Biomedical subjects

P T Walsh

Publications and source records attributed to P T Walsh.

7 recordsLinked to original sources

PubMed2005

A review of video exposure monitoring as an occupational hygiene tool.

This study reviews use of video exposure monitoring (VEM, also known as PIMEX) as an occupational hygiene tool since its inception in the mid-1980s. VEM involves the combination of real-time monitoring instruments, usually for gases/vapours and dust, with video of the worker's activities. VEM is an established method used by practitioners in different countries. The technical aspects of these VEM systems are described, then applications of VEM are discussed, focussing on task analysis, training (risk communication), encouraging worker participation in and motivation for improvements in the workplace environment and occupational hygiene research. The experiences from these applications are used to illustrate how exposure visualization with video can act as a catalyst, initiating a change process in the workplace. Finally, the role of VEM as a workplace improvement tool, now and in the future, is discussed.

Environmental Monitoring↗

PubMed2002

Performance testing of three portable, direct-reading dust monitors.

Three portable direct-reading dust monitors were tested in a recirculating dust tunnel and a calm air dust chamber against a range of industrial dusts with different size distributions to investigate sources of variation in their responses. Responses were found to be linear compared to reference gravimetric respirable samplers over a range of concentrations for a particular particle size distribution. Their calibration factors were dependant on particle size, particle composition and air velocity. If particle size and air velocity do not change significantly then the calibration factor can be applied to the monitor readings to give an accurate measure of dust concentration. The DataRam and HAM, factory calibrated against respirable dust concentration, were found to agree closely, whereas the Microdust gave higher readings, having been factory calibrated against total suspended particulate concentration. The calibration of the DataRam was significantly altered by either contamination of the optics with dust or by cleaning the optics. This was not observed with either the Microdust or HAM, since both monitors include a reference calibration element.

Air Pollutants, Occupational↗

PubMed2000

The insulin-like growth factor-I receptor is regulated by CD28 and protects activated T cells from apoptosis.

Co-stimulatory signals through the CD28 receptor enhance the survival of T cells that have their antigen receptor (TCR) engaged. Here we show that stimulation through the CD28 receptor in the absence of TCR engagement with either an anti-CD28 cross-linking antibody or the CD80 ligand transiently increases expression of the insulin-like growth factor-I receptor (IGF-IR) on T cells. Antibodies that block signaling through the IGF-IR decrease the survival of T cells activated through the TCR and CD28 in the presence of IL-2 by more than 50%, and also enhance susceptibility to Fas-induced apoptosis. CD28 stimulation increases IGF-IR expression on Jurkat cells, and exogenously added IGF-I can protect these cells from Fas-induced apoptosis. We conclude that CD28-mediated enhancement of IGF-IR expression provides activated T cells with essential survival signals that are independent of survival mediated by IL-2 and Bcl-xl.

Antibodies↗

PubMed2000

Computer-aided video exposure monitoring.

A computer-aided video exposure monitoring system was used to record exposure information. The system comprised a handheld camcorder, portable video cassette recorder, radio-telemetry transmitter/receiver, and handheld or notebook computers for remote data logging, photoionization gas/vapor detectors (PIDs), and a personal aerosol monitor. The following workplaces were surveyed using the system: dry cleaning establishments--monitoring tetrachoroethylene in the air and in breath; printing works--monitoring white spirit type solvent; tire manufacturing factory--monitoring rubber fume; and a slate quarry--monitoring respirable dust and quartz. The system based on the handheld computer, in particular, simplified the data acquisition process compared with earlier systems in use by our laboratory. The equipment is more compact and easier to operate, and allows more accurate calibration of the instrument reading on the video image. Although a variety of data display formats are possible, the best format for videos intended for educational and training purposes was the review-preview chart superimposed on the video image of the work process. Recommendations for reducing exposure by engineering or by modifying work practice were possible through use of the video exposure system in the dry cleaning and tire manufacturing applications. The slate quarry work illustrated how the technique can be used to test ventilation configurations quickly to see their effect on the worker's personal exposure.

Aerosols↗

PubMed1997

Cross-validatory selection of test and validation sets in multivariate calibration and neural networks as applied to spectroscopy.

Cross-validated and non-cross-validated regression models using principal component regression (PCR), partial least squares (PLS) and artificial neural networks (ANN) have been used to relate the concentrations of polycyclic aromatic hydrocarbon pollutants to the electronic absorption spectra of coal tar pitch volatiles. The different trends in the cross-validated and non-cross-validated results are discussed as well as a method for the production of a true cross-validated neural network regression model. It is shown that the methods must be compared through the errors produced in the validation sets as well as those given for the final model. Various methods for calculation of errors are described and compared. The separation of training, validation and test sets into fully independent groups is emphasized. PLS outperforms PCR using all indicators. ANNs are inferior to multivariate techniques for individual compounds but are reasonably effective in predicting the sum of PAHs in the mixture set.

Calibration↗

PubMed1993

Neural network classification of mutagens using structural fragment data.

A neural network was applied to a large, structurally heterogeneous data set of mutagens and non-mutagens to investigate structure-property relationships. Substructural data comprising a total of 1280 fragments were used as inputs. The training of the back-propagation networks was directed by an algorithm which selected an optimal subset of fragments in order to maximize their discriminating power, and a good predictive network. The system comprised three programs: the first used a keyfile of 100 fragments to generate training and test files, the second was the network itself and a procedure for ranking the effectiveness of these fragments and the third randomly replaced the lowest fragments. This cycle was then repeated. After running on a 386/33 PC several networks produced approximately 11% failures in the test set and 6% in the training set. By simplifying the output of the hidden layer it was possible to describe the hidden layer states in terms of clusters of mutagens and non-mutagens. Some of these clusters were structurally homogeneous and contained known mutagenic and non-mutagenic structural classes. This analysis provided a useful means of demonstrating how the network was classifying the data.

Cluster Analysis↗

PubMedDate not supplied

Structure-activity relationships for skin sensitization potential: development of structural alerts for use in knowledge-based toxicity prediction systems.

The development of qualitative structure-activity relationships for the prediction of skin sensitization potential, based on structural alerts (substructures associated with a toxicological mechanism), and suitable for incorporation as rules into a knowledge-based system is described. The structure dependence of the skin sensitization mechanism may be largely defined in terms of the presence or metabolic/nonmetabolic formation of protein reactive functional groups on the test compound and by the physicochemical requirements of significant skin penetration. The proposed structural alerts were tested on a data set of diverse chemicals. The results showed that the alerts have potential as preliminary indicators of skin sensitization potential for a wide range of low molecular weight chemicals.

Acylation↗