This PDF file contains the front matter associated with SPIE Proceedings 8358, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

It has proven a very difficult task to discriminate an actual BW threat from the natural occurring ambient particulate aerosol, which includes a significant fraction of particles consisting of mixed mineral and biological material. The interferent particles [clutter] (bio and non bio) concentration varies widely both by location, weather and season and diurnally. Naturally occurring background particulates are composed of fungal and bacterial spores both fragments and components, plant fragments and debris, animal fragments and debris, all of which may be associated with inert dust or combustion material. Some or all of which could also be considered to be an interferent to a biological warfare detector and cause these biodector systems to cause False Alarms by non specific BW bio detectors. I will share analysis of current long term background data sets.

A SWIR/MWIR spectroscopic lidar is proposed for standoff bio-agent cloud detection using simultaneous broadband differential scattering (DISC). Measurements and/or modeling of DISC spectra of simulants are revisited and the rational of the SWIR/MWIR DISC approach is explained, especially in light of the LWIR DISC experiments and conclusions done elsewhere. Preliminary results on the construction of a low power non-linear broadband source in the SWIR/MWIR are presented. Light from a 1064-nm pump laser is passed through a period and temperature tunable PPMgO:LN Optical Parametric Generator (OPG) to generate broadband light with a full width at half maximum (FWHM) of 10 to >100 nm in the SWIR/MWIR between 1.5 and 3.9 μm. Broadband coherent light from this source is to be emitted towards a cloud that generates back-scattering. This source is being used in a short-range chemical remote detection breadboard, showing the possible dual use of the setup. Light collected by the receiver telescope is coupled to a grating spectrometer and the return signal (DISC in the proposed setup) is detected using a gated MCT-APD array in much the same way clouds are interrogated using UV-LIF. A programmable volume of space along the laser beam path is imaged at the entrance of the spectrometer and 320 spectral channels can be measured simultaneously, attenuating the effects of atmospheric instabilities on DISC measurements. Proposed follow-on work will be presented.

Protection of fixed sites from chemical, biological, or radiological aerosol plume attacks depends on early warning so that there is time to take mitigating actions. Early warning requires continuous, autonomous, and rapid coverage of large surrounding areas; however, this must be done at an affordable cost. Once a potential threat plume is detected though, a different type of sensor (e.g., a more expensive, slower sensor) may be cued for identification purposes, but the problem is to quickly identify all of the potential threats around the fixed site of interest. To address this problem of low cost, persistent, wide area surveillance, an IR camera pod and multi-image stitching and processing algorithms have been developed for automatic recognition and tracking of aerosol plumes. A rugged, modular, static pod design, which accommodates as many as four micro-bolometer IR cameras for 45deg to 180deg of azimuth coverage, is presented. Various OpenCV¹ based image-processing algorithms, including stitching of multiple adjacent FOVs, recognition of aerosol plume objects, and the tracking of aerosol plumes, are presented using process block diagrams and sample field test results, including chemical and biological simulant plumes. Methods for dealing with the background removal, brightness equalization between images, and focus quality for optimal plume tracking are also discussed.

The development of smart peptide binders requires an understanding of the fundamental mechanisms of recognition which has remained an elusive grail of the research community for decades. Recent advances in automated discovery and synthetic library science provide a wealth of information to probe fundamental details of binding and facilitate the development of improved models for a priori prediction of affinity and specificity. Here we present the modeling portion of an iterative experimental/computational study to produce high affinity peptide binders to the Protective Antigen (PA) of Bacillus anthracis. The result is a general usage, HPC-oriented, python-based toolkit based upon powerful third-party freeware, which is designed to provide a better understanding of peptide-protein interactions and ultimately predict and measure new smart peptide binder candidates. We present an improved simulation protocol with flexible peptide docking to the Anthrax Protective Antigen, reported within the context of experimental data presented in a companion work.

Mass spectrometry based proteomic approaches are showing promising capabilities in addressing various biological and biochemical issues. Outer membrane proteins (OMPs) are often associated with virulence in gram-negative pathogens and could prove to be excellent model biomarkers for strain level differentiation among bacteria. Whole cells and OMP extracts were isolated from pathogenic and non-pathogenic strains of Francisella tularensis, Burkholderia thailandensis, and Burkholderia mallei. OMP extracts were compared for their ability to differentiate and delineate the correct database organism to an experimental sample and for the degree of dissimilarity to the nearest-neighbor database strains. This study addresses the comparative experimental proteome analyses of OMPs vs. whole cell lysates on the strain-level discrimination among gram negative pathogenic and non-pathogenic strains.

Recent advances in synthetic library engineering continue to show promise for the rapid production of reagent technology in response to biological threats. A synthetic library of peptide mutants built off a bacterial host offers a convenient means to link the peptide sequence, (i.e., identity of individual library members) with the desired molecular recognition traits, but also allows for a relatively simple protocol, amenable to automation. An improved understanding of the mechanisms of recognition and control of synthetic reagent isolation and evolution remain critical to success. In this paper, we describe our approach to development of peptide affinity reagents based on peptide bacterial display technology with improved control of binding interactions for stringent evolution of reagent candidates, and tailored performance capabilities. There are four key elements to the peptide affinity reagent program including: (1) the diverse bacterial library technology, (2) advanced reagent screening amenable to laboratory automation and control, (3) iterative characterization and feedback on both affinity and specificity of the molecular interactions, and (3) integrated multiscale computational prescreening of candidate peptide ligands including in silico prediction of improved binding performance. Specific results on peptides binders to Protective Antigen (PA) protein of Bacillus anthracis and Staphylococcal Enterotoxin B (SEB) will be presented. Recent highlights of on cell vs. off-cell affinity behavior and correlation of the results with advanced docking simulations on the protein-peptide system(s) are included. The potential of this technology and approach to enable rapid development of a new affinity reagent with unprecedented speed (less than one week) would allow for rapid response to new and constantly emerging threats.

We will examine the use of multi-wavelength UV resonance-Raman signatures to identify the effects of growth phase on different types of bacteria. Gram positive and gram-negative species, Escherichia coli, Bacillus cereus, Citrobacter koseri and Citrobacter braakii were grown to logarithmic and stationary phases in different culture media. Raman spectra of bacteria were obtained by sequential illumination of samples between 220 and 260 nm; a range which encompasses the resonance frequencies of cellular components. In addition to the information contained in the single spectrum, this two-dimensional signature contains information reflecting variations in resonance cross sections with illumination wavelength. Results of our algorithms in identifying the differences between these germs are discussed. Preliminary results indicate that growth affects the Raman signature, but not to an extent that would negate identification of the species.

