Journal articles: 'Free radicals in solution'

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Espenson, James H. "Organometallic free radicals in solution." Journal of Molecular Liquids 65-66 (November 1995): 205–12. http://dx.doi.org/10.1016/0167-7322(95)00853-1.

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Grampp, G., S. Landgraf, K. Rasmussen, and S. Strauss. "Dimerization of organic free radicals in solution." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 58, no. 6 (April 2002): 1219–26. http://dx.doi.org/10.1016/s1386-1425(01)00712-0.

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Chen, X., and C. N. Gillis. "Effect of free radicals on pulmonary vascular response to acetylcholine." Journal of Applied Physiology 71, no. 3 (September 1, 1991): 821–25. http://dx.doi.org/10.1152/jappl.1991.71.3.821.

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We describe a model of pulmonary endothelial injury caused by electrolysis-generated free radicals. Rabbit lungs were perfused in situ with Krebs solution at 37 degrees C containing 30 microM indomethacin. Electrolysis of this solution for 2 min, with a constant DC current of 20 mA, caused pulmonary vasoconstriction during the passage of current and converted subsequent acetylcholine-induced vasodilation to vasoconstriction. Electrolysis also inhibited endothelial-dependent vasodilation due to the calcium ionophore A23187 but not that due to sodium nitroprusside, suggesting that smooth muscle function was unaltered, while that of the endothelium of the lung is specifically modified by the stimulus. These effects were prevented by a mixture of superoxide dismutase and catalase or by sodium salicylate, which removes hydroxyl radicals from solution after electrolysis. Electrolysis-induced endothelial damage was less functionally obvious when electrolysis was applied during recirculation of Krebs solution, perhaps because recirculating perfusion may trigger release of either free radical scavengers or other protective substances. This technique offers a simple reproducible model to study free radical-related damage of endothelium in the intact lung.

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Wosiński, Stanisław, Jan Jurga, Zdzisław Kruczyński, Romuald Górski, Krzysztof Sobieralski, and Marek Siwulski. "An Esr Study of Free Radicals Scavenging by Red Tea." Ecological Chemistry and Engineering S 19, no. 1 (January 1, 2012): 47–54. http://dx.doi.org/10.2478/v10216-011-0005-z.

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An Esr Study of Free Radicals Scavenging by Red Tea Herbal tea is known to exhibit the scavenging of free radicals responsible for cellular damage. We studied the effect of water treated with reverse osmotic filter equipped with a special dielectric ceramic composite on the antioxidant activity of red tea. Methanol solution of DPPH was added to the tea extract and the RT decay of DPPH free radicals was studied by ESR spectroscopy. Red tea brewed from tap water treated with the composite filter was found to exhibit higher radical scavenging efficiency in comparison with that of the tea brewed from tap water, mineral water and reverse osmosis water.

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Das, Suresh, and Clemens von Sonntag. "The Oxidation of Trimethylamine by OH Radicals in Aqueous Solution, as Studied by Pulse Radiolysis, ESR, and Product Analysis. The Reactions of the Alkylamine Radical Cation, the Aminoalkyl Radical, and the Protonated Aminoalkyl Radical." Zeitschrift für Naturforschung B 41, no. 4 (April 1, 1986): 505–13. http://dx.doi.org/10.1515/znb-1986-0418.

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Hydroxyl radical reactions with trimethylamine in aqueous solution lead to the formation of the aminoalkyl radical (CH3)2NCH2 (A) and its conjugated acid (CH3)2HN+CH2 (AH+) as well as to the alkylamine radical cation (CH3)3N+(N+). These radicals are transform ed into each other by hydrolytic reactions, e.g.[xxx]Radicals AH+ are more acidic (pKa ≈ 3.6) than the radicals N+(pKa ≈ 8.0). Consequently, N+ predom inate over AH+ under quasi equilibrium conditions (e.g. in the presence of phosphate buffer) and are the only species observed by ESR in acid solutions. Reacting with the protonated amine. OH radicals abstract hydrogen at nitrogen and at carbon with comparable ease. Reaction of OH radicals with the free amine may initially also generate N+, beside H-abstraction at carbon. Radicals A’ absorb more strongly at 260 nm (ε = 3390 dm3mol-1cm-1) than the radical cation N+(ε = 950 dm3mol-1cm-1). Radical A' has reducing properties whereas radicals AH+ and N+ have oxidizing properties and hence can be monitored with p-nitroacetophenone (the reducing radicals), and Fe(CN)64- , N ,N'-tetramethyl-p-phenylenediamine and 2,2'-azinobis-(3-ethyl-benzthiazoline- 6-sulphonate) (the oxidizing radicals). These radicals mainly (≥ 85 % ) disproportionate. one of the products being formaldehyde

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Cai, Yu-Jun, Jin-Qiu Dai, Jian-Guo Fang, Lan-Ping Ma, Li-Fen Hou, Li Yang, and Zhong-Li Liu. "Antioxidative and free radical scavenging effects of ecdysteroids from Serratula strangulata." Canadian Journal of Physiology and Pharmacology 80, no. 12 (December 1, 2002): 1187–94. http://dx.doi.org/10.1139/y02-152.

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The antioxidative and free radical scavenging effects of four ecdysteroids, 20-hydroxyecdysone (E1), 25-deoxy-11,20-dihydroxyecdysone (E2), 24-(2-hydroxyethyl)-20-hydroxyecdysone (E3), and 20-hydroxyecdysone-20,22-monoacetonide (E4), isolated from the Chinese herbSerratula strangulata have been investigated in vitro. These ecdysteroids could protect human erythrocytes against oxidative hemolysis induced by a water-soluble azo initiator 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH). They could also inhibit the peroxidation of rat liver microsomes induced by hydroxyl radicals, as monitored by the formation of thiobarbituric acid reactive substances (TBARS), and prevent radical-induced decrease of membrane fluidity as determined by fluorescence polarization. They reacted with galvinoxyl radicals in homogeneous solution, and the pseudo-first-order rate constants were determined spectrophotometrically by following the disappearance of galvinoxyl radicals. Compounds E1 and (or) E3 were the most active in both antioxidative and radical-scavenging reactions.Key words: ecdysteroid, Serratula strangulata, free radical, erythrocyte, lipid peroxidation, antioxidant.

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Tkáč, Alexander, and Eva Hanušovská. "Reactivity of Free Radicals Generated from Neurotransmitters Studied by Electron Spin Resonance Spectroscopy." Collection of Czechoslovak Chemical Communications 69, no. 11 (2004): 2081–90. http://dx.doi.org/10.1135/cccc20042081.

