12 research outputs found
Modulated-laser source induction system for remote detection of infrared emissions of high explosives using laser-induced thermal emission
In a homeland security setting, the ability to detect explosives at a distance is a top
security priority. Consequently, the development of remote, noncontact detection systems continues
to represent a path forward. In this vein, a remote detection system for excitation of infrared
emissions using a CO2 laser for generating laser-induced thermal emission (LITE) is a
possible solution. However, a LITE system using a CO2 laser has certain limitations, such
as the requirement of careful alignment, interference by the CO2 signal during detection, and
the power density loss due to the increase of the laser image at the sample plane with the detection
distance. A remote chopped-laser induction system for LITE detection using a CO2 laser
source coupled to a focusing telescope was built to solve some of these limitations. Samples of
fixed surface concentration (500 μg∕cm2) of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) were
used for the remote detection experiments at distances ranging between 4 and 8 m. This system
was capable of thermally exciting and capturing the thermal emissions (TEs) at different times in
a cyclic manner by a Fourier transform infrared (FTIR) spectrometer coupled to a gold-coated
reflection optics telescope (FTIR-GT). This was done using a wheel blocking the capture of TE
by the FTIR-GT chopper while heating the sample with the CO2 laser. As the wheel moved, it
blocked the CO2 laser and allowed the spectroscopic system to capture the TEs of RDX.
Different periods (or frequencies) of wheel spin and FTIR-GT integration times were evaluated
to find dependence with observation distance of the maximum intensity detection, minimum
signal-to-noise ratio, CO2 laser spot size increase, and the induced temperature incremen
Artificial intelligence assisted Mid-infrared laser spectroscopy in situ detection of petroleum in soils
A simple, remote-sensed method of detection of traces of petroleum in soil combining
artificial intelligence (AI) with mid-infrared (MIR) laser spectroscopy is presented. A portable MIR
quantum cascade laser (QCL) was used as an excitation source, making the technique amenable to
field applications. The MIR spectral region is more informative and useful than the near IR region for
the detection of pollutants in soil. Remote sensing, coupled with a support vector machine (SVM)
algorithm, was used to accurately identify the presence/absence of traces of petroleum in soil mixtures.
Chemometrics tools such as principal component analysis (PCA), partial least square-discriminant
analysis (PLS-DA), and SVM demonstrated the e ectiveness of rapidly di erentiating between
di erent soil types and detecting the presence of petroleum traces in di erent soil matrices such as
sea sand, red soil, and brown soil. Comparisons between results of PLS-DA and SVM were based
on sensitivity, selectivity, and areas under receiver-operator curves (ROC). An innovative statistical
analysis method of calculating limits of detection (LOD) and limits of decision (LD) from fits of the
probability of detection was developed. Results for QCL/PLS-DA models achieved LOD and LD
of 0.2% and 0.01% for petroleum/soil, respectively. The superior performance of QCL/SVM models
improved these values to 0.04% and 0.003%, respectively, providing better identification probability
of soils contaminated with petroleum
Mid-Infrared laser spectroscopy detection and quantification of explosives in soils using multivariate analysis and artificial intelligence
A tunable quantum cascade laser (QCL) spectrometer was used to develop methods for
detecting and quantifying high explosives (HE) in soil based on multivariate analysis (MVA) and
artificial intelligence (AI). For quantification, mixes of 2,4-dinitrotoluene (DNT) of concentrations
from 0% to 20% w/w with soil samples were investigated. Three types of soils, bentonite, synthetic
soil, and natural soil, were used. A partial least squares (PLS) regression model was generated for
predicting DNT concentrations. To increase the selectivity, the model was trained and evaluated using
additional analytes as interferences, including other HEs such as pentaerythritol tetranitrate (PETN),
trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), and non-explosives such as benzoic acid
and ibuprofen. For the detection experiments, mixes of different explosives with soils were used to
implement two AI strategies. In the first strategy, the spectra of the samples were compared with
spectra of soils stored in a database to identify the most similar soils based on QCL spectroscopy.
