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Michael G. Kong - One of the best experts on this subject based on the ideXlab platform.
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Contrasting Characteristics of Gas–Liquid Reactive Species Induced by Pulse-Modulated RF and kHz Sinusoidal Plasma Jets
IEEE Transactions on Plasma Science, 2019Co-Authors: Han Xu, Xiaohua Wang, Weitao Wang, Michael G. KongAbstract:The pulse-modulated radio frequency (RF) and kHz sinusoidal voltages are used for the excitation of two plasma jets, for which the Reactive Species in the plasma plumes and in the treated water are comparatively studied. With the same discharge power, it is found that concentrations of aqueous Reactive Species generated by the kHz sinusoidal plasma jet are higher than that of the pulse-modulated RF plasma jet, especially for the short-lived Species OH. In addition, the comparison between the bacterial inactivation results is in accordance with that for the concentrations of aqueous Reactive Species for the two types of plasma jets. On the contrary, the emission spectra indicate that the gaseous Reactive Species such as OH(A) and O(3p5P) have much higher densities for the pulse-modulated RF plasma jet, which should ascribe to its higher electron density and electron temperature. Moreover, the concentrations of the aqueous Reactive Species and the emission intensities of the gaseous Reactive Species have similar variation trends for each of the plasma jets, as a function of the discharge power and the gap width. These results imply that the emission intensity could not reflect the relative concentration of an aqueous Reactive Species between these two plasma jets, but it could be used as an indicator of the concentration variation of an aqueous Reactive Species for each of the plasma jets. In addition, the phenomenon of electron trapping effect also indicates that the aqueous Reactive Species can be effectively generated only when more electrons act on the water sample.
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Contrasting characteristics of aqueous Reactive Species induced by cross-field and linear-field plasma jets
Journal of Physics D: Applied Physics, 2017Co-Authors: Chen Chen, Dingxin Liu, Zhijie Liu, Xiaohua Wang, Michael G. KongAbstract:A comparative study on aqueous Reactive Species in deionized water treated by two types of plasma jets is presented. Classified by the direction of the electric field in the jet device, a linear-field jet and cross-field jet have been set up. Concentrations of several aqueous Reactive Species are measured quantitatively by chemical fluorescent assays and electron spin resonance spectrometer. Results show that these two-type plasma jets would generate approximately the same gaseous Reactive Species under the same discharge power, but the linear-field plasma jet is much more efficient at delivering those Species to the remote deionized water. This leads to a much more aqueous short-lived Species including OH and produced in water, which are mainly correlated to the solvation of gaseous short-lived Species such as ions and electrons. Regarding the long-lived Species of aqueous H2O2, the concentration grows faster when treated by the linear-field plasma jet in the initial stage, but after 10 min it is similar to that treated by the cross-field counterpart due to the vapor–liquid equilibrium. The aqueous peroxynitrite is also predicted to be produced as a result of the air inclusion in the feeding gas.
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A New Surface Discharge Source: Plasma Characteristics and Delivery of Reactive Species
IEEE Transactions on Plasma Science, 2016Co-Authors: Bingchuan Wang, Xiaohua Wang, Zhiquan Zhang, Qiaosong Li, Michael G. KongAbstract:A new surface dielectric barrier discharge source containing a matrix of holes in the dielectric slice is put forward in this paper, for which the plasma characteristics and the delivery of Reactive Species to the downstream sample are studied for three experimental conditions, i.e., EC1 with a helium gas flow of 1 SLM through the holes, EC2 with an artificial air flow of 1 SLM, and EC3 without any gas flow. All the other conditions are kept the same. For the same discharge power of 2 W, it is found that the surface plasma in EC1 is comparatively more homogeneous, the discharge voltage is lower by ~12%, and the densities of Reactive Species are much higher, since the emission spectral lines of N2(C), N2+(B), He(3s3S), and O(3p5P) are stronger by at least sixfold. A petri dish of deionized water is put 5-mm downstream the surface discharge, in which the concentrations of nitrite, nitrate, H2O2, and NO are measured after the plasma treatment of 3 min. Compared with EC1, EC2, and EC3, it is found that the gas flow can increase the concentration of H2O2 by ~1.4-fold, but when helium is participated, a further increase of sixfold is achieved. Similarly, further increase is also found for the other three Reactive Species, which may be ascribed to the higher densities of gaseous Reactive oxygen and nitrogen Species in the helium-participated plasma and their larger diffusion coefficients in helium compared with that in air.
