Laser induced breakdown spectroscopy (LIBS) has been used to distinguish normal and malignant tumor cells from histological sections. LIBS measures concentrations of trace elements directly in real-time. It has been observed that the concentration of trace elements in normal and the tumor cells vary significantly. This technique can be incorporated with laser scalpel to monitor the cancer affected area during the surgery. LIBS spectrum of hair and nail has also been recorded. This technique has potential to be an automated, real-time diagnostic procedure for cancer that would greatly facilitate their diagnosis and classification.

Fiber loop ringdown spectroscopy is an emerging technique, introduced in the last few years, and has demonstrated its promise in optic fiber sensor development for a variety of applications. This paper describes a new double fiber loop ringdown system, consisting of an electronic portion and two fiber loops, which can detect environmental changes in each fiber loop simultaneously. We present a theoretical simulation of the optical output of the double loop ringdown system. The simulation is modeled by the superposition of each of the individual ringdown waveforms represented by a single exponential decay and an interference term that is characterized by a Bessel function. The theoretical results are in good agreement with the experimental observations. This method may be useful for signal processing in the double fiber loop ringdown system, which is developed for simultaneous sensing in separate locations.

The detection of polar molecules, like ketones and ethers, in a laser ion mobility spectrometer was investigated. Because the direct multiphoton ionization (MPI) for these compounds shows too high limits of detection (LOD) and intensive fragmentation of the molecular ions, alternative ionization methods based on ion-molecule-reactions (IMR) were investigated. These ionization methods should retain the advantages of the laser ionization. As examples for IMR two reaction classes, proton transfer reactions (PTR) and complex formation reactions (CFR), were studied. The PTR are based in a first step on the proton transfer from toluene radical cations to polar molecules. In a second step protonated dimers are formed. The CFR are characterized by the complex formation between aniline or phenol radical cations and polar molecules. All products are formed at atmospheric pressure and are characterized by transfer into a time-of-flight mass spectrometer. In both IMR the ionic reactants are formed selectively by 1+1 REMPI. The rates of the following IMR are near to the collision limit. Therefore the reactions are very efficient. The LOD for the analysis of selected ketones and ethers by IMR are in the low ppb-range, much lower than the corresponding LOD for direct MPI. The required laser intensities for the IMR are up to a factor of 1000 lower than the laser intensities for direct MPI. The fragmentation of the product ions is much lower for both IMR in comparison to direct MPI. The IMR allow the quantitative analysis of substance mixtures.

We report here that the hyper-Rayleigh scattering (HRS) technique which has emerged over the past decade as a powerful method to determine the microscopic non-linear optical (NLO) properties of species in solution, can be used to achieve the ultra-sensitive detection of single base-pair mismatch in oligonucleotide strands without any modification of DNA. A very distinct HRS intensity change has been observed after hybridization even at the concentration of 15 nano-molar probe ss-DNA. The HRS intensity enhanced by a factor of 20 after hybridization. The HRS intensity did not change when we added the target DNA with one base-pair mismatch with respect to probe DNA. Size dependent optical absorption and hyper Rayleigh scattering properties have been measured. The mechanism of size and distant dependence HRS intensity changed has been discussed.

We present a novel approach to a biological point detector system: extracting maximal information from fluorescence by using as much of the full excitation-emission-lifetime (XML) fluorescence space as can be conveniently gathered. Our paper has two parts. In the first part, we present initial XML spectral data gathered under Phase I of the DARPA Spectral-Sensing of Bio-Aerosols (SSBA) program using a commercial laboratory spectrofluorometer and illustrate its analysis in a multi-dimensional Principal Components Analysis (PCA) data space. We demonstrate classification using the spectral angle (SA) methodology developed for hyperspectral imaging in this PCA hyperspace. In the second part, we present a design for a custom trigger sensor developed in Phase II of the DARPA program. This Phase II sensor was motivated by the Phase I results and is intended to exploit them by gathering XML data at a rate consistent with near-real-time triggering.