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Free phenoxy radicals derived from catecholamine-type neurotransmitters (dopamine, noradrenaline, adrenaline) σ-coordinated to Co(III) chelates were generated by the reaction of π-coordinated tert-butylperoxy radicals with the neurotransmitters in non-polar solvent at ambient temperature. The ESR signals of the formed complexes are split into the basic octet line resulting from the interaction of the unpaired electron of the phenoxy radical with the 59Co nucleus (I = 7/2). Increasing the polarity of the solution starts the decomplexation and the liberated phenoxy radicals of the neurotransmitters disappear by recombination or by H-abstraction from the added antioxidant. When vitamin E is added to the system, only the ESR signal of the stable α-tocopheroxy radicals is detectable. Similarly, in the presence of the antiarrhytmic drug Stobadine, only the signal of the corresponding nitrogen-centred radical is seen. In the presence of both antioxidants, rapid H-transfer occurs from vitamin E to the Stobadine radicals.

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Ishizaka, Shin-ichi, and Masahiro Kotani. "Laser emission from transient organic free radicals in solution." Chemical Physics Letters 117, no. 3 (June 1985): 251–53. http://dx.doi.org/10.1016/0009-2614(85)80214-1.

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Dewaantari, Virdah Dwi, Setyabudi Setyabudi, and Kun Ismiyatin. "Antioxidant Potential of Epigallocatechin-3-gallate, Ascorbic Acid, and Sodium Ascorbate in Solution and Gel Forms by 2,2-diphenyl-1-picrylhydrazyl (DPPH) Assay." Conservative Dentistry Journal 11, no. 1 (June 30, 2021): 19. http://dx.doi.org/10.20473/cdj.v11i1.2021.19-23.

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Background: Free radicals are molecules without any electron pairs, unstable, and highly reactive. Antioxidants are needed to reduce free radicals. Antioxidants provide various benefits in dentistry as a preventive agent for caries, healing, bone formation, mouthwash, preventive and therapeutic cancer, and reduction of periodontal disease progressions. Additionally, research on antioxidants is still undergone due to the existence of free radical residues on bleached teeth. Epigallocatechin-3-gallate (EGCG), ascorbic acid (AA), and sodium ascorbate (SA) are ingridients that have antioxidant properties. Antioxidants can be in two forms solution and gel. Solutions have a higher substance releasing power than gel. Gel is extremely adhesive, so it does not flow easily. Meanwhile, solutions are rather unstable because it flows easily. Antioxidant activities were evaluated with 2,2-diphenyl-1-picrylhydrazyl (DPPH) Assay method. Purpose: Analyzing through literature reviews the potential antioxidants of EGCG, AA, and SA in solution and gel forms by DPPH Assay. Reviews: There were eight journal articles used in this review. The first article described antioxidant solutions in which EGCG was higher than sodium ascorbate. The second article showed that antioxidant gel EGCG was lower than sodium ascorbate. The third journal explained that ascorbic acid was higher than sodium ascorbate both in solution and gel forms. The other articles provided some information about the antioxidant activity percentages of EGCG, SA, and AA in the forms of gel and solutions by DPPH assay. Conclusion: EGCG has a higher antioxidant activity than SA, but it is lower when compared to AA in both solution and gel forms by DPPH assay.

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Aǧirbaş, Hikmet, and Richard A. Jackson. "Free radicals in solution. Part 10. The thermal decomposition of benzylphenylmercury in solution." J. Chem. Soc., Perkin Trans. 2, no. 3 (1987): 413–14. http://dx.doi.org/10.1039/p29870000413.

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Elliot, A. John, Shahsultan Padamshi, and Jana Pika. "Free-radical redox reactions of uranium ions in sulphuric acid solutions." Canadian Journal of Chemistry 64, no. 2 (February 1, 1986): 314–20. http://dx.doi.org/10.1139/v86-053.

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The radiolytic reduction of uranyl ions in degassed sulphuric acid solutions containing various organic solutes was studied. It was shown that while ĊOOH, CO2−, and α-hydroxy-alkyl radicals reduced uranyl ions, the β-hydroxy-alkyl radicals and those derived from gluconic acid could not affect the reduction. The oxidation of uranium(IV) by hydrogen peroxide at pH 0.7 involves hydroxyl radicals in a chain mechanism but at pH 2.0 the oxidation proceeds by a non-radical reaction pathway. From the enhancement of the rate of oxidation of uranium(IV) by oxygen in the presence of 2-propanol, a mechanism involving the perhydroxyl radical, which reconciles earlier published data on kinetics and oxygen tracer studies, is proposed for the oxygen-uranium(IV) reactions.

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12

Donkers, Robert L., and Derek G. Leaist. "Diffusion of Free Radicals in Solution. TEMPO, Diphenylpicrylhydrazyl, and Nitrosodisulfonate." Journal of Physical Chemistry B 101, no. 3 (January 1997): 304–8. http://dx.doi.org/10.1021/jp961957k.

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13

McLauchlan, K. A. "The detection and identification of transient free radicals in solution." Applied Magnetic Resonance 11, no. 3-4 (November 1996): 357–73. http://dx.doi.org/10.1007/bf03162233.

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14

Mahar, Z. A., G. Q. Shar, and A. R. Shaikh. "FREE RADICAL SCAVENGING POTENCY OF FIVE DATE PALM (PHOENIX DACTYLIFERA L.) FRUIT VARIETIES CULTIVATED IN KHAIRPUR MIR’S." Pakistan Journal of Agriculture, Agricultural Engineering and Veterinary Sciences 36, no. 2 (February 11, 2021): 101–5. http://dx.doi.org/10.47432/2020.36.2.3.

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The fruit of date palm (Phoenix dactylifera L.) is well-known for its several health blessings and dietary values and its wonderful supply of phenolics compounds and holds relatively exquisite antioxidant capacity. Therefore, the goal of this study is to investigate the free radical scavenging efficiency of the five-date types Aseel, Kupro, Karbala Wari, Asul Khurmo and Gajar Wari cultivated in district Khairpur Mir’s. These date varieties were screened with the help of DPPH assay to evaluate their free radical scavenging efficiency in different solvents. From the statistics, it turned into scrutinize that each extract has interesting antioxidant functionality against free radicals. The methanolic extract has more potential to incline the free radicals. It was concluded that the date variety Asul Khumro is shown excellent activity because it possesses lowest IC50 value 17.823µg/mL, followed by Gajar Wari 20.679 µg/mL in methanolic solution while Kupro 20.937µg/mL in Methanol + Water solution then relaxation of different date varieties at their mature Tamar level. It is concluded from the results that all dates fruit varieties at their final mature stage holds higher antioxidant potency and indicated that these date fruits have natural antioxidants.

