The Experts below are selected from a list of 177 Experts worldwide ranked by ideXlab platform

Z. Wu - One of the best experts on this subject based on the ideXlab platform.

  • Environmental dispersion in wetland flow
    Communications in Nonlinear Science and Numerical Simulation, 2020
    Co-Authors: L Zeng, G Q Chen, Hansong Tang, Z. Wu
    Abstract:

    For the typical case of a pulsed Contaminant Emission into a shallow wetland channel, a theoretical analysis is presented in this paper for the decay of the width-averaged mean concentration under environmental dispersion. The velocity profile of a fully developed steady flow through the wetland channel is obtained with that for the well-known plane Poiseuille flow as a special case. An environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classic analysis on dispersion, and corresponding environmental dispersivity is obtained by Aris’s method of moments and illustrated with an asymptotic time variation with stem dominated, transitional, and width-stem dominated stages. Analytical solution for the longitudinal decay of mean concentration due to environmental dispersion is rigorously derived and characterized with multiple time scales.

  • Environmental dispersion in a three-layer wetland flow with free-surface
    Communications in Nonlinear Science and Numerical Simulation, 2013
    Co-Authors: P. Wang, Z. Wu, G Q Chen
    Abstract:

    Abstract To further address the characteristic of Contaminant transport in wetlands of a multi-layer structure, environmental dispersion of a pulsed Contaminant Emission into a steady flow is analytically explored in this paper for the typical case of a respectively vegetated or packed three-layer wetland dominated with free-water-surface-effect. The hierarchical structure for the critical length and duration of the Contaminant cloud is illustrated for the dispersion of typical Contaminant constituents.

  • Environmental dispersion in a two-zone wetland
    Ecological Modelling, 2011
    Co-Authors: Z. Wu, G Q Chen, L Zeng
    Abstract:

    As an extension of the modelling on environmental dispersion in a single zone wetland [Zeng, L., Chen, G.Q., 2009. Ecological degradation and hydraulic dispersion of Contaminant in wetland. Ecol. Model., 222, 293-300], the typical case of a pulsed Contaminant Emission into a steady flow through a distinctively vegetated two-zone shallow wetland channel is analytically explored in this paper in terms of the longitudinal evolution of the lateral mean concentration under environmental dispersion. The velocity profile of a fully developed flow through the wetland is derived, with that for a single zone wetland flow included as a special case. Taylor's classical analysis and Aris's method of concentration moments for solute dispersion in a single phase fluid flow are rigorously generalized for the two-zone case of a wetland flow to develop the dispersion model and to determine the dispersivity, which is illustrated with an asymptotic time variation characterized by stem dominated, transitional, and width-stem dominated stages. For typical Contaminant constituents of chemical oxygen demand, biochemical oxygen demand, total phosphorus, total nitrogen and heavy metal, the evolution of Contaminant cloud is illustrated with the critical length and duration of the Contaminant cloud with constituent concentration beyond some given environmental standard level. © 2010 Elsevier B.V.

  • an ecological risk assessment model for a pulsed Contaminant Emission into a wetland channel flow
    Ecological Modelling, 2010
    Co-Authors: G Q Chen, L Zeng, Z. Wu
    Abstract:

    As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant Emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of Contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed Contaminant Emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under environmental dispersion. An environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classical analysis on dispersion in fluid flows. The velocity distribution and the environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris’s method of moments, the environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width–depth-stem dominated stage. Based on the solution for the evolution of Contaminant cloud in the wetland channel flow, critical length and duration of the Contaminant cloud with concentration beyond given environmental standard level are concretely illustrated for typical pollutant constituents in wastewater Emission. Under the same Emission intensity and environmental standard, the duration of Contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect.

  • An ecological risk assessment model for a pulsed Contaminant Emission into a wetland channel flow
    Ecological Modelling, 2010
    Co-Authors: G Q Chen, L Zeng, Z. Wu
    Abstract:

    As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant Emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of Contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed Contaminant Emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under environmental dispersion. An environmental dispersion model for the mean concentration is devised as an extension of Taylor's classical analysis on dispersion in fluid flows. The velocity distribution and the environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris's method of moments, the environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width-depth-stem dominated stage. Based on the solution for the evolution of Contaminant cloud in the wetland channel flow, critical length and duration of the Contaminant cloud with concentration beyond given environmental standard level are concretely illustrated for typical pollutant constituents in wastewater Emission. Under the same Emission intensity and environmental standard, the duration of Contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect. © 2010 Elsevier B.V.