Raman microspectroscopy and principal component analysis are used to decipher unique biomolecular information by monitoring the effect of residence time of Bacillus spores suspended in deionized water. Suspensions of viable spores of Bacillus anthracis Sterne (BA), Bacillus atrophaeus (BG), and Bacillus thuringiensis were prepared and spectrally monitored from initial deposition (time zero) and intermittently for seven days. Questions addressed include if spectral variations are significant with bacterial species and residence time under non-germination conditions, is the discrimination capability affected, and are there markers indicating pre-germination activity. Clear spectral distinction for the spore suspensions was observed with respect to residence time, however, when the residence time data were combined, discrimination analyses showed significant overlap between the BA and BG spores. Temporal spectral analyses at select wavenumbers suggest an increase in pre-germination activity from the freshly suspended to one day suspensions.

This paper reports a proof-of-principle study aimed at discriminating biological warfare (BW) simulants from common environmental bacteria in order to differentiate pathogenic endospores in situ, to aid any required response for hazard management. We used FTIR spectroscopy combined with multivariate analysis; FTIR is a versatile technique for the non-destructive analysis of a range of materials. We also report an evaluation of multiple pre-processing techniques and subsequent differences in cross-validation accuracy of two pattern recognition models (Support Vector Machines (SVM) and Principal Component - Linear Discriminant Analysis (PC-LDA)) for two classifications: a two class classification (Gram + ve spores vs. Gram -ve vegetative cells) and a six class classification (bacterial classification). Six bacterial strains Bacillus atrophaeus, Bacillus thuringiensis var. kurstaki, Bacillus thuringiensis, Escherichia coli, Pantaeoa agglomerans and Pseudomonas fluorescens were analysed.

Since the distribution of Bacillus anthracis causing spores through the US Postal System, there has been a persistent fear that biological warfare agents (BWAs) will be used by terrorists against our military abroad and our civilians at home. Despite the substantial effort to develop BWA analyzers, they remain either too slow, produce high falsealarm rates, lack sensitivity, or cannot be fielded. Consequently there remains a need for a portable analyzer that can overcome these limitations as expressed at the 2011 Biological Weapons Convention. To meet this need we have been developing a sample system that selectively binds BWAs and produce surface-enhanced Raman (SER) spectra using portable Raman spectrometers. Here we describe the use of a short peptide ligand functionalized on silver nanoparticles to selectively capture Bacillus cereus spores (a surrogate of B. anthracis) and their subsequent detection by SER spectroscopy. This technique was used to specifically detect B. cereus spores over closely related species like B. subtilis belonging to the same genus within 15 minutes. Sensitivity of the method was demonstrated by detecting 10⁴ B. cereus spores/mL of water. The technology, once developed should prove invaluable for rapid monitoring of BWAs, which will immensely help first responders and emergency personnel in implementing appropriate counter measures.

The current state of the art in the development of antibody alternatives is fraught with difficulties including mass production, robustness, and overall cost of production. The isolation of synthetic alternatives using peptide libraries offers great potential for recognition elements that are more stable and have improved binding affinity and target specificity. Although recent advances in rapid and automated discovery and synthetic library engineering continue to show promise for this emerging science, there remains a critical need for an improved fundamental understanding of the mechanisms of recognition. To better understand the fundamental mechanisms of binding, it is critical to be able to accurately assess binding between peptide reagents and protein targets. The development of empirical methods to analyze peptide-protein interactions is often overlooked, since it is often assumed that peptides can easily substitute for antibodies in antibody-derived immunoassays. The physico-chemical difference between peptides and antibodies represents a major challenge for developing peptides in standard immunoassays as capture or detection reagents. Analysis of peptide presents a unique challenge since the peptide has to be soluble, must be capable of target recognition, and capable of ELISA plate or SPR chip binding. Incorporating a plate-binding, hydrophilic peptide fusion (PS-tag) improves both the solubility and plate binding capability in a direct peptide ELISA format. Secondly, a solution based methods, affinity capillary electrophoresis (ACE) method is presented as a solution-based, affinity determination method that can be used for determining both the association constants and binding kinetics.

The combination of surface enhanced Raman spectroscopy (SERS) with a handheld Raman system would lead to a powerful portable device for defense and security applications. The Thermo Scientific FirstDefender RM instrument is a 785-nm handheld Raman spectrometer intended for rapid field identification of unknown solid and liquid samples. Its sensitivity and effectiveness for SERS-based detection was initially confirmed by evaluating detection of 1,2-di(4- pyridyl)ethylene as a reporter molecule on a silver nanorod (AgNR) substrate, and the results are comparable to those from a confocal Bruker Raman system. As avian influenza A viruses (AIV) are recognized as an important emerging threat to public health, this portable handheld Raman spectrometer is used, for the first time, to detect and identify avian influenza A viruses using a multi-well AgNR SERS chip. The SERS spectra obtained had rich peaks which demonstrated that the instrument can be effectively used for SERS-based influenza virus detection. According to the SERS spectra, these different influenza viruses were distinguished from the negative control via the principal component analysis and by partial least squares-discriminate analysis. Together, these results show that the combination effective SERS substrates when combined with a portable Raman spectrometer provides a powerful field device for chemical and biological sensing.

In immunoassay based biosensors development studies polymers, as a matrix, and thiol, amine and aldehyde derivative compounds, as a antibody linker, are to be experimented. Aim of this study is to test amine and acetate functional group containing derivatives in liquid phase in order to develop an antibody immobilization strategy for Quartz Crystal Microbalance (QCM) system. In our study, 4-aminothiophenol (4-AT), carboxylated-PVC (PVC-COOH) and aminated- PVC (PVC-NH₂) compared with each other as a coating material. Surface of the coated AT-cut gold crystals were characterized with Fourier Transform Infrared spectrometry (FTIR) and Scanning Electron Microscobe (SEM) and tested in a Bacillus anthracis (GenBank: GQ375871) spores immunoassay model system. Subsequently, a series of SEM micrographs were taken again in order to investigate surface morphology and show the presence of the B. anthracis spores on the sensor surface. When experimental results and SEM images were evaluated together, it was suggested that with the synthesis of PVC like open-chained polymers, containing -NH₂ and -SH functional groups, B. anthracis spore detection can be accomplished on QCM without requiring complicated immobilization procedures and expensive preliminary preparations.