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Vannier, Luc A., Chunxiang Yao, and František Tureček. "2-Deoxyribose Radicals in the Gas Phase and Aqueous Solution. Transient Intermediates of Hydrogen Atom Abstraction from 2-Deoxyribofuranose." Collection of Czechoslovak Chemical Communications 70, no. 11 (2005): 1769–86. http://dx.doi.org/10.1135/cccc20051769.

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A computational study at correlated levels of theory is reported to address the structures and energetics of transient radicals produced by hydrogen atom abstraction from C-1, C-2, C-3, C-4, C-5, O-1, O-3, and O-5 positions in 2-deoxyribofuranose in the gas phase and in aqueous solution. In general, the carbon-centered radicals are found to be thermodynamically and kinetically more stable than the oxygen-centered ones. The most stable gas-phase radical, 2-deoxyribofuranos-5-yl (5), is produced by H-atom abstraction from C-5 and stabilized by an intramolecular hydrogen bond between the O-5 hydroxy group and O-1. The order of radical stabilities is altered in aqueous solution due to different solvation free energies. These prefer conformers that lack intramolecular hydrogen bonds and expose O-H bonds to the solvent. Carbon-centered deoxyribose radicals can undergo competitive dissociations by loss of H atoms, OH radical, or by ring cleavages that all require threshold dissociation or transition state energies >100 kJ mol-1. This points to largely non-specific dissociations of 2-deoxyribose radicals when produced by exothermic hydrogen atom abstraction from the saccharide molecule. Oxygen-centered 2-deoxyribose radicals show only marginal thermodynamic and kinetic stability and are expected to readily fragment upon formation.

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Metreveli, N., L. Namicheishvili, K. Jariashvili, G. Mrevlishvili, and A. Sionkowska. "Mechanisms of the influence of UV irradiation on collagen and collagen-ascorbic acid solutions." International Journal of Photoenergy 2006 (2006): 1–4. http://dx.doi.org/10.1155/ijp/2006/76830.

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The study of the influence of UV irradiation on collagen solutions has shown the destabilization of the collagen molecule by calorimetric method. It is reflected both in changes of thermodynamic parameters of transition (Tm,ΔH,Cp=f(t)) and in the appearance of a low temperature peak, that is practically irreversible against rescanning. All these indicate that the important defects in the molecule occur. The ESR measurements have shown that the above-mentioned thermal changes are connected with the occurrence of free radicals in solution under UV irradiation. They interact with proline (Pro) residues of the protein with the appearance of secondary free radicals, with following migration to glycine (Gly) residues. The emergence of the free radicals at the Pro and then at the Gly residues may cause the dramatic structural defect resulting from the UV irradiation, which significantly alters the network of hydrogen bonds in the triple helix of the collagen molecule. All this is connected with destabilization of the collagen molecule, because the defects in amino acid residues probably lead to cleavage of covalent bonds near the damaged sites maintaining the triple helical structure. The presence of ascorbic acid in collagen solution protects the collagen molecule from occurring of secondary free radicals.

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Krilov, Dubravka, Greta Pifat, and Janko N. Herak. "Electron spin resonance spin-trapping study of peroxidation of human low density lipoprotein." Canadian Journal of Chemistry 66, no. 8 (August 1, 1988): 1957–60. http://dx.doi.org/10.1139/v88-315.

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The electron spin resonance spin-trapping method has been used for detection of radicals in human low density lipoprotein (LDL) solution saturated with oxygen. The trapped radicals could be detected after about a day in an antioxidant-free solution. Two types of radicals are formed and stabilized in the lipid domain of LDL. The nature of the trapped radicals remains unclear:kinetic considerations suggest the trapped radicals to be of the LO- type, while the spectroscopic parameters are in favour of L- type radicals.

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MCLAUCHLAN, K. A. "ChemInform Abstract: Detection and Identification of Transient Free Radicals in Solution." ChemInform 28, no. 28 (August 3, 2010): no. http://dx.doi.org/10.1002/chin.199728292.

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Khachatryan, Lavrent, and Barry Dellinger. "Environmentally Persistent Free Radicals (EPFRs)-2. Are Free Hydroxyl Radicals Generated in Aqueous Solutions?" Environmental Science & Technology 45, no. 21 (November 2011): 9232–39. http://dx.doi.org/10.1021/es201702q.

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Khachatryan, Lavrent, Cheri McFerrin, and Barry Dellinger. "Free vs. Bound Hydroxyl Radicals Generated by Environmentally Persistent Free Radicals in Aqueous Solutions." Free Radical Biology and Medicine 53 (November 2012): S149. http://dx.doi.org/10.1016/j.freeradbiomed.2012.10.404.

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Valcheva-Traykova, Maria L., Trayko T. Traykov, and Georgeta S. Bocheva. "Interaction Of Propylthiouracil With Model Systems Generating A Superoxide Radical." Journal of Biomedical and Clinical Research 7, no. 2 (December 1, 2014): 93–98. http://dx.doi.org/10.1515/jbcr-2015-0132.

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SummaryPropylthiouracil is used against Grave's Disease and for developing animal models of hypothyroidism. Apart from depressed metabolism, free radical-induced tissue damage has been registered as an effect from this drug. Superoxide is essential for generation of free radicals in tissues. The mutual effects of Propylthiouracil and superoxide radical have not been well investigated.Thein vitroeffects of Propylthiouracil on the free radicals in three model systems generating superoxide were measured using luminol-dependent chemiluminescence and spectrophotometry. The drug did not affect the formation of free radicals in the presence of potassium superoxide and in pyrogallol-oxygen solutions, while in the presence of the xanthine/xanthine oxidase system a distinct prooxidant effect was registered. The investigation of the system propylthiouracil/xanthine oxidase showed mild free radicals formation along with decreasing intensities of the drug's UV-specter.Ourin vitroinvestigation indicated that, along with the transformation of xanthine to uric acid over xanthine oxidase, some free radicals may be produced due to the interaction of propylthiouracil with the enzyme. It was proposed that this might contribute to thein vivofree radicals-induced tissue damage observed in the presence of propylthiouracil.

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Zhang, Hong, Gui Gan Fang, Hua Zheng, Yuan Heng Guo, and Kun Li. "Study on the Antioxidation of Lac Dye." Applied Mechanics and Materials 140 (November 2011): 451–58. http://dx.doi.org/10.4028/www.scientific.net/amm.140.451.