G Q Chen - One of the best experts on this subject based on the ideXlab platform.

  • Environmental dispersion in wetland flow
    Communications in Nonlinear Science and Numerical Simulation, 2020
    Co-Authors: L Zeng, G Q Chen, Hansong Tang, Z. Wu
    Abstract:

    For the typical case of a pulsed Contaminant Emission into a shallow wetland channel, a theoretical analysis is presented in this paper for the decay of the width-averaged mean concentration under environmental dispersion. The velocity profile of a fully developed steady flow through the wetland channel is obtained with that for the well-known plane Poiseuille flow as a special case. An environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classic analysis on dispersion, and corresponding environmental dispersivity is obtained by Aris’s method of moments and illustrated with an asymptotic time variation with stem dominated, transitional, and width-stem dominated stages. Analytical solution for the longitudinal decay of mean concentration due to environmental dispersion is rigorously derived and characterized with multiple time scales.

  • Environmental dispersion in a three-layer wetland flow with free-surface
    Communications in Nonlinear Science and Numerical Simulation, 2013
    Co-Authors: P. Wang, Z. Wu, G Q Chen
    Abstract:

    Abstract To further address the characteristic of Contaminant transport in wetlands of a multi-layer structure, environmental dispersion of a pulsed Contaminant Emission into a steady flow is analytically explored in this paper for the typical case of a respectively vegetated or packed three-layer wetland dominated with free-water-surface-effect. The hierarchical structure for the critical length and duration of the Contaminant cloud is illustrated for the dispersion of typical Contaminant constituents.

  • Ecological degradation and hydraulic dispersion of Contaminant in wetland
    Ecological Modelling, 2011
    Co-Authors: L Zeng, G Q Chen
    Abstract:

    For the typical case of a pulsed Contaminant Emission into a free surface wetland flow, a theoretical analysis is presented in this paper for the decay of the depth-averaged concentration under the combined action of ecological degradation and hydraulic dispersion. Based on a first-order reaction model extensively employed in related ecological risk assessment and environmental hydraulic design, the effect of ecological degradation is separated from the hydraulic effect via an exponential transformation for the general formulation for Contaminant transport. The speed profile of a fully developed steady flow through the wetland is obtained. A hydraulic dispersion model for the depth-averaged concentration is devised as an extension of Taylor’s classical analysis on dispersion, and corresponding hydraulic dispersivity is obtained by Aris’s method of moments. Analytical solution of depth-averaged concentration is rigorously derived and characterized. For typical pollutant constituents in wastewater Emission, the evolution of Contaminant cloud in the wetland flow is illustrated by critical length and duration of influenced region with Contaminant concentration beyond given environmental standard level, with essential implications for ecological risk assessment and environmental management.

  • Environmental dispersion in a two-zone wetland
    Ecological Modelling, 2011
    Co-Authors: Z. Wu, G Q Chen, L Zeng
    Abstract:

    As an extension of the modelling on environmental dispersion in a single zone wetland [Zeng, L., Chen, G.Q., 2009. Ecological degradation and hydraulic dispersion of Contaminant in wetland. Ecol. Model., 222, 293-300], the typical case of a pulsed Contaminant Emission into a steady flow through a distinctively vegetated two-zone shallow wetland channel is analytically explored in this paper in terms of the longitudinal evolution of the lateral mean concentration under environmental dispersion. The velocity profile of a fully developed flow through the wetland is derived, with that for a single zone wetland flow included as a special case. Taylor's classical analysis and Aris's method of concentration moments for solute dispersion in a single phase fluid flow are rigorously generalized for the two-zone case of a wetland flow to develop the dispersion model and to determine the dispersivity, which is illustrated with an asymptotic time variation characterized by stem dominated, transitional, and width-stem dominated stages. For typical Contaminant constituents of chemical oxygen demand, biochemical oxygen demand, total phosphorus, total nitrogen and heavy metal, the evolution of Contaminant cloud is illustrated with the critical length and duration of the Contaminant cloud with constituent concentration beyond some given environmental standard level. © 2010 Elsevier B.V.

