Physical Properties Of Radiation Research Articles

Predicting tumour radiosensitivity to deliver precision radiotherapy.

Owing to advances in radiotherapy, the physical properties of radiation can be optimized to enable individualized treatment; however, optimization is rarely based on biological properties and, therefore, treatments are generally planned with the assumption that all tumours respond similarly to radiation. Radiation affects multiple cellular pathways, including DNA damage, hypoxia, proliferation, stem cell phenotype and immune response. In this Review, we summarize the effect of these pathways on tumour responses to radiotherapy and the current state of research on genomic classifiers designed to exploit these variations to inform treatment decisions. We also discuss whether advances in genomics have generated evidence that could be practice changing and whether advances in genomics are now ready to be used to guide the delivery of radiotherapy alone or in combination.

Effects of X-ray irradiation on male sperm transfer ability and fertility in the sweetpotato weevils Euscepes postfasciatus (Coleoptera: Curculionidae) and Cylas formicarius (Coleoptera: Brentidae)

Gamma radiation from isotopic sources has been used in sterile insect technique (SIT) programs worldwide, but it might be difficult to continue using these sources in future SIT programs because of social issues. Therefore, an alternative sterilization source to gamma rays, such as X-rays, needs to be developed. The physical properties of radiation are different between gamma rays and X-rays: for example, X-rays have a shorter penetration depth than gamma rays. Therefore, X-rays may not fully confer male sterility, depending on the target pest insects. The present study investigated whether the West-Indian sweetpotato weevil Euscepes postfasciatus (Fairmaire) and the sweetpotato weevil Cylas formicarius (Fabricius) are sterilized by X-rays generated in a low-energy X-ray irradiator, without deterioration of male mating ability, at the doses currently used in the eradication programs for E. postfasciatus (150 Gy) and C. formicarius (200 Gy) using gamma rays at Okinawa, Japan. The results demonstrated that it is possible to use X-rays in future SIT programs for E. postfasciatus and C. formicarius, because X-ray irradiated males were almost completely sterilized without deterioration of their mating ability.

Systems biology and its potential role in radiobiology

About a century ago, Conrad Röentgen discovered X-rays, and Henri Becquerel discovered a new phenomenon, which Marie and Pierre Curie later coined as radio-activity. Since their seminal work, we have learned much about the physical properties of radiation and its effects on living matter. Alas, the more we discover, the more we appreciate the complexity of the biological processes that are triggered by radiation exposure and eventually lead (or do not lead) to disease. Equipped with modern biological methods of high-throughput experimentation, imaging, and vastly increased computational prowess, we are now entering an era where we can piece some of the multifold aspects of radiation exposure and its sequelae together, and develop a more systemic understanding of radiogenic effects such as radio-carcinogenesis than has been possible in the past. It is evident from the complexity of even the known processes that such an understanding can only be gained if it is supported by mathematical models. At this point, the construction of comprehensive models is hampered both by technical inadequacies and a paucity of appropriate data. Nonetheless, some initial steps have been taken already and the generally increased interest in systems biology may be expected to speed up future progress. In this context, we discuss in this article examples of relatively small, yet very useful models that elucidate selected aspects of the effects of exposure to ionizing radiation and may shine a light on the path before us.

X-irradiation of cells on glass slides has a dose doubling impact

Immunofluorescence detection of γH2AX foci is a widely used tool to quantify the induction and repair of DNA double-strand breaks (DSBs) induced by ionising radiation. We observed that X-irradiation of mammalian cells exposed on glass slides induced twofold higher foci numbers compared to irradiation with γ-rays. Here, we show that the excess γH2AX foci after X-irradiation are produced from secondary radiation particles generated from the irradiation of glass slides. Both 120kV X-rays and 137Cs γ-rays induce ∼20 γH2AX foci per Gy in cells growing on thin (∼2μm) plastic foils immersed in water. The same yield is obtained following γ-irradiation of cells growing on glass slides. However, 120kV X-rays produce ∼40 γH2AX foci per Gy in cells growing on glass, twofold greater than obtained using cells irradiated on plastic surfaces. The same increase in γH2AX foci number is obtained if the plastic foil on which the cells are grown is irradiated on a glass slide. Thus, the physical proximity to the glass material and not morphological differences of cells growing on different surfaces accounts for the excess γH2AX foci. The increase in foci number depends on the energy and is considerably smaller for 25kV relative to 120kV X-rays, a finding which can be explained by known physical properties of radiation. The kinetics for the loss of foci, which is taken to represent the rate of DSB repair, as well as the Artemis dependent repair fraction, was similar following X- or γ-irradiation, demonstrating that DSBs induced by this range of treatments are repaired in an identical manner.

