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| 2. |
- Hofmann, Jan Philipp, et al.
(författare)
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Dynamic response of chlorine atoms on a RuO2(110) model catalyst surface
- 2010
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 12:47, s. 15358-15366
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic behavior of surface accommodated chlorine atoms on RuO2(110) was studied by a variety of experimental methods including high resolution core level shift, thermal desorption-, and in situ infrared spectroscopy as well as in situ surface X-ray diffraction in combination with state-of-the-art density functional theory calculations. On the chlorinated RuO2(110) surface the undercoordinated oxygen atoms have been selectively replaced by chlorine. These strongly bound surface chlorine atoms shift from bridging to on-top sites when the sample is annealed in oxygen, while the reverse shift of Cl from on-top into bridge positions is observed during CO exposure; the vacant bridge position is then occupied by either chlorine or CO. For the CO oxidation reaction over chlorinated RuO2(110), the reactant induced site switching of chlorine causes a site-blocking of the catalytically active one-fold coordinatively unsaturated (1f-cus) Ru sites. This site blocking reduces the number of active sites and, even more important, on-top Cl blocks the free migration of the adsorbed reactants along the one-dimensional 1f-cus Ru rows, thus leading to a loss of catalytic activity.
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| 3. |
- Hofmann, Jan Philipp, et al.
(författare)
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Hydrogen-Promoted Chlorination of RuO2(110)
- 2010
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:24, s. 10901-10909
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution core-level photoemission spectroscopy and temperature-programmed reaction experiments together with density functional theory calculations were used to elucidate on the atomic scale the chlorination mechanism of ruthenium dioxide RuO2(110) by hydrogen chloride exposure. The surface-selective chlorination accounts for the extraordinary stability of the RuO2 catalyst in the Sumitomo process-the heterogeneously catalyzed oxidation of hydrogen chloride by oxygen. The selective replacement of bridging oxygen atoms by chlorine atoms depends on the formation of water molecules serving as leaving groups. Water is produced by the chlorine-assisted recombination of two neighboring surface hydroxyl groups at around 450 K, a temperature where water instantaneously leaves the surface. Finally, the bridging vacancy is rapidly filled in by chlorine atoms, thereby forming bridging chlorine atoms. Preadsorbed hydrogen has shown to facilitate the chlorination process for stoichiometry reasons. The general strategy of transforming bridging O atoms into a good leaving group has been corroborated by the chlorination of RuO2(110) via CO pretreatment with CO2 as the leaving group and subsequent Cl-2 exposure.
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| 4. |
- Pierer, Jörg, et al.
(författare)
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Photonic sensing of food allergy : integration and miniaturization
- 2012
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Ingår i: Smart Systems Integration.
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Konferensbidrag (refereegranskat)abstract
- Food allergies can provoke severe clinical reactions. Within the FP7 project POSITIVE a Lab-on-a-Chip platform for label-free quantitative allergen testing is under development. The system integrates fluidic handling, optical interrogation and a porous Silicon based bio sensor cartridge. Optical and fluidic concepts have been derived and partially tested with positive results on lab bench level. Further effort has to be spent on higher system integration and miniaturization of the components as well as signal processing and data evaluation. Model tests based on the immobilization of allergens and molecular recognition by specific antibodies have been established proofing the pre-treated porous Silicon membranes bio assay suitability.
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| 5. |
- Zuntini, Alexandre R., et al.
(författare)
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Phylogenomics and the rise of the angiosperms
- 2024
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Ingår i: NATURE. - 0028-0836 .- 1476-4687. ; 629, s. 843-850
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Tidskriftsartikel (refereegranskat)abstract
- Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods(1,2). A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome(3,4). Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins(5-7). However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes(8). This 15-fold increase in genus-level sampling relative to comparable nuclear studies(9) provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade.
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