Next, a preprocessing based on classical least squares (Pre-CLS) was applied to the spectra of soils
selected from the database. The parameter obtained based on the sum of the weights of Pre-CLS was
used to generate a simple binary discrimination model for distinguishing between contaminated and
uncontaminated soils, achieving an accuracy of 0.877. In the second AI strategy, the same parameter
was added to a principal component matrix obtained from spectral data of samples and used to
generate multi-classification models based on different machine learning algorithms. A random forest
model worked best with 0.996 accuracy and allowing to distinguish between soils contaminated with
DNT, TNT, or RDX and uncontaminated soils
Mid-Infrared Laser Spectroscopy Applications I: Detection of Traces of High Explosives on Reflective and Matte Substrates
Mid-infrared (MIR) lasers have revolutionized infrared vibrational spectroscopy, converting an already dominant spectroscopic analysis technique into an even more powerful, easier to use, and quicker turn-around cadre of versatile spectroscopic tools. A selection of applications, revisited under the umbrella of MIR laser-based properties, very high brightness, collimated beams, polarized sources, highly monochromatic tunable sources, and coherent sources, is included. Applications discussed concern enhanced detection, discrimination, and quantification of high explosives (HEs). From reflectance measurements of chemical residues on highly reflective metallic substrates to reflectance measurements of HEs deposited on non-reflective, matte substrates is discussed. Coupling with multivariate analyses (MVA) techniques of Chemometrics allowed near trace detection of HEs, with sharp discrimination from highly MIR absorbing substrates
Mid-Infrared Laser Spectroscopy Applications in Process Analytical Technology: Cleaning Validation, Microorganisms, and Active Pharmaceutical Ingredients in Formulations
Mid-infrared (MIR) lasers are very high-brightness energy sources that are replacing conventional thermal sources (globars) in many infrared spectroscopy (IRS) techniques. Although not all laser properties have been exploited in depth, properties such as collimation, polarization, high brightness, and very high resolution have contributed to recast IRS tools. Applications of MIR laser spectroscopy to process analytical technology (PAT) are numerous and important. As an example, a compact grazing angle probe mount has allowed coupling to a MIR quantum cascade laser (QCL), enabling reflectance-absorbance infrared spectroscopy (RAIRS) measurements. This methodology, coupled to powerful multivariable analysis (MVA) routines of chemometrics and fast Fourier transform (FFT) preprocessing of the data resulted in very low limits of detection of active pharmaceutical ingredients (APIs) and high explosives (HEs) reaching trace levels. This methodology can be used to measure concentrations of surface contaminants for validation of cleanliness of pharmaceutical and biotechnology processing batch reactors and other manufacturing vessels. Another application discussed concerns the enhanced detection of microorganisms that can be encountered in pharmaceutical and biotechnology plants as contaminants and that could also be used as weapons of mass destruction in biological warfare. In the last application discussed, the concentration of APIs in formulations was determined by MIR laser spectroscopy and was cross validated with high-performance liquid chromatography
Modeling of allergen proteins found in sea food products Modelagem de proteínas alergênicas em frutos do mar
Shellfish are a source of food allergens, and their consumption is the cause of severe allergic reactions in humans. Tropomyosins, a family of muscle proteins, have been identified as the major allergens in shellfish and mollusks species. Nevertheless, few experimentally determined three-dimensional structures are available in the Protein Data Base (PDB). In this study, 3D models of several homologous of tropomyosins present in marine shellfish and mollusk species (Chaf 1, Met e1, Hom a1, Per v1, and Pen a1) were constructed, validated, and their immunoglobulin E binding epitopes were identified using bioinformatics tools. All protein models for these allergens consisted of long alpha-helices. Chaf 1, Met e1, and Hom a1 had six conserved regions with sequence similarities to known epitopes, whereas Per v1 and Pen a1 contained only one. Lipophilic potentials of identified epitopes revealed a high propensity of hydrophobic amino acids in the immunoglobulin E binding site. This information could be useful to design tropomyosin-specific immunotherapy for sea food allergies.<br>Os mariscos são fontes de alérgenos alimentares e seu consumo é a causa de graves reações alérgicas em humanos. Tropomiosinas, uma família de proteínas musculares, foram identificadas como os principais alérgenos em espécies de crustáceos e moluscos. No entanto, poucas estruturas experimentais tridimensionais estão disponíveis no Protein Data Base (PDB). Neste trabalho, modelos 3D de vários homólogos de tropomiosinas presentes em moluscos marinhos e espécies de moluscos (Chaf 1, Met e1, Hom a1, v1 Per e Pen a1) foram construídas, validadas e seus epítopos de ligação de imunoglobulina E (IgE) foram identificados, utilizando ferramentas de bioinformática. Todos os modelos de proteína para esses alérgenos consistiam em longas alfa-hélices. Chaf 1, Met e1, e Hom a1 apresentaram seis regiões conservadas com similaridades de sequência para epítopos conhecidos, enquanto v1 Per e Pen a1 único. Potenciais lipofílicos de epítopos identificados revelaram uma alta propensão de aminoácidos hidrofóbicos em sítio de ligação IgE. Esta informação poderia ser útil para projetar imunoterapia específica para tropomiosina para alergias alimentares