Optical signatures of fresh and aged explosives are measured and compared to determine whether there exist differences in the signatures that can be exploited for detection. The explosives examined are RDX, TNT, and HMX, which have been heated for two weeks at 75 degrees centigrade or irradiated for two weeks with a 15-Watt ultraviolet lamp (254nm). The optical signatures are obtained by illuminating the samples with a sequence of laser wavelengths between 420nm and 620nm in 10 nm steps and measuring the spectra of light scattered from the sample at each laser wavelength. The measurements are performed on the Naval Research Laboratory's SWOrRD instrument. SWOrRD is capable of illuminating a sample with laser wavelength between 210nm and 2000nm, in steps of 0.1nm, and measuring the spectrum of light scattered from the sample at each wavelength. SWOrRD's broad tuning range, high average power (1- 300mW), narrow line width (< 4cm^-1), and rapid wavelength tunability enable these measurements. Results, based on more than 80 measurements - each at 21 sequential laser wavelengths, indicate that the variation in spectral line amplitude observed when altering laser illumination wavelength differs between fresh and aged explosives. Thus, an instrument for rapid and reagent-less differentiation between aged and fresh explosives, based on illumination with a few appropriately chosen laser wavelengths appears feasible.

This paper assesses the potential of detecting explosives (RDX, TNT, PETN, HMX, HMTD, Urea Nitrate) from a distance with a spectroscopic lidar system. For the study, the temporal and spectral resolutions of laser induced fluorescence lidar prototypes were enhanced. The integrated breadboards used easily available Nd:YAG laser wavelengths (266 nm, 355 nm, and 532 nm) to remotely detect the Raman signatures induced in traces of explosives deposited on surfaces. The spectroscopic lidar setup allows for time resolved measurements with high temporal resolution. Raman spectra are observable, even in the presence of fluorescence. Experiments with low average laser power (tens of mWs) have shown the unambiguous capability to detect and identify explosives at distances ranging up to 20 m. Thanks to the combination of UV wavelength for higher Raman cross-sections and efficient gated detection the 355 nm prototype yielded the best compromise. Excitation at 266 nm was expected to yield a better Raman response and was investigated. Less than optimal laser parameters, detection efficiency and strong fluorescence reduced the signal to noise ratio of the 266 nm signals with respect to those at 355 nm and 532 nm showing the importance of optimizing system parameters for high sensitivity detection. Besides the description of the prototypes and an early assessment of their performances, recommendations are also proposed to improve the instrument, leading to an efficient remote sensor for explosives.

Alakai Defense Systems has created a standoff explosive detection sensor called the Check Point Explosives Detection System for use at military check points. The system is designed to find trace level explosive residues from a standoff distance to thwart the transport and use of illegal homemade explosives, precursors and related contraband. Because of its standoff nature, this instrument could offer benefits to those searching for explosives, since it removes the searcher from harm's way if a detonation occurs. A short description of the instrument, improvements to the system over the past year, and a brief overview of recent testing are presented here.

The passive standoff monitoring of vapor precursors emanating from a location under surveillance can provide relevant information on the nature of products fabrication. Defence Research & Development Canada Valcartier recently completed the development and field-validation of a novel R&D prototype, MoDDIFS (Multi-option Differential Detection and Imaging Fourier Spectrometer), to address this remote sensing application. The proposed methodology combines the clutter suppression efficiency of the differential detection approach with the high spatial resolution provided by the hyperspectral imaging approach. This consists of integrating a differential CATSI-type (Compact ATmospheric Sounding Interferometer) sensor with the imaging capability of the Hyper-Cam infrared imager. The MoDDIFS sensor includes two configuration options, one for remote gas detection, and the other for polarization sensing of surface contaminants. This paper focuses on the infrared spectral detection of gases. A series of measurements done with MoDDIFS on selected laboratory solvents in vapor form are analyzed and discussed.

This paper provides a brief overview of the Raman-based standoff detection methods developed at FOI for the purpose of standoff explosives detection. The methods concerned are Raman imaging for particle detection and Resonance Enhanced Raman Spectroscopy for vapor detection. These methods are today reaching a maturity level that makes it possible to consider applications such as trace residue field measurements, on site post blast analysis and other security of explosives related applications. The paper will look into future possible applications of these technologies. Our group has extensive activities in applications of the technology, among others in projects for the Seventh Framework Program of the European Union. Some of these possible applications will be described and a look into future development needs will be made. As far as possible, applicability will be discussed with a view on realistic explosives trace availability for detection. Necessary data to make such realistic applicability assessment is not always available and a brief discussion on the applicability of using the developed Raman technology to obtain this kind of data will also be made. The aspects of transitioning from research to practical applications, considering also eye-safety of the system, will be discussed as well.

This paper describes the design of a deep-UV Raman imaging spectrometer operating with an excitation wavelength of 228 nm. The designed system will provide the ability to detect explosives (both traditional military explosives and home-made explosives) from standoff distances of 1-10 meters with an interrogation area of 1 mm x 1 mm to 200 mm x 200 mm. This excitation wavelength provides resonant enhancement of many common explosives, no background fluorescence, and an enhanced cross-section due to the inverse wavelength scaling of Raman scattering. A coded-aperture spectrograph combined with compressive imaging algorithms will allow for wide-area interrogation with fast acquisition rates. Coded-aperture spectral imaging exploits the compressibility of hyperspectral data-cubes to greatly reduce the amount of acquired data needed to interrogate an area. The resultant systems are able to cover wider areas much faster than traditional push-broom and tunable filter systems. The full system design will be presented along with initial data from the instrument. Estimates for area scanning rates and chemical sensitivity will be presented. The system components include a solid-state deep-UV laser operating at 228 nm, a spectrograph consisting of well-corrected refractive imaging optics and a reflective grating, an intensified solar-blind CCD camera, and a high-efficiency collection optic.

We demonstrate real-time stand-off detection and imaging of trace explosives using collinear, backscattered Coherent Anti-Stokes Raman Spectroscopy (CARS). Using a hybrid time-resolved broad-band CARS we identify nanograms of explosives on the millisecond time scale. The broad-band excitation in the near-mid-infrared region excites the vibrational modes in the fingerprint region, and the time-delayed probe beam ensures the reduction of any non-resonant contributions to the CARS signal. The strong coherent enhancement allows for recording Raman spectra in real-time. We demonstrate stand-off detection by acquiring, analyzing, and identifying vibrational fingerprints in real-time with very high sensitivity and selectivity. By extending the focused region from a 100-micron sized spot to a 5mm long line we can obtain the spectral information from an extended region of the remote target with high spatial resolution. We demonstrate fast hyperspectral imaging by one-dimensional scanning of the Line-CARS. The three-dimensional data structure contains the vibrational spectra of the target at each sampled location, which allows for chemical mapping of the remote target.