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Delivering fluxes of Reactive Species of cold atmospheric-pressure plasmas through the electrode sheath region
2012 Abstracts IEEE International Conference on Plasma Science, 2012Co-Authors: Aijun Yang, Felipe Iza, Dingxin Liu, Xiaohua Wang, Xingzhen Wang, Mingzhe Rong, Michael G. KongAbstract:Summary form only given. Cold atmospheric-pressure plasmas have received much attention; mainly rely on the potential use of Reactive Species generated in such plasmas. In most cases of application, such as plasma medicine, the Reactive Species have effects on a sample only after their penetration through the plasma sheath that is formed above the sample. In contrast to studies of generation and optimization of Reactive Species with the plasma itself, much less research has been reported on delivering of Reactive Species through the sheath region. The latter is quantitatively investigated in this paper for radio-frequency plasmas in atmospheric He+O 2 mixture, by means of a fluid model. It is found that the electrode fluxes of plasma Species are dominated by the plasma sheath, because the diffusion length is very small as a result of high collisionality at atmospheric pressure. So, the fluxes of Reactive plasma Species can be controlled by adjusting the sheath, which in turn can be controlled by altering, for example, the excitation frequency, the applied voltage, and the electrode gap. At a constant input electrical power, it is shown that high fluxes of Reactive plasma Species, particularly anions such as O 2 −, may be facilitated by low excitation frequency, small gap distance, or voltage bias applied to an electrode. This effect is particularly pronounced when the sheath thickness becomes comparable to the electrode gap distance.
Eva Bezak - One of the best experts on this subject based on the ideXlab platform.
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Validation and investigation of Reactive Species yields of Geant4‐ DNA chemistry models
Medical Physics, 2019Co-Authors: Dylan Peukert, Sebastien Incerti, Ivan M. Kempson, Michael Douglass, M. Karamitros, Gérard Baldacchino, Eva BezakAbstract:Purpose: Indirect biological damage due to Reactive Species produced in water radiolysis reactions is responsible for the majority of biological effect for low linear energy transfer (LET) radiation. Modeling water radiolysis and the subsequent interactions of Reactive Species, as well as track structures, is essential to model radiobiology on the microscale. Recently, chemistry models have been developed for Geant4-DNA to be used in combination with the comprehensive existing physics models. In the current work, the first detailed, independent, in silico validation of all Species yields with published experimental observations and comparison with other radiobiological simulations is presented. Additionally, the effect of LET of protons and heavier ions on Reactive Species yield in the model was examined, as well as the completeness of the chemical reactions following the radiolysis within the time after physical interactions simulated in the model. Methods: Yields over time of Reactive Species were simulated for water radiolysis by incident electrons, protons, alpha particles, and ions with various LETs using Geant4 and RITRACKS simulation tools. Water dissociation and recombination was simulated using Geant4 to determine the completeness of chemical reactions at the end of the simulation. Yield validation was performed by comparing yields simulated using Geant4 with experimental observations and other simulations. Validation was performed for all Species for low LET radiation and the solvated electron and hydroxyl radical for high LET ions. Results: It was found that the Geant4-DNA chemistry yields were generally in good agreement with experimental observations and other simulations. However, the Geant4-DNA yields for the hydroxyl radical and hydrogen peroxide at the end of the chemistry stage were found to be respectively considerably higher and lower than the experimentally observed yields. Increasing the LET of incident hadrons increased the yield of secondary Species and decreased the yield of primary