Using our experience in signal processing and optimization of complex systems we propose a new method to adaptive sensing of chemical content of vegetations. This framework is demonstrated for different agricultural plants using the neural network algorithm for classification of spectral curves and adaptive filtration. Utilization of characteristics of leaf reflectance spectrum, which are a relative characteristic of the light reflected from canopies, makes it possible to avoid the necessity of measuring the 100% reflectance standard and to provide the high resistance of the method to distorting factors in particular to soil reflectance contribution. For utilization of the method the numerical algorithms is proposed. Various estimation problems will be considered to illustrate the computational aspects of the proposed method. The software is based on digital filter, optimization approach and neural network algorithm for classification of chemical components. Supporting software for data management, storage, signal processing will be development. A concept of an intelligent sensor is considered.

A key limitation on the use of two-wavelength DIAL or its multi-spectral generalization is the unknown spectral structure of the topographically backscattered lidar signals in the absence of the target materials. Although some of the factors responsible for the background spectral structure can be measured in advance, others, such as the terrain differences are highly variable and usually unknown. For applications to tactical reconnainssance and high-altitude surveillance where the background is continuously changing, the inability to account for the background can seriously degrade sensor performance. This study describes a method for estimating both the spectral dependence of the background as well as the path-integrated concentration, or CL, from the same data set using dual Kalman filtering. The idea is to run parallel filters that estimate the background and CL using input from the other filter. The approach is illustrated on a variety of synthetic data sets and signal injections into background data collected by the U.S. Army WILDCAT sensor at Dugway Proving Ground.

There is a great need for high throughput and sensitive sensors for genetic analysis. These sensors can be used for varied purposes from monitoring gene expression in organims to speciation of possible pathogens. Consequently, an instrument capable of these tasks would be a great benefit for food and water safety, medical diagnostics and defense of military and civilian populations from biological threats. This work examines the development of a hybridization-based biosensor using a novel tapered fiber optic rpobe. The immobilization of single-stranded, synthetic ologinucleotides utilizing aminoproplytriethoxysilane and glutaraldehyde was implemented on the fiber optic sensor. Hybridization takes place with a complementary analyte sequence followed by a fluorescent, labeled signaling probe to form a sandwich assay. Following hybridization, the fiber is interrogated with a diode laser source and the resulting fluorescence signal is detected using a miniature spectrometer.

Quantitative, high resolution (0.1 cm^-1) infrared spectra have been acquired for a number of pressure broadened (101.3 KPa N₂), vapor phase chemicals including: Sarin (GB), Soman (GD), Tabun (GA), Cyclosarin (GF), VX, nitrogen mustard (HN3), sulfur mustard (HD) and Lewisite (L). The spectra are acquired using a heated, flow-through White cell of 5.6 m optical path length. Each reported spectrum represents a statistical fit to Beer's law, which allows for a rigorous calculation of uncertainty in the absorption coefficients. As part of an ongoing collaboration with the National Institute of Standards and Technology (NIST), cross-laboratory validation is a critical aspect of this work. In order to identify possible errors in the Dugway flow-through system, quantitative spectra of isopropyl alcohol from both NIST and Pacific Northwest National Laboratory (PNNL) are compared to similar data taken at the Dugway Proving Ground (DPG).

Comprehensive two-dimensional gas chromatography (GCxGC) is an emerging technology for chemical separation that provides an order-of-magnitude increase in separation capacity over traditional gas chromatography. GCxGC separates chemical species with two capillary columns interfaced by two-stage thermal desorption. Because GCxGC is comprehensive and has high separation capacity, it can perform multiple traditional analytical methods with a single analysis. GCxGC has great potential for a wide variety of environmental sensing applications, including detection of chemical warfare agents (CWA) and other harmful chemicals. This paper demonstrates separation of nerve agents sarin and soman from a matrix of gasoline and diesel fuel. Using a combination of an initial column separating on the basis of boiling point and a second column separating on the basis of polarity, GCxGC clearly separates the nerve agents from the thousands of other chemicals in the sample. The GCxGC data is visualized, processed, and analyzed as a two-dimensional digital image using a software system for GCxGC image processing developed at the University of Nebraska - Lincoln.