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To investigate the in vitro antioxidation and antimicrobial activity of the lac dye, in this study, three free radicals DPPH·, ABTS+and O2ˉ· are used as the test objects to evaluate the free radial scavenging ability of the lac dye by comparing the absorbance change of free radical solution under specific wavelength. The results showed that, the lac dye has scavenging activity on DPPH· and ABTS+, but has no scavenging activity on O2ˉ·; when the lac dye reached a certain concentration, its scavenging rate on DPPH· and ABTS+can be as high as 68% and 87% respectively, with the antioxidant activity respectively 0.20 times and 3.42 times of that of the ascorbic acid, indicating that the lac dye is a kind of natural pigment of a certain scavenging activity on free radicals.

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Tri Putri, Deby Kania, Beta Widya Oktiani, Candra Candra, and Rosihan Adhani. "ANTIOXIDANT ACTIVITY POTENCY OF CHITOSAN FROM HARUAN (CHANNA STRIATA) SCALES." Dentino : Jurnal Kedokteran Gigi 5, no. 2 (August 15, 2020): 139. http://dx.doi.org/10.20527/dentino.v5i2.8951.

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ABSTRACTBackground: Stimulation of inflammatory cells such as polymorphonuclear cells (PMN) will initiate to release free radicals in destroying bacteria. Excessive free radicals can damage cells in the body. Antioxidants as one of the body's defense systems will neutralize existing free radicals. Chitosan from Haruan scales in addition to being antimicrobial turned out to also be antioxidants. Objective: To know the antioxidant potential of chitosan from haruan (Channa striata) scales. Methods: This study is a pure experimental (true experimental design) with a post-test only with control group design using two treatment groups, with quantitative tests to calculate the amount of antioxidant activity of chitosan from fish scales using DPPH radical reduction method. The first treatment is 4, 6, 8 and 10 ppm standard ascorbic acid concentration with DPPH solution as positive control, and the second treatment is 200, 250, 300 and 350 ppm chitosan from Haruan scales concentration with DPPH solution. Results: The results showed that chitosan from Haruan fish scales have antioxidant activity with 50.513% percentage of inhibition at a maximum concentration of 350 ppm with an IC50 value of 356.98 ppm. The results of the independent T-test showed that there was a significant difference between the inhibition percentage of chitosan from haruan fish scales and the inhibition percentage of ascorbic acid (p = 0,000) (p <0.05). Conclusion: Chitosan from Haruan fish scales proved to have antioxidant activity.Keywords: Antioxidants, Chitosan, Haruan fish scalesABSTRACTBackground: Stimulation of inflammatory cells such as polymorphonuclear cells (PMN) will initiate to release free radicals in destroying bacteria. Excessive free radicals can damage cells in the body. Antioxidants as one of the body's defense systems will neutralize existing free radicals. Chitosan from Haruan scales in addition to being antimicrobial turned out to also be antioxidants. Objective: To know the antioxidant potential of chitosan from haruan (Channa striata) scales. Methods: This study is a pure experimental (true experimental design) with a post-test only with control group design using two treatment groups, with quantitative tests to calculate the amount of antioxidant activity of chitosan from fish scales using DPPH radical reduction method. The first treatment is 4, 6, 8 and 10 ppm standard ascorbic acid concentration with DPPH solution as positive control, and the second treatment is 200, 250, 300 and 350 ppm chitosan from Haruan scales concentration with DPPH solution. Results: The results showed that chitosan from Haruan fish scales have antioxidant activity with 50.513% percentage of inhibition at a maximum concentration of 350 ppm with an IC50 value of 356.98 ppm. The results of the independent T-test showed that there was a significant difference between the inhibition percentage of chitosan from haruan fish scales and the inhibition percentage of ascorbic acid (p = 0,000) (p <0.05). Conclusion: Chitosan from Haruan fish scales proved to have antioxidant activity. Keywords: Antioxidants, Chitosan, Haruan fish scales.

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Zhang, X. Z., R. C. Francis, D. B. Dutton, and R. T. Hill. "Article." Canadian Journal of Chemistry 76, no. 7 (July 1, 1998): 1064–69. http://dx.doi.org/10.1139/v98-103.

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Peracetic acid (Pa) is now being used for totally chlorine-free delignification and bleaching of wood pulps. During the process, metals desorb from the pulp fibers into the aqueous solution. Of the relevant metals in bleaching systems, cobalt(II) and vanadium(V) are the most potent in wastefully decomposing Pa to O2. In the present study, radical scavenging by N,N'-(5-nitro-1,3-phenylene)-bisglutaramide (GAMID) indicates that free-radical mechanisms are operative. Kinetic data support a free-radical decomposition mechanism previously described for Co(II). A similar type of mechanism, involving VO(OH)2(aq) and VO(OH)3(aq), is postulated to partially explain catalysis by vanadium.Key words: peracetic acid, peroxymonosulfuric acid, transition metals, free radicals, acetoxy radical, peracetoxy radical.

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Kelarev, A. V. "On the Jacobson radical of semigroup rings of commutative semigroups." Mathematical Proceedings of the Cambridge Philosophical Society 108, no. 3 (November 1990): 429–33. http://dx.doi.org/10.1017/s0305004100069322.

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Many authors have considered the radicals of semigroup rings of commutative semigroups. A list of the papers pertaining to this field is contained in [4]. In [1] Amitsur proved that, for any associative ring R and for every free commutative semigroup S, the equalities B(RS) = B(R)S and L(RS) = L(R)S hold, where B is the Baer radical and L is the Levitsky radical. A natural problem which arises is to describe semigroup rings RS such that π(RS) = π(R)S, where π is one of the most important radicals. For the Baer and Levitsky radicals and commutative semigroups a complete solution of the above problem follows from theorems 2·8 and 3·1 of [15].

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Lankin, V. Z., O. I. Shadyro, K. B. Shumaev, K. B. Shumaev, A. K. Tikhaze, and A. A. Sladkova. "Non-Enzymatic Methylglyoxal Formation From glucose Metabolites and Generation of Superoxide Anion Radical During Methylglyoxal-Dependent Cross-Links Reaction." Journal of Antioxidant Activity 1, no. 4 (September 25, 2019): 33–45. http://dx.doi.org/10.14302/issn.2471-2140.jaa-19-2997.