To fight against the explosives-related threats in defense and homeland security applications, a smarter sensing device that not only detects but differentiates multiple true threats from false positives caused by environmental interferents is essential. A new optical detection system is proposed to address these issues by using the temporal and spectroscopic information generated by the surface plasmon coupling emission (SPCE) effect. Innovative SPCE optics have been designed using Zemax software to project the fluorescence signal into clear "rainbow rings" on a CCD with subnanometer wavelength resolution. The spectroscopic change of the fluorescence signal and the time history of such changes due to the presence of a certain explosive analyte are unique and can be used to identify explosives. Thanks to high optical efficiency, reporter depositions as small as 160-μm in diameter can generate a sufficient signal, allowing a dense array of different reporters to be interrogated with wavelength multiplexing and detect a wide range of explosives. We have demonstrated detection and classification of explosives, such as TNT, NT, NM, RDX, PETN, and AN, with two sensing materials in a prototype.

Reliable active and passive hyperspectral imaging and detection of explosives and solid-phase chemical residue on surfaces remains a challenge and an active area of research. Both methods rely on reference libraries for material identification, but in many cases the reference spectra are either not available or do not sufficiently resemble the instrumental signals of light reflected, scattered, or emitted from real-world objects. We describe a physics-based model using the complex dielectric constant to explain what is often thought of as anomalous behavior of scattered or nonspecular signatures encountered in active and passive sensing of explosives or chemicals on surfaces and show modeling and experimental results for RDX.

Continuous efforts implemented by government agencies such as the United States Geological Survey (USGS) aim to manage and protect the integrity of the environment's natural resources. RDX is one of the most frequently utilized nitramine explosives for mining, demolition and munitions purposes in the United States (US). The degradation of RDX in natural environments is of particular importance as a result of the accumulation of consequential degradation products in nature. Specifically, RDX has the potential to be degraded by microorganisms resulting in hazardous levels of harmful degradation products in soil and groundwater. The necessity for the detection of these particular degradation products is emphasized as a consequence of their toxicity as these products are recognized as potential mutagens. Photo-assisted electrochemical detection (PAED) following HPLC-UV is used to develop an analytical method qualified for the assessment of RDX and degradation products. The technique offers unique selectivity possessed by the photochemical reactor coupled to EC detection serving to eliminate the need for repetitive analysis using different column technologies. Furthermore, on-line sample pretreatment is developed and optimized specifically for the preparation of samples consisting of RDX and degradation products. Analytical figures of merit determined for all target analytes using on-line SPE-HPLC-UV-PAED revealed detection limits in the sub part per billion range for RDX and degradation product MEDINA. The effectiveness of the method is exemplified in collaborative studies with the USGS in monitoring the degradation of RDX and formation of degradation products once the nitro explosive is subject to anaerobic microorganisms WBC-2.

The existing assortment of reference sample preparation methods presents a range of variability and reproducibility concerns, making it increasingly difficult to assess chemical detection technologies on a level playing field. We are investigating a drop-on-demand table-top printing platform which allows precise liquid sample deposition and is well suited for the preparation of uniform and reproducible reference materials. Current research focuses the development of a sample preparation protocol for explosive materials testing based on drop-on-demand technology. Device settings were determined for optimal droplet formation and velocity. Droplet mass and reproducibility were measured using ultraviolet-visible (UV-Vis) absorption and a sensitive microbalance. The results presented here demonstrate the operational factors that influence droplet dispensing for specific materials (e.g. energetic and interferents). Understanding these parameters allows for the determination of droplet and sample uniformity and reproducibility (typical calibration goodness of fit R² values of 0.991, relative standard deviation or RSD ≤ 5%), and thus the demonstrated development of a successful and robust methodology for energetic sample preparation.

Nitro- and inorganic-based energetic material is vaporized at atmospheric pressure using nonresonant, 70 femtosecond laser pulses prior to electrospray post-ionization and transfer into a time-of-flight mass spectrometer for mass analysis. Measurements of a nitro-based energetic molecule, cyclotrimethylenetrinitramine (RDX), adsorbed on metal and dielectric surfaces indicate nonresonant vaporization of intact molecules, demonstrating the universality of laser electrospray mass spectrometry (LEMS) technique for explosives. In addition, RDX is analyzed at a distance of 2 meters to demonstrate the remote detection capability of LEMS. Finally, the analysis and multivariate statistical classification of inorganic-based explosives containing ammonium nitrate, chlorate, perchlorate, black powder, and an organic-based explosive is presented, further expanding the capabilities of the LEMS technique for detection of energetic materials.

A field deployable detection kit for explosives and propellants using thin layer chromatography (TLC) has been developed at Lawrence Livermore National Laboratory (LLNL). The chemistry of the kit has been modified to allow for field detection of propellants (through propellant stabilizers), military explosives, peroxide explosives, nitrates and inorganic oxidizer precursors. For many of these target analytes, the detection limit is in the μg to pg range. A new miniaturized, bench prototype, field portable TLC (Micro TLC) kit has also been developed for the detection and identification of common military explosives. It has been demonstrated in a laboratory environment and is ready for field-testing. The kit is comprised of a low cost set of commercially available components specifically assembled for rapid identification needed in the field and identifies the common military explosives: HMX, RDX, Tetryl, Explosive D or picric acid, and TNT all on one plate. Additional modifications of the Micro TLC system have been made with fluorescent organosilicon co-polymer coatings to detect a large suite of explosives.

The University of Hawaii has been developing portable remote Raman systems capable of detecting chemicals in daylight from a safe standoff distance. We present data on standoff detection of chemicals used in the synthesis of homemade explosives (HME) using a portable standoff Raman system utilizing an 8-inch telescope. Data show that good-quality Raman spectra of various hazardous chemicals such as ammonium nitrate, potassium nitrate, potassium perchlorate, sulfur, nitrobenzene, benzene, acetone, various organic and inorganic chemicals etc. could be easily obtained from remote distances, tested up to 120 meters, with a single-pulse laser excitation and with detection time less than 1 μs. The system uses a frequency-doubled Nd:YAG pulsed laser source (532 nm, 100 mJ/pulse, 15 Hz, pulse width 10 ns) capable of firing a single or double pulse. The double-pulse configuration also allows the system to perform standoff LIBS (Laser-Induced Breakdown Spectroscopy) at 50 m range. In the standoff Raman detection, the doublepulse sequence simply doubles the signal to noise ratio. Significant improvement in the quality of Raman spectra is observed when the standoff detection is made with 1s integration time. The system uses a 50-micron slit and has spectral resolution of 8 cm^-1. The HME chemicals could be easily detected through clear and brown glass bottles, PP and HDPE plastic bottles, and also through fluorescent plastic water bottles. Standoff Raman detection of HME chemical from a 10 m distance through non-visible concealed bottles in plastic bubble wrap packaging is demonstrated with 1 s integration time. Possible applications of the standoff Raman system for homeland security and environmental monitoring are discussed.