While ion mobility spectrometry (IMS) has been used as a portable trace vapor detector, these handheld systems suffer from poor selectivity. Their low resolution makes confident identification of chemical species difficult. One major application for these IMS systems is in Homeland Defense. IMS systems are fielded for the detection of chemical warfare agents, explosives, narcotics, and other hazardous chemicals. Recently, a novel signal processing methodology using wavelet filtering, statistical evaluators, and genetic algorithms was demonstrated to improve sensitivity and specificity of an ion mobility spectrometer. Previous work involved a single (single polarity) IMS cell. Since both positive and negative ions are created in the same environment and a common sample interface is used for the dual IMS system, there is cross talk between the positive and negative cell. Typically, this cross talk provides little information on the identity of the chemical species present. However, using this new methodology, valuable sample information is obtained. Moreover, ion beam modulation has been incorporated to allow for the ion beam to be broken up into discrete packets. The modulation allows the rejection of common background interferents. This paper will present the process of using cell cross talk, ion beam modulation, and application and extension of the signal processing methodology. The application to field instrumentation will also be discussed.

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is employed to measure the spectral properties of a chemical agent simulant, ethyl methylphosphonate (EMPA) mixed with soil. DRIFTS is a quantitative technique that provides information about the intensity of vibrational absorption bands from the analyte in terms of the Kubelka-Munk model. The spectral properties of the neat oil, the soil matrix, and mixtures of the two over a range of relative proportions will be presented and discussed vis-a-vis the surface contamination detection problem.

Photoacoustic spectroscopy is a useful monitoring technique that is well suited for trace gas detection. The technique also possesses favorable detection characteristics when the system dimensions are scaled to a micro-system design. The objective of present work is to incorporate two strengths of the Army Research Laboratory (ARL), piezoelectric microelectromechanical systems (MEMS) and chemical and biological sensing into a monolithic MEMS photoacoutic trace gas sensor. We initially miniaturized a macro-cell design as a means to examine performance and design issues as the photoacoustics is scaled to a dimension approaching the MEMS level. A miniature non-MEMS photoacoutic resonance cell was fabricated and tested with resonator dimensions: diam.=1.5 mm, length = 30mm. Knowledge gained in these initial tests provide the basic information required to fabricate a MEMS scale device while maintaining the sensor integrity. Initial MEMS work is centered on fabrication of a lead zirconate titanate (PZT) microphone subsystem to be incorporated in the full photoacoustic device. PZT membrane microphones have been designed, fabricated and acoustically tested. Presently, the piezoelectric microphone performance has revealed the possibility of using a PZT microphone as the passive acoustic detection mechanism of a photoacoustic resonant cavity. Preliminary designs of the MEMS photoacoustic resonator incorporate a three-wafer design to create a monolithic MEMS photoacoustic cavity. Results will be presented describing the miniature photoacoustic cell capabilities and initial MEMS microphone performance. Preliminary results concerning the MEMS photoacoustic cell design will also be discussed.

A small, low-cost sensor capable of autonomous detection of a wide variety of chemical agents in either vapor, particulate or liquid phase is urgently needed. It now appears that this need also extends to homeland defense and the vast network of civilian security forces including police, fire, public health and emergency medical personnel. We are developing a low-cost, compact infrared Chemical Threat Monitor (CTM) that could meet this need. This palm-sized handheld instrument combines Foster-Miller's unique optical "wedge" technology coupled to novel, disposable infrared fiber optic sensors for sample collection. These technologies will be coupled to emerging high sensitivity, low-cost uncooled linear array infrared detectors optimized for this application. This combination will provide the individual user with most of the capability of today’s expensive FTIR units in a miniature robust unit that has no moving parts. In this paper we will describe the CTM device, its operation, and present preliminary results on liquid chemical agent simulants.

