The thin and medium filters of the EPIC camera on-board XMM-Newton: measured performance after more than 15 years of operation

After more than 15 years of operation of the EPIC camera on board the XMM-Newton X-ray observatory, we have reviewed the status of its Thin and Medium filters. We have selected a set of Thin and Medium back-up filters among those still available in the EPIC consortium and have started a program to investigate their status by different laboratory measurements including: UV/VIS transmission, Raman scattering, X-Ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Furthermore, we have investigated the status of the EPIC flight filters by performing an analysis of the optical loading in the PN offset maps to gauge variations in the optical and UV transmission. We both investigated repeated observations of single optically bright targets and performed a statistical analysis of the extent of loading versus visual magnitude at different epochs. We report the results of the measurements conducted up to now. Most notably, we find no evidence for change in the UV/VIS transmission of the back-up filters in ground tests spanning a 2 year period and we find no evidence for change in the optical transmission of the thin filter of the EPIC-pn camera from 2002 to 2012. We point out some lessons learned for the development and calibration programs of filters for X-ray detectors in future Astronomy missions

Manufacturing and testing a thin glass mirror shell with piezoelectric active control

Optics for future X-ray telescopes will be characterized by very large aperture and focal length, and will be made of lightweight materials like glass or silicon in order to keep the total mass within acceptable limits. Optical modules based on thin slumped glass foils are being developed at various institutes, aiming at improving the angular resolution to a few arcsec HEW. Thin mirrors are prone to deform, so they require a careful integration to avoid deformations and even correct forming errors. On the other hand, this offers the opportunity to actively correct the residual deformation: a viable possibility to improve the mirror figure is the application of piezoelectric actuators onto the non-optical side of the mirrors, and several groups are already at work on this approach. The concept we are developing consists of actively integrating thin glass foils with piezoelectric patches, fed by voltages driven by the feedback provided by X-rays. The actuators are commercial components, while the tension signals are carried by a printed circuit obtained by photolithography, and the driving electronic is a multi-channel low power consumption voltage supply developed inhouse. Finally, the shape detection and the consequent voltage signal to be provided to the piezoelectric array are determined in X-rays, in intra-focal setup at the XACT facility at INAF/OAPA. In this work, we describe the manufacturing steps to obtain a first active mirror prototype and the very first test performed in X-rays

Dynamic Stereoselection of Peptide Helicates and Their Selective Labeling of DNA Replication Foci in Cells

Although largely overlooked in peptide engineering, coordination chemistry offers a new set of interactions that opens unexplored design opportunities for developing complex molecular structures. In this context, we report new artificial peptide ligands that fold into chiral helicates in the presence of labile metal ions such as Fe(II) and Co(II). Heterochiral β turn promoting sequences encode the stereoselective folding of the peptide ligands and define the physicochemical properties of their corresponding metal complexes. CD and NMR spectroscopy in combination with computational methods allowed us to identify and determine the structure of two isochiral ΛΛ‐helicates, folded as topological isomers. Finally, in addition to the in vitro characterization of their selective binding to DNA three‐way junctions, cell microscopy experiments demonstrated that a rhodamine‐labeled Fe(II) helicate was internalized and selectively stains DNA replication factories in functional cells.Financial support from the Spanish grant RTI2018-099877-B-I00, the Xunta de Galicia (grupos con potencial de crecemento ED431B 2018/04, Centro singular de investigación de Galicia accreditation 2016–2019, ED431G/09, and ED431B 2018/04) and the European Union (European Regional Development Fund - ERDF) are gratefully acknowledged. J. G.-G. thanks the Spanish Ministry of Science and Innovation/Spanish Research Agency for his FPI fellowship. We also wish to express our gratitude to Soraya Learte-Aymamí for her assistance in the optimization of the EMSA assays. I. A. thanks Spanish Ministry of Science and Innovation/Spanish Research Agency (MCI/AEI/FEDER, RTI218- 096182-B-I00, CSIC13-4E-2076) and AGAUR (2017 SGR 208). G.S. L.R.-M. and J.-D.M. thank Spanish MINECO (grant CTQ2017-87889-P) and the Generalitat de Catalunya (2017SGR1323). G.S., thanks Regione Autonoma della Sardegna (grant RASSR79857) for his postdoctoral fellowship. L. R.-M. thanks the Generalitat de Catalunya for her FI fellowship. plasmid GFP-PCNAL2 was generously provided by Dr. Cristina Cardoso. Molecular graphics with UCSF Chimera, developed by the Resource for Biocomputing, Visualization, and Informatics at the University of California, San Francisco, with support from NIH P41-GM103311. 43 We are also grateful to Prof. Peter Scott of the IAS at the University of Warwick for his insights and advice during the preparation of this manuscript.Peer reviewe