A redetermination of the argon mole fraction in air has been undertaken in two samples of dried natural air using mass spectrometric analysis with reference to a suite of gravimetrically prepared synthetic dry air mixtures. The resulting measurement of the argon mole fraction was 9.332 mmol mol −1 with a combined standard uncertainty of 3 µmol mol −1 . This is significantly different from the value, 9.17 mmol mol −1 , conventionally employed in the CIPM formula for the determination of the density of moist air during mass standard comparisons. Using the presently reported argon mole fraction value in the CIPM formula rather than the conventional value removes the recently identified discrepancy between the two methods of determining the density of moist air during mass standard comparisons: the CIPM formula method and the air buoyancy artefacts method. Nitrogen, oxygen and carbon dioxide mole fractions in the dry air samples were obtained simultaneously.

Background Recently, the use of fine dust management mobile applications has been on the rise in South Korea. The aim of this study is to describe the current status of fine dust and air pollution mhealth apps used in Korea and to make qualitative assessments of them. Methods App search contents analysis 400 apps were searched using PM2.5, PM10 and yellow dust, the main keywords related to fine dust, referring to the preceding reference from December 30, 2019 to January 2, 2020. Among the apps searched, apps that meet all six criteria, such as those with 1) user score ≥4.0, 2) n of review Top 50, 3) those that do not duplicated, 4) apps that are related to the topic, 5) apps set in Korean, and 6) apps that do not have errors, were selected for the study. App assessment The app evaluation of the study utilizes the MARS scale, an app assessment tool developed overseas. The assessment was conducted for a week from January 3, 2020 to January 10, 2020. Each of the apps averaged scores evaluated over a week for each category and averaged over five categories for an overall quality score. Results The standard deviation of the information and functionality of the 30 apps was similar, with 3.62 (SD 0.38) and 3.58 (SD 0.43), respectively. On the other hand, engagement was the lowest with an average of 3.1 (SD 0.44). The average of aesthetics was 3.4 (SD 0.64), indicating that deviations between apps were very large Conclusions It is deemed necessary to improve the user interface (UI) and configuration of the app to enhance the application's engagement and aesthetics in order to increase the use of fine dust apps by consumers and gain effect. Key messages This research provided information that consumers can reasonably use and select mobile health apps by evaluating and reviewing the contents of fine dust and air pollution mobile health apps. this study is important in that it can serve as a reference for app developers to consider in future app development.