Raman and Laser Induced Fluorescence (LIF) spectroscopic techniques were used for studying Azotobacter vinelandii- a genus of free-living diazotrophic soil bacteria. Azotobacter has generated a great deal of interest owing to their unique mode of metabolism. It is a large, obligately aerobic soil bacterium, which has one of the highest respiratory rates known among living organisms and is able to grow on a wide variety of carbohydrates, alcohols and organic acids. The Raman Scattering of Azotobacter, incubated with gold nanoparticles, was examined with 532-nm as an excitation laser wavelength. The basic instrumentation for characterizing the bacteria by Raman spectroscopy employed a continuous wave (CW) frequency doubled Nd: YAG laser (532-nm) and a modified In-Photonics fiber optic state-of-art miniaturized Raman Probe. The surface enhancement effects allowed the observation of Raman spectra of such bacterial cells, and were excited in the visible region of wavelength at low incident power for minimum sample degradation. LIF spectra of Azotobacter were measured with a 410-nm CW diode laser as an excitation source, and a reflection probe to deliver laser beam on the sample and collect the LIF signal from the sample. Spectral contrast observed in gold particles conjugated bacteria, from nitrogen fixing and non-nitrogen fixing condition was analyzed for characterizing the bacteria cells, and the results are presented in the paper.

Diisocyanates are produced by the millions of tons per year and are used for the large scale production of polyurethane products that range from coatings, to solid castings, and to industrial foam products. Occupational exposure has been linked to asthma-like symptoms and is a significant occupational concern requiring personal monitoring devices for employees that are sensitive and accurate in the parts per billion range. A novel design fiber optic chemical sensor has been developed which has demonstrated sensitivity of 0.2 ppb (parts per billion) for a 20 minute exposure in air for multiple isocyanate species. Sensor response is very linear over the range of 0 to 25 ppb. The sensor is based on a novel, long fiber, evanescent wave design that provides high sensitivity while maintaining low materials cost. Experimental performance results are presented, as well as a novel measurement approach that provides excellent linearity. Sensitivity to interference by humidity is modest. Sensor packaging can be directly compatible for passive use in personal monitoring and the sensor us reusable. The sensor is simple and inexpensive to fabricate, and can be easy to process by the user in an automated instrument. Sensor processing is simple and is a nearly all dry process. The solid-state sensor can be packaged in a convenient size for personal monitoring. Highly quantitative sensor response is provided by a unique data analysis process that can be readily automated and provides high linearity over a range that is of direct applicability to sensing needs.

NiCl₂/SiO₂ sol gel materials are proposed for the first time for ammonia sensing. Thin films are prepared by spin coating or casting the solution on appropriate substrates and tested for sensitivity in ammonia environment. We report a uniform optical response over the visible spectrum in optical transmission. The main mechanism of operation is based on reversible physico-chemical complexation effects, which produce morphology alteration and result in enhanced optical scattering of the thin film material. Such ammonia sensor can find applications in industrial and environmental engineering fields including "on-line" process and quality control, environment monitoring and safety.

Fiber optic sensors that utilize evanescent field interactions as a detection mechanism have proven to be quite sensitive. We recently reported on the development of this type of distributed sensor for toxic chemicals such as HCN, H₂S, and Cl₂. The optical fibers are multimode and consist of a fused silica core and an agent-specific chemically-sensitive cladding. Upon exposure to the corresponding challenge gas, the cladding changes color, resulting in an attenuation of the light throughput of the fiber. These fibers were produced in long lengths using conventional fiber optic draw towers. However, failure mechanisms, such as indicator migration, crystallization, and oxidation, decrease the lifetime of the sensors. We report on recent progress we have made in the effort to optimize the sensor longevity with respect to these degradation mechanisms. The optimizations include covalent attachment of the indicators with the polymer cladding during fiber processing, and the use of antioxidants to minimize degradation.

