This paper describes the development and initial validation of a bioaerosol optical sensor model. This model was used
to help determine design parameters and estimate performance of a new low-cost optical sensor for detecting
bioterrorism agents. In order to estimate sensor performance in detecting biowarfare simulants and rejecting
environmental interferents, use was made of a previously reported catalog of EEM (excitation/emission matrix)
fluorescence cross-section measurements and previously reported multiwavelength-excitation biosensor modeling work.
In the present study, the biosensor modeled employs a single high-power 365 nm UV LED source plus an IR laser diode
for particle size determination. The sensor has four output channels: IR size channel, UV elastic channel and two
fluorescence channels. The sensor simulation was used to select the fluorescence channel wavelengths of 400-450 and
450-600 nm. Using these selected fluorescence channels, the performance of the sensor in detecting simulants and
rejecting interferents was estimated. Preliminary measurements with the sensor are presented which compare favorably
with the simulation results.
This paper describes work in modeling the performance of multiwavelength bioaerosol sensors. In particular, results are presented on modeling the performance of the Biological Agent Sensor Testbed (BAST), which employs LED UV sources at 280 and 340 nm. A previously developed catalog of Excitation/Emission Matrix (EEM) data for bioagents and interferents is used to determine fluorescence scattering for a specified particle mixture. These particle mixtures were applied to the model in order to assess discrimination performance. An initial comparison of simulated and measured BAST data is presented. This work was sponsored by DARPA under the Semiconductor Ultraviolet Optical Sources (SUVOS) program.
This paper reports on an investigation into optimal excitation and emission wavelengths for bioaerosol detection. Excitation/Emission Matrix (EEM) fluorescence data were gathered for a variety of materials, including biowarfare (BW) simulants, cell constituents, growth media and known interferents. These data were used to investigate multi-wavelength discrimination algorithms using pattern classification techniques. The results suggest that using two excitation wavelengths and narrower emission bands can improve discrimination between BW agents and interferents.
Detect-to-warn defense strategies against airborne contamination are based on providing warning to personnel to take temporary protective actions. The effectiveness of such detect-to-warn active strategies is measured by the reduction in contaminant exposure compared to passive exposure. Effectiveness depends on several factors, including the contaminant release and transport properties, the warning sensor performance and the protective actions taken. In this paper we analyze effectiveness for several specific scenarios where certain reasonable protective actions are assumed and sensor performance is varied. One type of scenario analyzed is the protection of outdoor personnel against an upwind instantaneous point release. Meteorological conditions such as wind speed, turbulence level and heat flux, which result in high exposure levels are assumed. Personnel are warned to temporarily use filter masks based on a warning signal from a sensor placed between them and the release point. Another type of scenario is the protection of personnel inside of a building using active ventilation control. The building air handling properties, such as air exchange and recirculation, degree of leakage and filtration and zone volume, are representative of modern office buildings. Different sensor locations and ventilation control strategies are chosen to defend against outside and inside instantaneous point releases. In each scenario, we evaluate the dependence of effectiveness on sensor sensitivity threshold and response time. In addition, we describe desired values of other sensor attributes, such as false positive sensing rate, size, power consumption, maintenance frequency and procurement cost, to support realistic deployment and operations.
A CW-coherent laser radar using a 20-watt CO2 laser has been constructed and deployed for the measurement of wake-vortex turbulence. This effort is part of the NASA Terminal Area Productivity Program and has the goal of providing information to further the understanding of the motion and decay of wake vortices as influenced by the local atmospheric conditions. To meet this goal, vortex measurements are made with the lidar along with simultaneous measurements from a suite of meteorological sensors which include a 150 foot instrumented tower, a profiler/RASS, sodar and balloon soundings. The information collected also includes airline flight data and beacon data. The operation of the lidar during two field deployments at Memphis International Airport are described as well as examples of vortex motion and decay measurements in various atmospheric conditions.
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