A high repetition rate, wavelength agile CO₂ laser has been developed at the Air Force Research Laboratory for use as a local oscillator in a heterodyne detection receiver. Rapid wavelength selection is required for measurements of airborne chemical vapors using the differential absorption lidar (DIAL) technique. Acousto-optic modulators are used in the local oscillator to tune between different wavelengths at high speeds (greater than 100 Hz) without the need for moving mechanical parts. Other advantages obtained by the use of acousto-optic modulators are laser output power control per wavelength and rugged packaging for field applications. A series of experiments to simultaneously characterize the radiometric and chemical detection sensitivities of heterodyne and direct detection DIAL systems is being performed at Kirtland AFB, NM, and will be described. The wvelength agile local oscillator (WALO) has been incorporated into a heterodyne receiver, with the Laser Airborne Remote Sensing (LARS) system providing the laser transmitter and direct detection receiver. The experiment series is studying radiometric issues, spread spectrum operation, the effects of target-induced speckle, and the influence of atmospheric turbulence for both detection mechanisms. Direct comparisons of the heterodyne and direct detection results will be presented, and the results will also be discussed in terms of the implications for fielding operational DIAL systems.

A novel methodology has been developed for the investigation of bacterial spores. Specifically, this method has been used to probe the spore coat composition of two different Bacillus stearothermophilus variants. This technique may be useful in many applications; most notably, development of novel detection schemes toward potentially harmful bacteria. This method would also be useful as an ancillary environmental monitoring system where sterility is of importance (i.e., food preparation areas as well as invasive and minimally invasive medical applications). This unique detection scheme is based on the near-infrared (NIR) Surface-Enhanced-Raman-Scattering (SERS) from single, optically trapped, bacterial spores. The SERS spectra of bacterial spores in aqueous media have been measured using SERS substrates based on ~60-nm diameter gold colloids bound to 3-Aminopropyltriethoxysilane derivatized glass. The light from a 787-nm laser diode was used to trap/manipulate as well as simultaneously excite the SERS of an individual bacterial spore. The collected SERS spectra were examined for uniqueness and the applicability of this technique for the strain discrimination of Bacillus stearothermophilus spores. Comparison of normal Raman and SERS spectra reveal not only an enhancement of the normal Raman spectral features but also the appearance of spectral features absent in the normal Raman spectrum.

A novel methodology has been developed for the determination (i.e., identification and quantification) of bacterial spores that may be useful in many applications; most notably, development of detection schemes toward potentially harmful biological agents such as Bacillus anthracis. In addition, this method would be useful as an environmental warning system where sterility is of importance (i.e., food preparation areas as well as invasive and minimally-invasive medical applications). This method is based on the infrared (1500 to 4000-nm) absorption of fatty acids and peptides extracted from the spore. The absorption spectra of several bacterial spore extracts in carbon disulfide solution have been measured. Further, the groups of absorption bands in this region are unique for each spore, which implies it may be possible to use this technique for their determination. The Bacillus spores studied were chosen because they are taxonomically close to each other as well as to Bacillus anthracis. Expectedly, the measured absorption bands are heavily overlapped since the extracted analytes are similar in structure for each Bacillus spore. Additionally, this makes it impossible to use a single wavelength for the determination of any bacterial spore species. However, it may be possible to use the infrared absorption technique in conjunction with the Partial Least Squares (PLS) regression method to develop statistical models for the determination of bacterial spores. Results will be presented concerning sampling, data treatment, and development of PLS models as well as application of these models in the determination of unknown Bacillus bacterial spores.

Bacteriorhodopsin (bR) is a small protein containing the chromophore retinal, and resides in the membrane of the Halobacterium salinarium. When the retinal absorbs a photon, a cycle of structural changes is triggered resulting in a cross-membrane proton transfer, which is used to generate energy for the organism. Many studies have been conducted to elucidate the dynamical structure - optical property relations, and the overall mechanism of photo-induced proton transport in bR is now well understood. On the other hand, site selective mutagenesis allows engineering of the original ("wild-type") bR, such that the protein can be made sensitive to specific chemicals or biological structures that consequently induce changes in the proton-transport. As such, bR provides a unique molecular platform onto which various functional elements can be built: peptide receptors for molecular recognition of pathogens (e.g. viruses, cancer cells, spores, bacteria, bio-toxins), fluorescent tags (using the inherent optical transduction mechanism of bR), and chemical anchors for capturing target cells. In particular, the stability of bR in extreme environments (pH range of 1 - 11, temperatures up to 110 °C) allows for optical detection under a large range of environmental conditions. In this paper we present and discuss experimental data of several bR mutants and their potential as chemical and biological sensors. In particular, the optical changes associated with metal ligand binding are discussed for two mutants, 170C and 169C/96N, as well as the optical changes associated with streptavidin-coated beads bound to bR with strep II tags inserted in the E/F loop.