Fuel is the single most import supply during war. Consider that the US Military is employing over 25,000 vehicles during Operation Iraqi Freedom. Most fuel is obtained locally, and must be characterized to ensure proper operation of these vehicles. Determination of fuel properties is currently determined using a deployed chemical laboratory. Unfortunately, each sample requires in excess of 5 hours to characterize. To overcome this limitation, we have developed a portable fuel analyzer capable of determine 7 fuel properties that allow determining fuel usage. The analyzer uses Raman spectroscopy to measure the fuel samples without preparation in 2 minutes. The challenge, however, is that as distilled fractions of crude oil, all fuels are composed of hundreds of hydrocarbon components that boil at similar temperatures, and performance properties can not be simply correlated to a single component, and certainly not to specific Raman peaks. To meet this challenge, we measured over 500 diesel and jet fuels from around the world and used chemometrics to correlate the Raman spectra to fuel properties. Critical to the success of this approach is laser excitation at 1064 nm to avoid fluorescence interference (many fuels fluoresce) and a rugged interferometer that provides 0.1 cm^-1 wavenumber (x-axis) accuracy to guarantee accurate correlations. Here we describe the portable fuel analyzer, the chemometric models, and the successful determination of these 7 fuel properties for over 30 unknown samples provided by the US Marine Corps, US Navy, and US Army.

In this paper, we present a novel fiber optic SP (surface plasmon) sensor for measuring liquid refractive index. The proposed system consists of a pulse circuit for alternatively flashing dual light emitting diodes (LEDs), the sensor with two optical couplers, and a detection circuit with a photo diode (PD). The wavelengths of dual LEDs are 612nm and 680nm. The used optical fiber is multimode, whose core diameter is 400 micrometer. The fiber is cut and the cladding of 1cm from the end surface is removed. Thick silver layer is evaporated onto the end surface as a mirror and then gold film of 60nm is evaporated around the core surface. The used wavelengths and thickness are determined by considering the optimum condition. The reflected light is detected by the PD. Compared the developed system with a conventional optical fiber SP sensor, which needs a white light and a spectrograph, the system is compact and low cost. Moreover, high sensitive detection system is achieved by monitoring the differential signal between signals corresponding to the wavelengths. Several solutions are measured. The results indicate that the sensor responses only depend on the refractive indices and measurable refractive index range is from 1.3293 to 1.3616.

Temperature compensation is a key issue that must be addressed in almost all sensors and is particularly relevant to chemical sensor systems. Although independent temperature measurement coupled with temperature calibration of the chemical sensor can be employed to address this issue, the difficulty of accurate temperature measurement of the sensor material remains a problem. We report here a novel solution to this issue and prove the principle in the context of optical oxygen sensing. The measurement technique involves the use of two temperature-calibrated, fluorescence based oxygen sensors that display different sensitivities to oxygen. The mathematical representation of this dual-element sensor results in a system of two equations that can be solved for both oxygen concentration and temperature. A numerical technique based on successive approximation has been developed that allows the use of non-linear calibration equations, which accurately describe the responses of the sensor membranes used and, therefore, yield accurate values for oxygen concentration and temperature. The oxygen sensitive membranes in question consist of the oxygen-sensitive, fluorescent ruthenium complex, [Ru(II)- tris(4,7-diphenyl-1,10-phenanthroline)]2+, (Ru(dpp)3 2+), immobilised in a porous sol-gel matrix. Sol-gel matrices that were derived from different precursors were used to yield membranes with different sensitivities. 3D calibration surfaces were generated for both sensor membranes using a temperature-controlled flow cell, yielding calibration equations with R2 values of > 0.9999 in both cases. This provides the system with a high degree of baseline accuracy. The principle of operation of the system has been verified experimentally. This has significant implications for the development of optical sensors, as the use of such a technique obviates the need for separate temperature measurement devices such as thermistors or thermocouples. While the technique has been demonstrated here using phase fluorometric oxygen sensors, it is applicable to a broad range of measurement situations,

