governments and public health officials with real-time data on public sentiments during a public health emergency. These data can be used to better disseminate key messages to the public.

Arterial stenosis is a common cardiovascular disease that restricts blood flow. A stenotic blood vessel creates tangent stress pressure, which lessens the arterial side and causes an aneurysm. The primary purpose of this study is to investigate blood flowing via an inclination pipe with stricture and expansion after stricture (widening) underneath the influence of a constant incompressible Casson liquid flowing with the magnetism field. The relations for surface shearing stress, pressure drop, flow resistance, and velocity are calculated analytically by applying a mild stenosis approximation. The effect of different physical characteristics on liquid impedance to flowing, velocity, and surface shearing stress are studied. With a non-Newtonian aspect of the Casson liquid, the surface shearing stress declines, and an impedance upturn. Side resistivity and shear-stress increase with the elevations of stricture, whilst together decreasing with a dilatation height.

HIV-1 Nef protein down-regulates several cell surface receptors through its interference with the cell sorting and trafficking machinery. Here we demonstrate for the first time the ability of Nef to down-regulate cell surface expression of the negative immune modulator CTLA-4. Down-regulation of CTLA-4 required the Nef motifs DD175, EE155 and LL165, all known to be involved in vesicle trafficking. Disruption of the lysosomal functions by pH-neutralizing agents prevented CTLA-4 down-regulation by Nef, demonstrating the implication of the endosomal/lysosomal compartments in this process. Confocal microscopy experiments visualized the co-localization between Nef and CTLA-4 in the early and recycling endosomes but not at the cell surface. Overall, our results provide a novel mechanism by which HIV-1 Nef interferes with the surface expression of the negative regulator of T cell activation CTLA-4. Down-regulation of CTLA-4 may contribute to the mechanisms by which HIV-1 sustains T cell activation, a critical step in viral replication and dissemination.

HIV-1 Nef protein down-regulates several cell surface receptors through its interference with the cell sorting and trafficking machinery. Here we demonstrate for the first time the ability of Nef to down-regulate cell surface expression of the negative immune modulator CTLA-4. Down-regulation of CTLA-4 required the Nef motifs DD175, EE155 and LL165, all known to be involved in vesicle trafficking. Disruption of the lysosomal functions by pH-neutralizing agents prevented CTLA-4 down-regulation by Nef, demonstrating the implication of the endosomal/lysosomal compartments in this process. Confocal microscopy experiments visualized the co-localization between Nef and CTLA-4 in the early and recycling endosomes but not at the cell surface. Overall, our results provide a novel mechanism by which HIV-1 Nef interferes with the surface expression of the negative regulator of T cell activation CTLA-4. Down-regulation of CTLA-4 may contribute to the mechanisms by which HIV-1 sustains T cell activation, a critical step in viral replication and dissemination.