Modeling of allergen proteins found in sea food products
Shellfish are a source of food allergens, and their consumption is the cause of severe allergic reactions in humans. Tropomyosins, a family of muscle proteins, have been identified as the major allergens in shellfish and mollusks species. Nevertheless, few experimentally determined three-dimensional structures are available in the Protein Data Base (PDB). In this study, 3D models of several homologous of tropomyosins present in marine shellfish and mollusk species (Chaf 1, Met e1, Hom a1, Per v1, and Pen a1) were constructed, validated, and their immunoglobulin E binding epitopes were identified using bioinformatics tools. All protein models for these allergens consisted of long alpha-helices. Chaf 1, Met e1, and Hom a1 had six conserved regions with sequence similarities to known epitopes, whereas Per v1 and Pen a1 contained only one. Lipophilic potentials of identified epitopes revealed a high propensity of hydrophobic amino acids in the immunoglobulin E binding site. This information could be useful to design tropomyosin-specific immunotherapy for sea food allergies
Classical Least Squares Discriminant 1 Analysis of High Explosives Detected on Cotton Fabrics by Quantum Cascade Laser Spectroscopy
Quantum cascade laser spectroscopy was used to detect the presence of residues of highly energetic materials (HEMs) on cotton fibers. The discrimination of the vibrational signals of HEMs from a highly mid-infrared (MIR) absorbing medium was achieved by a simple and fast spectral evaluation using the classical least squares (CLS) algorithm without preparation of standards. CLS focuses on minimizing the differences between spectral features of real spectra acquired by direct MIR spectroscopy and the spectral features of calculated spectra modeled from linear combinations of the spectra of the neat components: HEMs and the cotton fibers, and the bias. HEMs samples in several combinations with cotton fibers were used to validate the methodology. Three (3) independent sets of experiments considering binary, ternary, and quaternary combinations of components, including cotton, TNT, RDX, and PETN, were performed. The models parameters obtained from linear combinations of the calculated spectra were used to perform discrimination analyses and to determine the sensitivity and selectivity of the studied HEM with respect to the substrates and to each other. However, the discrimination analysis was not necessary to achieve successful detection of HEMs samples on cotton substrates. The only requirement to achieve HEM detection (determine the presence or absence of HEM on a substrate) is that the library contains the spectra of all the HEMs and substrates or that the later be added in the field, on the fly. In addition, the extracted spectral signals of several amounts of RDX on cotton (> 0.02 mg) were used to calculate the limit of detection (LOD) based on the spectral signalto- noise ratio (S/N). The calculated S/N values were obtained from the spectra for cotton dosed with several amounts of RDX deposited in decreasing mass order until the calculated S/N reached a value of 3. The LOD determined for RDX on cotton was 22 ± 6 μg
Anomaly Identification during Polymerase Chain Reaction for Detecting SARS-CoV-2 Using Artificial Intelligence Trained from Simulated Data
Real-time reverse transcription (RT) PCR is the gold standard for detecting Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), owing to its sensitivity and specificity, thereby meeting the demand for the rising number of cases. The scarcity of trained molecular biologists for analyzing PCR results makes data verification a challenge. Artificial intelligence (AI) was designed to ease verification, by detecting atypical profiles in PCR curves caused by contamination or artifacts. Four classes of simulated real-time RT-PCR curves were generated, namely, positive, early, no, and abnormal amplifications. Machine learning (ML) models were generated and tested using small amounts of data from each class. The best model was used for classifying the big data obtained by the Virology Laboratory of Simon Bolivar University from real-time RT-PCR curves for SARS-CoV-2, and the model was retrained and implemented in a software that correlated patient data with test and AI diagnoses. The best strategy for AI included a binary classification model, which was generated from simulated data, where data analyzed by the first model were classified as either positive or negative and abnormal. To differentiate between negative and abnormal, the data were reevaluated using the second model. In the first model, the data required preanalysis through a combination of prepossessing. The early amplification class was eliminated from the models because the numbers of cases in big data was negligible. ML models can be created from simulated data using minimum available information. During analysis, changes or variations can be incorporated by generating simulated data, avoiding the incorporation of large amounts of experimental data encompassing all possible changes. For diagnosing SARS-CoV-2, this type of AI is critical for optimizing PCR tests because it enables rapid diagnosis and reduces false positives. Our method can also be used for other types of molecular analyses