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| 2. |
- Ueda, K., et al.
(författare)
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Adsorption and Reaction of CO and NO on Ir(111) under Near Ambient Pressure Conditions
- 2016
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 59:5-7, s. 487-496
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption and reaction of CO and NO on Ir(111) have been studied by near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) together with low-energy electron diffraction, scanning tunneling microscopy, and mass spectroscopy (MS). Under both ultrahigh vacuum (UHV) and NAP conditions CO molecules occupy on-top sites of the Ir(111) surface at room temperature (RT) by forming two-dimensional clusters. Exposure to NO under UHV conditions at RT induces partially dissociative adsorption, while NAP NO exposure leads to a Ir(111) surface that is covered by molecular NO. We conducted in-operando NAP-XPS/MS observation of the NO + 13CO reaction under a NAP condition as a function of temperature. Below 210 °C adsorption of NO is inhibited by CO, while above 210 °C the CO inhibition is released due to partial desorption of CO and dissociative adsorption of NO starts to occur leading to associative formation of N2. Under the most active condition studied here the Ir surface is covered by a dense co-adsorption layer consisting of on-top CO, atomic N and O, which suggests that this reaction is not a NO-dissociation-limited process but a N2/CO2 formation-limited process.
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| 3. |
- Chiu, CH, et al.
(författare)
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Bichir HoxA cluster sequence reveals surprising trends in ray-finned fish genomic evolution
- 2004
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1549-5469 .- 1088-9051. ; 14:1, s. 11-17
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Tidskriftsartikel (refereegranskat)abstract
- The study of Hox clusters and genes provides insights into the evolution of genomic regulation of development. Derived ray-finned fishes (Actinopterygii, Teleostei) such as zebrafish and pufferfish possess duplicated Hox clusters that have undergone considerable sequence evolution. Whether these changes are associated with the duplication(s) that produced extra Hox clusters is unresolved because comparison with basal lineages is unavailable. We sequenced and analyzed the HoxA cluster of the bichir (Polypterus senegalus), a phylogenetically basal actinopterygian. Independent lines of evidence indicate that bichir has one HoxA cluster that is mosaic in its patterns of noncoding sequence conservation and gene retention relative to the HoxA clusters of human and shark, and the HoxAalpha and HoxAbeta clusters of zebrafish, pufferfish, and striped bass. HoxA cluster noncoding sequences conserved between bichir and euteleosts indicate that novel cis-sequences were acquired in the stem actinopterygians and maintained after cluster duplication. Hence, in the earliest actinopterygians, evolution of the single HoxA cluster was already more dynamic than in human and shark. This tendency peaked among teleosts after HoxA cluster duplication.
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| 4. |
- Sakamoto, K., et al.
(författare)
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Interaction of metastable molecular oxygen with the dangling bonds of a Si(111)-(7×7) surface
- 2001
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048 .- 1873-2526. ; 114-116, s. 489-494
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the interaction between metastable molecular oxygen and the adatom dangling bonds modified by the adsorption of atomic oxygen into the back-bonds of a Si(111)-(7×7) surface. Ultraviolet photoelectron spectroscopy shows that the metastable states increase in intensity faster but with a decrease in its saturated intensity as the coverage of atomic oxygen increases. This result suggests that the number of modified dangling bonds is not the only important factor for the adsorption process of metastable oxygen. Taking into account the observation of modified dangling bonds with different density of states in scanning tunneling microscopy, we conclude that the adsorption of the metastable oxygen species correlates closely with the density of states of the dangling bond.
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| 5. |
- Jones, Felicity C., et al.
(författare)
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The genomic basis of adaptive evolution in threespine sticklebacks
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 484:7392, s. 55-61
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Tidskriftsartikel (refereegranskat)abstract
- Marine stickleback fish have colonized and adapted to thousands of streams and lakes formed since the last ice age, providing an exceptional opportunity to characterize genomic mechanisms underlying repeated ecological adaptation in nature. Here we develop a high-quality reference genome assembly for threespine sticklebacks. By sequencing the genomes of twenty additional individuals from a global set of marine and freshwater populations, we identify a genome-wide set of loci that are consistently associated with marine-freshwater divergence. Our results indicate that reuse of globally shared standing genetic variation, including chromosomal inversions, has an important role in repeated evolution of distinct marine and freshwater sticklebacks, and in the maintenance of divergent ecotypes during early stages of reproductive isolation. Both coding and regulatory changes occur in the set of loci underlying marine-freshwater evolution, but regulatory changes appear to predominate in this well known example of repeated adaptive evolution in nature.
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