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Journal ArticleDOI

Re-evaluation of the thiocyanate dosimeter for pulse radiolysis

01 Jan 1995-Journal of the Chemical Society, Faraday Transactions (The Royal Society of Chemistry)-Vol. 91, Iss: 2, pp 279-281
TL;DR: In this article, the super-Fricke dosimeter was used as a secondary standard for the thiocyanate dosimeter in O2-saturated water and the results were improved to 3.47 ± 0.06.
Abstract: The thiocyanate dosimeter (10–2 mol dm–3 SCN– in O2-saturated water) has been standardised against the super-Fricke dosimeter (10–2 mol dm–3 FeII in O2-saturated 0.4 mol dm–3 H2SO4) using the hexacyanoferrate(II) dosimeter [5 × 10–3 mol dm–3 Fe(CN)64– in O2-saturated water] as a secondary standard. On the basis that G(FeIII)= 1.67 × 10–6 mol J–1 and IµFeIII= 220.4 m2 mol–1 at 304 nm and 25 °C in the super-Fricke dosimeter, we obtain GIµ[Fe(CN)63–]=(3.47 ± 0.06)× 10–5 m2 J–1 at 420 nm and GIµ(SCN)2˙–=(2.59 ± 0.05)× 10–4 m2 J–1 at 475 nm. These values remain unchanged when the solutions are saturated with air instead of O2 and are doubled in N2O-saturated solution.
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TL;DR: The results suggest that FLASH radiation may be a viable option for treating lung tumors and reduce the occurrence and severity of early and late complications affecting normal tissue.
Abstract: In vitro studies suggested that sub-millisecond pulses of radiation elicit less genomic instability than continuous, protracted irradiation at the same total dose. To determine the potential of ultrahigh dose-rate irradiation in radiotherapy, we investigated lung fibrogenesis in C57BL/6J mice exposed either to short pulses (≤500 ms) of radiation delivered at ultrahigh dose rate (≥40 Gy/s, FLASH) or to conventional dose-rate irradiation (≤0.03 Gy/s, CONV) in single doses. The growth of human HBCx-12A and HEp-2 tumor xenografts in nude mice and syngeneic TC-1 Luc + orthotopic lung tumors in C57BL/6J mice was monitored under similar radiation conditions. CONV (15 Gy) triggered lung fibrosis associated with activation of the TGF-b (transforming growth factor–b) cascade, whereas no complications developed after doses of FLASH below 20 Gy for more than 36 weeks after irradiation. FLASH irradiation also spared normal smooth muscle and epithelial cells from acute radiation-induced apoptosis, which could be reinduced by administrationofsystemicTNF-a(tumornecrosisfactor–a)beforeirradiation.Incontrast,FLASHwasasefficientasCONVinthe repression of tumor growth. Together, these results suggest that FLASH radiotherapy might allow complete eradication of lung tumors and reduce the occurrence and severity of early and late complications affecting normal tissue.

696 citations

Journal ArticleDOI
TL;DR: In this paper, the rate constants for the reaction of ciprofloxacin with several free radicals, OH, N 3 and SO 4 − as well as hydrated electrons were reported.
Abstract: Fluoroquinolones and their metabolites are found in surface and ground waters, indicating their ineffective removal by conventional water treatment technologies. Advanced oxidation processes (AOPs) are alternatives to traditional water treatments. They utilize free radical reactions to directly degrade fluoroquinolones. This work reports absolute rate constants for the reaction of ciprofloxacin with several free radicals, OH, N 3 and SO 4 − as well as hydrated electrons. Pulsed radiolysis experiments showed that OH, N 3 and e aq − reacted quickly with ciprofloxacin, with bimolecular reaction rate constants of (2.15 ± 0.10) × 10 10 , (2.90 ± 0.12) × 10 10 and (2.65 ± 0.15) × 10 10 M −1 s −1 , respectively, while the SO 4 − radical appeared not to react with ciprofloxacin. Transient spectra were observed for the intermediate radicals produced by hydroxyl and azide radical reactions. Moreover, ciprofloxacin can be degraded rapidly using a typical advanced oxidation process, TiO 2 photocatalysis, with half-lives of 1.9–10.9 min depending upon pH values. Seven degradation products were elucidated by LC/MS/MS analysis, and the degradation mechanism of ciprofloxacin was also tentatively proposed by combining the experimental evidence with theoretical calculations of frontier electron densities. The calculations suggest that the addition of a hydroxyl radical to ciprofloxacin and photo-hole direct attack is two predominant reaction pathways.

478 citations

Journal ArticleDOI
TL;DR: This paper is the first step in eventually realizing the formulation of a detailed kinetic destruction model for these four tetracycline antibiotics.

366 citations


Cites background from "Re-evaluation of the thiocyanate do..."

