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- Svirskiy, G. I., et al.
(författare)
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Comparative X-Ray Absorption Analysis of the Spectrum of Vacant Electronic States in Cobalt and Nickel Tetraphenylporphyrin Complexes
- 2018
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Ingår i: Physics of the solid state. - 1063-7834 .- 1090-6460. ; 60:3, s. 581-591
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Tidskriftsartikel (refereegranskat)abstract
- The energy distributions and the properties of the lower vacant electronic states in cobalt and nickel tetraphenylporphyrin complexes CoTPP and NiTPP are studied by X-ray absorption spectroscopy. Quasimolecular analysis of the experimental absorption spectra measured in the region of the 2p and 1s ionization thresholds of complexing metal atoms, as well as the 1s thresholds of ligand atoms (nitrogen and carbon), is based on the comparison of the corresponding spectra with each other and with the spectra of the simplest nickel porphyrin NiP. It has been established that, despite a general similarity of the spectra of nitrogen and carbon in CoTPP and NiTPP, the fine structure of the 2p and 1s absorption spectra of cobalt and nickel atoms are radically different. The observed differences in the spectra of cobalt and nickel are associated with the features of the energy distribution of vacant 3d electron states. The presence in CoTPP of the partially filled valence 3db2g molecular orbital (MO) results in the appearance in the cobalt spectra of a low-energy band, which is absent in the spectrum of nickel in NiTPP and leads to a doublet structure of transitions to b1g and e g MOs due to the exchange interaction between 3d electrons in partially filled 3db2g and 3db1g or 3de g MOs. The spectrum of vacant states in CoTPP differs from that in NiTPP also due to the smaller energy distance between 3db1g and e g MOs and the different positions of nonbonding MOs with the C2p character of the porphine ligand.
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| 3. |
- Vinogradov, N. A., et al.
(författare)
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The structural evolution of graphene/Fe(110) systems upon annealing
- 2017
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 111, s. 113-120
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Tidskriftsartikel (refereegranskat)abstract
- The thermal stability and the structural evolution of graphene grown on Fe(110) has been studied upon annealing in ultra-high vacuum conditions (UHV, P <= 10(-9) mbar) and in the presence of gaseous ethylene at a pressure of similar to 10(-6) mbar by grazing incidence X-ray diffraction. It was observed that upon annealing at temperatures below 630 degrees C, graphene on Fe is thermally stable. Exposure to ethylene at these temperatures promotes the formation of graphene while inhibiting its deterioration. Annealing graphene/Fe(110) at temperatures above 630 degrees C results in a fast degradation of graphene followed by carburization of the sample, that is the irreversible formation of various iron carbides, with the most common phases being Fe3C (cementite) and Fe7C3 (Eckstrom-Adcock carbide). Annealing of the carburized sample does not result in the formation of a detectable graphitic structure.
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| 4. |
- Putintseva, Yuliya A., et al.
(författare)
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Siberian larch (Larix sibirica Ledeb.) mitochondrial genome assembled using both short and long nucleotide sequence reads is currently the largest known mitogenome
- 2020
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Ingår i: BMC Genomics. - : BMC. - 1471-2164. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Plant mitochondrial genomes (mitogenomes) can be structurally complex while their size can vary from similar to 222 Kbp inBrassica napusto 11.3 Mbp inSilene conica. To date, in comparison with the number of plant species, only a few plant mitogenomes have been sequenced and released, particularly for conifers (the Pinaceae family). Conifers cover an ancient group of land plants that includes about 600 species, and which are of great ecological and economical value. Among them, Siberian larch (Larix sibiricaLedeb.) represents one of the keystone species in Siberian boreal forests. Yet, despite its importance for evolutionary and population studies, the mitogenome of Siberian larch has not yet been assembled and studied. Results: Two sources of DNA sequences were used to search for mitochondrial DNA (mtDNA) sequences: mtDNA enriched samples and nucleotide reads generated in the de novo whole genome sequencing project, respectively. The assembly of the Siberian larch mitogenome contained nine contigs, with the shortest and the largest contigs being 24,767 bp and 4,008,762 bp, respectively. The total size of the genome was estimated at 11.7 Mbp. In total, 40 protein-coding, 34 tRNA, and 3 rRNA genes and numerous repetitive elements (REs) were annotated in this mitogenome. In total, 864 C-to-U RNA editing sites were found for 38 out of 40 protein-coding genes. The immense size of this genome, currently the largest reported, can be partly explained by variable numbers of mobile genetic elements, and introns, but unlikely by plasmid-related sequences. We found few plasmid-like insertions representing only 0.11% of the entire Siberian larch mitogenome. Conclusions: Our study showed that the size of the Siberian larch mitogenome is much larger than in other so far studied Gymnosperms, and in the same range as for the annual flowering plantSilene conica(11.3 Mbp). Similar to other species, the Siberian larch mitogenome contains relatively few genes, and despite its huge size, the repeated and low complexity regions cover only 14.46% of the mitogenome sequence.
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