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Robert S Dewoskin - One of the best experts on this subject based on the ideXlab platform.
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PBPK models in risk assessment--A focus on Chloroprene.
Chemico-biological interactions, 2007Co-Authors: Robert S DewoskinAbstract:Mathematical models are increasingly being used to simulate events in the exposure-response continuum, and to support quantitative predictions of risks to human health. Physiologically based pharmacokinetic (PBPK) models address that portion of the continuum from an external chemical exposure to an internal dose at a target site. Essential data needed to develop a PBPK model include values of key physiological parameters (e.g., tissue volumes, blood flow rates) and chemical specific parameters (rate of chemical absorption, distribution, metabolism, and elimination) for the species of interest. PBPK models are commonly used to: (1) predict concentrations of an internal dose over time at a target site following external exposure via different routes and/or durations; (2) predict human internal concentration at a target site based on animal data by accounting for toxicokinetic and physiological differences; and (3) estimate variability in the internal dose within a human population resulting from differences in individual pharmacokinetics. Himmelstein et al. [M.W. Himmelstein, S.C. Carpenter, P.M. Hinderliter, Kinetic modeling of beta-Chloroprene metabolism. I. In vitro rates in liver and lung tissue fractions from mice, rats, hamsters, and humans, Toxicol. Sci. 79 (1) (2004) 18-27; M.W. Himmelstein, S.C. Carpenter, M.V. Evans, P.M. Hinderliter, E.M. Kenyon, Kinetic modeling of beta-Chloroprene metabolism. II. The application of physiologically based modeling for cancer dose response analysis, Toxicol. Sci. 79 (1) (2004) 28-37] developed a PBPK model for Chloroprene (2-chloro-1,3-butadiene; CD) that simulates Chloroprene disposition in rats, mice, hamsters, or humans following an inhalation exposure. Values for the CD-PBPK model metabolic parameters were obtained from in vitro studies, and model simulations compared to data from in vivo gas uptake studies in rats, hamsters, and mice. The model estimate for total amount of metabolite in lung correlated better with rodent tumor incidence than did the external dose. Based on this PBPK model analytical approach, Himmelstein et al. [M.W. Himmelstein, S.C. Carpenter, M.V. Evans, P.M. Hinderliter, E.M. Kenyon, Kinetic modeling of beta-Chloroprene metabolism. II. The application of physiologically based modeling for cancer dose response analysis, Toxicol. Sci. 79 (1) (2004) 28-37; M.W. Himmelstein, R. Leonard, R. Valentine, Kinetic modeling of beta-Chloroprene metabolism: default and physiologically-based modeling approaches for cancer dose response, in: IISRP Symposium on Evaluation of Butadiene & Chloroprene Health Effects, September 21, 2005, TBD--reference in this proceedings issue of Chemical-Biological Interactions] propose that observed species differences in the lung tumor dose-response result from differences in CD metabolic rates. The CD-PBPK model has not yet been submitted to EPA for use in developing the IRIS assessment for Chloroprene, but is sufficiently developed to be considered. The process that EPA uses to evaluate PBPK models is discussed, as well as potential applications for the CD-PBPK model in an IRIS assessment.
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PBPK models in risk assessment--A focus on Chloroprene.
Chemico-Biological Interactions, 2007Co-Authors: Robert S DewoskinAbstract:Abstract Mathematical models are increasingly being used to simulate events in the exposure-response continuum, and to support quantitative predictions of risks to human health. Physiologically based pharmacokinetic (PBPK) models address that portion of the continuum from an external chemical exposure to an internal dose at a target site. Essential data needed to develop a PBPK model include values of key physiological parameters (e.g., tissue volumes, blood flow rates) and chemical specific parameters (rate of chemical absorption, distribution, metabolism, and elimination) for the species of interest. PBPK models are commonly used to: (1) predict concentrations of an internal dose over time at a target site following external exposure via different routes and/or durations; (2) predict human internal concentration at a target site based on animal data by accounting for toxicokinetic and physiological differences; and (3) estimate variability in the internal dose within a human population resulting from differences in individual pharmacokinetics. Himmelstein et al. [M.W. Himmelstein, S.C. Carpenter, P.M. Hinderliter, Kinetic modeling of beta-Chloroprene metabolism. I. In vitro rates in liver and lung tissue fractions from mice, rats, hamsters, and humans, Toxicol. Sci. 79 (1) (2004) 