| 1. |
- A Hulten, Maj, et al.
(författare)
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On the origin of the maternal age effect in trisomy 21 Down syndrome: the Oocyte Mosaicism Selection model
- 2010
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Ingår i: Reproduction. - 1470-1626 .- 1476-3990. ; 139:1, s. 1-9
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Forskningsöversikt (refereegranskat)abstract
- We have recently documented that trisomy 21 mosaicism is common in human foetal ovaries. On the basis of this observation we propose that the maternal age effect in Down syndrome (DS) is caused by the differential behaviour of trisomy 21 in relation to disomy 21 oocytes during development from foetal life until ovulation in adulthood. in particular, we suggest that trisomy 21 oocytes, lagging behind those that are disomic, may escape the timed pruning of the seven million in foetal life to the 300-400 finally selected for ovulation. The net effect of this preferential elimination will be an accumulation of trisomy 21 oocytes in the ovarian reserve of older women. We here highlight the implications of this Oocyte Mosaicism Selection (OMS) model with respect to the prevalent view that the maternal age effect is complex, dependent on many different biological and environmental factors. We examine conclusions drawn from recent large-scale studies in families, tracing DNA markers along the length of chromosome 21q between parents and DS children, in comparison to the OMS model. We conclude that these family linkage data are equally compatible with the maternal age effect originating from the accumulation of trisomy 21 oocytes with advancing maternal age. One relatively straightforward way to get to grips with what is actually going on in this regard would be to compare incidence of trisomy 21 oocytes (and their pairing configurations) in foetal ovaries with that in oocytes at the meiosis I stage from adult women.
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| 2. |
- Aalberg, Toril, et al.
(författare)
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The framing of politics as strategy and game : A review of concepts, operationalizations and key findings
- 2012
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Ingår i: Journalism - Theory, Practice & Criticism. - : SAGE Publications. - 1464-8849 .- 1741-3001. ; 13:2, s. 162-178
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Forskningsöversikt (refereegranskat)abstract
- A key concept in research on the media coverage of politics is the game or strategy frame. Contrasted with coverage of politics as issues, theframing of politics as a strategic game is marked by features such as winning and losing as the central concern and a focus on how candidates or parties are doing in opinion polls. The pervasiveness of such framing is, however, disputed since (1) the way in which the frames are conceptualized and operationalized differs significantly; and (2) while some use terms such as 'game frame' and 'strategy frame' as synonymous, others argue that there is a conceptual difference between them. Against this background, this article reviews research on the media's framing ofpolitics as a strategic game, what concepts have been used, and how they have been operationalized; and suggests a synthesis and ways of improving conceptual clarity and comparability in research on the media's use of strategy and/or game frames. © SAGE Publications 2011.
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| 3. |
- Abbasi, Maisam, et al.
(författare)
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Themes and challenges in making supply chains environmentally sustainable
- 2012
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Ingår i: Supply Chain Management. - : Emerald. - 1359-8546. ; 17:5, s. 517-530
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Forskningsöversikt (refereegranskat)abstract
- Purpose - The purpose of this article is to explore themes and challenges in making supply chains environmentally sustainable. Design/methodology/approach - The study began with a systematic review, and content analysis of articles in top-ranking related journals from logistics, transport, sustainability and environmental areas, and ended with research propositions contributing to the further advancement of supply chain management. Findings - The findings illustrate the major themes published in 18 journals concentrating on sustainable supply chains with special focus on environmental issues. From the systematic review five major areas of challenges for supply chain management are derived: costs, complexity, operationalisation, mindset and cultural changes, and uncertainties. From all of these areas synthesising discussions are provided and research propositions suggested. It is concluded that there is a great need for models and frameworks that consider the complexity involved, take holistic perspectives, and challenge the basic assumptions underlying most of the research published (i.e. reductionism, positivism and economic growth). Research limitations/implications - Sustainability in this article is mainly related to environmental issues. Analysis of complex interactions between environmental, social and economic aspects might provide opportunities for future research. Practical implications - The results presented in this paper provide a systematic structure for classifying issues related to logistics sustainability; something which will be beneficial for managers and policy-makers when they approach sustainable supply chain management challenges. Originality/value - This paper provides propositions for research based on the emergent outcome of challenges that can guide research, industry and policy-makers in future sustainability efforts.
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| 4. |
- Abbasi, Saeed, et al.
