Induction and processing of the radiation-induced gamma-H2AX signal and Its link to the underlying pattern of DSB: A combined experimental and modelling study

We present here an analysis of DSB induction and processing after irradiation with X-rays in an extended dose range based on the use of the γH2AX assay. The study was performed by quantitative flow cytometry measurements, since the use of foci counting would result in reasonable accuracy only in a limited dose range of a few Gy. The experimental data are complemented by a theoretical analysis based on the GLOBLE model. In fact, original aim of the study was to test GLOBLE predictions against new experimental data, in order to contribute to the validation of the model. Specifically, the γH2AX signal kinetics has been investigated up to 24 h after exposure to increasing photon doses between 2 and 500 Gy. The prolonged persistence of the signal at high doses strongly suggests dose dependence in DSB processing after low LET irradiation. Importantly, in the framework of our modelling analysis, this is related to a gradually increased fraction of DSB clustering at the micrometre scale. The parallel study of γH2AX dose response curves shows the onset of a pronounced saturation in two cell lines at a dose of about 20 Gy. This dose is much lower than expected according to model predictions based on the values usually adopted for the DSB induction yield (≈ 30 DSB/Gy) and for the γH2AX foci extension of approximately 2 Mbp around the DSB. We show and discuss how theoretical predictions and experimental findings can be in principle reconciled by combining an increased DSB induction yield with the assumption of a larger genomic extension for the single phosphorylated regions. As an alternative approach, we also considered in our model the possibility of a 3D spreading-mechanism of the H2AX phosphorylation around the induced DSB, and applied it to the analysis of both the aspects considered. Our results are found to be supportive for the basic assumptions on which GLOBLE is built. Apart from giving new insights into the H2AX phosphorylation process, experiments performed at high doses are of relevance in the context of radiation therapy, where hypo-fractionated schemes become increasingly popular

Technological Method for Deposition of Radio-Reflecting Coating on Components of Large Space Antenna

Het betreft het aanbrengen van een reflecterende laag op bijvoorbeeld een carbon fiber reflector, zodat de verliezen bij reflectie aan de reflector verminderd kunnen worden. Reflection properties of carbon fiber reinforced plastics are not perfect. When the losses are too high in an instrument antenna, and moreover increase with frequency, one has to improve the situation. This can be done with different methods. One can use vacuum deposition of a metal. Here the article was written in order to provide such method as one of the possible solutions for improvement of the Radio Astron deployable reflector antenna (deployable panels, which can be metallised). Moreover the loss is anisotropic, in other words, different for the two orthogonal polarisations (linear) with different phase as well. Such a metallisation improves the situation. Different metals can be used, the proposed situation was just available at the time in Applied Physics Institute

van der Waals metal-organic framework as an excitonic material for advanced photonics

\u3cp\u3evan der Waals metal-organic framework (MOF) is used as an excitonic material for advanced photonics. van der Waals supports different types of excitons and provides a dimensional confinement effect, which is especially pronounced for 2D structures and strongly changes the exciton parameters. The restrictions can also be overcome by creating microcavities with Bragg mirrors made of atomically thin organic semiconductors inside. Such a device is an elegant solution for manipulation of exciton states by light, but its construction remains highly sophisticated.\u3c/p\u3