18–27; M.W. Himmelstein, S.C. Carpenter, M.V. Evans, P.M. Hinderliter, E.M. Kenyon, Kinetic modeling of beta-Chloroprene metabolism. II. The application of physiologically based modeling for cancer dose response analysis, Toxicol. Sci. 79 (1) (2004) 28–37] developed a PBPK model for Chloroprene (2-chloro-1,3-butadiene; CD) that simulates Chloroprene disposition in rats, mice, hamsters, or humans following an inhalation exposure. Values for the CD-PBPK model metabolic parameters were obtained from in vitro studies, and model simulations compared to data from in vivo gas uptake studies in rats, hamsters, and mice. The model estimate for total amount of metabolite in lung correlated better with rodent tumor incidence than did the external dose. Based on this PBPK model analytical approach, Himmelstein et al. [M.W. Himmelstein, S.C. Carpenter, M.V. Evans, P.M. Hinderliter, E.M. Kenyon, Kinetic modeling of beta-Chloroprene metabolism. II. The application of physiologically based modeling for cancer dose response analysis, Toxicol. Sci. 79 (1) (2004) 28–37; M.W. Himmelstein, R. Leonard, R. Valentine, Kinetic modeling of β-Chloroprene metabolism: default and physiologically-based modeling approaches for cancer dose response, in: IISRP Symposium on Evaluation of Butadiene & Chloroprene Health Effects, September 21, 2005, TBD—reference in this proceedings issue of Chemical–Biological Interactions] propose that observed species differences in the lung tumor dose–response result from differences in CD metabolic rates. The CD-PBPK model has not yet been submitted to EPA for use in developing the IRIS assessment for Chloroprene, but is sufficiently developed to be considered. The process that EPA uses to evaluate PBPK models is discussed, as well as potential applications for the CD-PBPK model in an IRIS assessment.
Ali Akbar Entezami - One of the best experts on this subject based on the ideXlab platform.
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Characterization of thermal, mechanical
2016Co-Authors: Bakhshali Massoumi, Farzaneh Farjadbeh, Robab Mohammadi, Ali Akbar EntezamiAbstract:Synthesis of conductive adhesives based on epoxy resin/nanopolyaniline and Chloroprene rubber/nanopolyaniline
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Synthesis of conductive adhesives based on epoxy resin/nanopolyaniline and Chloroprene rubber/nanopolyaniline: Characterization of thermal, mechanical and electrical properties
Journal of Composite Materials, 2012Co-Authors: Bakhshali Massoumi, Farzaneh Farjadbeh, Robab Mohammadi, Ali Akbar EntezamiAbstract:Dodecylbenzenesulfonic acid-doped polyaniline was prepared by sonication method. Electrically conductive blends were prepared by mixing a polyaniline–dodecylbenzenesulfonic acid salt with epoxy resin and Chloroprene rubber. The nanostructure of the conductive blends was studied by scanning electron microscopy. The polyaniline/epoxy resin and polyaniline/Chloroprene rubber showed threshold concentrations of polyaniline (5 and 10 wt%, respectively) for electrical conduction. The electrical conductivity of both polyaniline/epoxy resin and polyaniline/Chloroprene rubber increased with the addition of polyaniline–dodecylbenzenesulfonic acid, reaching values higher than 1.89 × 10−2 and 7.50 × 10−4 S/cm with 50 wt% of polyaniline–dodecylbenzenesulfonic acid. The structures of conductive adhesives were investigated by Fourier transform infrared spectroscopy. Also the thermal, mechanical, and adhesion strength properties of blends containing different amounts of polyaniline–dodecylbenzenesulfonic acid were determined.
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Synthesis of conductive adhesives based on epoxy resin/nanopolyaniline and Chloroprene rubber/nanopolyaniline: Characterization of thermal, mechanical and electrical properties
Journal of Composite Materials, 2012Co-Authors: Bakhshali Massoumi, Farzaneh Farjadbeh, Robab Mohammadi, Ali Akbar EntezamiAbstract:Dodecylbenzenesulfonic acid-doped polyaniline was prepared by sonication method. Electrically conductive blends were prepared by mixing a polyaniline–dodecylbenzenesulfonic acid salt with epoxy resin and Chloroprene rubber. The nanostructure of the conductive blends was studied by scanning electron microscopy. The polyaniline/epoxy resin and polyaniline/Chloroprene rubber showed threshold concentrations of polyaniline (5 and 10 wt%, respectively) for electrical conduction. The electrical conductivity of both polyaniline/epoxy resin and polyaniline/Chloroprene rubber increased with the addition of polyaniline–dodecylbenzenesulfonic acid, reaching values higher than 1.89 × 10−2 and 7.50 × 10−4 S/cm with 50 wt% of polyaniline–dodecylbenzenesulfonic acid. The structures of conductive adhesives were investigated by Fourier transform infrared spectroscopy. Also the thermal, mechanical, and adhesion strength properties of blends containing different amounts of polyaniline–dodecylbenzenesulfonic acid were determined.
