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| 2. |
- Brauer, H.E., et al.
(författare)
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Na intercalation of VSe2 studied by photoemission and scanning tunneling microscopy
- 1997
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 55:15, s. 10022-10026
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Tidskriftsartikel (refereegranskat)abstract
- In situ Na intercalation of the layered compound VSe2 has been studied with photoemission and scanning tunneling microscopy. Core-level spectroscopy proves that Na deposited in UHV onto the VSe2 surface rapidly intercalates, leaving only small amounts at the surface. The scanning tunneling microscopy measurements show that the intercalated Na is not uniformly distributed between the VSe2 layers, but preferentially in two-dimensional islands. Thus the surface region is divided into intercalated and nonintercalated areas. Hole-like features in the intercalated areas are interpreted as locally missing Na.
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| 3. |
- Clark, R M, et al.
(författare)
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Superdeformation in bismuth
- 1996
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 53:1, s. 117-123
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Tidskriftsartikel (refereegranskat)abstract
- High angular momentum states in Bi-195-197 are populated in two reactions: W-183(F-19,xn)Bi-202-x and Ta-181(Ne-20,xn)Bi-201-x at beam energies of 108 and 123 MeV, respectively. Gamma rays were detected using the Gammasphere array. Three weakly populated rotational sequences have been found. They each have properties characteristic of other superdeformed bands in this mass region. On the basis of cross-bombardment information we believe that one band belongs to each of Bi-195, Bi-196, and Bi-197. The properties of the bands in the odd-Bi nuclei are best reproduced if the odd proton occupies the favored signature of the [651]1/2 orbital, while the band in Bi-196 has this same proton configuration coupled to an additional N=7 (j(15/2)) neutron. The relative behavior of the J((2)) moments of inertia can be qualitatively understood in terms of Pauli-blocking effects.
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| 4. |
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| 5. |
- Andersson, D.I, et al.
(författare)
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Antibiotikaresistens här för att stanna?
- 1998
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Ingår i: Läkartidningen. - 0023-7205 .- 1652-7518. ; 95:37, s. 3940-3944
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)
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| 6. |
- Andersson, Dan I, et al.
(författare)
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Muller's ratchet decreases fitness of a DNA-based microbe
- 1996
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 93:2, s. 906-907
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Tidskriftsartikel (refereegranskat)abstract
- Muller proposed that an asexual organism will inevitably accumulate deleterious mutations, resulting in an increase of the mutational load and an inexorable, ratchet-like, loss of the least mutated class [Muller, H.J. (1964) Mutat. Res. 1, 2-9]. The operation of Muller's ratchet on real populations has been experimentally demonstrated only in RNA viruses. However, these cases are exceptional in that the mutation rates of the RNA viruses are extremely high. We have examined whether Muller's ratchet operates in Salmonella typhimurium, a DNA-based organism with a more typical genomic mutation rate. Cells were grown asexually under conditions expected to result in high genetic drift, and the increase in mutational load was determined. S. typhimurium accumulated mutations under these conditions such that after 1700 generations, 1% of the 444 lineages tested had suffered an obvious loss of fitness, as determined by decreased growth rate. These results suggest that in the absence of sex and with high genetic drift, genetic mechanisms, such as back or compensatory mutations, cannot compensate for the accumulation of deleterious mutations. In addition, we measured the appearance of auxotrophs, which allowed us to calculate an average spontaneous mutation rate of approximately 0.3-1.5 x 10(-9) mutations per base pair per generation. This rate is measured for the largest genetic target studied so far, a collection of about 200 genes.
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| 7. |
- Baldsiefen, G, et al.
(författare)
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Shears bands in Pb-193
- 1996
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 54:3, s. 1106-1116
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Tidskriftsartikel (refereegranskat)abstract
- Four bands of enhanced dipole transitions, with weak crossovers, have been observed in Pb-195. Three of these bands are connected to the spherical levels. in addition, the spherical level scheme has been extended. The nuclear spectroscopy was done with the early implementation of GAMMASPHERE and HERA arrays of Get detectors. The nucleus Pb-193 was populated in the Yb-174(Mg-24,5n) reaction at beam energies of 129, 131, and 134 MeV. The experimental results are compared to tilted-axis cranking calculations. The systematical behavior of the dipole bands in the heavier odd-A Pb isotopes, Pb-195,Pb-197,Pb-199,Pb-201, is also discussed.
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| 8. |
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| 9. |
- Björkman, Johanna, et al.
(författare)
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Novel ribosomal mutations affecting translational accuracy, antibiotic resistance and virulence of Salmonella typhimurium
- 1999
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Ingår i: Molecular Microbiology. - : BLACKWELL SCIENCE LTD. - 0950-382X .- 1365-2958. ; 31:1, s. 53-58
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Many mutations in rpsL cause resistance to, or dependence on, streptomycin and are restrictive (hyperaccurate) in translation. Dependence on streptomycin and hyperaccuracy can each be reversed phenotypically by mutations in either rpsD or rpsE. Such compensatory mutations have been shown to have a ram phenotype (ribosomal ambiguity), increasing the level of translational errors. We have shown recently that restrictive rpsL alleles are also associated with a loss of virulence in Salmonella typhimurium. To test whether ram mutants could reverse this loss of virulence, we have isolated a set of rpsD alleles in Salmonella typhimurium. We found that the rpsD alleles restore the virulence of strains carrying restrictive rpsL alleles to a level close to that of the wild type. Unexpectedly, three out of seven mutant rpsD alleles tested have phenotypes typical of restrictive alleles of rpsL, being resistant to streptomycin and restrictive (hyperaccurate) in translation. These phenotypes have not been previously associated with the ribosomal protein S4. Furthermore, all seven rpsD alleles (four ram and three restrictive) can phenotypically reverse the hyperaccuracy associated with restrictive alleles of rpsL. This is the first demonstration that such compensations do not require that the compensating rpsD allele has a ribosomal ambiguity (ram) phenotype.
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| 10. |
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