ABSTRACT
Planned exposures of rodents to diesel exhaust required development of an exhaust generation and delivery system flexible enough to accommodate varied experimental designs. The features of the exposure system built to meet these needs are summarized. Essential aspects including both the exhaust dilution and delivery system and the computer monitoring and control functions are described. During the first 29 weeks of a study with target particle concentrations of 350, 3500, and 7000 micrograms/m3, the achieved values were 310, 3360, and 6830 micrograms/m3 with coefficients of variation of 23, 10, and 9%, respectively. The system has now operated reliably for more than 24 months.
Subject(s)
Vehicle Emissions/toxicity , Animals , Computers , Equipment and Supplies , Gases/analysis , Mice , Particle Size , Rats , Vehicle Emissions/analysisABSTRACT
This document describes the attributes of an alpha spectroscopy counting and analysis system called Low Level Pulse Height Analysis (LLPHA). It was developed for multi-sample alpha spectroscopy analysis. The LLPHA system is controlled by a MIK-11/2 microcomputer with 28K of memory and uses a double-density, dual floppy disk for data storage. Detectors are interfaced to the computer via CAMAC (Computer Automated Measurement and Control) equipment. The system simultaneously supports 32 active and independent surface-barrier alpha-particle detectors. It operates with the total collection rate of up to 300 counts/sec from all active detectors, using 128 channels per spectrum and a dynamic energy range of 1.4 MeV. The system is not limited, however, to these conditions. In addition to spectral acquisition, the system provides analysis functions which include peak identification, curve-smoothing, integration, linear and logarithmic scale graphics, and corrections for base-line shift, dead-time, and background counts. These functions can be implemented while other spectra are being collected. The LLPHA system represents a highly cost-effective means of acquiring alpha spectrometric data from a large number of samples simultaneously and with rapid data analysis capability.