Tetracycline (TC) is a significant class of antibiotic drugs in human and veterinary medicine. Its extensive use may lead to pollution in the marine environment and residues in foods of animal origin. To perform TC analysis in the field, a portable TC-specific analyzer was developed based on europium-sensitized luminescence. A 385 nm light emitting diode (LED) is used in pulsed mode as the light source to selectively excite TC. In comparison to a conventional xenon flashlamp, its narrower emission band and cleaner post-pulse extinction lead to reduced background and improved sensitivity. The time-resolved luminescence (TRL) signal is detected by a photomultiplier tube (PMT) that is gated to minimize its response to the LED pulse. The energy of individual LED pulses is monitored by a photodiode (PD) for signal normalization. Both instrument operation and data processing are controlled by a laptop computer running a custom LabVIEW program. The PD and the PMT signals are acquired at 4-μs time resolution and 12-bit amplitude resolution. The instrument performance is evaluated using oxytetracycline, a significant member of the TC antibiotics, as a target analyte. The analyzer achieves a 0-3 ppm linear dynamic range (r² = 0.9988) and a 0.021-ppb limit of detection with a typical 5% relative standard deviation.

Acid Rock Drainage (ARD) that causes severe ground water deterioration and mobilization of potentially toxic elements is one of the persistent environmental problems in countries with a developed extractive industries. In brief, it results from exothermic process of sulfide minerals decomposition in mining waste deposited at the surface in the presence of atmospheric oxygen and moisture/infiltration water from precipitation. To attenuate the environmental impact of extractive wastes, the European Commission issued adequate legislative documents: a Directive on the management of waste from the extractive industries (2006) and a Reference document on Best Available Techniques for Management of Tailings and Waste-Rock in Mining Activities (BREF, 2004). These documents oblige the extractive industry to intercept the generation of ARD. Simultaneously, mining waste is an attractive material widely used in civil engineering as a common fill. This results in the need of early-warning monitoring of a potential of disposed/reused mining waste to generate acidic and/or highly mineralized leachate and of the efficiency of interceptive/insulation protection measures. The performance-based off-site techniques comprise sampling waste material along the waste layer profile by drilling, with subsequent pore solution extraction and analysis by ICP-MS. Though detailed and precise, these techniques are time-consuming and expensive, thus being limited to few randomly selected profiles. Large area of the sites and heterogeneity of a material causes problems with proper selection of representative profiles and therefore with evaluation of the environmental behavior of a reused or disposed material. For better characterization of a problematic site, its screening with cone penetrometer integrated with real-time, downhole sensing devices equipped with sensors for measurements of temperature, pH, rock moisture content and conductivity seems to be the best solution, giving the most important information concerning reactivity of a material in the waste layer and efficiency of protective measures.

A Photomultiplier Tube (PMT) based optical fiber Raman sensor was developed for online monitoring of nitrogen/oxygen concentration ratios in gaseous mixtures. The sensor employed a frequency doubled 532 nm continuous wave (CW) Nd:YAG laser and a modified In-Photonics fiber optic state-of-art miniaturized Raman Probe. The gaseous mixture was enclosed in a high pressure cell and subjected to varying degrees of pressure. Raman signal of gaseous nitrogen and oxygen were first analyzed with a miniature spectrometer. The detection system was then replacing by a Labview interfaced PMT module for fast data acquisition and real time monitoring of relative Raman signals of nitrogen and oxygen. Instrumentation features and sensor performances with different detection systems (i.e. spectrometer and PMT) is presented in the paper.