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The paper explores the formation of a-oxoaldehydes during the interaction of glucose metabolites with hydroxyl or alkoxyl radicals. Hydroxyl radicals were generated under radiolysis of aqueous solutions, and alkoxyl radicals (t-BuO) were obtained in the model system tert-butyl hydroperoxide/Fe2+. High-performance liquid chromatography revealed that methylglyoxal was one of the organic products resulting from t-BuO-induced transformations of fructose-1,6-bisphosphate under hypoxic conditions. The interaction of lysine and methylglyoxal one of the main targets of a-oxoaldehydes in proteins was also studied. As chemiluminescence and EPR spectroscopy demonstrated, this reaction generates a methylglyoxal anion radical, a cation-radical of methylglyoxal dialkylamine and a superoxide anion radical. EPR signal of methylglyoxal-derived free radicals was observed in hypoxia, whereas only the trace amounts of these free radicals were recorded in the aerated reaction medium.

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Venkateswaran, Krishnan, Mary V. Barnabas, Zhennan Wu, and David C. Walker. "Loss of muonium in nonhomogeneous processes studied by level-crossing resonance." Canadian Journal of Physics 68, no. 9 (September 1, 1990): 957–61. http://dx.doi.org/10.1139/p90-136.

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Level-crossing resonance spectroscopy has been used to determine the yield of muonium atoms formed in water and in hexane through production of muonated free radicals. In the presence of high concentrations of solutes, which yield radicals, all muons injected into the solutions are found either in diamagnetic molecules or free radicals. However, at low concentrations, the free-radical yield was smaller and a "missing fraction" appeared. Inverse yield against inverse concentration plots were not linear, indicating that reactions leading to loss occurred with nonhomogeneously distributed species from the muon's expanding track.

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Autsavapromporn, Narongchai, Jintana Meesungnoen, Ianik Plante, and Jean-Paul Jay-Gerin. "Monte Carlo simulation study of the effects of acidity and LET on the primary free-radical and molecular yields of water radiolysis — Application to the Fricke dosimeter." Canadian Journal of Chemistry 85, no. 3 (March 1, 2007): 214–29. http://dx.doi.org/10.1139/v07-021.

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Monte Carlo simulations are used to investigate the effects of acidity (pH) on the primary yields of various chemical species produced in the radiolysis of de-aerated aqueous sulfuric acid solutions over the range from neutral solution to 0.4 mol/L H2SO4. The effects of the quality of radiation, measured in terms of linear energy transfer (LET), have also been studied for LET varying from ~0.3 to 15 keV/µm at ambient temperature. Our results show that an increase in acidity (1 < pH < 4) leads to an increase in the yield [Formula: see text] of the "reducing" free radicals (hydrated electron and H atom) and a slight increase in G·OH and [Formula: see text], while there is a slight decrease in [Formula: see text] At pH < 1, OH radicals react with HSO4- anions to form SO4·– radicals, resulting in a steep decrease in G.OH. By contrast, in the range of pH from ~4 to 7, the calculated yield values are independent of sulfuric acid concentration. In both neutral water and 0.4 mol/L H2SO4 (pH 0.46) solutions, the primary molecular yields increase upon increasing LET to ~15 keV/µm with a concomitant decrease in those of free radicals. As an exception, GH. at first increases with LET, reaching a maximum near 6.5 keV/µm before decreasing steeply at higher LET. The results obtained are generally in good agreement with available experimental data over the whole acidity and LET ranges studied. Finally, as an application, we have simulated the radiation-induced oxidation of ferrous sulfate solutions in aerated aq. 0.4 mol/L H2SO4 (Fricke dosimeter) as a function of time up to ~50 s and addressed the effects of LET on the resulting ferric ion yield at 25 °C. The production of Fe3+ ions is highly sensitive to free-radical yields, especially H atoms (via formation of HO2), resulting in a marked decline of G(Fe3+) with increasing LET. The general trend of the observed variation of G(Fe3+) with radiation quality is well reproduced by our computed Fe3+ ion yield values.Key words: liquid water, acidic (H2SO4) aqueous solutions, radiolysis, free-radical and molecular yields, linear energy transfer (LET), Fricke dosimeter, Monte Carlo simulations.

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29

Yi, Chunlin, Lihong Song, Qingfeng Wu, Zhaohui Li, Weibin Zhang, and Ke Yin. "Enhanced photodegradation of diphenhydramine in aqueous solution containing natural sand particles." RSC Advances 10, no. 29 (2020): 17228–34. http://dx.doi.org/10.1039/d0ra02019b.

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30

Khachatryan, Lavrent, Cheri A. McFerrin, Randall W. Hall, and Barry Dellinger. "Environmentally Persistent Free Radicals (EPFRs). 3. Free versus Bound Hydroxyl Radicals in EPFR Aqueous Solutions." Environmental Science & Technology 48, no. 16 (July 29, 2014): 9220–26. http://dx.doi.org/10.1021/es501158r.

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31

Daval, Jean-Luc, Jean-François Ghersi-Egea, Jean Oillet, and Violette Koziel. "A Simple Method for Evaluation of Superoxide Radical Production in Neural Cells under Various Culture Conditions: Application to Hypoxia." Journal of Cerebral Blood Flow & Metabolism 15, no. 1 (January 1995): 71–77. http://dx.doi.org/10.1038/jcbfm.1995.8.

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To evaluate the potential deleterious influence of oxygen-derived free radicals following hypoxia in a model of primary culture of neurons obtained from the fetal rat brain, superoxide radicals were measured as a function of time in the extracellular medium. Neuronal cells were grown for 8 days in the presence or absence of serum, then incubated in a buffered Krebs–Ringer solution containing 60 μ M acetyl-cytochrome c. The rate of superoxide radical formation was quantified spectrophotometrically by measuring the specific reduction of acetyl-cytochrome c. Under normoxic conditions (95% air-5% CO2), basal production of superoxide that increased with time was recorded. It was significantly more pronounced in cells grown in serum-free medium. Under both culture conditions, acute hypoxia (95% N2–5% CO2) for 6 h increased superoxide radical amounts in the extracellular medium, and they were still enhanced 3 h after reoxygenation. The addition of superoxide dismutase to the incubating medium abolished the detection of superoxide radicals. The present study describes a new reliable method for superoxide radical measurement in cells in vitro and demonstrates hypoxia/reoxygenation-induced overproduction of superoxide in cultured neurons that may account for cell injury.

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32

Venkateshwaran, G., and Anil Kumar. "Solution of free radical polymerization." Journal of Applied Polymer Science 45, no. 2 (May 15, 1992): 187–215. http://dx.doi.org/10.1002/app.1992.070450201.

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33

Chamine, Ramez, Mircea Alexandru Mateescu, Stéphane Roger, Nobuharu Yamaguchi, Jacques de Champlain, and Réginald Nadeau. "Protective effects of ceruloplasmin against electrolysis-induced oxygen free radicals in rat heart." Canadian Journal of Physiology and Pharmacology 69, no. 10 (October 1, 1991): 1459–64. http://dx.doi.org/10.1139/y91-218.

