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Roy M Harrison - One of the best experts on this subject based on the ideXlab platform.
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Graphical Analysis of the performance of venturi scrubbers for particle abatement part i rapid collection efficiency evaluation
Aerosol Science and Technology, 2007Co-Authors: Alexia A Economopoulou, Roy M HarrisonAbstract:Based on the well-established theoretical formulations of Calvert (1970) and Yung et al. (1978), Graphical tools are developed for estimating the overall collection efficiency of venturi scrubbers under the specified design and operating conditions. Both Graphical solutions deliver the accuracy of the original theoretical models, subject to the assumption of a lognormal input particle size distribution. The nomographs produced can be used by environmental engineers for performing convenient Analysis of venturi performance and alternative design evaluations, and as part of a wider methodology for compiling particulate matter emission inventories. Combined with the Graphical models developed in Part II, the present work sets the stage for conducting size-specific emission inventories (e.g., PM 2.5 , PM 10 , TPM) for sources controlled by venturi scrubbers.
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Graphical Analysis of the performance of venturi scrubbers for particle abatement part ii size distribution of penetrating particles
Aerosol Science and Technology, 2007Co-Authors: Alexia A Economopoulou, Roy M HarrisonAbstract:Graphical tools are developed that provide convenient estimation of the size distribution of particles penetrating venturi scrubbers, based on the well-established theoretical formulations of Calvert (1970) and Yung et al. (1978). The Graphical solutions, produced through functional Analysis and numerical methods, deliver the accuracy of the original theoretical models under the specified venturi design and operating conditions, subject to the assumption of lognormal input particle size distribution. While Part I describes estimation of the overall particle abatement efficiency, the work in this article allows estimation of the size distribution of emitted particles. The generated nomographs can therefore be used as part of a methodology for compiling size-specific particulate matter emission inventories.
Jean Logan - One of the best experts on this subject based on the ideXlab platform.
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a strategy for removing the bias in the Graphical Analysis method
Journal of Cerebral Blood Flow and Metabolism, 2001Co-Authors: Jean Logan, Joanna S Fowler, Nora D Volkow, Yushin Ding, Genejack Wang, David AlexoffAbstract:Top of pageAbstract The Graphical Analysis method, which transforms multiple time measurements of plasma and tissue uptake data into a linear plot, is a useful tool for rapidly obtaining information about the binding of radioligands used in PET studies. The strength of the method is that it does not require a particular model structure. However, a bias is introduced in the case of noisy data resulting in the underestimation of the distribution volume (DV), the slope obtained from the Graphical method. To remove the bias, a modification of the method developed by Feng et al. (1993), the generalized linear least squares (GLLS) method, which provides unbiased estimates for compartment models was used. The one compartment GLLS method has a relatively simple form, which was used to estimate the DV directly and as a smoothing technique for more general classes of model structures. In the latter case, the GLLS method was applied to the data in two parts, that is, one set of parameters was determined for times 0 to T1 and a second set from T1 to the end time. The curve generated from these two sets of parameters then was used as input to the Graphical method. This has been tested using simulations of data similar to that of the PET ligand [11C]-d-threo-methylphenidate (MP, DV = 35 mL/mL) and 11C raclopride (RAC, DV = 1.92 mL/mL) and compared with two examples from image data with the same tracers. The noise model was based on counting statistics through the half-life of the isotope and the scanning time. Five hundred data sets at each noise level were analyzed. Results (DV) for the Graphical Analysis (DVG), the nonlinear least squares (NLS) method (DVNLS), the one-tissue compartment GLLS method (DVF), and the two part GLLS followed by Graphical Analysis (DVFG) were compared. DVFG was found to increase somewhat with increasing noise and in some data sets at high noise levels no estimate could be obtained. However, at intermediate levels it provided a good estimation of the true DV. This method was extended to use a reference tissue in place of the input function to generate the distribution volume ratio (DVR) to the reference region. A linearized form of the simplified reference tissue method of Lammertsma and Hume (1996) was used. The DVR generated directly from the model (DVRFL) was compared with DVRFG (determined from a "smoothed" uptake curve as for DVFG) using the Graphical method. Keywords: Positron emission tomography, Kinetic modeling, Graphical Analysis, Distribution volume
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Graphical Analysis of pet data applied to reversible and irreversible tracers
Nuclear Medicine and Biology, 2000Co-Authors: Jean LoganAbstract:The differential equations of compartmental Analysis form the basis of the models describing the uptake of tracers used in imaging studies. Graphical analyses convert the model equations into linear plots, the slopes of which represent measures of tracer binding. The Graphical methods are not dependent upon a particular model structure but the slopes can be related to combinations of the model parameters if a model structure is assumed. The input required is uptake data from a region of interest vs time and an input function that can either be plasma measurements or uptake data from a suitable reference region. Graphical methods can be applied to both reversible and irreversibly binding tracers. They provide considerable ease of computation compared to the optimization of individual model parameters in the solution of the differential equations generally used to describe the binding of tracers. Conditions under which the Graphical techniques are applicable and some problems encountered in separating tracer delivery and binding are considered. Also the effect of noise can introduce a bias in the distribution volume which is the slope of the Graphical Analysis of reversible tracers. Smoothing techniques may minimize this problem and retain the model independence. In any case Graphical techniques can provide insight into the binding kinetics of tracers in a visual way.
