(Mis)Information on Digital Platforms: Quantitative and Qualitative Analysis of Content From Twitter and Sina Weibo in the COVID-19 Pandemic.

Background: Misinformation about COVID-19 on social media has presented challenges to public health authorities during the pandemic. This paper leverages qualitative and quantitative content analysis on cross-platform, cross-national discourse and misinformation in the context of COVID-19. Specifically, we investigated COVID-19-related content on Twitter and Sina Weibo-the largest microblogging sites in the United States and China, respectively. Objective: Using data from 2 prominent microblogging platform, Twitter, based in the United States, and Sina Weibo, based in China, we compared the content and relative prevalence of misinformation to better understand public discourse of public health issues across social media and cultural contexts. Methods: A total of 3,579,575 posts were scraped from both Sina Weibo and Twitter, focusing on content from January 30, 2020, within 24 hours of when WHO declared COVID-19 a "public health emergency of international concern," and a week later, on February 6, 2020. We examined how the use and engagement measured by keyword frequencies and hashtags differ across the 2 platforms. A 1% random sample of tweets that contained both the English keywords "coronavirus" and "covid-19" and the equivalent Chinese characters was extracted and analyzed based on changes in the frequencies of keywords and hashtags and the Viterbi algorithm. We manually coded a random selection of 5%-7% of the content to identify misinformation on each platform and compared posts using the WHO fact-check page to adjudicate accuracy of content. Results: Both platforms posted about the outbreak and transmission, but posts on Sina Weibo were less likely to reference topics such as WHO, Hong Kong, and death and more likely to cite themes of resisting, fighting, and cheering against coronavirus. Misinformation constituted 1.1% of Twitter content and 0.3% of Sina Weibo content-almost 4 times as much on Twitter compared to Sina Weibo. Conclusions: Quantitative and qualitative analysis of content on both platforms points to lower degrees of misinformation, more content designed to bolster morale, and less reference to topics such as WHO, death, and Hong Kong on Sina Weibo than on Twitter.

Quantitative relationship between the structures and properties of VOCs and SOA formation on the surfaces of acidic aerosol particles.

In this research, all the efforts, based on a series of molecular dynamics simulations on the interfacial process between VOC-contaminated air and acidic sulfate, were made to find how the structures and properties of VOCs are related to the formation of SOAs. The experimental fractional aerosol coefficients (FACs) were used to quantify the SOA formation and 14 VOC species were chosen based on the atmosphere inventory and the FAC magnitude. Finally, the quantitative relationship (QR) was found through the FAC as a function of the two variables the total valid interactions (Tg) and the diffusion coefficient (D), with R square 0.94. Meanwhile, the effect of water was explored and the QR was proved to be rational and reliable. The QR not only explained the SOA formation capacity of VOCs, but could also predict the SOA formation of new molecules.

New insights into the formation mechanism of gold nanoparticles using dopamine as a reducing agent.

Dopamine (DA), a simplified mimic of mussel proteins, can be employed as a reductant in the preparation of Au nanoparticles (AuNPs) due to its inherent catechol building block. The widely accepted mechanism of AuNP formation using DA as the reductant assumes that the reduction of Au(III) ions involves the two-electron oxidation of DA, where the corresponding phenol and phenolates serve as the reductive species to yield quinone. We herein report a novel insight into the mechanism of formation of AuNPs using DA as the reductant. We demonstrate that the synthesis of AuNPs requires the prior oxidation of the DA to form quinone units, which then catalyze the formation of semiquinones. These semiquinone radicals (SMQs) reduce the Au(III) ions to form the initial AuNPs, and further growth is then catalyzed by the first AuNPs, with nucleation occurring where the SMQs, phenols, and phenolates can serve as reductive species. In addition, DA oxidizes and polymerizes to form a polydopamine capping layer on the AuNPs. We therefore expect that the novel mechanism proposed herein may promote us to furthermore explore the production of noble metal NPs using other polyphenols.

[Cerebrosides isolated from Arisaema flavum].