According to the EU Water Framework Directive 2000/60/EU (WFD, 2000), water quality should be compulsory assessed for all bodies of usable groundwater basins (GWB). The assessment has to be accomplished in two stages: (i) preliminary assessment for identification of GWBs of poor or unsatisfactorily elucidated water quality; (ii) detailed assessment for GWBs that do not fulfill the good chemical status criteria. If this analysis confirms poor quality of ground waters, they should be subjected to a monitoring in order to found out the cause of a threat and ways of its interception. Both FWD and the draft EU Directive on the protection of groundwater against pollution (GWD, 2004) distinguish only poor or good chemical status of water, while GWD comprises a list of chemical constituents, for which the EU Member States should develop uniform threshold values by the end of 2006. The chemical status of groundwater in the selected Koprzywianka River drainage basin was evaluated within the 6FP BRIDGE project aimed at realization of this task on the basis of 37-point monitoring network with use of both national (RMS, 2004) and European (GWD, 2004) chemical parameter lists. These data were used for point and spatial evaluation of groundwater chemical status. For spatial evaluation (drainage basin and particular GWBs), the data aggregated by mean and median methods were used. The results show a better precision of groundwater status assessment both by point and spatial methods, and a need of a careful selection of monitoring points separately for shallow and deep circulation. It has been proved that the spatial assessment should be carried out on the basis of median, and not mean concentrations recommended by GWD (2004), as chemical constituents in ground waters usually display a log-normal distribution that is not susceptible to deformation to such extent as mean values.

Light fractions produced after vehicles dismantling are conventionally defined as "fluff" or Automotive Shredder Residue (ASR). They represent about the 25% of the weight of a car and are usually constituted by materials characterized by intrinsic low specific gravity (i.e. plastics, rubber, synthetic foams, etc.). Fluff is usually polluted by metal contaminants (i.e. copper, aluminum, brass, iron, etc.), that strongly affect, especially in the final fractions, the possibility to utilize such material as fuel in co-combustion process, reducing the waste disposal and increasing at the same time energy production. In this paper, innovative selection-control architectures, based on hyperspectral imaging, in the visible- near infrared (VIS-NIR) field, have been investigated. In order to define suitable inspection strategies for the recognition and separation between useful (fluff) and polluting (metals) materials, samples of light and heavy plastics and metals have been collected in a recycling plant. Reflectance spectra have been acquired in the VIS-NIR field (400-1000 nm). Results showed as the different materials are characterized by different spectral signatures and that recognition of plastics and metals can be obtained adopting a wavelength ratio in the NIR (700-1000 nm) field.

Absorption and emission spectroscopy measurements have been extensively and effectively utilized in the probing and monitoring of gases. As in any real experimental situation, the measurement of absorption or emission profiles results in a loss of information due to practical limitations, such as a finite precision of the detector. Also, it is now accepted that there is a relationship between information loss and thermodynamics. Hence, the question "How much information, in bits, is lost when making a practical spectroscopic measurement and how much heat is generated in the process?" arises. Shannon's information theoretical concepts are used to quantify the information lost due to the finite precision in wavelength measurement, of a detector used in a spectroscopic measurement. The heat generated in such a detector is also studied. The relationship between the heat generated and information lost as a result of the finite precision of a practical detector is investigated.

The Oak Ridge Research Reactor (ORRR) was operated as an isotope production and irradiation facility from March 1958 until March 1987. The U.S. Department of Energy (DOE) permanently shut down and removed the fuel from the ORRR in 1987. The water level must be maintained in the ORRR pool as shielding for radioactive components still located in the pool. The DOE Office of Environmental Management (EM) needs to decontaminate and demolish the ORRR as part of the Oak Ridge cleanup program. In February 2004, increased pit corrosion was noted in the pool's 6- mm (¼")-thick aluminum liner in the section nearest where the radioactive components are stored. If pit corrosion has significantly penetrated the aluminum liner, then DOE EM must accelerate its decommissioning and demolition (D and D) efforts or look for alternatives for shielding the irradiated components. The goal of Mississippi State University's Institute for Clean Energy Technology (ICET) is to provide a determination of the extent and depth of corrosion. Results from the work will facilitate ORNL in making reliable disposition decisions. ICET's inspection approach is to quantitatively estimate the amount of corrosion using Fourier transform profilometry (FTP). FTP is a non-contact 3-D shape measurement technique. By projecting a fringe pattern onto a target surface and observing its deformation due to surface irregularities from a different view angle, FTP is capable of determining the height (depth) distribution of the target surface, thus reproducing the profile of the target accurately. ICET has previously demonstrated that its FTP system can quantitatively estimate the volume and depth of removed and residual material to high accuracy.