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Graphical Analysis of pet data applied to reversible and irreversible tracers
Quantitative Analysis of Tumor Biochemistry Using PET and SPECT Bethesda MD (US) 11 18 1999--11 19 1999, 1999Co-Authors: Jean LoganAbstract:Graphical Analysis refers to the transformation of multiple time measurements of plasma and tissue uptake data into a linear plot, the slope of which is related to the number of available tracer binding sites. This type of Analysis allows easy comparisons among experiments. No particular model structure is assumed, however it is assumed that the tracer is given by bolus injection and that both tissue uptake and the plasma concentration of unchanged tracer are monitored following tracer injection. The requirement of plasma measurements can be eliminated in some cases when a reference region is available. There are two categories of Graphical methods which apply to two general types of ligands--those which bind reversibly during the scanning procedure and those which are irreversible or trapped during the time of the scanning procedure.
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distribution volume ratios without blood sampling from Graphical Analysis of pet data
Journal of Cerebral Blood Flow and Metabolism, 1996Co-Authors: Jean Logan, Joanna S Fowler, Nora D Volkow, Yushin Ding, Genejack Wang, David AlexoffAbstract:The distribution volume ratio (DVR), which is a linear function of receptor availability, is widely used as a model parameter in imaging studies. The DVR corresponds to the ratio of the DV of a receptor-containing region to a nonreceptor region and generally requires the measurement of an arterial input function. Here we propose a Graphical method for determining the DVR that does not require blood sampling. This method uses data from a nonreceptor region with an average tissue-to-plasma efflux constant k2 to approximate the plasma integral. Data from positron emission tomography studies with [15C]raclopride (n = 20) and [11C]d-threo-methylphenidate ([11C]dMP) (n = 8) in which plasma data were taken and used to compare results from two Graphical methods, one that uses plasma data and one that does not. k2 was 0.163 and 0.051 min−1 for [11C]raclopride and [11C]dMP, respectively. Results from both methods were very similar, and the average percentage difference between the methods was −0.11% for [11C]raclop...
Alexia A Economopoulou - One of the best experts on this subject based on the ideXlab platform.
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Graphical Analysis of the performance of venturi scrubbers for particle abatement part i rapid collection efficiency evaluation
Aerosol Science and Technology, 2007Co-Authors: Alexia A Economopoulou, Roy M HarrisonAbstract:Based on the well-established theoretical formulations of Calvert (1970) and Yung et al. (1978), Graphical tools are developed for estimating the overall collection efficiency of venturi scrubbers under the specified design and operating conditions. Both Graphical solutions deliver the accuracy of the original theoretical models, subject to the assumption of a lognormal input particle size distribution. The nomographs produced can be used by environmental engineers for performing convenient Analysis of venturi performance and alternative design evaluations, and as part of a wider methodology for compiling particulate matter emission inventories. Combined with the Graphical models developed in Part II, the present work sets the stage for conducting size-specific emission inventories (e.g., PM 2.5 , PM 10 , TPM) for sources controlled by venturi scrubbers.
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Graphical Analysis of the performance of venturi scrubbers for particle abatement part ii size distribution of penetrating particles
Aerosol Science and Technology, 2007Co-Authors: Alexia A Economopoulou, Roy M HarrisonAbstract:Graphical tools are developed that provide convenient estimation of the size distribution of particles penetrating venturi scrubbers, based on the well-established theoretical formulations of Calvert (1970) and Yung et al. (1978). The Graphical solutions, produced through functional Analysis and numerical methods, deliver the accuracy of the original theoretical models under the specified venturi design and operating conditions, subject to the assumption of lognormal input particle size distribution. While Part I describes estimation of the overall particle abatement efficiency, the work in this article allows estimation of the size distribution of emitted particles. The generated nomographs can therefore be used as part of a methodology for compiling size-specific particulate matter emission inventories.
John J Mann - One of the best experts on this subject based on the ideXlab platform.