  • ...2 10 4 m J ) with average doses of 3–5 Gy per 2–3 ns pulse (Buxton and Stuart, 1995)....

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Journal ArticleDOI
TL;DR: It has been observed that folic acid can not only scavenge thiyl radicals but can also repair these thiols at physiological pH and a significant inhibition property in microsomal lipid peroxidation is observed.

354 citations

Journal ArticleDOI
TL;DR: In this article, the role of peroxymonosulfate anion radical (O3SOO• or SO5•-) intermediate during radical-induced chain oxidation of HSO3/SO32- in oxygenated aqueous solution was evaluated.
Abstract: This study reevaluates the role of peroxymonosulfate anion radical (-O3SOO• or SO5•-) intermediate during radical-induced chain oxidation of HSO3-/SO32- in oxygenated aqueous solution. The SO5•- radical absorption band in the UV is weak: e = 1065 ± 80 M-1 cm-1 at λmax (260−265 nm). The SO5•- radical takes part in two radical−radical and four radical−solute reactions, partially producing the other chain carrier, the SO4•- radical, in either case. In this study, employing the pulse-radiolysis technique but adopting a new approach, these two types of reactions of the SO5•- radical have been separately quantified (at room temperature). For example, over pH 3.5−12, the branching ratio of (SO5•- + SO5•-) reactions giving rise to either the SO4•- radical or S2O82- is found to remain ∼1. The respective reaction rate constants for I → 0 are (2.2 ± 0.3) and (2.1 ± 0.3) × 108 M-1 s-1. The (SO5•- + HSO3-) reactions in acid pH follow two paths, forming the SO4•- radical in one and regenerating the SO3•- radical in th...

195 citations

References
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Journal ArticleDOI
TL;DR: In this article, the rate constants for over 3500 reaction are tabulated, including reaction with molecules, ions and other radicals derived from inorganic and organic solutes, and the corresponding radical anions, ⋅O− and eaq−, have been critically pulse radiolysis, flash photolysis and other methods.
Abstract: Kinetic data for the radicals H⋅ and ⋅OH in aqueous solution,and the corresponding radical anions, ⋅O− and eaq−, have been critically pulse radiolysis, flash photolysis and other methods. Rate constants for over 3500 reaction are tabulated, including reaction with molecules, ions and other radicals derived from inorganic and organic solutes.

9,887 citations

Journal ArticleDOI
TL;DR: In this article, the thiocyanate dosimeter was calibrated against the Fricke system to obtain a value of 46,400 +-600 (molecules/100 eV) for the product of yield and extinction coefficient of (SCN)/sub 2/O-saturated solutions.
Abstract: A study was undertaken to calibrate the thiocyanate dosimeter most commonly used for determination of OH concentration in pulse radiolysis experiments. The dosimeter which involves 10/sup -2/ M SCN/sup -/ in N/sub 2/O-saturated solutions was calibrated against the Fricke system. The calibration led to a value of 46,400 +- 600 (molecules/100 eV) M/sup -1/ cm/sup -1/ for the product of yield and extinction coefficient of (SCN)/sub 2//sup -/ at 10/sup -2/ M SCN/sup -/. This yield is 10-15% greater than most previously quoted values. It is emphasized that yields of OH scavenging processes are significantly dependent on solute concentration and that reports of radiolysis dosimetry should specify the reference system being used in order that results may be correlated. (BLM)

239 citations

Journal ArticleDOI
TL;DR: In this paper, the radiation chemical yield for oxidation of ferrocyanide by OH produced in the fast electron radiolysis of N/sub 2/O-saturated aqueous solutions was found to increase from a low concentration limiting yield of 5.2 to values in excess of 6.7.
Abstract: The radiation chemical yield for oxidation of ferrocyanide by OH produced in the fast electron radiolysis of N/sub 2/O-saturated aqueous solutions is found to increase from a low concentration limiting yield of 5.2 to values in excess of 6.7 for ferrocyanide concentrations above 0.1 M. This observed dependence reflects competition between the scavenging reaction and track recombination processes involving OH radicals which occurs on a time scale greater than 10/sup -9/s. By extrapolation an additional yield of -- 1.5 is estimated for OH radicals which recombine at still shorter times. These scavenging studies show that significant amounts of recombination occur within the track even at times as long as 10/sup -6/s. Secondary radicals produced within the track are also subject to recombination processes as is illustrated by the low concentration limit which shows that most OH radicals produced from N/sub 2/O within the track do not escape from the track. In general, for concentrations of reactive solutes greater than -- 10/sup -4/ M, i.e., for k(S) > 10/sup 6/ s/sup -1/, scavenging of OH from the track will contribute significantly to the observed yields and this effect must be taken into account in comparing the results from different radiolytic systems.

220 citations