Reflector surface modelling - a European collaboration

The topic of this paper is the work carried out in Work Package 2.3-2 of the EU network ACE. This work package is concerned with the modelling of the surfaces of modern reflector antennas. In particular the problems associated with homogenisation of periodic structures are described together with an application example. An accurate MoM solutions for periodic structure is presented. A new, fast and very efficient interpolation technique for frequency selective surfaces is introduced and linked to high frequency techniques to speed up radiation calculation processes

Leaky-wave slot array antenna fed by a dual reflector system

This work proposes a leaky-wave slot array antenna fed by a dual offset Gregorian reflector system realized by pins in a parallel plate waveguide. The radiating part of the antenna is composed by parallel slots etched on one side of the same parallel plate waveguide. The dual offset Gregorian reflector system is fed by an arrangement constituted by two vias and a grid, also constituted by pins. A prototype of the antenna has been designed, manufactured and successfully tested. The low profile, low cost and high efficiency of the antenna render it suited for a variety of radar or telecom applications

Reflection confocal nanoscopy using a super-oscillatory lens

A Superoscillatory lens (SOL) is known to produce a sub-diffraction hotspot which is useful for high-resolution imaging. However, high-energy rings called sidelobes coexist with the central hotspot. Additionally, SOLs have not yet been directly used to image reflective objects due to low efficiency and poor imaging properties. We propose a novel reflection confocal nanoscope which mitigates these issues by relaying the SOL intensity pattern onto the object and use conventional optics for detection. We experimentally demonstrate super-resolution by imaging double bars with 330 nm separation using a 632.8 nm excitation and a 0.95 NA objective. We also discuss the enhanced contrast properties of the SOL nanoscope against a laser confocal microscope, and the degradation of performance while imaging large objects.Comment: 17 pages, 15 figures, supplementary include

EBG enhanced feeds for the improvement of the aperture efficiency of reflector antennas

We describe the use of electromagnetic bandgap (EBG) super-layers to improve the shape of reflectors illumination function. Following an investigation of the leaky wave pole singularities of the EBG Green's function, the shape of the radiation patterns of small apertures in ground planes are optimized. The maximization of the reflector aperture efficiency can be obtained by properly tuning the super layers geometrical parameters. A prototype of such feed has been designed, manufactured and tested. The results indicate that the inclusion of the EBG, increases the aperture efficiency of the feed+reflector system to values higher than 80%, over a 10% bandwidth. These low profile feeds are compatible with printed circuit board and/or integrated technology

Properties of leaky waves supported by grounded dielectric super-layers and implications on the design of reflector feeds

The design strategy that uses dielectric super-layers with neighboring wave-guides closed in matched loads constitutes a worst case scenario as far as the performance enhancement is concerned and finds applicability in radiometric imaging arrays. On the other side the design strategy that uses dielectric super-layers with neighboring wave-guides closed in properly tuned reactive loads can be seen as best case scenario representative of a multi beam system for a telecommunication satellite with independent channels

Inhibiting DNA methylation as a strategy to enhance adipose-derived stem cells differentiation. Focus on the role of Akt/mTOR and Wnt/β-catenin pathways on adipogenesis

Adipose-derived mesenchymal stem cells (ASCs) represent a valid therapeutic option for clinical application in several diseases, due to their ability to repair damaged tissues and to mitigate the inflammatory/immune response. A better understanding of the underlying mechanisms regulating ASC biology might represent the chance to modulate their in vitro characteristics and differentiation potential for regenerative medicine purposes. Herein, we investigated the effects of the demethylating agent 5-azacytidine (5-aza) on proliferation, clonogenicity, migration, adipogenic differentiation and senescence of ASCs, to identify the molecular pathways involved. Through functional assays, we observed a detrimental effect of 5-aza on ASC self-renewal capacity and migration, accompanied by actin cytoskeleton reorganization, with decreased stress fibers. Conversely, 5-aza treatment enhanced ASC adipogenic differentiation, as assessed by lipid accumulation and expression of lineage-specific markers. We analyzed the involvement of the Akt/mTOR, MAPK and Wnt/beta-catenin pathways in these processes. Our results indicated impairment of Akt and ERK phosphorylation, potentially explaining the reduced cell proliferation and migration. We observed a 5-aza-mediated inhibition of the Wnt signaling pathway, this potentially explaining the pro-adipogenic effect of the drug. Finally, 5-aza treatment significantly induced ASC senescence, through upregulation of the p53/p21 axis. Our data may have important translational implications, by helping in clarifying the potential risks and advantages of using epigenetic treatment to improve ASC characteristics for cell-based clinical approaches