Spatial distributions of airborne transmission risk on commuter buses: Numerical case study using computational fluid and particle dynamics with computer-simulated persons.

Commuter buses have a high passenger density relative to the interior cabin volume, and it is difficult to maintain a physical/social distance in terms of airborne transmission control. Therefore, it is important to quantitatively investigate the impact of ventilation and air-conditioning in the cabin on the airborne transmission risk for passengers. In this study, comprehensive coupled numerical simulations using computational fluid and particle dynamics (CFPD) and computer-simulated persons (CSPs) were performed to investigate the heterogeneous spatial distribution of the airborne transmission risk in a commuter bus environment under two types of layouts of the ventilation system and two types of passenger densities. Through a series of particle transmission analysis and infection risk assessment in this study, it was revealed that the layout of the supply inlet/exhaust outlet openings of a heating, ventilation, and air-conditioning (HVAC) system has a significant impact on the particle dispersion characteristics inside the bus cabin, and higher infection risks were observed near the single exhaust outlet in the case of higher passenger density. The integrated analysis of CFPD and CSPs in a commuter bus cabin revealed that the airborne transmission risk formed significant heterogeneous spatial distributions, and the changes in air-conditioning conditions had a certain impact on the risk.

Changes in thermal comfort, core temperature, and body weight during simulated parcel home-delivery in summer and winter.

Our aim was to determine differences in thermal comfort during simulated one-day parcel home delivery between summer and winter. Six young healthy males performed experiments in summer (up to 31°C) and winter (up to 8°C). After baseline measurement in a chamber, subjects drove a truck to a prespecified location for outside measurements. They performed 4 sets of 100-m walk with carrying 5-kg plate during the first 50-m walk at 100 m/min, separated by 7-min driving in each of the morning and the afternoon. Subjects could ingest water ad libitum in outside and set the cockpit temperature by themselves during driving. Thermal sensation and comfort were recorded using a subjective scale at the first and the last sets of each morning and afternoon session, while esophageal temperature (Tes) was monitored (thermocouples). Body weight was measured before and the end of experiment. We found that 1) whole-body comfort decreased in summer and the decrease was greater than winter with higher Tes and 2) changes in body weight were 0.7 and 0.3 kg through whole day in summer and winter, respectively. In summary, thermal comfort during working worsened in summer, possibly related with higher core temperature and greater decrease in body weight.

Identification of Turbid Compounds Generated in Sugarcane Vinegar.

Sugarcane vinegar is produced in various countries of southern Asia. It is also a niche product of the Kagoshima and Okinawa Prefectures in Japan. Turbid compounds are sometimes found in sugarcane vinegar, thereby lowering the market value. In this study, the turbid compounds were precipitated with a 1:2 (v/v) volume of ethanol, and they were identified as α-1,6-glucan using enzymatic digestion tests and 13C nuclear magnetic resonance analysis. Moreover, Lactobacillus nagelii was isolated from sugarcane juice, and it produced α-1,6-glucan when grown with sugar. The turbid compounds found in sugarcane vinegar were assumed to be α-1,6-glucan produced from sugar by lactic acid bacteria that exist in sugarcane juice.