A standard spectroscopic sensor technique for classification of materials is Laser Induced Breakdown Spectroscopy (LIBS). Though LIBS, as an Atomic Emission Spectroscopy (AES) technique, is generally separated from signal processing based classification techniques, they strongly interact in the design of sensor systems. Strict disciplinary separation results in approaches that inadequately address the mass, power consumption and other portability parameters of the ultimate sensor. Modifications in the sensor design approach and of the classification processing techniques reduce redundancies in the system, resulting in more compact overall systems. An engineering thermodynamic approach to the plasma description, as part of a predictor-corrector style classification loop, is used to reduce system requirements for material classification. This paper presents results for the compaction of the model system. In this work, a nontraditional approach is made to reduce the modeling system to a configuration compatible with the incorporation of the model onto a compact DSP structure. Calculation of partition function tables allows heuristic adjustments to a thermodynamic description of the LIBS plasma. Once the plasma environment is established, rate equation descriptions can establish detailed balance and predict the emission properties of the sample. The resulting model must be compatible with compact, low power, computation schemes, such as multi-core DSPs as part of a predictor-corrector classifier.

First responders have the need to quickly assess a situation; Understanding if there are biological or explosive hazards present can influence a plan of action. The need for real-time information, however, precludes most laboratory analysis techniques. The requirement of not disturbing a sample until it is understood makes the problem even more challenging. Visual identification can go a long way in assessing a threat, and now technologies in the mid-infrared (2 to 20 μm) spectral region allow extending that "vision" into a spectral region known for its chemical identification capabilities. This paper considers the fusion of tunable quantum cascade lasers with infrared focal plane arrays to create a true chemical imager. Instrumentation is developed that allows real-time chemical analysis of residues and powders in a noncontact fashion. Identification of explosive residues and biological powders are considered as examples of use of this new technology for first responders. As opposed to many fielded technologies that allow only point detection of substances, and often require many seconds to analyze a sample, mid-infrared chemical imagers provide context in addition to sample analysis in real time. They are also ideal for image fusion techniques combining visual images with chemical images from an infrared multispectral analysis. This type of chemical overlay on live video provides first responders with a powerful tool for rapid threat assessment.

We report a novel surface enhanced Raman Scattering (SERS) substrate platform based on a common filter paper adsorbed with plasmonic nanostructures. Paper based SERS substrate overcomes many of the challenges associated with conventional SERS substrates based on rigid substrates such as silicon and glass. The paper-based design results in a substrate that combines all of the advantages of conventional rigid and planar SERS substrates in a dynamic flexible scaffolding format. We discuss the fabrication, physical characterization and SERS activity of our novel substrates using non-resonant analytes.

Sensitive, accurate and reliable methods are needed for the detection and identification of hazardous materials (chemical, biological, and energetic) in the field. Utilizing such a sensing capability incorporated into a portable detection system would have wide spread beneficial impact to the U.S. military and first responder communities. Surface enhanced Raman scattering (SERS) is increasingly becoming a reputable technique for the real-time, dynamic detection and identification of hazard materials. SERS is particularly advantageous as it does not suffer from interferences from water, requires little to no sample preparation, is robust and can be used in numerous environments, is relatively insensitive to the wavelength of excitation employed, and produces a narrow-band spectral signature unique to the molecular vibrations of the analyte. We will report on the characterization and sensing capabilities of these next generation SERS substrates for the detection of energetic materials (ammonium nitrate, TNT, PETN, and RDX). Additionally, new efforts producing highly uniform samples, with known concentrations of energetic materials inkjet printed onto the SERS sensing surface using a precisely calibrated MicroJet system will be shown.

This paper reports the LIBS studies on elemental composition detection and identification by employing a femtosecond (fs) fiber laser. High quality LIBS spectra were obtained in air using near-infrared fs fiber laser coupled with a broadband high sensitivity spectrometer without gating control. Specific ion and neutral emission lines of different materials have been characterized by line scanning, including metals, glasses and even explosive materials. Different laser parameters including pulse energy, repetition rate, scanning speed and integration times have been investigated to optimize the sensitivity. Results show that faster scanning speed and higher pulse energies can greatly enhance the signal level and reduce the integration time. The LIBS spectra are highly reproducible at different repetition rates up to 1 MHz. Furthermore, detection of explosive materials was also achieved and both the constituent elemental emission and the CN and C2 molecules emission were collected. Compared with conventional LIBS, fs fiber laser based LIBS system have advantages of less sample heating and damage, better spatial resolution and signal to background ratio, compact, reliable and cost-effective. This shows a potential portable LIBS system for versatile and rapid analysis of chemical and special explosive materials.

The excellent chemical identification ability of Raman based spectroscopy provides a versatile and widely applicable method to identify hazards within a complex chemical environment. However, the small spontaneous Raman scattering cross section can limit standoff detection of trace quantities. Coherent anti-Stokes Raman scattering provides the same chemical specificity, but with the potential for much greater signal due to coherent addition in the non-linear spectroscopy. Utilizing CARS, we have demonstrated μg/cm² level detection of an explosive simulant using a single laser producing less than 8mW of laser power in the near IR. This detection level was achieved on a simulant present as only a small part within a polymer mixture. In addition, we present standoff chemical images of trace compounds within a complex chemical environment, which effectively demonstrate the unique capabilities of the method. Further, the temporal pulse shape can be tailored to excite specific Raman transitions, adding versatility to this method.

Photon Systems in collaboration with JPL are continuing development of a new technology robot-mounted or hand-held sensor for reagentless, short-range, standoff detection and identification of trace levels chemical, biological, and explosive (CBE) materials on surfaces. This deep ultraviolet CBE sensor is the result of ongoing Army STTR and DTRA programs. The evolving 15 lb, 20 W, lantern-size sensor can discriminate CBE from background clutter materials using a fusion of deep UV excited resonance Raman (RR) and laser induced native fluorescence (LINF) emissions collected is less than 1 ms. RR is a method that provides information about molecular bonds, while LINF spectroscopy is a much more sensitive method that provides information regarding the electronic configuration of target molecules. Standoff excitation of suspicious packages, vehicles, persons, and other objects that may contain hazardous materials is accomplished using excitation in the deep UV where there are four main advantages compared to near-UV, visible or near-IR counterparts. 1) Excited between 220 and 250 nm, Raman emission occur within a fluorescence-free region of the spectrum, eliminating obscuration of weak Raman signals by fluorescence from target or surrounding materials. 2) Because Raman and fluorescence occupy separate spectral regions, detection can be done simultaneously, providing a much wider set of information about a target. 3) Rayleigh law and resonance effects increase Raman signal strength and sensitivity of detection. 4) Penetration depth into target in the deep UV is short, providing separation of a target material from its background or substrate.