Species. The effect of LET on the yield of the hydroxyl radical at 100 ns simulated with Geant4 was in good agreement with experimental measurements. Additionally, by the end of the simulation only 40% of dissociated water molecules had been recombined and the rate of recombination was slowing. Conclusions: The yields simulated using Geant4 are within reasonable agreement with experimental observations. Higher LET radiation corresponds with increased yields of secondary Species and decreased yields of primary Species. These trends combined with the LET having similar effects on the 100 ns hydroxyl radical yield for Geant4 and experimental measurements indicate that Geant4 accurately models the effect of LET on radiolysis yields. The limited recombination within the modeled chemistry stage and the slowing rate of recombination at the end of the stage indicate potential
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Validation and investigation of Reactive Species yields of Geant4‐DNA chemistry models
Medical physics, 2018Co-Authors: Dylan Peukert, Sebastien Incerti, Ivan M. Kempson, Michael Douglass, M. Karamitros, Gérard Baldacchino, Eva BezakAbstract:PURPOSE Indirect biological damage due to Reactive Species produced in water radiolysis reactions is responsible for the majority of biological effect for low linear energy transfer (LET) radiation. Modeling water radiolysis and the subsequent interactions of Reactive Species, as well as track structures, is essential to model radiobiology on the microscale. Recently, chemistry models have been developed for Geant4-DNA to be used in combination with the comprehensive existing physics models. In the current work, the first detailed, independent, in silico validation of all Species yields with published experimental observations and comparison with other radiobiological simulations is presented. Additionally, the effect of LET of protons and heavier ions on Reactive Species yield in the model was examined, as well as the completeness of the chemical reactions following the radiolysis within the time after physical interactions simulated in the model. METHODS Yields over time of Reactive Species were simulated for water radiolysis by incident electrons, protons, alpha particles, and ions with various LETs using Geant4 and RITRACKS simulation tools. Water dissociation and recombination was simulated using Geant4 to determine the completeness of chemical reactions at the end of the simulation. Yield validation was performed by comparing yields simulated using Geant4 with experimental observations and other simulations. Validation was performed for all Species for low LET radiation and the solvated electron and hydroxyl radical for high LET ions. RESULTS It was found that the Geant4-DNA chemistry yields were generally in good agreement with experimental observations and other simulations. However, the Geant4-DNA yields for the hydroxyl radical and hydrogen peroxide at the end of the chemistry stage were found to be respectively considerably higher and lower than the experimentally observed yields. Increasing the LET of incident hadrons increased the yield of secondary Species and decreased the yield of primary Species. The effect of LET on the yield of the hydroxyl radical at 100 ns simulated with Geant4 was in good agreement with experimental measurements. Additionally, by the end of the simulation only 40% of dissociated water molecules had been recombined and the rate of recombination was slowing. CONCLUSIONS The yields simulated using Geant4 are within reasonable agreement with experimental observations. Higher LET radiation corresponds with increased yields of secondary Species and decreased yields of primary Species. These trends combined with the LET having similar effects on the 100 ns hydroxyl radical yield for Geant4 and experimental measurements indicate that Geant4 accurately models the effect of LET on radiolysis yields. The limited recombination within the modeled chemistry stage and the slowing rate of recombination at the end of the stage indicate potential long-range indirect biological damage.
Dylan Peukert - One of the best experts on this subject based on the ideXlab platform.
