Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre-including this research content-immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.
Liquid metals exhibit remarkable mechanical properties, in particular large surface tension and low viscosity. However, these properties are greatly affected by oxidation when exposed to air. We measure the viscosity, surface tension, and contact angle of gallium (Ga) and a eutectic galliumindium alloy (eGaIn) while controlling such oxidation by surrounding the metal with an acid bath of variable concentration. Rheometry measurements reveal a yield stress directly attributable to an oxide skin that obscures the intrinsic behavior of the liquid metals. We demonstrate how the intrinsic viscosity can be obtained with precision through a scaling technique that collapses lowand high-Reynolds number data. Measuring surface tension with a pendant drop method, we show that the oxide skin generates a surface stress that mimics surface tension and develop a simple model to relate this to the yield stress obtained from rheometry. We find that yield stress, surface tension, and contact angle all transition from solid-like to liquid behavior at the same critical acid concentration, thereby quantitatively confirming that the wettability of these liquid metals is due to the oxide skin. I. INTRODUCTIONLiquid metals combine the largest surface tension of any fluid with high density and conductivity 1−3 . Several of these metals, in particular liquid gallium and its alloys, are desired also for their low melting points and their wetting properties and have been used for thin film coatings 4,5 , as moldable electronic interconnects 6 , or as penetrating contrast agents for the visualization of grain boundaries or micro-cracks 7−9 . However, the dynamical properties of liquid metals are significantly more complex than those of simple Newtonian liquids. At small applied stresses liquid gallium and its alloys show a solid-like elastic response 10,11 , and high-temperature molten metals under steady state arXiv:1201.4828v1 [physics.flu-dyn]
Thin streams of liquid commonly break up into characteristic droplet patterns owing to the surface-tension-driven Plateau-Rayleigh instability. Very similar patterns are observed when initially uniform streams of dry granular material break up into clusters of grains, even though flows of macroscopic particles are considered to lack surface tension. Recent studies on freely falling granular streams tracked fluctuations in the stream profile, but the clustering mechanism remained unresolved because the full evolution of the instability could not be observed. Here we demonstrate that the cluster formation is driven by minute, nanoNewton cohesive forces that arise from a combination of van der Waals interactions and capillary bridges between nanometre-scale surface asperities. Our experiments involve high-speed video imaging of the granular stream in the co-moving frame, control over the properties of the grain surfaces and the use of atomic force microscopy to measure grain-grain interactions. The cohesive forces that we measure correspond to an equivalent surface tension five orders of magnitude below that of ordinary liquids. We find that the shapes of these weakly cohesive, non-thermal clusters of macroscopic particles closely resemble droplets resulting from thermally induced rupture of liquid nanojets.
Background To investigate through a two-stage clinic-based screening, the frequency and clinical features of risk for psychosis syndromes in a Chinese help-seeking sample. Method 2101 consecutive new patients ages 15–45 were recruited at their first visit to the Shanghai Mental Health Center (SMHC) and screened with the Prodromal Questionnaire -brief version (PQ-B) and questions about genetic risk. The Structured Interview for Prodromal Syndromes (SIPS) was administered to a sub-sample to estimate rates of psychosis and clinical high risk (CHR) for psychosis syndromes. Results The frequency estimate of CHR syndromes in the total sample was 4.2%. Among 89 CHR patients, more than two-thirds met criteria for Attenuated Positive Symptom Syndrome (APSS); and nearly a quarter met the criteria for Genetic Risk and Deterioration Syndrome (GRDS). The frequency of CHR syndromes peaked between the ages of 16–21 years and declined with subsequent age. The mean total and distress scores on the PQ-B in subjects with APSS and psychosis were significantly higher than in individuals with GDRS and patients without psychosis or CHR. High frequencies and strong correlations were found among some positive and non-specific symptoms in SIPS interviews. Among the 53 CHR participants who were followed-up for two years, 14 (26.4%) converted to psychosis. Of the non-converters, 53.8% were diagnosed with Axis I disorders. Conclusions This two stage screening method can enhance detection of Chinese CHR patients in clinical settings. The validity of the procedures for detecting CHR is supported by rates of transition to psychosis and of non-converter Axis I disorders that are comparable to those reported in meta-analyses.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.