Properties of radicals formed by the irradiation of wool fibers.
ABSTRACT Wool fibers of different sample conditions were irradiated in different atmospheres by (60)Co gamma-rays and were studied by electron spin resonance method (ESR). It was found that a large percentage of the alpha-carbon radicals of polymer main chain were more long-lived radicals. The ESR measurements of irradiated cortex samples of the wool fibers proved that most radicals from the cortex were long-lived ones. Low water content (as low as 27.5%) in the reaction system did not greatly affect the radical formation, but higher water contents would reduce the radical concentrations dramatically and accelerate their decaying process. The results will be of help in property modification of wool products by radiation graft copolymerization.
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ABSTRACT: Dosimetry based on the detection by electron paramagnetic resonance (EPR) spectroscopy of ionizing radiation-induced radicals is an established method for the retrospective dosimetry of past exposures and the dosimetry of potentially exposed persons in radiological emergencies. The dose is estimated by measuring the physical damage induced in materials contained in objects placed on or next to the potentially exposed person. The aim of this paper is to survey the current literature about methodologies and materials that have been proposed for EPR dosimetry, in order to identify those that could be suitable for population triage according to criteria such as ubiquity, non invasiveness and easy sample collection, presence of a post-irradiation EPR signal, negligible background signal, linearity of dose-response relationship, minimum detection limit and post-irradiation signal stability. The paper will survey the features of sugar, plastics, glass, clothing tissues, and solid biological tissues (nails, hair and calcified tissues).Annali dell'Istituto superiore di sanita 01/2009; 45(3):287-96. · 0.76 Impact Factor
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ABSTRACT: The effect of electron beam irradiation on silk fibroin (SF) fiber-reinforced poly(ε-caprolactone) (PCL) composite was investigated by mechanical test, scanning electron microscope, dynamic mechanical thermal analysis, electron paramagnetic resonance (EPR) analysis, and Fourier transform infrared (FTIR) analysis. The results indicate that electron beam irradiation can affect the static and dynamic mechanical properties of PCL and SF/PCL composite, depending on the irradiation dose. PCL shows maximum strength and modulus at the irradiation dose of 200 kGy, and the SF/PCL composite with 45% fiber content exhibits maximum strength and modulus at the doses of 150 kGy. EPR analysis shows that during irradiation, both PCL and SF fiber can produce free radicals. Some transformations or reactions of radicals may take place between PCL and SF fiber and enhance the interfacial interaction. The microstructures of tensile fracture also show an improvement in interfacial interaction between fiber and matrix after irradiation. FTIR analysis shows that chain scissions also occur in both PCL and SF fiber during irradiation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009Journal of Applied Polymer Science 04/2009; 113(2):1063 - 1069. · 1.40 Impact Factor
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ABSTRACT: There is now an increased need for accident dosimetry due to the increased risk of significant exposure to ionizing radiation from terrorism or accidents. In such scenarios, dose measurements should be made in individuals rapidly and with sufficient accuracy to enable effective triage. Electron paramagnetic resonance (EPR) is a physical method of high potential for meeting this need, providing direct measurements of the radiation-induced radicals, which are unambiguous signatures of exposure to ionizing radiation. For individual retrospective dosimetry, EPR in tooth enamel is a proven and effective technique when isolated teeth can be obtained. There are some promising developments that may make these measurements feasible without the need to remove the teeth, but their field applicability remains to be demonstrated. However, currently it is difficult under emergency conditions to obtain tooth enamel in sufficient amounts for accurate dose measurements. Since fingernails are much easier to sample, they can be used in potentially exposed populations to determine if they were exposed to life-threatening radiation doses. Unfortunately, only a few studies have been carried out on EPR radiation-induced signals in fingernails, and, while there are some promising aspects, the reported results were generally inconclusive. In this present paper, we report the results of a systematic investigation of the potential use of fingernails as retrospective radiation dosimeters.Radiation Measurements. 01/2009;