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- Barack, Leor, et al.
(författare)
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Black holes, gravitational waves and fundamental physics : a roadmap
- 2019
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 36:14
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Forskningsöversikt (refereegranskat)abstract
- The grand challenges of contemporary fundamental physics dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'.
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- Lasser, Gregor, 1983, et al.
(författare)
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Implementation and Far-Field Calibration of an 8×8 37-40 GHz Phased Array with Vivaldi Aperture
- 2022
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. ; 2022-June, s. 933-936
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Konferensbidrag (refereegranskat)abstract
- A 64 element phased array is implemented using an all metal Vivaldi aperture and 16 commercial beamforming ICs integrated on a 10-layer RF -PCB. The interconnects within the PCB are designed using circular barrels to avoid unwanted resonances, as is demonstrated by full wave simulation. The use of a non-isolated power combiner in receive mode is validated by comparing two far-field calibration techniques, resulting in measured high-fidelity beams steering up to 50°.
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- Shi, Lei, 1981, et al.
(författare)
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Evolution of Bacterial Protein-Tyrosine Kinases and Their Relaxed Specificity Toward Substrates
- 2014
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Ingår i: Genome Biology and Evolution. - : Oxford University Press (OUP). - 1759-6653. ; 6:4, s. 800-817
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Tidskriftsartikel (refereegranskat)abstract
- It has often been speculated that bacterial protein-tyrosine kinases (BY-kinases) evolve rapidly and maintain relaxed substrate specificity to quickly adopt new substrates when evolutionary pressure in that direction arises. Here, we report a phylogenomic and biochemical analysis of BY-kinases, and their relationship to substrates aimed to validate this hypothesis. Our results suggest that BY-kinases are ubiquitously distributed in bacterial phyla and underwent a complex evolutionary history, affected considerably by gene duplications and horizontal gene transfer events. This is consistent with the fact that the BY-kinase sequences represent a high level of substitution saturation and have a higher evolutionary rate compared with other bacterial genes. On the basis of similarity networks, we could classify BY kinases into three main groups with 14 subgroups. Extensive sequence conservation was observed only around the three canonical Walker motifs, whereas unique signatures proposed the functional speciation and diversification within some subgroups. The relationship between BY-kinases and their substrates was analyzed using a ubiquitous substrate (Ugd) and some Firmicute-specific substrates (YvyG and YjoA) from Bacillus subtilis. No evidence of coevolution between kinases and substrates at the sequence level was found. Seven BY-kinases, including well-characterized and previously uncharacterized ones, were used for experimental studies. Most of the tested kinases were able to phosphorylate substrates from B. subtilis (Ugd, YvyG, and YjoA), despite originating from very distant bacteria. Our results are consistent with the hypothesis that BY-kinases have evolved relaxed substrate specificity and are probably maintained as rapidly evolving platforms for adopting new substrates.
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