| 1621. |
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| 1622. |
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| 1623. |
- Privon, G., et al.
(författare)
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The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120-5453
- 2017
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 835:2, s. Article Number: 213-
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Tidskriftsartikel (refereegranskat)abstract
- We present new Atacama Large Millimeter/submillimeter Array Band 7 (?340 GHz) observations of the dense gas tracers HCN, HCO+, and CS in the local, single-nucleus, ultraluminous infrared galaxy IRAS 13120-5453. We find centrally enhanced HCN (4-3) emission, relative to HCO+ (4-3), but do not find evidence for radiative pumping of HCN. Considering the size of the starburst (0.5 kpc) and the estimated supernovae rate of ?1.2 yr-1, the high HCN/HCO+ ratio can be explained by an enhanced HCN abundance as a result of mechanical heating by the supernovae, though the active galactic nucleus and winds may also contribute additional mechanical heating. The starburst size implies a high ?IR of 4.7 × 1012 L? kpc-2, slightly below predictions of radiation-pressure limited starbursts. The HCN line profile has low-level wings, which we tentatively interpret as evidence for outflowing dense molecular gas. However, the dense molecular outflow seen in the HCN line wings is unlikely to escape the Galaxy and is destined to return to the nucleus and fuel future star formation. We also present modeling of Herschel observations of the H2O lines and find a nuclear dust temperature of ?40 K. IRAS 13120-5453 has a lower dust temperature and ?IR than is inferred for the systems termed "compact obscured nuclei (CONs)" (such as Arp 220 and Mrk 231). If IRAS 13120-5453 has undergone a CON phase, we are likely witnessing it at a time when the feedback has already inflated the nuclear ISM and diluted star formation in the starburst/active galactic nucleus core.
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| 1624. |
- Pälike, Heiko, et al.
(författare)
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A Cenozoic record of the equatorial Pacific carbonate compensation depth
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 488:7413, s. 609-614
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.
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| 1625. |
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| 1626. |
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| 1627. |
- Rossberg, Axel G., et al.
(författare)
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Lets Train More Theoretical Ecologists - Here Is Why
- 2019
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Ingår i: Trends in Ecology & Evolution. - : ELSEVIER SCIENCE LONDON. - 0169-5347 .- 1872-8383. ; 34:9, s. 759-762
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Tidskriftsartikel (övrigt vetenskapligt)abstract
- A tangled web of vicious circles, driven by cultural issues, has prevented ecology from growing strong theoretical roots. Now this hinders development of effective conservation policies. To overcome these barriers in view of urgent societal needs, we propose a global network of postgraduate theoretical training programs.
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| 1628. |
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| 1629. |
- Sackton, Timothy B, et al.
(författare)
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Dynamic evolution of the innate immune system in Drosophila.
- 2007
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Ingår i: Nat Genet. - 1061-4036. ; 39:12, s. 1461-8
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Tidskriftsartikel (refereegranskat)abstract
- The availability of complete genome sequence from 12 Drosophila species presents the opportunity to examine how natural selection has affected patterns of gene family evolution and sequence divergence among different components of the innate immune system. We have identified orthologs and paralogs of 245 Drosophila melanogaster immune-related genes in these recently sequenced genomes. Genes encoding effector proteins, and to a lesser extent genes encoding recognition proteins, are much more likely to vary in copy number across species than genes encoding signaling proteins. Furthermore, we can trace the apparent recent origination of several evolutionarily novel immune-related genes and gene families. Using codon-based likelihood methods, we show that immune-system genes, and especially those encoding recognition proteins, evolve under positive darwinian selection. Positively selected sites within recognition proteins cluster in domains involved in recognition of microorganisms, suggesting that molecular interactions between hosts and pathogens may drive adaptive evolution in the Drosophila immune system.
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| 1630. |
- Shirani, A, et al.
(författare)
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Multiple sclerosis in older adults: the clinical profile and impact of interferon Beta treatment
- 2015
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Ingår i: BioMed research international. - : Hindawi Limited. - 2314-6141 .- 2314-6133. ; 2015, s. 451912-
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Tidskriftsartikel (refereegranskat)abstract
- Background. We examined (1) patient characteristics and disease-modifying drug (DMD) exposure in late-onset (LOMS, ≥50 years at symptom onset) versus adult-onset (AOMS, 18–<50 years) MS and (2) the association between interferon-beta (IFNβ) and disability progression in older relapsing-onset MS adults (≥50 years).Methods. This retrospective study (1980–2004, British Columbia, Canada) included 358 LOMS and 5627 AOMS patients. IFNβ-treated relapsing-onset MS patients aged ≥50 (regardless of onset age, 90) were compared with 171 contemporary and 106 historical controls. Times to EDSS 6 from onset and from IFNβeligibility were examined using survival analyses.Results. LOMS patients (6%) were more likely to be male, with motor onset and a primary-progressive course, and exhibit faster progression and were less likely to take DMDs. Nonetheless, 57% were relapsing-onset, of which 31% were prescribed DMDs, most commonly IFNβ. Among older relapsing-onset MS adults, no significant association between IFNβexposure and disability progression was found when either the contemporary (hazard ratio [HR]: 0.46; 95% CI: 0.18–1.22) or historical controls (HR: 0.54; 95% CI: 0.20–1.42) were considered.Conclusion. LOMS differed clinically from AOMS. One-third of older relapsing-onset MS patients were prescribed a DMD. IFNβexposure was not significantly associated with reduced disability in older MS patients.
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