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The potentially injurious effects of oxygen-derived free radicals (OFR) on the myocardium can be prevented in part by pretreatment with OFR scavengers or antioxidants. Since ceruloplasmin (CP) has been shown to possess potent antioxidant activity and scavenge a variety of OFR in vitro, we have undertaken to study its protective effects against myocardial injury induced by OFR. CP was freshly purified by a fast method that minimized proteolytic enzyme degradation. Free radicals were generated by the electrolysis (10 mA DC current for 1 min) of a Krebs–Henseleit solution perfusing an isolated rat heart preparation under constant pressure conditions. CP (0.25 μM) afforded 80 and 63% protection (n = 8, p < 0.05), respectively, against the deleterious effects of electrolysis-induced OFR on left ventricular pressure and coronary flow. The increase in left ventricular end diastolic pressure used here as an index of heart failure did not occur in the presence of 0.25 μM CP. Moreover, CP significantly reduced the increase of norepinephrine washout in the effluent perfusate after electrolysis suggesting a protection against free radical-induced injury to sympathetic nerve endings.Key words: oxygen free radicals, heart, ceruloplasmin, superoxide dismutase, norepinephrine.

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34

Jewell, Deborah Rae, Lukose Mathew, and John Warkentin. "Rate constant for chlorine abstraction from CCl4 by the 5-hexenyl radical." Canadian Journal of Chemistry 65, no. 2 (February 1, 1987): 311–15. http://dx.doi.org/10.1139/v87-052.

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Cyclization of the 5-hexenyl free radical to the cyclopentylmethyl free radical was used to clock chlorine atom abstraction by 5-hexenyl from carbon tetrachloride in solution. The source of 5-hexenyl radicals was 5-hexenyl[1-hydroxy-1-methyl-ethyl]diazene ((CH3)2C(OH)N=N(CH2)4CH=CH2), which decomposes thermally in CCl4 by a radical chain mechanism to afford chloroform, acetone, nitrogen, 6-chloro-1-hexene, cyclopentylchloromethane, 1-hexene, and methylcyclopentane as primary products. 6-Chloro-1-hexene is converted, in part, to a secondary product, 1,1,1,3,7-pentachloroheptane, by radical chain addition of CC14 to the double bond. The rate constant for chlorine atom abstraction, kCl, was calculated from the product composition and the known rate constant for cyclization of the 5-hexenyl radical. For the temperature range 274–353 K, kCl is given by log (kCl/M−1 s−1) = (8.4 ± 0.3) − (6.2 ± 0.4)/θ where θ = 2.3 RT kcal mol−1, which leads to [Formula: see text]. This value is significantly smaller than recently reported estimates for other primary alkyl radicals.

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35

Nilsson, U. A., O. Lundgren, E. Haglind, and A. C. Bylund-Fellenius. "Radical production during in vivo intestinal ischemia and reperfusion in the cat." American Journal of Physiology-Gastrointestinal and Liver Physiology 257, no. 3 (September 1, 1989): G409—G414. http://dx.doi.org/10.1152/ajpgi.1989.257.3.g409.

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Free radical formation was studied with electron spin resonance during 2 h of intestinal ischemia in the cat, at a blood flow less than 5 ml.min-1.100 g-1, followed by 30-min reperfusion. A modification of the spin trapping technique was used to stabilize highly reactive free radicals. The rate of secondary radical formation was 0.32 +/- 0.06 mumol.min-1.100 g intestine-1 before ischemia and increased to a maximum of 0.66 +/- 0.09 mumol.min-1.100 g-1 during the first minutes of reperfusion (mean +/- SE, n = 5). This could be prevented either by maintaining intestinal blood flow at 8-15 ml.min-1.100 g-1, by administering allopurinol before and during ischemia, or by perfusing the intestinal lumen with an O2-saturated buffer solution during ischemia, resulting in maximum rates of radical production during reperfusion of 0.37 +/- 0.04 (n = 6), 0.33 +/- 0.04 (n = 5), and 0.39 +/- 0.13 mumol.min-1.100 g-1 (n = 5), respectively. The results demonstrate that free radicals are produced in the intestine during reperfusion after a period of reduced blood flow below a certain critical level, and that inhibition of xanthine oxidase and prevention of hypoxia will eliminate this radical production.

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36

TAKAHASHI, Naohiro, and Ronald P. MASON. "Identification of Free Radicals Formed from Nitrodiphenyl Ethers by Irradiation in Solution." Journal of Pesticide Science 12, no. 4 (1987): 745–48. http://dx.doi.org/10.1584/jpestics.12.745.

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37

Wardman, Peter. "Reduction Potentials of One‐Electron Couples Involving Free Radicals in Aqueous Solution." Journal of Physical and Chemical Reference Data 18, no. 4 (October 1989): 1637–755. http://dx.doi.org/10.1063/1.555843.

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38

McLauchlan, Keith A. "Why can transient free radicals be observed in solution using ESR techniques?" Chemical Society Reviews 22, no. 5 (1993): 325. http://dx.doi.org/10.1039/cs9932200325.

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39

Okamoto, Koichi, Noboru Hirota, and Masahide Terazima. "Comments on “Diffusion of Free Radicals in Solution. TEMPO, Diphenylpicrylhydrazyl, and Nitrosodisulfonate”." Journal of Physical Chemistry A 101, no. 29 (July 1997): 5380–81. http://dx.doi.org/10.1021/jp971223n.

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40

Milovanović, Branislav, Jelica Ilić, Ivana M. Stanković, Milana Popara, Milena Petković, and Mihajlo Etinski. "A simulation of free radicals induced oxidation of dopamine in aqueous solution." Chemical Physics 524 (August 2019): 26–30. http://dx.doi.org/10.1016/j.chemphys.2019.05.001.

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41

Liu, Ya Na, Hui Tian, and An Heng Si. "Study on UV/O₃ of Methyl Violet Wastewater." Advanced Materials Research 518-523 (May 2012): 3208–11. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.3208.

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Ultraviolet ozone process was used to eliminate Methyl Violet, the effects of the type of research process, the initial solution pH, dye concentration and free radical quenching agent N-butanol on its degradation rate were studied. The experimental results showed that: comparing to UV, O3, UV/O3 three types of technology, UV and O3 technology had significant synergies, the degradation rate of Methyl Violet solution achieve 99.58% at 50min for the initial concentration of 100mg/L. increasing pH value resulted in increasing degradation rate, the degradation rate achieved 99. 8% at 50min under alkaline conditions. The remove rate decreased with increasing initial concentrations. Quenchers of free radicals inhibited the generation of hydroxyl radical and induced decreasing degradation rate. The degradation reaction of Methyl Violet by UV/O3 followed first-order law.

