Biomedical subjects

Maosheng Yao

Publications and source records attributed to Maosheng Yao.

3 recordsLinked to original sources

PubMed2006

Use of portable microbial samplers for estimating inhalation exposure to viable biological agents.

Portable microbial samplers are being increasingly used to determine the presence of microbial agents in the air; however, their performance characteristics when sampling airborne biological agents are largely unknown. In addition, it is unknown whether these samplers could be used to assess microbial inhalation exposure according to the particle sampling conventions. This research analyzed collection efficiencies of MAS-100, Microflow, SMA MicroPortable, Millipore Air Tester, SAS Super 180, BioCulture, and RCS High Flow portable microbial samplers when sampling six bacterial and fungal species ranging from 0.61 to 3.14 microm in aerodynamic diameter. The efficiencies with which airborne microorganisms were deposited on samplers' collection medium were compared to the particle inhalation and lung deposition convention curves. When sampling fungi, RCS High Flow and SAS Super 180 deposited 80%-90% of airborne spores on agar - highest among investigated samplers. Other samplers showed collection efficiencies of 10%-60%. When collecting bacteria, RCS High Flow and MAS-100 collected 20%-30%, whereas other samplers collected less than 10% of these bioparticles. Comparison of samplers' collection efficiencies with particle inhalation convention curves showed that RCS High Flow and SAS Super 180 could be used to assess inhalation exposure to particles larger than 2.5 microm, such as fungal spores. Performance of RCS High Flow sampler was also reflective of the particle lung deposition pattern when sampling both bacteria and fungi. MAS-100 and SAS Super 180 matched the total deposition curve fairly well when collecting bacterial and fungi species, respectively. For other tested samplers, we observed substantial discrepancies between their performances and particle deposition efficiencies in the lung. The results show that feasibility of applying portable microbial samplers for exposure assessment depends on a particular sampler model and microbial species.

Aerosols↗

PubMed2005

Inactivation of microorganisms using electrostatic fields.

This research investigated whether electrostatic fields can be used to inactivate surface-borne and airborne microorganisms. Vegetative cells of Pseudomonas fluorescens and Bacillus subtilis var. niger were deposited on filters and subjected to electrostatic fields of different strengths and polarities for controlled time periods. In addition, P. fluorescens bacteria, which represent sensitive species, were aerosolized and exposed to electrostatic fields of up to +/- 10 kV/cm. The results have shown that more than 90% of the P. fluorescens cells deposited on the surface of nonconductive filters are inactivated when fields of 15 kV/cm are applied for 30 min or longer. Similar effects were observed when P. fluorescens were exposed to fields of 5 and 10 kV/cm for 2 h. In contrast, the culturability of B. subtilisvar. niger cells exposed under the same conditions did not substantially decrease. Exposure of airborne P. fluorescens to +/- 10 kV/cm for 30 s also did not result in a significant reduction of culturability. This research has shown that specific combinations of electrostatic field strength and exposure time can be used to effectively inactivate certain bacterial cells deposited on nonconductive surfaces. For the investigated conditions, the treatment was not effective for bacteria in the airborne state.

Air Pollution↗

PubMed2005

Use of subsampled traffic data to estimate roadway emissions, including conversion to MOBILE6 vehicle classifications.

Air quality is degraded by many factors, among which the emissions from on-road vehicles play a significant role. Timely and accurate estimate of such emissions becomes very important for policy-making and effective control measures. However, lack of traffic data and outdated emission software make this task difficult. This research has demonstrated a new method that facilitates the vehicular emission inventories at the local level by using shorter-time Highway Performance Monitoring System (HPMS) traffic data along with the latest U.S. Environment Protection Agency (EPA) emission modeling software, MOBILE6. The conversion methodology was developed for converting readily available HPMS traffic volume data into EPA MOBILE-based traffic classifications, and a corresponding software program was written for automating the process. EPA MOBILE6 model was used to obtain emissions of nitrogen oxides (NOx), volatile organic compound (VOC), and cabon monoxide (CO) emitted by the parent traffic and subsampled traffic data, and these emissions were additionally compared. The case study has shown that the difference of the magnitude between the emission estimates produced by certain subsampled and parent traffic data are minor, indicating that subsampled HPMS data can be used for reporting parent traffic emissions. It was also observed that traffic emissions follow a Weibull distribution, and NOx emissions were more sensitive to the traffic data composition than VOC and CO. Lastly, use of average emission values of 20 or 30 consecutive minutes appears to be valid for representing hourly emissions.

Air Pollutants↗