The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
Marc Theóbald - One of the best experts on this subject based on the ideXlab platform.
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Self-Radiolysis of Tritiated Water Stored in Zeolites 4A: Production and Behavior of H 2 and O 2
Journal of Physical Chemistry C, 2015Co-Authors: Laëtitia Frances, Mikaël Douilly, Manuel Grivet, Didier Ducret, Marc TheóbaldAbstract:Radiolysis of confined water and self-Radiolysis of tritiated water give rise to several unanswered questions. To take into account this double specificity, we studied systems of zeolites 4A containing tritiated water at different water loading ratios. Two tritiated waters were synthesized at the volumetric activities of 27 and 60 TBq L −1. For each one, five samples were prepared, differentiated by their water loading ratios, expressed in percentage, close to 4%, 7%, 11%, 14%, and 19%. The study of the Radiolysis in those systems revealed a double role of zeolites 4A: first, they increase the decomposition of water. Then they enhance the recombination of the major stable radiolytic products detected. We actually evidenced a total recombi-nation between H 2 and O 2 , which is catalyzed by the zeolites.
Hand, Kevin P. - One of the best experts on this subject based on the ideXlab platform.
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Endogenic and Exogenic Contributions to Visible-wavelength Spectra of Europa's Trailing Hemisphere
'American Astronomical Society', 2020Co-Authors: Trumbo, Samantha K., Brown, Michael E., Hand, Kevin P.Abstract:The composition of Europa's trailing hemisphere reflects the combined influences of endogenous geologic resurfacing and exogenous sulfur Radiolysis. Using spatially resolved visible-wavelength spectra of Europa obtained with the Hubble Space Telescope, we map multiple spectral features across the trailing hemisphere and compare their geographies with the distributions of large-scale geology, magnetospheric bombardment, and surface color. Based on such comparisons, we interpret some aspects of our spectra as indicative of purely exogenous sulfur Radiolysis products and other aspects as indicative of Radiolysis products formed from a mixture of endogenous material and magnetospheric sulfur. The spatial distributions of two of the absorptions seen in our spectra -- a widespread downturn toward the near-UV and a distinct feature at 530 nm -- appear consistent with sulfur allotropes previously suggested from ground-based spectrophotometry. However, the geographies of two additional features -- an absorption feature at 360 nm and the spectral slope at red wavelengths -- are more consistent with endogenous material that has been altered by sulfur Radiolysis. We suggest irradiated sulfate salts as potential candidates for this material, but we are unable to identify particular species with the available data.Comment: 10 pages, 1 table, 5 figures, published in The Astronomical Journa
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Endogenic and Exogenic Contributions to Visible-wavelength Spectra of Europa’s Trailing Hemisphere
'American Astronomical Society', 2020Co-Authors: Trumbo, Samantha K., Brown, Michael E., Hand, Kevin P.Abstract:The composition of Europa's trailing hemisphere reflects the combined influences of endogenous geologic resurfacing and exogenous sulfur Radiolysis. Using spatially resolved visible-wavelength spectra of Europa obtained with the Hubble Space Telescope, we map multiple spectral features across the trailing hemisphere and compare their geographies with the distributions of large-scale geology, magnetospheric bombardment, and surface color. Based on such comparisons, we interpret some aspects of our spectra as indicative of purely exogenous sulfur Radiolysis products and other aspects as indicative of Radiolysis products formed from a mixture of endogenous material and magnetospheric sulfur. The spatial distributions of two of the absorptions seen in our spectra—a widespread downturn toward the near-UV and a distinct feature at 530 nm—appear consistent with sulfur allotropes previously suggested from ground-based spectrophotometry. However, the geographies of two additional features—an absorption feature at 360 nm and the spectral slope at red wavelengths—are more consistent with endogenous material that has been altered by sulfur Radiolysis. We suggest irradiated sulfate salts as potential candidates for this material, but we are unable to identify particular species with the available data
Laëtitia Frances - One of the best experts on this subject based on the ideXlab platform.
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Self-Radiolysis of Tritiated Water Stored in Zeolites 4A: Production and Behavior of H 2 and O 2
Journal of Physical Chemistry C, 2015Co-Authors: Laëtitia Frances, Mikaël Douilly, Manuel Grivet, Didier Ducret, Marc TheóbaldAbstract:Radiolysis of confined water and self-Radiolysis of tritiated water give rise to several unanswered questions. To take into account this double specificity, we studied systems of zeolites 4A containing tritiated water at different water loading ratios. Two tritiated waters were synthesized at the volumetric activities of 27 and 60 TBq L −1. For each one, five samples were prepared, differentiated by their water loading ratios, expressed in percentage, close to 4%, 7%, 11%, 14%, and 19%. The study of the Radiolysis in those systems revealed a double role of zeolites 4A: first, they increase the decomposition of water. Then they enhance the recombination of the major stable radiolytic products detected. We actually evidenced a total recombi-nation between H 2 and O 2 , which is catalyzed by the zeolites.
