Biomedical subjects

Peter de B Harrington

Publications and source records attributed to Peter de B Harrington.

5 recordsLinked to original sources

PubMed2005

SIMPLISMA and ALS applied to two-way nonlinear wavelet compressed ion mobility spectra of chemical warfare agent simulants.

Ion mobility spectrometry is a rapid scanning measurement method for which compression methods that facilitate the handling of large collections of data are beneficial. Peak distortion in reconstructed ion mobility spectra from linear wavelet compression is problematic in that artifact peaks may cause false positive alarms. Peak shifting also may cause false alarms if target peaks shift out of or interfering peaks shift into detection windows. Nonlinear wavelet compression (NLWC) preserves peak shape and can lessen the degree of distortion, shifting, and artifact peaks in the reconstructed spectra. NLWC was applied to achieve high compression and fidelity in the reconstructed spectra. Another benefit is that NLWC improves signal-to-noise ratios and thus the models built from compressed data are improved. By compressing both the drift time order and the spectrum acquisition order, greater compressions maybe achieved. A two-way nonlinear wavelet compression method that incorporates alternating least squares (2W-NLWC-ALS) algorithm was devised by applying ALS to partially reconstructed wavelet coefficients generated from two-way NLWC. The number of components in a data set can be determined automatically using ASIMPLISMA. The smaller ALS models are saved as the final compressed data and can be used to reconstruct the entire data set efficiently without maintaining the compressed wavelet coefficient matrix of the original data set. The 2W-NLWC-ALS algorithm provides greater compression ratios compared to regular wavelet compression and interpretable models. Using this method, large volumes of data can be acquired and easily evaluated through a simple compressed model. A compression ratio of 510 ppm, root-mean-square error (E(RMS)) of 6.3 mV (full-scale signal is usually 1 V or larger), and relative root-mean-square error (RE(RMS)) of 1.62% were achieved for data sets collected by CAM. A compression ratio of 46 ppm, E(RMS) of 9.2 mV, and RE(RMS) of 0.42% were achieved for data sets collected with an ITEMISER instrument. The 2W-NLWC-ALS algorithm is an efficient compression method that provides the benefits of a simple model.

Algorithms↗

PubMed2005

[Detection of trace organic compounds by using ion mobility spectrometry and SIMPLISMA].

Ion mobility spectrometry (IMS) is a sensitive means for detection of trace volatile organic compounds. This technique has been used as a routine method for some organic compounds in forensic science, environmental and pharmaceutical analysis, etc. SIMPLISMA (simple-to-use-interactive self-modeling mixture analysis) is an effective method for large-scale data processing. In the present work, SIMPLISMA has been applied to process IMS data of three methanephosphonate esters. The SIMPLISMA can retain the peak characteristics and eliminate much of the noises of the IMS measurements. The processed spectral data can be subsequently used for other computations, such as curve resolution and pattern recognition etc.

Chemistry Techniques, Analytical↗

PubMed2004

Two-dimensional nonlinear wavelet compression of ion mobility spectra of chemical warfare agent simulants.

Ion mobility spectrometry (IMS) affords miniaturized hand-held devices that can be used for monitoring and remote measurement. Because such instruments have limits on storage capacity or bandwidth for wireless transmission, data compression is important. Furthermore, all instruments should be operated with the fastest possible sampling rates because a signal-to-noise gain can be achieved by wavelet compression. Linear wavelet compression (LWC) applied to IMS data may cause peak distortion when the spectra are reconstructed. Nonlinear wavelet compression (NLWC) precisely preserves the peak location (i.e., drift time), height, and shape. IMS data of three chemical warfare simulants, dimethyl methylphosphonate, triethyl phosphate, and dipropyleneglycol monomethyl ether, were collected from an Ion Track ITEMISER and a Graseby Ionics detector CAM. Two-dimensional NLWC was used to compress the IMS data in the drift time and data acquisition dimensions on IMS data of chemical warfare simulants. NLWC was applied to achieve a compression factor of 1/128 with relative error of root-mean-square of <0.25% in the reconstructed spectra. A method was also developed and evaluated for optimizing compression.

Journal Article↗

PubMed2004

Nonlinear wavelet compression of ion mobility spectra from ion mobility spectrometers mounted in an unmanned aerial vehicle.

Linear and nonlinear wavelet compression of ion mobility spectrometry (IMS) data are compared and evaluated. IMS provides low detection limits and rapid response for many compounds. Nonlinear wavelet compression of ion mobility spectra reduced the data to 4-5% of its original size, while eliminating artifacts in the reconstructed spectra that occur with linear compression, and the root-mean-square reconstruction error was 0.17-0.20% of the maximum intensity of the uncompressed spectra. Furthermore, nonlinear wavelet compression precisely preserves the peak location (i.e., drift time). Small variations in peak location may occur in the reconstructed spectra that were linearly compressed. A method was developed and evaluated for optimizing the compression. The compression method was evaluated with in-flight data recorded from ion mobility spectrometers mounted in an unmanned aerial vehicle (UAV). Plumes of dimethyl methylphosphonate were disseminated for interrogation by the UAV-mounted IMS system. The daublet 8 wavelet filter exhibited the best performance for these evaluations.

Journal Article↗

PubMed2003

Trace explosive detection in aqueous samples by solid-phase extraction ion mobility spectrometry (SPE-IMS).

Law enforcement agencies use ion mobility spectrometers for the detection of explosives, drugs of abuse, and chemical warfare agents. Ion mobility spectrometry (IMS) has the advantages of short analysis times, detections in the parts per billion concentrations, and high sensitivity. On-site environmental analysis of explosives or explosive residues in water is possible with ion mobility spectrometers. Unfortunately, the direct analysis of low levels of explosives in water is difficult. Extraction provides a method for pre-concentrating the analytes and removing interferents. Coupling solid-phase extraction (SPE) with IMS is useful for the identification of trace amounts of explosives in water. Commercially available SPE disks were used. After extraction, the sample disk is inserted into the ion mobility spectrometer, where the analytes are thermally desorbed from the disk. Concentrations as low as one part per trillion were detected with a Barringer Ionscan 350. An external computer and acquisition software (LabVIEW, National Instruments) were used to collect data. SIMPLISMA (SIMPLe-to-use-Interactive Self-modeling Mixture Analysis) was applied to the data to resolve features that vary with respect to time.

Aniline Compounds↗