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Validation and investigation of Reactive Species yields of Geant4‐ DNA chemistry models
Medical Physics, 2019Co-Authors: Dylan Peukert, Sebastien Incerti, Ivan M. Kempson, Michael Douglass, M. Karamitros, Gérard Baldacchino, Eva BezakAbstract:Purpose: Indirect biological damage due to Reactive Species produced in water radiolysis reactions is responsible for the majority of biological effect for low linear energy transfer (LET) radiation. Modeling water radiolysis and the subsequent interactions of Reactive Species, as well as track structures, is essential to model radiobiology on the microscale. Recently, chemistry models have been developed for Geant4-DNA to be used in combination with the comprehensive existing physics models. In the current work, the first detailed, independent, in silico validation of all Species yields with published experimental observations and comparison with other radiobiological simulations is presented. Additionally, the effect of LET of protons and heavier ions on Reactive Species yield in the model was examined, as well as the completeness of the chemical reactions following the radiolysis within the time after physical interactions simulated in the model. Methods: Yields over time of Reactive Species were simulated for water radiolysis by incident electrons, protons, alpha particles, and ions with various LETs using Geant4 and RITRACKS simulation tools. Water dissociation and recombination was simulated using Geant4 to determine the completeness of chemical reactions at the end of the simulation. Yield validation was performed by comparing yields simulated using Geant4 with experimental observations and other simulations. Validation was performed for all Species for low LET radiation and the solvated electron and hydroxyl radical for high LET ions. Results: It was found that the Geant4-DNA chemistry yields were generally in good agreement with experimental observations and other simulations. However, the Geant4-DNA yields for the hydroxyl radical and hydrogen peroxide at the end of the chemistry stage were found to be respectively considerably higher and lower than the experimentally observed yields. Increasing the LET of incident hadrons increased the yield of secondary Species and decreased the yield of primary Species. The effect of LET on the yield of the hydroxyl radical at 100 ns simulated with Geant4 was in good agreement with experimental measurements. Additionally, by the end of the simulation only 40% of dissociated water molecules had been recombined and the rate of recombination was slowing. Conclusions: The yields simulated using Geant4 are within reasonable agreement with experimental observations. Higher LET radiation corresponds with increased yields of secondary Species and decreased yields of primary Species. These trends combined with the LET having similar effects on the 100 ns hydroxyl radical yield for Geant4 and experimental measurements indicate that Geant4 accurately models the effect of LET on radiolysis yields. The limited recombination within the modeled chemistry stage and the slowing rate of recombination at the end of the stage indicate potential
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Validation and investigation of Reactive Species yields of Geant4‐DNA chemistry models
Medical physics, 2018Co-Authors: Dylan Peukert, Sebastien Incerti, Ivan M. Kempson, Michael Douglass, M. Karamitros, Gérard Baldacchino, Eva BezakAbstract:PURPOSE Indirect biological damage due to Reactive Species produced in water radiolysis reactions is responsible for the majority of biological effect for low linear energy transfer (LET) radiation. Modeling water radiolysis and the subsequent interactions of Reactive Species, as well as track structures, is essential to model radiobiology on the microscale. Recently, chemistry models have been developed for Geant4-DNA to be used in combination with the comprehensive existing physics models. In the current work, the first detailed, independent, in silico validation of all Species yields with published experimental observations and comparison with other radiobiological simulations is presented. Additionally, the effect of LET of protons and heavier ions on Reactive Species yield in the model was examined, as well as the completeness of the chemical reactions following the radiolysis within the time after physical interactions simulated in the model. METHODS Yields over time of Reactive Species were simulated for water radiolysis by incident electrons, protons, alpha particles, and ions with various LETs using Geant4 and RITRACKS simulation tools. Water dissociation and recombination was simulated using Geant4 to determine the completeness of chemical reactions at the end of the simulation. Yield validation was performed by comparing yields simulated using Geant4 with experimental observations and other simulations. Validation was performed for all Species for low LET radiation and the solvated electron and hydroxyl radical for high LET ions. RESULTS It was found that the Geant4-DNA chemistry yields were generally in good agreement with experimental observations and other simulations. However, the Geant4-DNA yields for the hydroxyl radical and hydrogen peroxide at the end of the chemistry stage were found to be respectively considerably higher and lower than the experimentally observed yields. Increasing the LET of incident hadrons increased the yield of secondary Species and decreased the yield of primary Species. The effect of LET on the yield of the hydroxyl radical at 100 ns simulated with Geant4 was in good agreement with experimental measurements. Additionally, by the end of the simulation only 40% of dissociated water molecules had been recombined and the rate of recombination was slowing. CONCLUSIONS The yields simulated using Geant4 are within reasonable agreement with experimental observations. Higher LET radiation corresponds with increased yields of secondary Species and decreased yields of primary Species. These trends combined with the LET having similar effects on the 100 ns hydroxyl radical yield for Geant4 and experimental measurements indicate that Geant4 accurately models the effect of LET on radiolysis yields. The limited recombination within the modeled chemistry stage and the slowing rate of recombination at the end of the stage indicate potential long-range indirect biological damage.
