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- Schulz, A, et al.
(författare)
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Arctic ozone loss in threshold conditions: Match observations in 1997/1998 and 1998/1999
- 2001
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Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES. - : AMER GEOPHYSICAL UNION. - 0747-7309. ; 106:D7, s. 7495-7503
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Tidskriftsartikel (refereegranskat)abstract
- Chemical ozone loss rates inside the Arctic polar vortex were determined in early 1998 and early 1999 by using the Match technique based on coordinated ozonesonde measurements. These two winters provide the only opportunities in recent years to investigat
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| 4. |
- Hillier, Ladeana W, et al.
(författare)
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Sequence and comparative analysis of the chicken genome provide unique perspectives on vertebrate evolution
- 2004
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 432:7018, s. 695-716
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Tidskriftsartikel (refereegranskat)abstract
- We present here a draft genome sequence of the red jungle fowl, Gallus gallus. Because the chicken is a modern descendant of the dinosaurs and the first non-mammalian amniote to have its genome sequenced, the draft sequence of its genome--composed of approximately one billion base pairs of sequence and an estimated 20,000-23,000 genes--provides a new perspective on vertebrate genome evolution, while also improving the annotation of mammalian genomes. For example, the evolutionary distance between chicken and human provides high specificity in detecting functional elements, both non-coding and coding. Notably, many conserved non-coding sequences are far from genes and cannot be assigned to defined functional classes. In coding regions the evolutionary dynamics of protein domains and orthologous groups illustrate processes that distinguish the lineages leading to birds and mammals. The distinctive properties of avian microchromosomes, together with the inferred patterns of conserved synteny, provide additional insights into vertebrate chromosome architecture.
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| 6. |
- Beer, Martin E, et al.
(författare)
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Red giant depletion in globular cluster cores
- 2004
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 348:2, s. 679-686
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the observed depletion of red giants in the cores ofpost-core-collapse globular clusters. In particular, the evolutionaryscenario we consider is a binary consisting of two low-mass stars whichundergoes two common-envelope phases. The first common-envelope phaseoccurs when the primary is a red giant resulting in a helium white dwarfand main-sequence star in a detached binary. The second common-envelopephase occurs shortly after the secondary becomes a red giant. During thesecond common-envelope phase, the degenerate helium cores mergeresulting in a core mass greater than the helium burning limit and theformation of a horizontal branch star. We show that stellar encountersenhance this evolutionary route in post-core-collapse clusters. Theseencounters increase the population of binary secondaries which wouldhave evolved on to the red giant branch in the recent past.
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| 9. |
- Davies, Melvyn B, et al.
(författare)
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Blue straggler production in globular clusters
- 2004
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 349:1, s. 129-134
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Tidskriftsartikel (refereegranskat)abstract
- Recent Hubble Space Telescope observations of a large sample of globular clusters reveal that every cluster contains between 40 and 400 blue stragglers.The population does not correlate with either stellar collision rate (as would be expected if all blue stragglers were formed via collisions) or total mass (as would be expected if all blue stragglers were formed via the unhindered evolution of a subset of the stellar population). In this paper, we support the idea that blue stragglers are made through both channels. The number produced via collisions tends to increase with cluster mass. In this paper we show how the current population produced from primordial binaries decreases with increasing cluster mass;exchange encounters with third, single stars in the most massivec lusters tend to reduce the fraction of binaries containing a primary close to the current turn-off mass. Rather, their primaries tend to be somewhat more massive (~1-3 Msolar) and have evolved off the main sequence, filling their Roche lobes in the past, often converting their secondaries into blue stragglers (but more than 1 Gyr or so ago and thus they are no longer visible as blue stragglers). We show that this decline in the primordial blue straggler population is likely to be offset by the increase in the number of blue stragglers produced via collisions. The predicted total blue straggler population is therefore relatively independent of cluster mass, thus matching the observed population. This result does not depend on any particular assumed blue straggler lifetime.
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