In recent years, several manufactures of IR imaging devices have launched commercial models applicable to a wide range of chemical species. These cameras are rugged and sufficiently sensitive to detect low concentrations of toxic and combustible gases. Bertin Technologies, specialized in the design and supply of innovating systems for industry, defense and health, has developed a stand-off gas imaging system using a multi-spectral infrared imaging technology. With this system, the gas cloud size, localization and evolution can be displayed in real time. This technology was developed several years ago in partnership with the CEB, a French MoD CBRN organization. The goal was to meet the need for early warning caused by a chemical threat. With a night & day efficiency of up to 5 km, this process is able to detect Chemical Warfare Agents (CWA), critical Toxic Industrial Compounds (TIC) and also flammable gases. The system has been adapted to detect industrial spillage, using off-the-shelf uncooled infrared cameras, allowing 24/7 surveillance without costly frequent maintenance. The changes brought to the system are in compliance with Military Specifications (MS) and primarily focus on the signal processing improving the classification of the detected products and on the simplification of the Human Machine Interface (HMI). Second Sight MS is the only mass produced, passive stand-off CWA imaging system with a wide angle (up to 60°) already used by several regular armies around the world. This paper examines this IR gas imager performance when exposed to several CWA, TIC and simulant compounds. First, we will describe the Second Sight MS system. The theory of gas detection, visualization and classification functions has already been described elsewhere, so we will just summarize it here. We will then present the main topic of this paper which is the results of the tests done in laboratory on live agents and in open field on simulant. The sensitivity threshold of the camera measured in laboratory, on some CWA (G, H agents...) and TIC (ammonia, sulfur dioxide...) will be given. The result of the detection and visualization of a gas cloud in open field testing for some simulants (DMMP, SF₆) at a far distance will be also shown.

A novel approach to optical detection of airborne explosive vapor using a combination of cavity enhanced ab- sorption spectroscopy (CEAS) and diusion time of ight (DiTOF) is reported. The direct optical detection of explosive vapors by absorption presents a number of unique challenges due to low vapor pressures of explosive compounds, a lack of resolved spectral features, and the presence of interfering species with overlapping absorp- tion spectra. By recording the changing optical absorption as sampled atmosphere diuses into an explosive-free buer gas, the concentration of explosive molecules may be determined using a Bayesian statistical signal process- ing technique. This technique avoids the need for laser wavelength scans while simultaneously providing robust background rejection. The use of xed laser wavelengths allows for the use of cavity-locked cavity ring-down or cavity-locked direct cavity transmission absorption measurements with high data acquisition rates and signi- cantly reduces the complexity of the laser system by eliminating the need for precision wavelength monitoring. This allows for the development of compact, eld deployable sensors based on this technique. Experimental demonstration of the simultaneous detection of multiple species of hydrocarbon tracer molecules at 4295 cm⁻¹ will be reported. The results of the current work will be applied to the detection of TNT vapor to show a projected sensitivity of 2 pptv in a diesel exhaust background.

We describe and demonstrate a trace gas detector using a variation of cavity ring down spectroscopy (CRDS) in which we modulate the laser frequency and use off-axis alignment to simplify the sensor design and make it more suitable for deployment in vibration-prone environments. The use of off-axis alignment reduces the sensitivity to vibration and optical feedback. Modulation of the laser frequency eliminates signal fluctuations that can arise due to laser drift and incomplete averaging of the cavity modes, and thus removes the need for precision locking or frequency stabilization of the laser.

Smiths Detection and Intelligent Optical Systems have developed prototypes for the Lightweight Autonomous Chemical Identification System (LACIS) for the US Department of Homeland Security. LACIS is to be a handheld detection system for Chemical Warfare Agents (CWAs) and Toxic Industrial Chemicals (TICs). LACIS is designed to have a low limit of detection and rapid response time for use by emergency responders and could allow determination of areas having dangerous concentration levels and if protective garments will be required. Procedures for protection of responders from hazardous materials incidents require the use of protective equipment until such time as the hazard can be assessed. Such accurate analysis can accelerate operations and increase effectiveness. LACIS is to be an improved point detector employing novel CBRNE detection modalities that includes a militaryproven ruggedized ion mobility spectrometer (IMS) with an array of electro-resistive sensors to extend the range of chemical threats detected in a single device. It uses a novel sensor data fusion and threat classification architecture to interpret the independent sensor responses and provide robust detection at low levels in complex backgrounds with minimal false alarms. The performance of LACIS prototypes have been characterized in independent third party laboratory tests at the Battelle Memorial Institute (BMI, Columbus, OH) and indoor and outdoor field tests at the Nevada National Security Site (NNSS). LACIS prototypes will be entering operational assessment by key government emergency response groups to determine its capabilities versus requirements.

Microfluidics has proven to be a very effective technology for the identification of biological and chemical analytes in a CBRNE scenario. As it will be shown in the following, the required steps of those analytical processes are manifold making the development of an integrated microfluidic device a complicated project with a high level of technological risk, because all necessary analytical processes have to be implemented into a single device. The implementation is initiated by a dissection of the biochemical workflow into mandatory bio-analytical steps and the resulting protocol for each of those steps is translated into an appropriate design of a chip-based unit. In this report, examples for such chipbased functional modules are given. In addition, examples for a merging of positively tested modules into an integrated chip are shown and, finally, representatives for a smooth interaction between outer world, microfluidic chip, and chip driving instrument are presented.

The rapid and accurate detection and identification of chemical warfare agents and toxic industrial chemicals can be critical to the protection of military and civilian personnel. The use of gas chromatography (GC) - mass spectrometry (MS) can provide both the sensitivity and selectivity required to identify unknown chemicals in complex (i.e. real-world) environments. While most widely used as a laboratory-based technique, recent advances in GC, MS, and sampling technologies have led to the development of a hand-portable GC/MS system that is more practical for field-based analyses. The unique toroidal ion trap mass spectrometer (TMS) used in this instrument has multiple benefits related to size, weight, start-up time, ruggedness, and power consumption. Sample separation is achieved in record time (~ 3 minutes) and with high resolution using a state-of-the-art high-performance low-thermal-mass GC column. In addition to providing a system overview highlighting its most important features, the presentation will focus on the chromatographic and mass spectral performance of the system. Results from exhaustive performance testing of the new instrument will be introduced to validate its unique robustness and ability to identify targeted and unknown chemicals.