Sylwia Ptasinska - One of the best experts on this subject based on the ideXlab platform.
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Total yield of Reactive Species originating from an atmospheric pressure plasma jet in real time.
Biological chemistry, 2018Co-Authors: Ek Adhikari, Vladimir Samara, Sylwia PtasinskaAbstract:It is now well established that plasma-induced Reactive Species are key agents involved in many biochemical reactions. This work reports on the formation of plasma Reactive Species in an acidified ferrous sulfate (Fricke) solution interacting with an atmospheric pressure plasma jet (APPJ). A yield of ferric (Fe3+) ions measured using in situ absorption spectroscopy was attributed to the formation of plasma Reactive Species provided and/or originated in the solution. The results indicated that the number of Reactive Species formed was proportional to plasma frequency and voltage. However, the Fe3+ yield per pulse decreased with increased frequency. To obtain a better understanding of the processes and Species involved in the chemical reactions due to plasma exposure, Fe3+ yields were calculated and compared to the experimental data. At higher frequencies, there was insufficient time to complete all the reactions before the next pulse reached the solution; at lower frequencies, the Fe3+ yield was higher because of the relatively longer time available for reactions to occur. In addition, the comparison between DNA damage levels and Fe3+ yields was investigated under different experimental conditions in order to verify the usefulness of both the Fricke solution and the DNA molecule as a probe to characterize APPJs.
Michael J. Davies - One of the best experts on this subject based on the ideXlab platform.
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Reactive Species formed on proteins exposed to singlet oxygen.
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2003Co-Authors: Michael J. DaviesAbstract:Singlet oxygen (1O2) is believed to be generated in biological systems by a range of endogenous processes (e.g. enzymatic and chemical reactions) and exogenous stimuli (e.g. UV or visible light in the presence of a sensitiser). Kinetic data is consistent with proteins being a major target for 1O2, with damage occurring preferentially at Trp, His, Tyr, Met, and Cys side-chains. Reaction with each of these residues gives rise to further Reactive Species. In the case of Trp and Tyr, initial poorly characterised endoperoxides are believed to undergo ring-opening reactions to give hydroperoxides, which can be reduced to the corresponding alcohols; other products arising from radical intermediates can also be generated, particularly in the presence of UV light and metal ions. With His side-chains, poorly characterised peroxides are also formed. Reaction with Met and Cys has been proposed to occur via zwitterionic peroxy intermediates. Peroxides are also generated on isolated proteins, and protein within intact cells, via1O2-mediated reactions. The peroxides formed on Trp, Tyr, and His peptides, as well as on proteins, have been shown to induce damage to other targets, with molecular oxidation of thiol residues an important reaction. This can result in the inactivation of cellular enzymes and the oxidation of other biological targets. Protein cross-linking and aggregation can also be induced by Reactive Species formed on photo-oxidised proteins, though the nature of the Species that participate in such reactions is poorly understood. These secondary reactions, and particularly those involving hydroperoxides, may play a key role in the induction of secondary damage (bystander effects) in systems subject to photo-oxidation.
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Reactive Species and their accumulation on radical-damaged proteins
Trends in biochemical sciences, 1993Co-Authors: Roger T. Dean, Steven P. Gieseg, Michael J. DaviesAbstract:Hydroperoxides and catechols are described as novel Reactive products of radical attack on proteins. These Species, like other components of oxidized and otherwise damaged proteins, may accumulate in some biological systems. We propose that the Reactive Species may then attack other biomolecules, and constitute both a marker and a mechanism of age-related pathologies.