  • an ecological risk assessment model for a pulsed Contaminant Emission into a wetland channel flow
    Ecological Modelling, 2010
    Co-Authors: G Q Chen, L Zeng, Z. Wu
    Abstract:

    As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant Emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of Contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed Contaminant Emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under environmental dispersion. An environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classical analysis on dispersion in fluid flows. The velocity distribution and the environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris’s method of moments, the environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width–depth-stem dominated stage. Based on the solution for the evolution of Contaminant cloud in the wetland channel flow, critical length and duration of the Contaminant cloud with concentration beyond given environmental standard level are concretely illustrated for typical pollutant constituents in wastewater Emission. Under the same Emission intensity and environmental standard, the duration of Contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect.

Lorraine M. Conroy - One of the best experts on this subject based on the ideXlab platform.

  • Characterization of size-specific particulate matter Emission rates for a simulated medical laser procedure - A pilot study
    Annals of Occupational Hygiene, 2015
    Co-Authors: Ramon Lopez, Julia F Lippert, Steven E. Lacey, Nurtan A. Esmen, Li C. Liu, Lorraine M. Conroy
    Abstract:

    Prior investigation on medical laser interaction with tissue has suggested device operational parameter settings influence laser generated air Contaminant Emission, but this has not been systematically explored. A laboratory-based simulated medical laser procedure was designed and pilot tested to determine the effect of laser operational parameters on the size-specific mass Emission rate of laser generated particulate matter. Porcine tissue was lased in an Emission chamber using two medical laser systems (CO2, λ = 10600nm; Ho:YAG, λ = 2100nm) in a fractional factorial study design by varying three operational parameters (beam diameter, pulse repetition frequency, and power) between two levels (high and low) and the resultant plume was measured using two real-time size-selective particle counters. Particle count concentrations were converted to mass Emission rates before an analysis of variance was used to determine the influence of operational parameter settings on size-specific mass Emission rate. Particle shape and diameter were described for a limited number of samples by collecting particles on polycarbonate filters, and photographed using a scanning electron microscope (SEM) to examine method of particle formation. An increase in power and decrease in beam diameter led to an increase in mass Emission for the Ho:YAG laser at all size ranges. For the CO2 laser, Emission rates were dependent on particle size and were not statistically significant for particle ranges between 5 and 10 µm. When any parameter level was increased, Emission rate of the smallest particle size range also increased. Beam diameter was the most influential variable for both lasers, and the operational parameters tested explained the most variability at the smallest particle size range. Particle shape was variable and some particles observed by SEM were likely created from mechanical methods. This study provides a foundation for future investigations to better estimate size-specific mass Emission rates and particle characteristics for additional laser operational parameters in order to estimate occupational exposure, and to inform control strategies.

  • a pilot study to determine medical laser generated air Contaminant Emission rates for a simulated surgical procedure
    Journal of Occupational and Environmental Hygiene, 2014
    Co-Authors: Julia F Lippert, Steven E. Lacey, John E Franke, Lorraine M. Conroy, J.c Breskey, Ramon Lopez, Nurtan A. Esmen
    Abstract:

    The U.S. Occupational Safety and Health Administration (OSHA) estimates that half a million health-care workers are exposed to laser surgical smoke each year. The purpose of this study was to establish a methodology to (1) estimate Emission rates of laser-generated air Contaminants (LGACs) using an Emission chamber, and to (2) perform a screening study to differentiate the effects of three laser operational parameters. An Emission chamber was designed, fabricated, and assessed for performance to estimate the Emission rates of gases and particles associated with LGACs during a simulated surgical procedure. Two medical lasers (Holmium Yttrium Aluminum Garnet [Ho:YAG] and carbon dioxide [CO2]) were set to a range of plausible medical laser operational parameters in a simulated surgery to pyrolyze porcine skin generating plume in the Emission chamber. Power, pulse repetition frequency (PRF), and beam diameter were evaluated to determine the effect of each operational parameter on Emission rate using a fractio...

  • A pilot study to determine medical laser generated air Contaminant Emission rates for a simulated surgical procedure
    Journal of Occupational and Environmental Hygiene, 2014
    Co-Authors: Julia F Lippert, Steven E. Lacey, John E Franke, Lorraine M. Conroy, J.c Breskey, Nurtan A. Esmen, Ramon Lopez, Li C. Liu
    Abstract:

    The U.S. Occupational Safety and Health Administration (OSHA) estimates that half a million health-care workers are exposed to laser surgical smoke each year. The purpose of this study was to establish a methodology to (1) estimate Emission rates of laser-generated air Contaminants (LGACs) using an Emission chamber, and to (2) perform a screening study to differentiate the effects of three laser operational parameters. An Emission chamber was designed, fabricated, and assessed for performance to estimate the Emission rates of gases and particles associated with LGACs during a simulated surgical procedure. Two medical lasers (Holmium Yttrium Aluminum Garnet [Ho:YAG] and carbon dioxide [CO2]) were set to a range of plausible medical laser operational parameters in a simulated surgery to pyrolyze porcine skin generating plume in the Emission chamber. Power, pulse repetition frequency (PRF), and beam diameter were evaluated to determine the effect of each operational parameter on Emission rate using a fractional factorial design. The plume was sampled for particulate matter and seven gas phase combustion byproduct Contaminants (benzene, ethylbenzene, toluene, formaldehyde, hydrogen cyanide, carbon dioxide, and carbon monoxide): the gas phase Emission results are presented here. Most of the measured concentrations of gas phase Contaminants were below their limit of detection (LOD), but detectable measurements enabled us to determine laser operation parameter influence on CO2 Emissions. Confined to the experimental conditions of this screening study, results indicated that beam diameter was statistically significantly influential and power was marginally statistically significant to Emission rates of CO2 when using the Ho:YAG laser but not with the carbon dioxide laser; PRF was not influential vis-a-vis Emission rates of these gas phase Contaminants. © 2014 Copyright © 2014 JOEH, LLC.

L Zeng - One of the best experts on this subject based on the ideXlab platform.

  • Environmental dispersion in wetland flow
    Communications in Nonlinear Science and Numerical Simulation, 2020
    Co-Authors: L Zeng, G Q Chen, Hansong Tang, Z. Wu
    Abstract:

    For the typical case of a pulsed Contaminant Emission into a shallow wetland channel, a theoretical analysis is presented in this paper for the decay of the width-averaged mean concentration under environmental dispersion. The velocity profile of a fully developed steady flow through the wetland channel is obtained with that for the well-known plane Poiseuille flow as a special case. An environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classic analysis on dispersion, and corresponding environmental dispersivity is obtained by Aris’s method of moments and illustrated with an asymptotic time variation with stem dominated, transitional, and width-stem dominated stages. Analytical solution for the longitudinal decay of mean concentration due to environmental dispersion is rigorously derived and characterized with multiple time scales.

  • Ecological degradation and hydraulic dispersion of Contaminant in wetland
    Ecological Modelling, 2011
    Co-Authors: L Zeng, G Q Chen
    Abstract:

    For the typical case of a pulsed Contaminant Emission into a free surface wetland flow, a theoretical analysis is presented in this paper for the decay of the depth-averaged concentration under the combined action of ecological degradation and hydraulic dispersion. Based on a first-order reaction model extensively employed in related ecological risk assessment and environmental hydraulic design, the effect of ecological degradation is separated from the hydraulic effect via an exponential transformation for the general formulation for Contaminant transport. The speed profile of a fully developed steady flow through the wetland is obtained. A hydraulic dispersion model for the depth-averaged concentration is devised as an extension of Taylor’s classical analysis on dispersion, and corresponding hydraulic dispersivity is obtained by Aris’s method of moments. Analytical solution of depth-averaged concentration is rigorously derived and characterized. For typical pollutant constituents in wastewater Emission, the evolution of Contaminant cloud in the wetland flow is illustrated by critical length and duration of influenced region with Contaminant concentration beyond given environmental standard level, with essential implications for ecological risk assessment and environmental management.

  • Environmental dispersion in a two-zone wetland
    Ecological Modelling, 2011
    Co-Authors: Z. Wu, G Q Chen, L Zeng
    Abstract:

    As an extension of the modelling on environmental dispersion in a single zone wetland [Zeng, L., Chen, G.Q., 2009. Ecological degradation and hydraulic dispersion of Contaminant in wetland. Ecol. Model., 222, 293-300], the typical case of a pulsed Contaminant Emission into a steady flow through a distinctively vegetated two-zone shallow wetland channel is analytically explored in this paper in terms of the longitudinal evolution of the lateral mean concentration under environmental dispersion. The velocity profile of a fully developed flow through the wetland is derived, with that for a single zone wetland flow included as a special case. Taylor's classical analysis and Aris's method of concentration moments for solute dispersion in a single phase fluid flow are rigorously generalized for the two-zone case of a wetland flow to develop the dispersion model and to determine the dispersivity, which is illustrated with an asymptotic time variation characterized by stem dominated, transitional, and width-stem dominated stages. For typical Contaminant constituents of chemical oxygen demand, biochemical oxygen demand, total phosphorus, total nitrogen and heavy metal, the evolution of Contaminant cloud is illustrated with the critical length and duration of the Contaminant cloud with constituent concentration beyond some given environmental standard level. © 2010 Elsevier B.V.