The Global War on Terror has made rapid detection and identification of chemical and biological agents a priority for Military and Homeland Defense applications. Reliable real-time detection of these threats is complicated by our enemy's use of a diverse range of materials. Therefore, an adaptable platform is necessary. Photoacoustic spectroscopy (PAS) is a useful monitoring technique that is well suited for trace detection of gaseous media. This method routinely exhibits detection limits at the parts-per-billion (ppb) or sub-ppb range. The versatility of PAS also allows for the investigation of solid and liquid analytes. Current research utilizes quantum cascade lasers (QCLs) in combination with an air-coupled solid-phase photoacoustic cell design for the detection of condensed phase material films deposited on a surface. Furthermore, variation of the QCL pulse repetition rate allows for identification and molecular discrimination of analytes based solely on photoacoustic spectra collected at different film depths.

The gas cloud imager (GCI) is a passive uncooled multispectral camera capable of unprecedented sensitivity for analyzing hydrocarbon gas mixtures in a scene. The GCI is currently finishing its final stages of development, and promises to obtain a 220×220 image of gas concentrations at 30 frames/sec, allowing for real-time display in a compact instrument without moving parts. We summarize measurement approach and discuss the advantages of the GCI instrument design against conventional instruments.

This paper describes a practical photoacoustic spectroscopy technique applied to remote sensing of chemicals in an open environment. A laboratory system that consists of a high-power CO₂ laser and an open-field acoustic resonator is described. The acoustic resonator is a combination of a parabolic reflector and a narrow-band cylindrical acoustic resonator that resonates at the laser modulation frequency. The performance of the resonator is theoretically analyzed and experimentally verified. Significant improvement in signal-to-noise ratio has been achieved. Detection of gas-phase photoacoustic signals was demonstrated at a remote distance of several meters from the target. Potential applications to the detection of condensed-phase chemicals are discussed; the detection of the photoacoustic spectrum of trinitrotoluene (TNT) in an open environment is presented.

Recently, a new method of remote detection of concealed radioactive materials was proposed. This method is based on focusing high-power short wavelength electromagnetic radiation in a small volume where the wave electric field exceeds the breakdown threshold. In the presence of free electrons caused by ionizing radiation, in this volume an avalanche discharge can then be initiated. When the wavelength is short enough, the probability of having even one free electron in this small volume in the absence of additional sources of ionization is low. Hence, a high breakdown rate will indicate that in the vicinity of this volume there are some materials causing ionization of air. To prove this concept a 0.67 THz gyrotron delivering 200-300 kW power in 10 microsecond pulses is under development. This method of standoff detection of concealed sources of ionizing radiation requires a wide range of studies, viz., evaluation of possible range, THz power and pulse duration, production of free electrons in air by gamma rays penetrating through container walls, statistical delay time in initiation of the breakdown in the case of low electron density, temporal evolution of plasma structure in the breakdown and scattering of THz radiation from small plasma objects. Most of these issues are discussed in the paper.

Data obtained with BNL's National Synchrotron Light Source (NSLS) has helped to elucidate, in detail, the roles of non-uniformity and extended defects on the performance of CZT detectors, as well as the root cause of device polarization during exposure to a high flux of incident X-rays. Measurements of carrier traps will be reported, including their nature and relationships to different growth methods (conventional Bridgman, high-pressure Bridgman, traveling heater, and floating zone methods). Most findings will be correlated with the performance of spectrometer-grade CZT Xray and gamma detectors, and new directions to resolve the material deficiencies will be offered.

Solid-state thermal neutron detectors are desired to replace ³He tube based technology for the detection of special nuclear materials. ³He tubes have some issues with stability, sensitivity to microphonics and very recently, a shortage of ³He. There are numerous solid-state approaches being investigated that utilize various architectures and material combinations. By using the combination of high-aspect-ratio silicon PIN pillars, which are 2 μm wide with a 2 μm separation, arranged in a square matrix, and surrounded by ¹⁰B, the neutron converter material, a high efficiency thermal neutron detector is possible. Besides intrinsic neutron detection efficiency, neutron to gamma discrimination is an important figure of merit for unambiguous signal identification. In this work, theoretical calculations and experimental measurements are conducted to determine the effect of structure design of pillar structured thermal neutron detectors including: intrinsic layer thickness, pillar height, substrate doping and incident gamma energy on neutron to gamma discrimination.

Traditional projection x-ray imaging utilizes only the information from the primary photons. Low-angle coherent scatter images can be made simultaneous to the primary images and provide additional information. To speed up acquisition time for coherent scatter projection imaging, we developed disentangling algorithms for the overlapping scatter patterns generated by multi pencil-beam geometries. A system at the Canadian Light Source synchrotron was configured which utilizes a custom collimator designed to convert a 33.17 keV monoenergetic fan beam from a Laue monochromator into multiple pencil beams by using 3 mm thick tungsten alloy stoppers. The pencil beams then travel through the sample and are absorbed by a tungsten bar. A digital flat panel detector records the superimposed scatter patterns from the beams. The sample is scanned through the beams using an automated step-and-shoot setup. The pixel value of the coherent scatter image is generated by integrating the radial profile (scatter intensity versus scattering angle) over an angular range. An MLEM-based iterative method and a least-squares method were developed to disentangle the scatter patterns. Although past work has primarily been applied to medicine, other applications include non-destructive testing and security.

A neutron spectroscopic technique for plutonium content measurement is described. The technique exploits the kinematic cuto of neutron emission from (α, n) reactions on oxygen. The Watt spectrum of ssion neutron emission extends to higher energies without such a cuto. ⁴He scintillation detectors were calibrated with an energy cut to reject neutrons of low energies, thereby making the detectors sensitive only to ssion neutrons but not to neutrons from the (α, n) reaction on oxygen. Experimental results are presented. Simulations are discussed to evaluate possible self shielding eects. Furthermore, numerous factors in uencing gamma rejection are discussed.

