Background: The clinical performance of six molecular diagnostic tests and a rapid antigen test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were clinically evaluated for the diagnosis of coronavirus disease 2019 (COVID-19) in self-collected saliva. Methods: Saliva samples from 103 patients with laboratory-confirmed COVID-19 (15 asymptomatic and 88 symptomatic) were collected on the day of hospital admission. SARS-CoV-2 RNA in saliva was detected using a quantitative reverse-transcription polymerase chain reaction (RT-qPCR) laboratory-developed test (LDT), a cobas SARS-CoV-2 high-throughput system, three direct RT-qPCR kits, and reverse-transcription loop mediated isothermal amplification (RT-LAMP). The viral antigen was detected by a rapid antigen immunochromatographic assay. Results: Of the 103 samples, viral RNA was detected in 50.5–81.6% of the specimens by molecular diagnostic tests and an antigen was detected in 11.7% of the specimens by the rapid antigen test. Viral RNA was detected at a significantly higher percentage (65.6–93.4%) in specimens collected within 9 d of symptom onset compared to that of specimens collected after at least 10 d of symptom onset (22.2–66.7%) and that of asymptomatic patients (40.0–66.7%). Conclusions: Self-collected saliva is an alternative specimen option for diagnosing COVID-19. LDT RT-qPCR, cobas SARS-CoV-2 high-throughput system, direct RT-qPCR except for one commercial kit, and RT-LAMP showed sufficient sensitivity in clinical use to be selectively used according to clinical settings and facilities. The rapid antigen test alone is not recommended for initial COVID-19 diagnosis because of its low sensitivity.

The electrochemical oxidation behaviors of the surfaces of platinum nanoparticles, one of the key phenomena in fuel cell developments, were investigated in situ and in real time, via time-resolved hard X-ray diffraction and energy dispersive X-ray absorption spectroscopy. Combining two complementary structural analyses, dynamical and inhomogenous structural changes occurring at the surfaces of nanoparticles were monitored on an atomic level with a time resolution of less than 1 s. After oxidation at 1.4 V vs RHE (reversible hydrogen electrode) in a 0.5 M H(2)SO(4) solution, longer Pt-O bonds (2.2-2.3 A that can be assigned to OHH and/or OH species) were first formed on the surface through the partial oxidation of water molecules. Next, these species turned to shorter Pt-O bonds (2.0 A, adsorbed atomic oxygen), and atomic oxygen was incorporated into the inner part of the nanoparticles, forming an initial monolayer oxide that had alpha-PtO(2)-like local structures with expanded Pt-Pt bonds (3.1 A). Finally, quasi-three-dimensional oxides with longer Pt-(O)-Pt bonds (3.5 A, precursor for beta-PtO(2)) grew on the surface, at almost 100 s after oxidation. Despite the very complex oxidation mechanism on the atomic level, XANES analysis indicated that the charge transfer from platinum to the adsorbed oxygen species was almost constant and rather small, that is, about 0.5 electrons per oxygen, up to two monolayers of oxygen. This means that ionic polarization hardly develops at this stage of the surface platinum's "oxide" growth.

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