(författare)
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Particle emissions from rail traffic : a literature review
- 2013
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Ingår i: Critical reviews in environmental science and technology. - USA : Taylor & Francis. - 1064-3389 .- 1547-6537. ; 43:23, s. 2211-2244
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Forskningsöversikt (refereegranskat)abstract
- Particle emissions are a drawback of rail transport. This work is a comprehensive presentation of recent research into particle emissions from rail vehicles. Both exhaust and non-exhaust particle emissions are considered when examining particle characteristics such as PM10, and PM2.5 concentration levels, size, morphology, composition, as well as adverse health effects, current legislation, and available and proposed solutions for reducing such emissions. High concentration levels in enclosed rail traffic environments are reported and some toxic effects of the particles. We find that only a few limited studies have examined the adverse health effects of non-exhaust particle emissions and that no relevant legislation exists. Thus further research in this area is warranted.
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| 5. |
- Abbott, Jessica K.
(författare)
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Intra-locus sexual conflict and sexually antagonistic genetic variation in hermaphroditic animals
- 2011
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 278:1703, s. 161-169
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Forskningsöversikt (refereegranskat)abstract
- Intra-locus sexual conflict results when sex-specific selection pressures for a given trait act against the intra-sexual genetic correlation for that trait. It has been found in a wide variety of taxa in both laboratory and natural populations, but the importance of intra-locus sexual conflict and sexually antagonistic genetic variation in hermaphroditic organisms has rarely been considered. This is not so surprising given the conceptual and theoretical association of intra-locus sexual conflict with sexual dimorphism, but there is no a priori reason why intra-locus sexual conflict cannot occur in hermaphroditic organisms as well. Here, I discuss the potential for intra-locus sexual conflict in hermaphroditic animals and review the available evidence for such conflict, and for the existence of sexually antagonistic genetic variation in hermaphrodites. I argue that mutations with asymmetric effects are particularly likely to be important in mediating sexual antagonism in hermaphroditic organisms. Moreover, sexually antagonistic genetic variation is likely to play an important role in inter-individual variation in sex allocation and in transitions to and from gonochorism (separate sexes) in simultaneous hermaphrodites. I also describe how sequential hermaphrodites may experience a unique form of intra-locus sexual conflict via antagonistic pleiotropy. Finally, I conclude with some suggestions for further research.
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| 6. |
- Abbott, Jessica K., et al.
(författare)
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Obtaining snapshots of genetic variation using hemiclonal analysis
- 2011
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Ingår i: Trends in Ecology & Evolution. - : Elsevier BV. - 0169-5347 .- 1872-8383. ; 26:7, s. 359-368
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Forskningsöversikt (refereegranskat)abstract
- Hemiclones are naturally occurring or artificially produced individuals that share a single specific genetic haplotype. Natural hemiclones are produced via hybridization between two closely related species, whereas hemiclonal analysis in Drosophila is carried out in the laboratory via crosses with artificially created 'clone-generator' females with a specific genetic make-up. Hemiclonal analysis in Drosophila has been applied successfully to date to obtain measures of standing genetic variation for numerous traits. Here, we review the current hemiclonal literature and suggest future directions for hemiclonal research, including its application in molecular and genomic studies, and the adaptation of natural hemiclonal systems to carry out Drosophila-type studies of standing genetic variation.
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| 7. |
- Abbott, R., et al.
(författare)
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Hybridization and speciation
- 2013
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 26:2, s. 229-246
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Forskningsöversikt (refereegranskat)abstract
- Hybridization has many and varied impacts on the process of speciation. Hybridization may slow or reverse differentiation by allowing gene flow and recombination. It may accelerate speciation via adaptive introgression or cause near-instantaneous speciation by allopolyploidization. It may have multiple effects at different stages and in different spatial contexts within a single speciation event. We offer a perspective on the context and evolutionary significance of hybridization during speciation, highlighting issues of current interest and debate. In secondary contact zones, it is uncertain if barriers to gene flow will be strengthened or broken down due to recombination and gene flow. Theory and empirical evidence suggest the latter is more likely, except within and around strongly selected genomic regions. Hybridization may contribute to speciation through the formation of new hybrid taxa, whereas introgression of a few loci may promote adaptive divergence and so facilitate speciation. Gene regulatory networks, epigenetic effects and the evolution of selfish genetic material in the genome suggest that the Dobzhansky-Muller model of hybrid incompatibilities requires a broader interpretation. Finally, although the incidence of reinforcement remains uncertain, this and other interactions in areas of sympatry may have knock-on effects on speciation both within and outside regions of hybridization.
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| 8. |
- Abdo, A. A., et al.