  • an ecological risk assessment model for a pulsed Contaminant Emission into a wetland channel flow
    Ecological Modelling, 2010
    Co-Authors: G Q Chen, L Zeng, Z. Wu
    Abstract:

    As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant Emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of Contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed Contaminant Emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under environmental dispersion. An environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classical analysis on dispersion in fluid flows. The velocity distribution and the environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris’s method of moments, the environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width–depth-stem dominated stage. Based on the solution for the evolution of Contaminant cloud in the wetland channel flow, critical length and duration of the Contaminant cloud with concentration beyond given environmental standard level are concretely illustrated for typical pollutant constituents in wastewater Emission. Under the same Emission intensity and environmental standard, the duration of Contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect.

  • An ecological risk assessment model for a pulsed Contaminant Emission into a wetland channel flow
    Ecological Modelling, 2010
    Co-Authors: G Q Chen, L Zeng, Z. Wu
    Abstract:

    As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant Emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of Contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed Contaminant Emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under environmental dispersion. An environmental dispersion model for the mean concentration is devised as an extension of Taylor's classical analysis on dispersion in fluid flows. The velocity distribution and the environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris's method of moments, the environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width-depth-stem dominated stage. Based on the solution for the evolution of Contaminant cloud in the wetland channel flow, critical length and duration of the Contaminant cloud with concentration beyond given environmental standard level are concretely illustrated for typical pollutant constituents in wastewater Emission. Under the same Emission intensity and environmental standard, the duration of Contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect. © 2010 Elsevier B.V.

Julia F Lippert - One of the best experts on this subject based on the ideXlab platform.

  • Characterization of size-specific particulate matter Emission rates for a simulated medical laser procedure - A pilot study
    Annals of Occupational Hygiene, 2015
    Co-Authors: Ramon Lopez, Julia F Lippert, Steven E. Lacey, Nurtan A. Esmen, Li C. Liu, Lorraine M. Conroy
    Abstract:

    Prior investigation on medical laser interaction with tissue has suggested device operational parameter settings influence laser generated air Contaminant Emission, but this has not been systematically explored. A laboratory-based simulated medical laser procedure was designed and pilot tested to determine the effect of laser operational parameters on the size-specific mass Emission rate of laser generated particulate matter. Porcine tissue was lased in an Emission chamber using two medical laser systems (CO2, λ = 10600nm; Ho:YAG, λ = 2100nm) in a fractional factorial study design by varying three operational parameters (beam diameter, pulse repetition frequency, and power) between two levels (high and low) and the resultant plume was measured using two real-time size-selective particle counters. Particle count concentrations were converted to mass Emission rates before an analysis of variance was used to determine the influence of operational parameter settings on size-specific mass Emission rate. Particle shape and diameter were described for a limited number of samples by collecting particles on polycarbonate filters, and photographed using a scanning electron microscope (SEM) to examine method of particle formation. An increase in power and decrease in beam diameter led to an increase in mass Emission for the Ho:YAG laser at all size ranges. For the CO2 laser, Emission rates were dependent on particle size and were not statistically significant for particle ranges between 5 and 10 µm. When any parameter level was increased, Emission rate of the smallest particle size range also increased. Beam diameter was the most influential variable for both lasers, and the operational parameters tested explained the most variability at the smallest particle size range. Particle shape was variable and some particles observed by SEM were likely created from mechanical methods. This study provides a foundation for future investigations to better estimate size-specific mass Emission rates and particle characteristics for additional laser operational parameters in order to estimate occupational exposure, and to inform control strategies.

  • a pilot study to determine medical laser generated air Contaminant Emission rates for a simulated surgical procedure
    Journal of Occupational and Environmental Hygiene, 2014
    Co-Authors: Julia F Lippert, Steven E. Lacey, John E Franke, Lorraine M. Conroy, J.c Breskey, Ramon Lopez, Nurtan A. Esmen
    Abstract:

    The U.S. Occupational Safety and Health Administration (OSHA) estimates that half a million health-care workers are exposed to laser surgical smoke each year. The purpose of this study was to establish a methodology to (1) estimate Emission rates of laser-generated air Contaminants (LGACs) using an Emission chamber, and to (2) perform a screening study to differentiate the effects of three laser operational parameters. An Emission chamber was designed, fabricated, and assessed for performance to estimate the Emission rates of gases and particles associated with LGACs during a simulated surgical procedure. Two medical lasers (Holmium Yttrium Aluminum Garnet [Ho:YAG] and carbon dioxide [CO2]) were set to a range of plausible medical laser operational parameters in a simulated surgery to pyrolyze porcine skin generating plume in the Emission chamber. Power, pulse repetition frequency (PRF), and beam diameter were evaluated to determine the effect of each operational parameter on Emission rate using a fractio...