Influence of different curing systems on the physico-mechanical properties and stability of SBR and NR rubbers

The physical properties of radiation, sulfur and peroxide-cured styrene–butadiene rubber (SBR) and natural rubber (NR) were compared. The dependence of the mechanical properties of the radiation-vulcanized SBR and NR on the coagent concentration and radiation dose was studied. The effect of thermal aging on the mechanical properties of the different rubber formulations was discussed. The radiation-cured formulations of SBR have superior mechanical properties and thermal stability compared with those of the chemically vulcanized compounds. Whereas, the radiation-cured formulations of NR have similar mechanical properties but superior thermal stability (based on the % change in E after thermal aging), when compared with those of the sulfur-vulcanized compounds and slightly better than those of the peroxide-vulcanized compounds.

The Role of Coagulants on the Preparation of Dipped film from Radiation Vulcanized Natural Rubber Latex

The effect of coagulants on the preparation of dipped film with good physical properties was studied. In order to optimize various parameters like coagulant concentration, latex concentration, and former dipping time in latex and coagulant, the effect of coagulant on the physical properties of radiation vulcanized natural rubber latex film was evaluated. Calcium nitrate, calcium chloride, and ammonium nitrate were used as the coagulant by dissolving either in water or ethanol. Calcium nitrate solution was found to be the best one among the coagulants used.

Book Reviews

This is another excellent book from the series of Medical Physics Handbooks. Professor Kathren has provided historical interest throughout his book so that the reader does not lose contact with the fact that radiation protection is a constantly developing field. The chapters on the physical properties of radiation, units and dose are well documented and the simple calculations of absorbed dose from activity provide a neat translation into SI units for those still struggling with conversions.

An Assessment of the Role of Microdosimetry in Radiobiology

A brief outline is given of the concepts of microdosimetry and the development of the theory of dual radiation action, which was proposed as the link between the physical properties of radiation (microdosimetry) and their biological effects. A good deal of experimental evidence was consistent with the theory in its original site model form, but there were also areas of significant disagreement. More recent experiments with ultrasoft x rays and beams of correlated ions have provided critical tests which have shown that the site model does not give an adequate description of the mechanism of radiation action. A large proportion, at least, of the radiation-induced lesions are produced by highly localized energy concentrations without the need for long-range interaction of sublesions. Attempts have been made to allow for such lesions within the original postulates of the theory of dual radiation action by development of the distance model or generalized formalism using a distance-dependent interaction probability. Some of the present limitations of this approach are discussed. An alternative hypothesis, involving dose-dependent repair acting directly upon the lesions, is described. A comparison is made between consequences of these two alternative approaches. The validity of the application of microdosimetric measurements to a varietymore » of problems is considered.« less

A comparison of the physical properties of radiation and sulfur-cured poly(butadiene–co–styrene)

The physical properties of radiation- and sulfur-cured poly(butadiene-co-styrene)-based stocks were compared. It was found that the measured lower ultimate strength of radiation-cured stocks is in part attributable to the difference in the glass transition temperatures of the stocks cured by the two methods (an increase in T/sub g/ is caused by sulfur curing). Another factor contributing to the difference in performance is the apparent nonuniform crosslink density distribution in radiation-cured stocks containing carbon black filler. A higher crosslink density in the immediate vacinity of carbon black particles was postulated based on a to-be-expected distribution of secondary electron energy at interfaces with an appreciable change in density between neighboring phases. The invoked difference in network topology, supported by solvent swelling measurements on sulfur- and radiation-crosslinked vulcanizates can explain not only the slightly lower ultimate strength of radiation-cured stocks but also the superior fatigue and crack propagation performance measured for these vulcanizates. Finally, theoretical arguments were presented to explain the inferred large strength deficiency of radiation-cured rubbers reported by other investigators on the basis of chain scissions encountered during radiation crosslinking.

The physical properties of radiation cured rubbers

The physical properties of radiation cured rubbers

Physical properties of radiation induced and growth defects in II–VI semiconductors

Abstract Defects in wurtzite single crystals of ZnS, ZnSe and CdS have been observed by means of both scanning and transmission electron microscopy. Application of the scanning technique to the observation of cathodoluminescence in these materials has demonstrated localized effects on the emission close to twin boundaries and stacking faults in the as-grown crystals, which may be interpreted in terms of changes in band gap at the defect. This method has also been applied to heavy ion bombarded crystals; in addition, transmission electron microscope studies have been made of these irradiated samples and the annealing behaviour of the radiation damage has been observed. Finally, in-situ optical absorption experiments have been carried out on samples irradiated at liquid nitrogen temperature, and effects on the characteristic exciton absorption have been noted.