An etched silicon gold plated lamellar mirror is demonstrated as a fixed-wavelength intracavity selector for the far-infrared p-Ge laser, facilitating spectroscopic applications. The depth of the selective mirror, which defines the laser operation wavelength, can be precisely controlled during the etching process. The third-order Fabry-Perot resonance of this selector yields an active cavity finesse of at least 0.06.

Contamination avoidancerefers to the military doctrine of avoiding or minimizing the effects of Chemical and Biological (CB) threats. The location, identification and tracking of CB hazards are also major concern for Homeland CB defense. Several advanced detector systems for both chemical and biological threats are being developed for the Armed Services. Current test equipment and methodologies are inadequate for the complete evaluation of these emerging detector systems. Improvements are needed across the entire test spectrum from agent-simulation correction studies and equipment upgrades to field testing techniques. The Contamination Avoidance Detector Test Suite (CADTS) project is funded by the Central Test and Evaluation Investment Program (CTEIP) under the auspices of the Director for Operational Test and Evaluation (DOT&E). This agency is responsible to DoD and congress for the adequate testing of any military hardware before release to the warfighter. This paper discusses the issues involved in CB testing and provides an overview of the characteristics and status of the key capabilities that were selected for funding.

The Joint Chemical Agent Detector (JCAD) has continued development through 2002. The JCAD has completed Contractor Validation Testing (CVT) that included chemical warfare agent testing, environmental testing, electromagnetic interferent testing, and platform integration validation. The JCAD provides state of the art chemical warfare agent detection capability to military and homeland security operators. Intelligence sources estimate that over twenty countries have active chemical weapons programs. The spread of weapons of mass destruction (and the industrial capability for manufacture of these weapons) to third world nations and terrorist organizations has greatly increased the chemical agent threat to U.S. interests. Coupled with the potential for U.S. involvement in localized conflicts in an operational or support capacity, increases the probability that the military Joint Services may encounter chemical agents anywhere in the world. The JCAD is a small (45 in3), lightweight (2 lb.) chemical agent detector for vehicle interiors, aircraft, individual personnel, shipboard, and fixed site locations. The system provides a common detection component across multi-service platforms. This common detector system will allow the Joint Services to use the same operational and support concept for more efficient utilization of resources. The JCAD detects, identifies, quantifies, and warns of the presence of chemical agents prior to onset of miosis. Upon detection of chemical agents, the detector provides local and remote audible and visual alarms to the operators. Advance warning will provide the vehicle crew and other personnel in the local area with the time necessary to protect themselves from the lethal effects of chemical agents. The JCAD is capable of being upgraded to protect against future chemical agent threats. The JCAD provides the operator with the warning necessary to survive and fight in a chemical warfare agent threat environment.

Chemical sensors have been attractive for scientific research and industrial applications. This paper proposes that the detection and recognition of a chemical concentrate can be achieved by means of passive and compact size fiber optic sensor based on "Fiber Bragg Gratings Technology". A mathematical model of a short period fiber Bragg gratings chemical sensor has developed.

The use of Surface Enhanced Raman Scattering (SERS) for biological detection has brought up the question of detection limits and how these detection limits apply to the application. For most biological detection uses of SERS, a high detection probability is needed for a relatively small amount of biological specimen. This is especially true for the detection of S. enteriditis (Salmonella) bacteria that may be present on minute concentrations , for example, in food products. Using SERS we have identified the associated antibody conjugated with 12nm diameter Au colloid. Our preliminary results show small fractals with a disperse distance of about 1 monomer diameter (12nm) between the colloidal gold monomers may enhance the SERS emission. We also investigate the possibility that a conformation change may induce an increase in the aromatic amino acid contribution. We then compare the antibody SERS alone to SERS of antibody conjugated to Salmonella bacteria. The use of SERS as a bacterial detection method leads to the possibility for detection of small amounts (<10,000 bacteria/ml) of Salmonella bacteria. In our study we obtained a detection limit of 10⁶ bacteria/ml using gold as a SERS active substrate.