D. Douglas Walker - One of the best experts on this subject based on the ideXlab platform.
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Radiolysis of sodium and potassium tetraphenylborate in aqueous systems
The Journal of Physical Chemistry, 1991Co-Authors: Avinash K. Gupta, Robert J. Hanrahan, D. Douglas WalkerAbstract:The {sup 60}Co {gamma}-Radiolysis of soluble and insoluble tetraphenylborate (TPB) salts in aqueous solution was studied at 25C. In the Radiolysis of air-saturated 0.05 M sodium tetraphenylborate (NaTPB) solution the products and their G values are hydrogen, 0.46; biphenyl, 1.9; benzene, 1.3; and phenol, 0.41. Deposition of 4.4 Mrad caused the pH to increase from 8.2 to 9.8. Radiolysis of NaTPB solution produced hydrogen at the same rate as Radiolysis of water. In the Radiolysis of 10 wt % solid potassium tetraphenylborate (KTPB) aqueous slurries, the Radiolysis products were analyzed from the aqueous layer and also after dissolving the solid in acetone so as to release trapped products into solution. Benzene was the major product along with trace amounts of biphenyl and phenol. Only 10% of the benzene (G = 0.71) was released during Radiolysis; 90% (G = 7.1) was released when the solid was dissolved in acetone. The Radiolysis mechanism is discussed in terms of two alternate pathways for the reaction of OH{sup {sm bullet}} radical with TPB{sup {minus}} ion, involving electron transfer or OH{sup {sm bullet}} addition to the aromatic ring.
Michael G. Kontominas - One of the best experts on this subject based on the ideXlab platform.
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Radiolysis products and sensory properties of electron beam irradiated high barrier food packaging films containing a buried layer of recycled low density polyethylene
Food Additives and Contaminants Part A-chemistry Analysis Control Exposure & Risk Assessment, 2010Co-Authors: Stavroula Chytiri, Kyriakos A Riganakos, Anastasia V Badeka, Michael G. KontominasAbstract:The aim was to study the effect of electron-beam irradiation on the production of Radiolysis products and sensory changes in experimental high-barrier packaging films composed of polyamide (PA), ethylene-vinyl alcohol (EVOH) and low-density polyethylene (LDPE). Films contained a middle buried layer of recycled LDPE, while films containing 100% virgin LDPE as the middle buried layer were taken as controls. Irradiation doses ranged between zero and 60 kGy. Generally, a large number of Radiolysis products were produced during electron-beam irradiation, even at the lower absorbed doses of 5 and 10 kGy (approved doses for food ‘cold pasteurization’). The quantity of Radiolysis products increased with irradiation dose. There were no significant differences in Radiolysis products identified between samples containing a recycled layer of LDPE and those containing virgin LDPE (all absorbed doses), indicating the ‘functional barrier’ properties of external virgin polymer layers. Sensory properties (mainly taste) of...
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Radiolysis products and sensory properties of electron-beam irradiated high barrier food packaging films containing a buried layer of recycled low density polyethylene
Food Additives and Contaminants, 2010Co-Authors: Stavroula Chytiri, Kyriakos A Riganakos, Anastasia V Badeka, Michael G. KontominasAbstract:The aim of the present work was to study the effect of electron-beam irradiation on the production of Radiolysis products and sensory changes in experimental high barrier packaging films composed of polyamide (PA), ethylene–vinyl alcohol (EVOH) and low density polyethylene (LDPE). Films contained a middle buried layer of recycled low density polyethylene (LDPE), while films containing 100% virgin LDPE as the middle buried layer were taken as controls. Irradiation doses ranged between 0 and 60 kGy. Generally, a large number of Radiolysis products were produced during e-beam irradiation even at the lower absorbed doses of 5 and 10 kGy (approved doses for food “cold pasteurization”). Amount of Radiolysis products increased with irradiation dose. There were no significant differences in Radiolysis products identified between samples containing a recycled layer of LDPE and those containing virgin LDPE (all absorbed doses), indicating the “functional barrier” properties of external virgin polymer layers. Sensory properties (mainly taste) of potable water were affected after contact with irradiated as low as 5 kGy packaging films. This effect increased with increasing irradiation dose.
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Radiolysis products and sensory properties of electron-beam-irradiated high-barrier food-packaging films containing a buried layer of recycled low-density polyethylene.
Food Additives and Contaminants Part A-chemistry Analysis Control Exposure & Risk Assessment, 2010Co-Authors: Stavroula Chytiri, Kyriakos A Riganakos, Anastasia V Badeka, Michael G. KontominasAbstract:The aim was to study the effect of electron-beam irradiation on the production of Radiolysis products and sensory changes in experimental high-barrier packaging films composed of polyamide (PA), ethylene-vinyl alcohol (EVOH) and low-density polyethylene (LDPE). Films contained a middle buried layer of recycled LDPE, while films containing 100% virgin LDPE as the middle buried layer were taken as controls. Irradiation doses ranged between zero and 60 kGy. Generally, a large number of Radiolysis products were produced during electron-beam irradiation, even at the lower absorbed doses of 5 and 10 kGy (approved doses for food 'cold pasteurization'). The quantity of Radiolysis products increased with irradiation dose. There were no significant differences in Radiolysis products identified between samples containing a recycled layer of LDPE and those containing virgin LDPE (all absorbed doses), indicating the 'functional barrier' properties of external virgin polymer layers. Sensory properties (mainly taste) of potable water were affected after contact with irradiated as low as 5 kGy packaging films. This effect increased with increasing irradiation dose.
