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Gregg A. Lithgow

Bio: Gregg A. Lithgow is an academic researcher from University of California, San Diego. The author has contributed to research in topics: Laser-induced breakdown spectroscopy & Particle. The author has an hindex of 6, co-authored 8 publications receiving 322 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a spectrally broadband laser-induced breakdown spectroscopy (LIBS) system was used for laboratory measurements on some common biological agent simulants, which were compared to those of common, naturally occurring biological aerosol components (pollen and fungal spores) to determine the potential of LIBS for discriminating biological agents from natural background aerosols.
Abstract: Laser-induced breakdown spectroscopy (LIBS) is examined as a potential method for detecting airborne biological agents. A spectrally broadband LIBS system was used for laboratory measurements on some common biological agent simulants. These measurements were compared to those of common, naturally occurring biological aerosol components (pollen and fungal spores) to determine the potential of LIBS for discriminating biological agents from natural background aerosols. A principal components analysis illustrates that linear combinations of the detected atomic lines, which are present in different ratios in each of the samples tested, can be used to discriminate biological agent simulants from other biological matter. A more sensitive, narrowband LIBS instrument was used to demonstrate the detection of single simulant (Bg) particles in the size range 1-5 μm. Ca, Mg, and Na, which are present in varying concentrations between 0.3 and 11% (by mass) in the Bg particles, were observed in single particles using LIBS.

179 citations

Journal ArticleDOI
TL;DR: In this article, laser-induced breakdown spectroscopy (LIBS) was used to measure the distribution of seven species in individual ambient aerosol particles during an 8-day period from 26 August to 2 September 2002 at the Pittsburgh Aerosol Supersite.

64 citations

Journal ArticleDOI
TL;DR: In this paper, two sets of optics were used to image different regions of a LIBS plasma and simultaneously collect spectra from single particles, and strong variation and lack of correlation between the two measurement channels suggest that emission from a single particle is localized within the plasma.
Abstract: Particle location with respect to the plasma volume and the focal volume of the collection optics is identified as an important source of uncertainty in single-aerosol laser-induced breakdown spectroscopy (LIBS) measurements. Two sets of optics were used to image different regions of a LIBS plasma and simultaneously collect spectra from single particles. Strong variation and lack of correlation between the two measurement channels suggest that emission from a single particle is localized within the plasma. Measurement precision and detection efficiency were improved by imaging a larger plasma region, thus integrating the spatially distributed signal.

28 citations

Journal ArticleDOI
TL;DR: In this article, the effect of the location of particles within the plasma volume on the laser-induced breakdown spectroscopy signal for single-particle measurements is investigated, and three methods of collecting plasma emission are compared to determine the influence of plasma imaging on particle hit detection rates and signal precision.

26 citations

Patent
08 Oct 2011
TL;DR: In this paper, the authors described a method for detecting particle composition using an aerosol inlet of a particle detector, where the received particles were carried within a stream of gas and charged using a charger to have a charge.
Abstract: Techniques and devices are disclosed for detecting particle composition. In one aspect, a method performed by a detector to detect particles includes receiving particles at an aerosol inlet of the detector. The method includes carrying the received particles within a stream of gas and charging the particles within the stream of gas using a charger to have a charge. The method includes transporting the charged particles to a location of a collection electrode. The method includes biasing the collection electrode to a voltage using a high-voltage supply to attract either negatively or positively charged particles, and analyzing the particles.

18 citations


Cited by
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Journal ArticleDOI
TL;DR: The current state-of-the-art of analytical LIBS is summarized, providing a contemporary snapshot of LIBS applications, and highlighting new directions in laser-induced breakdown spectroscopy, such as novel approaches, instrumental developments, and advanced use of chemometric tools are discussed.
Abstract: The first part of this two-part review focused on the fundamental and diagnostics aspects of laser-induced plasmas, only touching briefly upon concepts such as sensitivity and detection limits and largely omitting any discussion of the vast panorama of the practical applications of the technique. Clearly a true LIBS community has emerged, which promises to quicken the pace of LIBS developments, applications, and implementations. With this second part, a more applied flavor is taken, and its intended goal is summarizing the current state-of-the-art of analytical LIBS, providing a contemporary snapshot of LIBS applications, and highlighting new directions in laser-induced breakdown spectroscopy, such as novel approaches, instrumental developments, and advanced use of chemometric tools. More specifically, we discuss instrumental and analytical approaches (e.g., double- and multi-pulse LIBS to improve the sensitivity), calibration-free approaches, hyphenated approaches in which techniques such as Raman and fluorescence are coupled with LIBS to increase sensitivity and information power, resonantly enhanced LIBS approaches, signal processing and optimization (e.g., signal-to-noise analysis), and finally applications. An attempt is made to provide an updated view of the role played by LIBS in the various fields, with emphasis on applications considered to be unique. We finally try to assess where LIBS is going as an analytical field, where in our opinion it should go, and what should still be done for consolidating the technique as a mature method of chemical analysis.