Fluorescence lifetime sensing is useful to measure temperature in harsh environments. We implemented the technique using samarium doped materials. The sample was exposed to a pulsed laser beam and the resulting lifetime was measured. A plot of lifetime versus temperature exhibited a linear dependence. A small change in temperature produced a significant change in lifetime, which is important in measuring temperature accurately. This technique is an alternative when conventional techniques are not suitable.

Developments of techniques such as confocal microscopy are been of great interest for the petroleum industry. Confocal images permits through of direct observation, obtain the acquisition and interpretation of in situ information of the petroleum emulsions systems, without requirement of sample pretreatments and can be applied to samples of high optical density as crude oils. This property of the confocal technique is of great utility for studies of the colloidal structural evolution in dark samples as asphaltenes, and water in crude oils emulsions. In this work, the applicability of a homemade confocal microscope is shown. Studies of stability of colloidal suspensions (asphaltenes and emulsions) such as aggregation kinetic, flocculation dynamic, and characterization of colloidal system are showed by confocal images. The aggregation process of flocculated asphaltenes for Furrial crude oils was showed through of high-resolution micrographics image, and their colloidal structural evolution are described by an analysis of size distribution of flocculated asphaltenes particles. Additional, the images of the dynamics in the drop size and drop size distributions during the initial stage of the separation of water drops from Furrial crude oils were also reported. This technique directly permitted for example, visualization of the coalescence of small droplets to form large ones from water-in-crude oil emulsions and visualize the morphology of flocculated asphaltenes.

A fast responding interrogation system based on intensity modulation using fiber Bragg gratings (FBG) has been developed to interrogate long period fiber grating (LPFG) sensor. Temperature and dynamic strain monitoring using this system have been successfully demonstrated. The performance of long period fiber grating (LPFG) sensors written in single cladding (SC) and double cladding (DC) fibers have been compared. This system is capable of resolving strain to 0.2με and 0.4με at a loading frequency of 20 Hz, and temperature resolution to 0.02°C and 0.19°C, by using LPFG in the single cladding (SC-LPFG) and double cladding (DC-LPFG) respectively.

The development of global ocean color models for remote sensing imagery with high accuracy is an important goal for Earth Science Research. Estimates of the concentration of dissolved and particulate materials in water can be derived by inversion of remote sensing imagery, that is, remote sensing reflectance based on empirical or semi-analytical models of reflectance water constituents. The efficacy of these models depends on accurate measurements of the spectral absorption of dissolved and particulate materials in natural waters. However, traditional methods using expensive laboratory spectrophotometers to measure the absorption of dissolved and particulate materials require special handling and storage prior to measurement. Further, their detection limit is often insufficient to detect the typically low dissolved and particulate matter seawater concentrations. Liquid core waveguides designed for portable instrumentation to measure the absorption of dissolved organic matter and particulate matter will be described. Traditionally, particulate matter is determined via the "quantitative filtering technique" (QFT), where particulate matter is concentrated on a Glass Fiber Filter (GFF) pad and its forward absorption measured with a laboratory based spectrophotometer and an integrating sphere. Performance and design of an inexpensive and portable fiber-optic-based GFF filter holder are discussed. Effective pathlength and numerical aperture of the sample cells are determined. Further, dissolved and particulate absorption is measured.