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determination of volume of distribution using likelihood estimation in Graphical Analysis elimination of estimation bias
Journal of Cerebral Blood Flow and Metabolism, 2003Co-Authors: Ramin V Parsey, Todd R Ogden, John J MannAbstract:The Graphical Analysis uses an ordinary least squares (OLS) fitting of transformed data to determine the total volume of distribution (VT) and is not dependent upon a compartmental model configuration. This method, however, suffers from a noise-dependent bias. Approaches for reducing this bias include incorporating a presmoothing step, minimizing the squared perpendicular distance to the regression line, and conducting multilinear Analysis. The solution proposed by Ogden, likelihood estimation in Graphical Analysis (LEGA), is an estimation technique in the original (nontransformed) domain based upon standard likelihood theory that incorporates the specific assumptions made on the noise inherent in the measurements. To determine the impact of this new method upon the noise-dependent bias, we compared VT determinations by compartmental modeling, Graphical Analysis (GA), and LEGA in 36 regions of interest in dynamic PET data from 25 healthy volunteers injected with [11C]-WAY-100635 and [11C]-McN-5652, which are agents used to image the serotonin 1A receptor and serotonin transporter, respectively. As predicted by simulations, LEGA eliminates the noise-dependent bias associated with GA using OLS. This method is a valuable addition to the tools available for the quantification of radioligand binding data in PET and SPECT.
David Alexoff - One of the best experts on this subject based on the ideXlab platform.
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a strategy for removing the bias in the Graphical Analysis method
Journal of Cerebral Blood Flow and Metabolism, 2001Co-Authors: Jean Logan, Joanna S Fowler, Nora D Volkow, Yushin Ding, Genejack Wang, David AlexoffAbstract:Top of pageAbstract The Graphical Analysis method, which transforms multiple time measurements of plasma and tissue uptake data into a linear plot, is a useful tool for rapidly obtaining information about the binding of radioligands used in PET studies. The strength of the method is that it does not require a particular model structure. However, a bias is introduced in the case of noisy data resulting in the underestimation of the distribution volume (DV), the slope obtained from the Graphical method. To remove the bias, a modification of the method developed by Feng et al. (1993), the generalized linear least squares (GLLS) method, which provides unbiased estimates for compartment models was used. The one compartment GLLS method has a relatively simple form, which was used to estimate the DV directly and as a smoothing technique for more general classes of model structures. In the latter case, the GLLS method was applied to the data in two parts, that is, one set of parameters was determined for times 0 to T1 and a second set from T1 to the end time. The curve generated from these two sets of parameters then was used as input to the Graphical method. This has been tested using simulations of data similar to that of the PET ligand [11C]-d-threo-methylphenidate (MP, DV = 35 mL/mL) and 11C raclopride (RAC, DV = 1.92 mL/mL) and compared with two examples from image data with the same tracers. The noise model was based on counting statistics through the half-life of the isotope and the scanning time. Five hundred data sets at each noise level were analyzed. Results (DV) for the Graphical Analysis (DVG), the nonlinear least squares (NLS) method (DVNLS), the one-tissue compartment GLLS method (DVF), and the two part GLLS followed by Graphical Analysis (DVFG) were compared. DVFG was found to increase somewhat with increasing noise and in some data sets at high noise levels no estimate could be obtained. However, at intermediate levels it provided a good estimation of the true DV. This method was extended to use a reference tissue in place of the input function to generate the distribution volume ratio (DVR) to the reference region. A linearized form of the simplified reference tissue method of Lammertsma and Hume (1996) was used. The DVR generated directly from the model (DVRFL) was compared with DVRFG (determined from a "smoothed" uptake curve as for DVFG) using the Graphical method. Keywords: Positron emission tomography, Kinetic modeling, Graphical Analysis, Distribution volume
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distribution volume ratios without blood sampling from Graphical Analysis of pet data
Journal of Cerebral Blood Flow and Metabolism, 1996Co-Authors: Jean Logan, Joanna S Fowler, Nora D Volkow, Yushin Ding, Genejack Wang, David AlexoffAbstract:The distribution volume ratio (DVR), which is a linear function of receptor availability, is widely used as a model parameter in imaging studies. The DVR corresponds to the ratio of the DV of a receptor-containing region to a nonreceptor region and generally requires the measurement of an arterial input function. Here we propose a Graphical method for determining the DVR that does not require blood sampling. This method uses data from a nonreceptor region with an average tissue-to-plasma efflux constant k2 to approximate the plasma integral. Data from positron emission tomography studies with [15C]raclopride (n = 20) and [11C]d-threo-methylphenidate ([11C]dMP) (n = 8) in which plasma data were taken and used to compare results from two Graphical methods, one that uses plasma data and one that does not. k2 was 0.163 and 0.051 min−1 for [11C]raclopride and [11C]dMP, respectively. Results from both methods were very similar, and the average percentage difference between the methods was −0.11% for [11C]raclop...