S. Ohya - One of the best experts on this subject based on the ideXlab platform.
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Dielectric properties of thermally degraded Chloroprene rubber
Polymer Degradation and Stability, 2010Co-Authors: H. Kuwahara, Seiichi Sudo, M. Iijima, S. OhyaAbstract:We performed dielectric measurements on thermally aged carbon-black-filled Chloroprene rubber (CR). Primary and secondary processes were observed in unaged and thermally aged CR. The primary process is due to the cooperative motion of Chloroprene chains in CR, and the secondary process is due to the local motion of Chloroprene chains. For the primary process, the relaxation time slightly increases and symmetric shape parameter of the loss spectrum decreases with increasing aging time. For the secondary process, the relaxation strength decreases with increasing aging time, and reaches zero after 50 h. These changes in the dielectric relaxation parameters are due to the progress of the dehydrochlorination reaction at the Chloroprene chains.
Z. Pelzbauer - One of the best experts on this subject based on the ideXlab platform.
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Growth reaction in the radical polymerization of Chloroprene
Journal of Polymer Science Part C: Polymer Symposia, 2007Co-Authors: František Hrabák, Milan Bezděk, Vlasta Hynková, Z. PelzbauerAbstract:The effects of solvent, molecular weight regulator, and concentration of initiator and emulsifier on the polymerization rate of Chloroprene in the latex particle was studied. By a modification in the method for the determination of the latex particle size by means of soap sorption, errors of conductometric titration due to the liberation of hydrochloric acid and dilution of latex were reduced. The found data were used to calculate the velocity constant of the growth reaction of Chloroprene and its temperature dependence in the range of 10–35°C.
Bakhshali Massoumi - One of the best experts on this subject based on the ideXlab platform.
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Characterization of thermal, mechanical
2016Co-Authors: Bakhshali Massoumi, Farzaneh Farjadbeh, Robab Mohammadi, Ali Akbar EntezamiAbstract:Synthesis of conductive adhesives based on epoxy resin/nanopolyaniline and Chloroprene rubber/nanopolyaniline
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Synthesis of conductive adhesives based on epoxy resin/nanopolyaniline and Chloroprene rubber/nanopolyaniline: Characterization of thermal, mechanical and electrical properties
Journal of Composite Materials, 2012Co-Authors: Bakhshali Massoumi, Farzaneh Farjadbeh, Robab Mohammadi, Ali Akbar EntezamiAbstract:Dodecylbenzenesulfonic acid-doped polyaniline was prepared by sonication method. Electrically conductive blends were prepared by mixing a polyaniline–dodecylbenzenesulfonic acid salt with epoxy resin and Chloroprene rubber. The nanostructure of the conductive blends was studied by scanning electron microscopy. The polyaniline/epoxy resin and polyaniline/Chloroprene rubber showed threshold concentrations of polyaniline (5 and 10 wt%, respectively) for electrical conduction. The electrical conductivity of both polyaniline/epoxy resin and polyaniline/Chloroprene rubber increased with the addition of polyaniline–dodecylbenzenesulfonic acid, reaching values higher than 1.89 × 10−2 and 7.50 × 10−4 S/cm with 50 wt% of polyaniline–dodecylbenzenesulfonic acid. The structures of conductive adhesives were investigated by Fourier transform infrared spectroscopy. Also the thermal, mechanical, and adhesion strength properties of blends containing different amounts of polyaniline–dodecylbenzenesulfonic acid were determined.
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Synthesis of conductive adhesives based on epoxy resin/nanopolyaniline and Chloroprene rubber/nanopolyaniline: Characterization of thermal, mechanical and electrical properties
Journal of Composite Materials, 2012Co-Authors: Bakhshali Massoumi, Farzaneh Farjadbeh, Robab Mohammadi, Ali Akbar EntezamiAbstract:Dodecylbenzenesulfonic acid-doped polyaniline was prepared by sonication method. Electrically conductive blends were prepared by mixing a polyaniline–dodecylbenzenesulfonic acid salt with epoxy resin and Chloroprene rubber. The nanostructure of the conductive blends was studied by scanning electron microscopy. The polyaniline/epoxy resin and polyaniline/Chloroprene rubber showed threshold concentrations of polyaniline (5 and 10 wt%, respectively) for electrical conduction. The electrical conductivity of both polyaniline/epoxy resin and polyaniline/Chloroprene rubber increased with the addition of polyaniline–dodecylbenzenesulfonic acid, reaching values higher than 1.89 × 10−2 and 7.50 × 10−4 S/cm with 50 wt% of polyaniline–dodecylbenzenesulfonic acid. The structures of conductive adhesives were investigated by Fourier transform infrared spectroscopy. Also the thermal, mechanical, and adhesion strength properties of blends containing different amounts of polyaniline–dodecylbenzenesulfonic acid were determined.