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2025
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Summary
The circumscription of the tribe Vernonieae (Compositae) has been problematic due to the reorganisation of the polyphyletic genus Vernonia and the creation of many small genera. Recent phylogenetic studies have focused on the relationships within Vernonieae but few studies have explored the generic relationships within subtribe Piptocarphinae. Of note, some diagnostic features of Piptocarphinae are not unique to the subtribe and are found in other Vernonieae genera. In this study, we explored the phylogenetic relationships in Piptocarphinae, the genus boundaries in this subtribe and tested the infrageneric affinities of the paleate species, using previously published and newly generated nuclear ITS sequences for 65% of the genera of American Vernonieae. Results agree with previous phylogenetic studies, where nearly all subtribes are seemingly paraphyletic or polyphyletic. Piptocarphinae emerges as polyphyletic and should be reduced to contain only the monophyletic Piptocarpha, whereas Critoniopsis is monophyletic only if Cuatrecasanthus is included. We propose placing Cuatrecasanthus and Joseanthus in synonymy of Critoniopsis, resulting in eight new combinations: C. chimborazensis, C. giannasii, C. flexipappa, C. kingii, C. lanceolatus, C. sandemanii, C. sparrei and C. trichotoma and a new name, C. boekei. Piptocoma also resolves as non-monophyletic but no taxonomic recommendations are made, as few species have been sampled in phylogenies so far. We present a new combination in the genus Piptocarpha, P. glomerulata. The presence of paleae likely emerged independently at least three times in American Vernonieae. Paleate receptacles are present in three different series in Piptocarpha subg. Piptocarpha, which indicates that paleae have likely arisen twice in the evolution of Piptocarpha. Finally, a brief discussion about the adaptive function of paleae and pappus is provided. - Book : ()
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AbstractBackgroundVery high‐energy electrons (VHEEs) in radiotherapy may offer several potential advantages over conventional electron beams and other techniques, for example, the fact that they can be used at ultra‐high dose rates (UHDRs), therefore enabling FLASH radiotherapy. However, the production of secondary particles at high energies (50–200 MeV) has yet to be studied in detail for this technique currently under development.PurposeThe aim of this work was to examine the secondary dose produced by VHEEs, with particular emphasis on bremsstrahlung photons and neutrons, for two beam delivery systems (double scattering [DS] and pencil beam scanning [PBS]).MethodsThe electron, X‐ray, and neutron doses arising from two beam delivery systems (DS or PBS) were computed using Monte Carlo (MC) simulations in the TOPAS (TOol for PArticle Simulation)/Geant4 toolkit, and a preliminary assessment of the secondary dose for a clinical VHEE treatment was performed using a whole‐body phantom. An evaluation of the secondary dose produced by this preliminary design of a VHEE nozzle set in a clinical proton facility was performed, taking into account realistic PBS or DS nozzle configurations.ResultsThe mean doses received by a patient undergoing DS‐VHEE irradiation were found to be up to 5.3‐fold and 6.8‐fold higher for in‐field or out‐of‐field organs for photons and neutrons, respectively, compared to the PBS‐VHEE plan. The results for the secondary neutron dose in intracranial treatments also demonstrate the characteristic of VHEE compared to proton beams for reducing the out‐of‐field secondary neutron dose. The dose to the public area that could be delivered to meet regulatory limits surrounding a possible treatment room in a proton therapy facility was assessed. A regulatory limit of 0.5 µSv/h would give a restriction of 49 and 83 Gy per patient and per fraction for DS and PBS, respectively.ConclusionsThis work describes a method to simulate and compare secondary radiation doses resulting from scattered, scanned VHEE or proton therapy treatments. The results indicate that a conventionally shielded proton therapy room results in acceptable public doses for a preliminary VHEE design and could be of interest for radiation protection purposes and for similar setups. Other facilities with differing layouts may, however, lead to different conclusions, requiring further studies.- Book : ()
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AbstractAqueous metal‐selenium batteries based on chalcogenide cathodes, despite their multi‐electron conversion‐type redox reactions and rapid kinetics, suffer from short lifespans and unclear capacity degradation mechanisms. The interfacial interactions between doped carbon and chalcogenides correlate closely with the electrochemical structural evolution. Hence, flower‐like Cu2−xSe wrapped with ultrathin N‐doped carbon layer (Cu2−xSe@N‐C) is synthesized via a simple γ radiation‐pyrolysis route for the first time. The Cu2−xSe@N‐C cathode displays a high‐rate performance and long‐term stability, with a respective capacity of 310.6 mAh g−1 at 20 A g−1 and a capacity retention rate of 92.9% after 30 000 cycles over 2000 h at 5 A g−1. Ex situ X‐ray diffraction and X‐ray photoelectron spectroscopy confirm the reversible Cu storage mechanism of the Cu2−xSe@N‐C cathode and the issues of volume expansion and oxidative dissolution related to the capacity degradation of the Cu2−xSe cathode. Furthermore, X‐ray absorption analysis and theoretical calculations reveal the presence of Se─C interactions between the ultrathin N‐doped carbon and Cu2−xSe. As a result, the physical and chemical dual‐protection of N‐doped carbon via Se‐C not only effectively stabilizes the structural evolution of Cu2−xSe but also endows it with faster electrode reaction kinetics.- Book : ()
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