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42

Kawata, Hiroyuki, Masahiro Kohno, Kohei Nukina, Isanori Horiuchi, Hisataka Goda, Tomomi Kuwahara, Kosei Yoshimori, Akimitsu Miyaji, Toshiaki Kamachi, and Toshikazu Yoshikawa. "Identifying the chloroperoxyl radical in acidified sodium chlorite solution." PLOS ONE 16, no. 5 (May 26, 2021): e0252079. http://dx.doi.org/10.1371/journal.pone.0252079.

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The present study identified the active radical species in acidic sodium chlorite and investigated the feasibility of quantifying these species with the diethylphenylenediamine (DPD) method. Electron spin resonance (ESR) spectroscopy was used to identify the active species generated in solutions containing sodium chlorite (NaClO2). The ESR signal was directly observed in an acidified sodium chlorite (ASC) aqueous solution at room temperature. This ESR signal was very long-lived, indicating that the radical was thermodynamically stable. The ESR parameters of this signal did not coincide with previously reported values of the chlorine radical (Cl●) or chlorine dioxide radical (O = Cl●-O and O = Cl-O●). We refer to this signal as being from the chloroperoxyl radical (Cl-O-O●). Quantum chemical calculations revealed that the optimal structure of the chloroperoxyl radical is much more thermodynamically stable than that of the chlorine dioxide radical. The UV-visible spectrum of the chloroperoxyl radical showed maximum absorbance at 354 nm. This absorbance had a linear relationship with the chloroperoxyl radical ESR signal intensity. Quantifying the free chlorine concentration by the DPD method also revealed a linear relationship with the maximum absorbance at 354 nm, which in turn showed a linear relationship with the chloroperoxyl radical ESR signal intensity. These linear relationships suggest that the DPD method can quantify chloroperoxyl radicals, which this study considers to be the active species in ASC aqueous solution.

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43

Wolff, S. P., and R. T. Dean. "Fragmentation of proteins by free radicals and its effect on their susceptibility to enzymic hydrolysis." Biochemical Journal 234, no. 2 (March 1, 1986): 399–403. http://dx.doi.org/10.1042/bj2340399.

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Defined radical species generated radiolytically were allowed to attack proteins in solution. The hydroxyl radical (OH.) in the presence of O2 degraded bovine serum albumin (BSA) to specific fragments detectable by SDS/polyacrylamide-gel electrophoresis; fragmentation was not obvious when the products were analysed by h.p.l.c. In the absence of O2 the OH. cross-linked the protein with bonds stable to SDS and reducing conditions. The superoxide (O2-.) and hydroperoxyl (HO2.) radicals were virtually inactive in these respects, as were several other peroxyl radicals. Fragmentation and cross-linking could also be observed when a mixture of biosynthetically labelled cellular proteins was used as substrate. Carbonyl and amino groups were generated during the reaction of OH. with BSA in the presence of O2. Changes in fluorescence during OH. attack in the absence of O2 revealed both loss of tryptophan and changes in conformation during OH. attack in the presence of O2. Increased susceptibility to enzymic proteolysis was observed when BSA was attacked by most radical systems, with the sole exception of O2-.. The transition-metal cations Cu2+ and Fe3+, in the presence of H2O2, could also fragment BSA. The reactions were inhibited by EDTA, or by desferal and diethylenetriaminepenta-acetic acid (‘DETAPAC’) respectively. The increased susceptibility to enzymic hydrolysis of radical-damaged proteins may have biological significance.

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44

Blättler, C., F. Jent, and H. Paul. "A novel radical-triplet pair mechanism for chemically induced electron polarization (CIDEP) of free radicals in solution." Chemical Physics Letters 166, no. 4 (March 1990): 375–80. http://dx.doi.org/10.1016/0009-2614(90)85046-f.

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45

Rima, Jamil, Kamil Rahme, and Karrine Assaker. "Advanced Oxidation of Olive Mill Wastewater OMW by an Oxidative Free- Radical Process Induced With Zero Valent Iron." Journal of Food Research 3, no. 6 (August 7, 2014): 70. http://dx.doi.org/10.5539/jfr.v3n6p70.

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The degradation of olive mill wastewater (OMW) with hydroxyl radicals generated from zero-valent iron and hydrogen peroxide has been investigated by means of chemical oxygen demand (COD) and phenolic compounds analyses. The mechanism uses zero-valent iron activated by oxygen at room temperature to generate Hydroxyl-free radicals that subsequently oxidize organic constituents and clean wastewater. The effects of the iron mass, the pH and the organic matter concentration have been studied. Our experimental results demonstrate that the continuous presence of oxygen and iron in an acidic solution with a pH 2-4 allows the generation of maximum hydroxyl free radicals. The lack of oxygen prevents oxidative reaction, and then the generation of free radicals cannot occur. Coloration of OMW disappeared and phenolic compound decreased after 40 minutes of reaction time. The results show that Fe0/H+ /air or oxygen, could be considered as an effective alternative solution for the treatment of OMW.

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46

Mathew, Lukose, Emmanuel Y. Osei-Twum, and John Warkentin. "Thermolysis of α-hydroperoxyalkyl diazenes. Spin trapping of radical intermediates and spin trapping kinetics." Canadian Journal of Chemistry 69, no. 9 (September 1, 1991): 1398–402. http://dx.doi.org/10.1139/v91-206.

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α-Hydroperoxyalkyl diazenes (Me2C(OOH)N=NR, 1, R = CH2CF3, CH2CH2OMe, CH(Me)2, CMe3, CH2Ph, Ph, CH2CH2OPh, and c-C3H5CD2) decompose in benzene, at 50 °C or less, by a mechanism involving free radical (R•) intermediates. The radicals were trapped with 1-methyl-4-nitroso-3,5-diphenylpyrazole, 2, to afford spin adducts (nitroxyls) that were observed by ESR spectroscopy. When the solvent was ethyl vinyl ether, radicals from 1 (R = CH2CH2OPh) were trapped by the solvent and the adduct radicals so formed were spin trapped by 2. These observations support free radical mechanisms for thermolysis of 1 and for the hydroxyalkylations that occur when 1 are decomposed in solutions containing enol ethers or other unsaturated substrates. The ring-opening of cyclopropylmethyl radicals (cpm) to 3-butenyl radicals was used to estimate the rate constant for radical trapping by 2. For cpm the rate constant is given by log kcpm = (10.7 ± 0.4) − (3.9 ± 0.5)/θ where θ = 2.3 RT kcal mol−1. At 25 °C, the spin trapping rate constant has the value 6.9 × 107 M−1 s−1. Key words: hydroperoxyalkyl diazenes; radicals, spin trapping; spin trapping, rate constant.

