Biomedical subjects

Neil Holling

Publications and source records attributed to Neil Holling.

3 recordsLinked to original sources

PubMed2006

Evaluation of performance reference compounds in polyethylene-based passive air samplers.

Polyethylene-based passive air samplers (PSDs) were loaded with performance reference compounds (PRCs) and deployed in a wind tunnel to examine the effects of wind speed on sampler performance. PRCs could be loaded reproducibly into PSDs, with coefficients of variation only exceeding 20% for the more volatile compounds. When PSDs were exposed to low (0.5-1.5 m s-1) and high (3.5-4.5 m s-1) wind speeds, PRC loss rate constants generally increased with increasing wind speed and decreased with increasing sampler/air partition coefficients. PSD-based air concentrations calculated using PRC loss rate constants and sampler/air partition coefficients and air concentrations measured using active samplers compared closely. PRCs can be used to account for the effect of differences in wind speeds on sampler performance and measure air concentrations with reasonable accuracy.

Air Pollutants↗

PubMed2006

Photodegradation of polyaromatic hydrocarbons in passive air samplers: field testing different deployment chambers.

Semi-permeable membrane devices (SPMDs) were loaded with deuterated anthracene and pyrene as performance reference compounds (PRCs) and deployed at a test site in four different chambers (open and closed box chamber, bowl chamber and cage chamber) for 29 days. The losses of PRCs and the uptake of polyaromatic hydrocarbons (PAHs) from the ambient air were quantified. UV-B levels measured in each deployment chamber indicated that SPMDs would be exposed to the most UV-B in the cage chamber and open box chamber. Significantly less PAHs were quantified in SPMDs deployed in the cage chamber and open box chamber compared to samplers from the other two chambers, suggesting that photodegradation of PAHs had occurred. The loss of PRCs confirmed these results but also showed that photodegradation was occurring in the closed box chamber. The bowl chamber appears to provide the best protection from the influence of direct photodegradation.

Air Pollutants↗

PubMed2006

Investigation of cuticular hydrocarbons for determining the age and survivorship of australasian mosquitoes.

The cuticular hydrocarbon (CH) technique of age grading mosquitoes was evaluated for use on laboratory-reared Aedes aegypti (L.), Anopheles farauti (Laveran), and Ochlerotatus vigilax (Skuse). Gas chromatography/mass spectroscopy was used to determine the relative abundance of five alkanes in hexane extracts from the legs of individual mosquitoes. Age-related changes to relative hydrocarbon abundances were observed from An. farauti and Ae. aegypti, which are vectors of malaria and dengue, respectively. Female An. farauti were classified into two age categories (1-5 and >/= 5 days old at 27 degrees C) and Ae. aegypti into three age categories (1 to < 5, 5 to < 9 and >/= 9 days old at 27 degrees C) based on these changes. However, there was an absence of predicable age-related changes to hydrocarbon abundance in Oc. vigilax. Simulation modeling was used to construct sequential sampling guidelines for the application of this technique to estimate the survivorship of Ae. aegypti and An. farauti populations. These guidelines define the relationship between the survival rate, number of mosquitoes sampled, CH-based predictions of age, and the accuracy of survival rate estimates. They demonstrated, for example, that if 19% of a population of Ae. aegypti is estimated to be >/= 9 days old by CH analysis, an estimate of the daily survival rate from the exponential model should be based on a sample of 200 mosquitoes for the survival rate estimate to be within 5% of the actual rate. However, if only 10% of the population is estimated to be >/= 9 days old, 500 mosquitoes would need to be analyzed for the survival rate estimate to be of equivalent accuracy.

Aedes↗