Silica gel, Sephadex LH-20, and reverse phase (C-18) column chromatography were used for the research of chemical constituents occurred in Arisaema flavum(Forsk.) Schott. The structures were elucidated by comparison physico-chemical properties and NMR spectroscopic data with those of known compounds. Seventeen cerebrosides were identified as 1-O-ß-D-glucopyranosyl-(2S, 3R, 4E, 8E)-2-[(2'(R)-acetoxyoctadecanoyl)amido]-4, 8-octadecadiene-1, 3-diol (1), 2'-O-acetylsoyacerebroside I (2), 1-O-(ß-D-glucopyranosyl)-(2S, 3R, 4E, 13Z)-2-[(2'R)-2-hydroxytetradecanoylamino]-1, 3-dihydroxy-4, 13-docosadiene (3), (2S, 3R, 4E, 8E)1-(ß-D-glucopyranosyl)-3-hydroxy-2-[(R)-2'-hydroxyhexadecanoyl]amino-9-methyl-4, 8-heptadecadiene (4), (2S, 3R, 4E, 8E)1-(ß-D-glucopyranosyl)-3-hydroxy-2-[(R)-2'-hydroxyhexadecanoyl]amino-9-methyl-4, 8-octadecadiene (5), (2S, 3R, 4E, 8E)1-(ß-D-glucopyranosyl)-3-hydroxy-2-[(R)-2'-hydroxypalmitoyl]amino-9-methyl-4, 8-octadecadiene (6), (2S, 3R, 4E, 8E)1-(ß-D-glucopyranosyl)-3-hydroxy-2-[(R)-2'-hydroxyoctadecanoyl]amino-9-methyl-4, 8-octadecadiene (7), 1-O-(ß-D-glucopyranosyl)-(2S, 3R, 4E, 8E)-2-[(R)-2'-hydroxytetradecanoylamino]-4, 8-octadecadiene-1, 3-diol (8), 1-O-(ß-D-glucopyranosyl)-(2S, 3R, 4E, 8E)-2-[(R)-2'-hydroxypentadecanoylamino]-4, 8-octadecadiene-1, 3-diol (9), 1-O-(ß-D-glucopyranosyl)-(2S, 3R, 4E, 8E)-2-[(R)-2'-hydroxyhexadecanoylamino]-4, 8-octadecadiene-1, 3-diol (10), 1-O-(ß-D-glucopyranosyl)-(2S, 3R, 4E, 8Z)-2-[(R)-2'-hydroxyhexadecanoylamino]-4, 8-octadecadiene-1, 3-diol (11), 1-O-(ß-D-glucopyranosyl)-(2S, 3R, 4E, 8E)-2-[(R)-2'-hydroxyoctadecanoylamino]-1, 3-hydroxy-4, 8-octadecadiene (12), 1-O-(ß-D-glucopyranosyl)-(2S, 3R, 4E)-2-[(R)-2'-hydroxytetracosanoylamino]-1, 3-hydroxy-4-hexadecane (13), 1-O-(ß-D-glucopyranosyl)-(2S, 3R, 4R, 8Z)-2N-[(2'R)-2'-hydroxytetracosanoyl]-8-(Z)-octadecene-1, 3, 4-triol (14), 1-O-(ß-D-glucopyranosyl)-(2S, 3S, 4E, 8E)-2N-[(2'R)-2'-hydroxyhexadecanoyl]-4-(E), 8-(Z)-octadecadiene-1, 3-diol (15), typhoniside A (16), and 1-O-ß-D-glucopyranosyl-(2S, 3R, 8E)-2-[(2'R)-2-hydroxypalmitoylamino]-8-octadecene-1, 3-diol (17). Compounds 1 and 2 were isolated from the plant for the first time, while the remained compounds were isolated from the genus Arisaema for the first time.

Dereplication of known pregnane glycosides and structural characterization of novel pregnanes in Marsdenia tenacissima by high-performance liquid chromatography and electrospray ionization-tandem mass spectrometry.

In the search for novel natural products in plants, particularly those with potential bioactivity, it is important to efficiently distinguish novel compounds from previously isolated, known compounds, a process known as dereplication. In this study, electrospray ionization-multiple stage tandem mass spectrometry (ESI-MS(n)) was used to study the behaviour of 12 pregnane glycosides and genins previously isolated from Marsdenia tenacissima, a traditional Chinese medicinal plant, as a basis for dereplication of compounds in a plant extract. In addition to [M + Na](+) and [M + NH(4)](+) ions, a characteristic [M-glycosyl + H](+) ion was observed in full-scan mode with in-source fragmentation. Sequential in-trap collision-induced dissociation of [M + Na](+) ions from 11,12-diesters revealed consistent preferred losses of substituents first from C-12, then from C-11, followed by losses of monosaccharide fragments from the C-3 tri- and tetrasaccharide substituents. A crude methanol extract of M. tenacissima stems was analysed using high-performance liquid chromatography coupled to ESI-MS. Several previously isolated pregnane glycosides were dereplicated, and the presence of an additional nine novel pregnane glycosides is predicted on the basis of the primary and fragment ions observed, including two with a previously unreported C(4)H(7)O C-11/C-12 substituent of pregnane glycosides. This study is the first report of prediction of the structures of novel pregnane glycosides in a crude plant extract by a combination of in-source fragmentation and in-trap collision-induced dissociation and supports the usefulness of LC-ESI-MS(n) not only for dereplication of active compounds in extracts of medicinal plants but also for detecting the presence of novel related compounds.