This work focuses on progress in gaining a better understanding of the polymorphic nature of the UO₃ and UO₃-water system; one of several important materials associated with the nuclear fuel cycle. The UO₃-water system is complex and has not been fully characterized, even though these species are common throughout the fuel cycle. For example, most production schemes for UO₃ result in a mixture of up to six different polymorphic phases, and small differences in these conditions will affect phase genesis that ultimately results in measureable changes to the end product. Here we summarize our efforts to better characterize the UO₃-water system with optical techniques for the purpose of developing some predictive capability of estimating process history and utility, e.g. for polymorphic phases of unknown origin. Specifically, we have investigated three industrially relevant production pathways of UO₃ and discovered a previously unknown low temperature route to β-UO₃. Powder x-ray diffraction and optical spectroscopies were utilized in our characterization of the UO₃-water system. Pure phases of UO₃, its hydrolysis products and starting materials were used to establish optical spectroscopic signatures for these compounds. Preliminary aging studies were conducted on the α- and γ- phases of UO₃.

Naturally occurring dysprosium is attractive as a neutron detector because of its high thermal neutron capture cross section and high natural abundance. Neutron-induced transmutation of ¹⁶⁴Dy results in production of stable isotopes of holmium and erbium (the latter only at sufficiently high neutron fluxes), due to beta decays caused by nucleus instability. This mechanism, unaffected by gamma radiation, can be used to unambiguously detect neutrons, without having to discriminate against an accompanying gamma flux. Optically-enabled thermal neutron detection can be based on significant differences in optical properties of Dy and Ho or Er, which allows to determine the relative fractions of Dy, and Ho, and E in an irradiated sample. In our search for the most sensitive method of differentiating between Dy and Ho residing in the same host material, we produced various Dy- and Ho-containing nanocrystals and uniformly dispersed them in a PMMA polymer matrix. Optical properties of the nanocomposites were analyzed by means of absorption and PL spectroscopy. We also report on neutron irradiation experiments with Dy-containing nanocrystals and our attempts to optically detect neutron-induced conversion of Dy into Ho.

Certain insulating solids can store a fraction of the absorbed energy when irradiated by ionizing radiation. The stored energy can be released subsequently by heating or optical stimulation. As a result, light may be emitted through Thermoluminescence (TL) or Optically-Stimulated Luminescence (OSL) and electrons may be emitted through Thermally-Stimulated Electron Emission (TSEE) or Optically-Stimulated Electron Emission (OSEE). TL and OSL are widely used in current radiation dosimetry systems. However, despite considerable research effort during the early 1970s, SEE was not commonly adopted for dosimetry applications. One of the main reasons is that SEE is a surface phenomenon, while luminescence is a bulk phenomenon, making SEE more susceptible to humidity, absorption of gases, minor physical defects and handling, both before and after irradiation. Nevertheless, it has been recognized that SEE may be useful for homeland security applications in nuclear forensics, where dose accuracy is not the primary performance metric. In this research, we are investigating the use of SEE for nuclear forensic applications. Many common materials, both natural and man-made, exhibit the phenomenon, providing an opportunity to use the environment itself as an in-situ radiation detector. We have designed and constructed a unique prototype reader for conducting SEE measurements. We have demonstrated that the SEE measurements from a variety of materials are quantitatively reproducible and correlated to radiation exposure. Due to the broad applicability of SEE, significant additional studies are warranted to optimize this novel technique for nuclear forensic and other applications.

This paper presents a system-level description of the I-SCAD^® Standoff Chemical Agent Detector, a passive Fourier Transform InfraRed (FTIR) based remote sensing system, for detecting chemical vapor threats. The passive infrared detection system automatically searches the 7 to 14 micron region of the surrounding atmosphere for agent vapor clouds. It is capable of operating while on the move to accomplish reconnaissance, surveillance, and contamination avoidance missions. Additionally, the system is designed to meet the needs for application on air and sea as well as ground mobile and fixed site platforms. The lightweight, passive, and fully automatic detection system scans the surrounding atmosphere for chemical warfare agent vapors. It provides on-the-move, 360-deg coverage from a variety of tactical and reconnaissance platforms at distances up to 5 km. The core of the system is a rugged Michelson interferometer with a flexure spring bearing mechanism and bi-directional data acquisition capability. The modular system design facilitates interfacing to many platforms. A Reduced Field of View (RFOV) variant includes novel modifications to the scanner subcomponent assembly optical design that gives extended performance in detection range and detection probability without sacrificing existing radiometric sensitivity performance. This paper will deliver an overview of system.

Using diffractive micro-lenses configured in an array and placed in close proximity to the focal plane array will enable a small compact simultaneous multispectral imaging camera. This approach can be applied to spectral regions from the ultraviolet (UV) to the long-wave infrared (LWIR). The number of simultaneously imaged spectral bands is determined by the number of individually configured diffractive optical micro-lenses (lenslet) in the array. Each lenslet images at a different wavelength determined by the blaze and set at the time of manufacturing based on application. In addition, modulation of the focal length of the lenslet array with piezoelectric or electro-static actuation will enable spectral band fill-in allowing hyperspectral imaging. Using the lenslet array with dual-band detectors will increase the number of simultaneous spectral images by a factor of two when utilizing multiple diffraction orders. Configurations and concept designs will be presented for detection application for biological/chemical agents, buried IED's and reconnaissance. The simultaneous detection of multiple spectral images in a single frame of data enhances the image processing capability by eliminating temporal differences between colors and enabling a handheld instrument that is insensitive to motion.

Differential reflectometry has been shown to be a sensitive and fast tool to detect explosive substances on surfaces such as luggage and parcel. This paper elucidates the influence of several parameters on the sensitivity of the technique. An expression for the reflected intensity that contains the influence of angle of incidence, wavelength of the incident light, and surface roughness has been established. The feature used to identify and detect TNT stems mainly from the diffuse component of the reflected light. This spectral "finger-print" shape does not change by varying these parameters. The maximum sensitivity is obtained for samples which are strongly diffusive and weakly specular.

Peptide display libraries offer an alternative method to existing antibody development methods enabling rapid isolation of highly stable reagents for detection of new and emerging biological threats. Bacterial display libraries are used to isolate new peptide reagents within 1 week, which is simpler and timelier than using competing display library technology based on phage or yeast. Using magnetic sorting methods, we have isolated peptide reagents with high affinity and specificity to staphylococcal enterotoxin B (SEB), a suspected food pathogen. Flow cytometry methods were used for on-cell characterization and the binding affinity (K_d) of this new peptide reagent was determined to be 56 nm with minimal cross-reactivity to other proteins. These results demonstrated that magnetic sorting for new reagents using bacterial display libraries is a rapid and effective method and has the potential for current and new and emerging food pathogen targets.