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47

Rabaeh, Khalid, and Ahmed Basfar. "Optical evaluation of dithizone solution as a new radiochromic dosimeter." Pigment & Resin Technology 49, no. 4 (February 28, 2020): 249–53. http://dx.doi.org/10.1108/prt-10-2019-0091.

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Purpose The purpose of this paper is to propose a new dithizone solution dosimeter for high radiation applications such as polymers applications and food irradiation. Design/methodology/approach Gamma-rays cell of Co-60 source with 8.4 kGy/h dose rate was used to irradiate the dithizone solutions at different irradiation temperatures. The optical measurements of unirradiated and irradiated dithizone dye solution dosimeters were performed using a UV/VIS spectrophotometer at absorption peaks of 421 and 515 nm. Findings The new dosimeter improved significantly with the increase of dithizone dye concentrations from 0.025 to 0.1 mM. The dosimeter shows a perfect pre- and post-irradiation stability after irradiation for five days. Because of irradiation temperature dependence, the dithizone solution dosimeter should be corrected under actual processing conditions. Practical implications Dosimetry is a key point in quality control of radiation processing to assure that uniform and correct radiation doses are delivered to a region of interest. Therefore, this study introduces a dithizone solution dosimeter for high-dose radiation applications such as food irradiation, polymers applications and agriculture. Originality/value Ionizing radiation interacted with the ethanol solvent, resulting in the formation of free radicals, then these free radicals interacted with the dithizone molecule and changed the dye color from yellow to orange.

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48

Haire, D. Larry, Yashige Kotake, and Edward G. Janzen. "An EPR/ENDOR study of aminoxyls (nitroxides) capable of intramolecular bonding: hydroxyalkyl radical spin adducts of nitrones." Canadian Journal of Chemistry 66, no. 8 (August 1, 1988): 1901–11. http://dx.doi.org/10.1139/v88-307.

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A comparison of the effect of solvent and 13C labeling (of the radical addend) on the EPR (electron paramagnetic resonance) spectra of hydroxyalkyl vs. alkyl radical adducts of α-phenyl-N-tert-butyl nitrone (PBN) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) has been investigated. The solution ENDOR spectra in toluene and in ethanol are the first examples studied of aminoxyls with hydroxyl substituents in close proximity to the free radical centre. Diastereomeric mixtures of hydroxyalkyl radical adducts are clearly resolved by ENDOR spectroscopy. Conformations of these radicals have been assigned based on the 1H and 13C hyperfine splittings (HFS's) and by differential optimum ENDOR temperatures. Definitive assignments of carbon-centered radical adducts of DMPO and PBN are shown to be feasible by monitoring the β-13C HFS's of the radical addend. Long-range γ-H HFS's from the added radical group can be observed when the deuterated spin trap PBN-d14 is used. The production of 13C labeled hydroxyalkyl adducts of nitrones (e.g., DMPO–13CH2OH, from the reaction of hydroxyl radicals with added 13CH3OH) is shown to be useful as an improved EPR spectroscopic method for the verification of the presence of hydroxyl radicals.

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49

Feletou, M., and P. M. Vanhoutte. "Relaxation of canine coronary artery to electrical stimulation: limited role of free radicals." American Journal of Physiology-Heart and Circulatory Physiology 253, no. 4 (October 1, 1987): H884—H889. http://dx.doi.org/10.1152/ajpheart.1987.253.4.h884.

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Electrical stimulation induces tetrodotoxin-insensitive relaxation of the canine coronary artery. The present study was designed to verify whether this relaxation involves the production of oxygen-derived free radicals. Isolated rings of canine coronary arteries were suspended for isometric tension recording in organ chambers filled with Krebs-Ringer bicarbonate solution. They were stimulated electrically (9 V, 3 Hz, 2 ms for 2 min) by means of two platinum electrodes during contractions evoked by various vasoactive agonists. Under control conditions, electrical stimulation caused rapid, reversible relaxations. Superoxide dismutase in association with catalase or mannitol, sodium ascorbate, dimethyl sulfoxide, and glutathione did not inhibit the relaxation caused by stimulation applied for only 2 min; neither did the removal of chloride ions from the salt solution nor the association of Cl-free solution in the presence of mannitol, superoxide dismutase, and catalase. Prolonging the electrical stimulation (9 V, 3 Hz, 2 ms) for up to 20 min produced a secondary relaxation. This second phase was inhibited by sodium ascorbate. These experiments indicate that the rapid relaxation induced by short-lasting electrical stimulation is probably not due to the generation of oxygen-derived free radicals. However, prolonged stimulation causes the production of such radicals, which then evoke irreversible inhibition of the vascular smooth muscle of the canine coronary artery.

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Zúñiga-Benítez, Henry, Jafar Soltan, and Gustavo Peñuela. "Ultrasonic degradation of 1-H-benzotriazole in water." Water Science and Technology 70, no. 1 (April 30, 2014): 152–59. http://dx.doi.org/10.2166/wst.2014.210.

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This paper reports on the effect of different parameters of ultrasonic power, pollutant initial concentration, pH and the presence of co-existing chemical species (oxygen, nitrogen, ozone, and radical scavengers) on the ultrasonic degradation of the endocrine disruptor 1-H-benzotriazole. Increasing the 1-H-benzotriazole initial concentration from 41.97 to 167.88 μM increased the pollutant degradation rate by 40%. Likewise, a high applied ultrasonic power enhanced the extent of 1-H-benzotriazole removal and its initial degradation rate, which was accelerated in the presence of ozone and oxygen, but inhibited by nitrogen. The most favorable pH for the ultrasonic degradation was acidic media, reaching ∼90% pollutant removal in 2 h. The hydroxyl free radical concentration in the reaction medium was proportional to the ultrasound power and the irradiation time. Kinetic models based on a Langmuir-type mechanism were used to predict the pollutant sonochemical degradation. It was concluded that degradation takes place at both the bubble–liquid interfacial region and in the bulk solution, and OH radicals were the main species responsible for the reaction. Hydroxyl free radicals were generated by water pyrolysis and then diffused into the interfacial region and the bulk solution where most of the solute molecules were present.

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Journal articles on the topic 'Free radicals in solution'

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