Steven D. Campbell

Applications of Photoacoustic Spectroscopy to Problems in Dermatology Research

The technique of photoacoustic spectroscopy (PAS) was applied in two areas of dermatology research: 1) drug detection and drug diffusion rates in skin, and 2) thermal properties and water content of skin. The drug studies involved detection of the drug tetracycline in the skin and determination of the diffusion rate of the drug through the skin. The water content studies involved determining the thermal properties of the epidermis as a function of water content and the effect of the water concentration gradient across the epidermis. A multilayer model for the photoacoustic effect was developed to account for the nonuniform thermal properties of the intact skin arising from the water concentration gradient. This model was used to determine the width of the region comprising the diffusional barrier in skin. The width of the barrier region was found to correspond to that of the outermost layer of the epidermis, the stratum corneum. This finding coincides with previous research indicating that the stratum corneum comprises the primary barrier to the diffusion of water through the epidermis.

Wavelength Comparison Study for Bioaerosol Detection

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.

Measurements of aircraft wake vortices at Memphis International Airport with a cw CO2 coherent laser radar

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.

Multi-sensor processing for aircraft surveillance in mixed radar/ADS-B environments.

This paper addresses some of the challenges involved in providing aircraft surveillance in a mixed radar/ADS-B environment. These challenges include time synchronization, bias mitigation and maneuver detection. The impact of these factors upon aircraft separation accuracy is evaluated. These impacts are then compared to current and proposed future surveillance requirements.

Bioaerosol optical sensor model development and initial validation

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.

Multiwavelength bioaerosol sensor performance modeling

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.

Airport surveillance requirements validation using Monte Carlo simulation

This paper describes Monte Carlo simulation results for validating airport surveillance requirements. A fast-time ATC simulator was used to assess the effect on airport efficiency and aircraft safety as surveillance parameters were varied. The results were used to identify the minimum surveillance performance needed to meet operational efficiency and safety requirements.

The Tower Flight Data Manager prototype system

The Tower Flight Data Manager (TFDM) will serve as the next generation air traffic control tower automation platform for surface and local airspace operations. TFDM provides three primary enhancements over current systems: consolidation of diverse data and information sources into a single platform; electronic data exchange, including flight data entries, within and outside the tower cab; and a suite of decision support capabilities leveraging TFDMs access to external data sources and systems. This paper describes a TFDM prototype system that includes integrated surveillance, flight data, and decision support display components. Enhancements in airport configuration management, runway assignment, taxi routing, sequencing and scheduling, and departure route assurance are expected to yield significant benefits in delay reduction, fuel savings, additional capacity, improved access, enhanced safety, and reduced environmental impact. Data are provided on system performance and air traffic controller acceptance from simulation studies and a preliminary field demonstration at Dallas / Ft. Worth International Airport.

CORRIDOR INTEGRATED WEATHER SYSTEM (CIWS) COCKPIT WEATHER DISPLAY DATA LINK DEMONSTRATION

This paper reports on a demonstration in support of the NASA Weather Information Communications (WINCOMM) program of providing Corridor Integrated Weather System (CIWS) weather products for cockpit display via data link. The CIWS weather products include the Regional Convective Weather Forecast (RCWF), which provides up to one-hour forecasts of storm activity. CIWS graphical weather products are compressed using the Lincoln-developed Weather-Huffman compression technique and then transmitted using a generic data link interface developed to allow a variety of methods (e.g., VDL-2, SATCOM, etc) to be employed in the demonstration. The interface definition is sufficiently general to accommodate both broadcast and request/reply modes of operation, and to allow selection of the appropriate parameters (i.e., data rate, image size, etc) for a particular type of data link. The received products are decompressed and displayed on a PC laptop qualified for flight use in NASA testbed aircraft. A Graphical User Interface (GUI) was developed for the airborne display in conformance with FIS-B weather data display requirements and emerging Electronic Flight Bag (EFG) standards. Results are presented on supportable update rates for various data links for routine and worst-case weather conditions.

Detect-to-warn scenarios for defense against airborne contaminants

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.