  • A pilot study to determine medical laser generated air Contaminant Emission rates for a simulated surgical procedure
    Journal of Occupational and Environmental Hygiene, 2014
    Co-Authors: Julia F Lippert, Steven E. Lacey, John E Franke, Lorraine M. Conroy, J.c Breskey, Nurtan A. Esmen, Ramon Lopez, Li C. Liu
    Abstract:

    The U.S. Occupational Safety and Health Administration (OSHA) estimates that half a million health-care workers are exposed to laser surgical smoke each year. The purpose of this study was to establish a methodology to (1) estimate Emission rates of laser-generated air Contaminants (LGACs) using an Emission chamber, and to (2) perform a screening study to differentiate the effects of three laser operational parameters. An Emission chamber was designed, fabricated, and assessed for performance to estimate the Emission rates of gases and particles associated with LGACs during a simulated surgical procedure. Two medical lasers (Holmium Yttrium Aluminum Garnet [Ho:YAG] and carbon dioxide [CO2]) were set to a range of plausible medical laser operational parameters in a simulated surgery to pyrolyze porcine skin generating plume in the Emission chamber. Power, pulse repetition frequency (PRF), and beam diameter were evaluated to determine the effect of each operational parameter on Emission rate using a fractional factorial design. The plume was sampled for particulate matter and seven gas phase combustion byproduct Contaminants (benzene, ethylbenzene, toluene, formaldehyde, hydrogen cyanide, carbon dioxide, and carbon monoxide): the gas phase Emission results are presented here. Most of the measured concentrations of gas phase Contaminants were below their limit of detection (LOD), but detectable measurements enabled us to determine laser operation parameter influence on CO2 Emissions. Confined to the experimental conditions of this screening study, results indicated that beam diameter was statistically significantly influential and power was marginally statistically significant to Emission rates of CO2 when using the Ho:YAG laser but not with the carbon dioxide laser; PRF was not influential vis-a-vis Emission rates of these gas phase Contaminants. © 2014 Copyright © 2014 JOEH, LLC.

  • determination of laser generated air Contaminant Emission rates in a simulated surgical procedure
    2013
    Co-Authors: Julia F Lippert
    Abstract:

    The Occupational Safety and Health Administration estimates that half of a million surgical staff are exposed to laser smoke each year. The type and intensity of exposure is dependent in part on the way a laser is used during surgery. The purpose of this study was to estimate Emission rates of the gas phase constituents of laser generated air Contaminants using a validated Emission chamber methodology while differentiating the effects of the laser operational parameters of power, pulse-repetition frequency, and beam diameter on the estimated Emission rates and ultimately estimating a range of plausible occupational exposures. Two medical lasers (Holmium and CO2) were set at varying operational parameters in a simulated laser surgery on porcine skin in a validated Emission chamber. The plume was sampled for seven chemical agents (including volatile organic compounds, formaldehyde, hydrogen cyanide, carbon dioxide, carbon monoxide) selected to represent tissue combustion by-products. The effect of each operational parameter on Emission rates was determined using a fractional factorial design coupled with a sequential screening process that evaluated the parameters for their influence on Emission rates after each round of data collection. Measured concentrations of each agent were either below the limit of detection or well below occupational exposure guidelines. Our preliminary results under these experimental conditions suggest that only beam diameter was a statistically influential parameter to estimated Emission rates using the Holmium laser, while none of the operational parameters examined influenced Emission rates using the CO2 laser. Estimated exposures were three orders of magnitude below occupational exposure limits. This exploratory study identified operational parameters that influence Emission of laser generated air Contaminants, and established a laboratory simulation protocol that may be used in future investigations to characterize the influence of these and additional parameters that may affect Contaminant generation for emerging technologies and clinical applications. In the future, this protocol will be refined to distinguish influential operational parameters and develop an effects model that can be used to estimate a variety of occupational exposures.