1,159 citations

Journal ArticleDOI
22 Feb 2012-Tellus B
TL;DR: A review of the current knowledge on major categories of primary biological aerosol particles (PBAP): bacteria and archaea, fungal spores and fragments, pollen, viruses, algae and cyanobacteria, biological crusts and lichens and others like plant or animal fragments and detritus is presented in this article.
Abstract: Atmospheric aerosol particles of biological origin are a very diverse group of biological materials and structures, including microorganisms, dispersal units, fragments and excretions of biological organisms. In recent years, the impact of biological aerosol particles on atmospheric processes has been studied with increasing intensity, and a wealth of new information and insights has been gained. This review outlines the current knowledge on major categories of primary biological aerosol particles (PBAP): bacteria and archaea, fungal spores and fragments, pollen, viruses, algae and cyanobacteria, biological crusts and lichens and others like plant or animal fragments and detritus. We give an overview of sampling methods and physical, chemical and biological techniques for PBAP analysis (cultivation, microscopy, DNA/RNA analysis, chemical tracers, optical and mass spectrometry, etc.). Moreover, we address and summarise the current understanding and open questions concerning the influence of PBAP on the atmosphere and climate, i.e. their optical properties and their ability to act as ice nuclei (IN) or cloud condensation nuclei (CCN). We suggest that the following research activities should be pursued in future studies of atmospheric biological aerosol particles: (1) develop efficient and reliable analytical techniques for the identification and quantification of PBAP; (2) apply advanced and standardised techniques to determine the abundance and diversity of PBAP and their seasonal variation at regional and global scales (atmospheric biogeography); (3) determine the emission rates, optical properties, IN and CCN activity of PBAP in field measurements and laboratory experiments; (4) use field and laboratory data to constrain numerical models of atmospheric transport, transformation and climate effects of PBAP. Keywords: primary biological atmospheric aerosol; climate; cloud condensation nuclei; biology; atmospheric ice nuclei (Published: 22 February 2012) Citation: Tellus B 2012, 64 , 15598, DOI: 10.3402/tellusb.v64i0.15598

1,034 citations

Journal ArticleDOI
TL;DR: Basic diagnostics aspects of laser-induced breakdown spectroscopy are focused on and a review of the past and recent LIBS literature pertinent to this topic is presented and previous research on non-laser-based plasma literature, and the resulting knowledge, is emphasized.
Abstract: Laser-induced breakdown spectroscopy (LIBS) has become a very popular analytical method in the last decade in view of some of its unique features such as applicability to any type of sample, practically no sample preparation, remote sensing capability, and speed of analysis The technique has a remarkably wide applicability in many fields, and the number of applications is still growing From an analytical point of view, the quantitative aspects of LIBS may be considered its Achilles' heel, first due to the complex nature of the laser–sample interaction processes, which depend upon both the laser characteristics and the sample material properties, and second due to the plasma–particle interaction processes, which are space and time dependent Together, these may cause undesirable matrix effects Ways of alleviating these problems rely upon the description of the plasma excitation-ionization processes through the use of classical equilibrium relations and therefore on the assumption that the laser-induced

835 citations

Journal ArticleDOI
TL;DR: In this paper, the chemical properties of particulate matter (PM) in diesel vehicle exhaust at a time when emission regulations, diesel technology development, and particle characterization techniques are all undergoing rapid change are examined.

820 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used a single-pulse laser source over a doublepulse system as the most suitable source for the stand-off analysis of organic samples for the detection and characterization of energetic materials at distances up to 45 m using standoff laser induced breakdown spectroscopy (LIBS).
Abstract: The detection and characterization of energetic materials at distances up to 45 m using stand-off laser induced breakdown spectroscopy (LIBS) has been demonstrated. A field-portable open-path LIB spectrometer working under a coaxial configuration was used. A preliminary study allowed choosing a single-pulse laser source over a double-pulse system as the most suitable source for the stand-off analysis of organic samples. The C2 Swan system, as well as the hydrogen, oxygen and nitrogen emission intensity ratios were the necessary parameters to identify the analyte as an organic explosive, organic non-explosive and non-organic samples. O/N intensity ratios of 2.9 and 2.16 with relative standard deviations of 4.03% and 8.36% were obtained for 2,4-dinitrotoluene and aluminium samples, respectively. A field test with known samples and a blind test were carried out at a distance of 30 m from the sample. Identification of energetic compounds in such conditions resulted in 19 correct results out of 21 samples.

240 citations