(författare)
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PKS 1502+106 : A new and distant gamma-ray blazar in outburst discovered by the fermi large area telescope
- 2010
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 710:1, s. 810-827
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Forskningsöversikt (refereegranskat)abstract
- The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope discovered a rapid (similar to 5 days duration), high-energy (E > 100 MeV) gamma-ray outburst from a source identified with the blazar PKS 1502+106 (OR 103, S3 1502+10, z = 1.839) starting on 2008 August 5 (similar to 23 UTC, MJD 54683.95), and followed by bright and variable flux over the next few months. Results on the gamma-ray localization and identification, as well as spectral and temporal behavior during the first months of the Fermi all-sky survey, are reported here in conjunction with a multiwaveband characterization as a result of one of the first Fermi multifrequency campaigns. The campaign included a Swift ToO (followed up by a 16 day observation on August 7-22, MJD 54685-54700), VLBA (within the MOJAVE program), Owens Valley Radio Observatory (OVRO) 40 m, Effelsberg-100 m, Metsahovi-14 m, RATAN-600, and Kanata-Hiroshima radio/optical observations. Results from the analysis of archival observations by INTEGRAL, XMM-Newton, and Spitzer space telescopes are reported for a more complete picture of this new gamma-ray blazar. PKS 1502+106 is a sub-GeV peaked, powerful flat spectrum radio quasar (luminosity at E > 100 MeV, L-gamma, is about 1.1 x 10(49) erg s(-1), and black hole mass likely close to 10(9) M-circle dot), exhibiting marked gamma-ray bolometric dominance, in particular during the asymmetric outburst (L-gamma/L-opt similar to 100, and 5 day averaged flux F-E > 100MeV = 2.91 +/- 1.4 x 10(-6) ph cm(-2) s(-1)), which was characterized by a factor greater than 3 of flux increase in less than 12 hr. The outburst was observed simultaneously from optical to X-ray bands (F0.3-10keV = 2.18(-0.12)(+0.15) x 10(-12) erg cm(-2) s(-1), and hard photon index similar to 1.5, similar to past values) with a flux increase of less than 1 order of magnitude with respect to past observations, and was likely controlled by Comptonization of external-jet photons produced in the broad-line region (BLR) in the gamma-ray band. No evidence of a possible blue bump signature was observed in the optical-UV continuum spectrum, while some hints for a possible 4 day time lag with respect to the gamma-ray flare were found. Nonetheless, the properties of PKS 1502+106 and the strict optical/UV, X-, and gamma-ray cross-correlations suggest the contribution of the synchrotron self-Compton (SSC), in-jet, process should dominate from radio to X- rays. This mechanism may also be responsible for the consistent gamma-ray variability observed by the LAT on longer timescales, after the ignition of activity at these energies provided by the BLR-dissipated outburst. Modulations and subsequent minor, rapid flare events were detected, with a general fluctuation mode between pink-noise and a random-walk. The averaged gamma-ray spectrum showed a deviation from a simple power law, and can be described by a log-parabola curved model peaking around 0.4-0.5 GeV. The maximum energy of photons detected from the source in the first four months of LAT observations was 15.8 GeV, with no significant consequences on extragalactic background light predictions. A possible radio counterpart of the gamma-ray outburst can be assumed only if a delay of more than three months is considered on the basis of opacity effects at cm and longer wavelengths. The rotation of the electric vector position angle observed by VLBA from 2007 to 2008 could represent a slow field odering and alignment with respect to the jet axis, likely a precursor feature of the ejection of a superluminal radio knot and the high-energy outburst. This observing campaign provides more insight into the connection between MeV-GeV flares and the moving, polarized structures observed by the VLBI.
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| 9. |
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| 10. |
- Abeler-Dörner, Lucie, et al.
(författare)
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Butyrophilins: an emerging family of immune regulators
- 2012
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Ingår i: Trends in immunology. - : Elsevier BV. - 1471-4906 .- 1471-4981. ; 33:1, s. 34-41
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Forskningsöversikt (refereegranskat)abstract
- Butyrophilins (Btns) and butyrophilin-like (Btnl) molecules are emerging as novel regulators of immune responses in mice and humans. Several clues point to their probable importance: many of the genes are located within the MHC; they are structurally related to B7-co-stimulatory molecules; they are functionally implicated in T cell inhibition and in the modulation of epithelial cell-T cell interactions; and they are genetically associated with inflammatory diseases. Nonetheless, initial immersion into the current literature can uncover confusion over even basic information such as gene names and expression patterns, and seemingly conflicting data regarding the biological activities of different family members. This review addresses each of these issues, concluding with the attractive potential of Btn and Btnl molecules to act as specific attenuators of tissue-associated inflammatory responses.
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