From the viewpoint of g-jitter effect on the diffusion coefficient of fine particles, the particle migration by non-stochastic Brownian force was numerically discussed with the report of shuttle mission STS-85 regarding the increase of diffusion coefficient in micro-gravity field. In the numerical analysis, a physical model based on the generalized Langevin equation was constructed for the evaluation of dynamic light scattering. Most results showed no increase in the diffusion coefficient within the framework of our model, but some types of particle migration with oscillatory acceleration by the g-jitter effect at very low frequency still indicated a possibility on such a boost for the diffusion coefficient.
The concentrations of airborne organic phosphate triesters (11 compounds) were measured. The samples were collected from 44 rooms of 22 houses, 22 offices of 11 buildings and 17 points outdoors in Tokyo. Air sampling was carried out using a quartz fiber filter for the first stage and a solid phase extraction disc (EmporeTM C18) for the second stage at a flow rate of 10 l/min for 24 hours. The samples were extracted with acetone and organic phosphate triesters were analyzed by GC-FPD. The six compounds detected in almost all indoor air were triethylphosphate (TEP), tributylphosphate (TBP), tris(2-chloroisopropyl)phosphate (TCIPP), tris(2-chloroethyl)phosphate (TCEP), tris(butoxyethyl)phosphate (TBEP) and triphenylphosphate (TPHP). The compound detected with the highest median concentration in houses was TBP (12.0 ng/m3), while that in offices was TCIPP (19.3 ng/m3). The median concentration ratio of indoor to outdoor of these 6 compounds varied from 2.1 to 18.3. A comparison of houses and offices in terms of concentration showed that the median of the 6 compounds were higher in offices, but the maximum were higher in houses. In particular the maximum concentration of TCIPP in houses was as high as 14 μg/m3, which was 115 times higher than that in offices.
The purpose of this study was to examine how many particles and airborne microorganisms are dispersed through nurses' care and to describe the distribution of particles in laminar airflow. Although the amenity in biological clean room (BCR) is of great importance for reverse-isolated patients, taking care of a patient in BCR with direct contact or face-to-face is strictly limited in many facilities in Japan. Nurses have conceived from their experiences that they could benefit more from active intervention rather than strict isolation of an immunocompromised patient, and some literatures have supported this. However, little was known about the actual risk of air contamination caused by nurses. We built a mockup patient room with HEPA filter unit and conducted an experimental study using bed making, which appears to generate the most number of particles compared to other nursing care behaviors. While changing unwoven or cotton sheets, we got samples of M Air TTM to find colonies of bacteria and the number of particles by laser particle counter. There were some difference in particle diameter spectrum between unwoven sheets and cotton bed sheets.