| 1. |
- Adcox, K, et al.
(författare)
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Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX Collaboration
- 2005
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Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474. ; 757:1-2, s. 184-283
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Forskningsöversikt (refereegranskat)abstract
- Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (PT), elliptic flow, two-particle correlations, nonstatistical fluctuations, and suppression of particle production at high PT. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.
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| 2. |
- Adler, S. S., et al.
(författare)
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High transverse momentum eta meson production in p+p, d+Au, and Au+Au collisions at root s(NN)=200 GeV
- 2007
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 75:2
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Forskningsöversikt (refereegranskat)abstract
- Inclusive transverse momentum spectra of eta mesons in the range p(T)approximate to 2-12 GeV/c have been measured at midrapidity (vertical bar eta vertical bar < 0.35) by the PHENIX experiment at RHIC in p+p,d+Au, and Au+Au collisions at root s(NN)=200 GeV. The eta mesons are reconstructed through their eta ->gamma gamma channel for the three colliding systems as well as through the eta ->pi(0)pi(+)pi(-) decay mode in p+p and d+Au collisions. The nuclear modification factor in d+Au collisions, R-dAu(p(T))approximate to 1.0-1.1, suggests at most only modest p(T) broadening ("Cronin enhancement"). In central Au+Au reactions, the eta yields are significantly suppressed, with R-AuAu(p(T))approximate to 0.2. The ratio of eta to pi(0) yields is approximately constant as a function of p(T) for the three colliding systems in agreement with the high-p(T) world average of R-eta/pi(0)approximate to 0.5 in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions for a wide range of center-of-mass energies (root sNN approximate to 3-1800 GeV) as well as, for high scaled momentum x(p), in e(+)e(-) annihilations at root s=91.2 GeV. These results are consistent with a scenario where high-p(T) eta production in nuclear collisions at the Relativistic Heavy Ion Collider is largely unaffected by initial-state effects but where light-quark mesons (pi(0),eta) are equally suppressed due to final-state interactions of the parent partons in the dense medium produced in Au+Au reactions.
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| 3. |
- Duan, Rui-Dong, et al.
(författare)
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Sphingolipid hydrolysis enzymes in the gastrointestinal tract
- 1999
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Ingår i: Methods in Enzymology. - 0076-6879. ; 311, s. 276-286
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Forskningsöversikt (refereegranskat)abstract
- In the intestinal tract, there are enzymes that hydrolyze both endogenous and exogenous sphingolipids. The alkaline sphingomyelinases (SMase) of the gut and human bile have been most studied, and a major part of this chapter discusses these enzymes. It also discusses studies of ceramidase, glycosylceramidase, and the digestion of dietary sphingolipids. In the intestinal tract, a distinct enzyme that hydrolyzes SM was discovered in 1969 by Nilsson and named “alkaline SMase.” The alkaline SMase activity is localized specifically in the intestinal tract and is not detectable in other organs, including brain, kidney, lung, spleen, testis, pancreas, and stomach, or in milk and urine. The intestinal alkaline SMase is not bacterial in origin as similar activity is found in ordinary mice and germ-free mice and in meconium of human fetus as early as 26 weeks of gestation. In the intestines of different experimental animals, the highest activities were in rat, mouse, pig, and baboon, lower activity in rabbit, and little activity in the guinea pig. Whether these species differences indicate genetic variation or an influence of diet composition on the expression of the enzyme in the intestine is unknown.
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| 4. |
- Hasselquist, Dennis, et al.
(författare)
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Maternal transfer of antibodies in vertebrates: trans-generational effects on offspring immunity.
- 2009
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Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2970 .- 0962-8436. ; 364:1513, s. 51-60
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Forskningsöversikt (refereegranskat)abstract
- Maternal effects by which females provide their offspring with non-genetic factors such as hormones, nutrients and antibodies can have an important impact on offspring fitness. In vertebrates, maternal antibodies (matAb) are transferred from the mother, via the placenta, egg yolk or milk during lactation to offspring until they are 2 weeks (birds), 4-10 weeks (rodents) and 9 months (humans) old, respectively. matAb transfer can have direct effects on offspring growth rate in birds and rodents, probably by passively protecting the newborn from common pathogens before their endogenous immune system has matured. Indirect long-term effects of matAb transfer on the offspring's own immunity can be synergistic, if matAb act as antigen templates of the accumulated immunological experience of the mother and educate the newborn's immune system. However, it may also be suppressive if matAb reduce antigen presentation to the newborn resulting in antigen-specific blocking of offspring endogenous immunity. Our aim is to review the mechanisms and direct effects of matAb transfer in vertebrates with an emphasis on birds, outline a framework for research on the long-term effects of matAb on the endogenous immune system of the mature offspring and encourage ecological and evolutionary studies of matAb transfer in non-domesticated animals.
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| 5. |
- Hasselquist, Dennis, et al.
(författare)
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Physiological mechanisms mediating costs of immune responses: what can we learn from studies of birds?
- 2012
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Ingår i: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 83:6, s. 1303-1312
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Forskningsöversikt (refereegranskat)abstract
- Activating the immune system has associated fitness costs, both immediate costs in the form of reduced current reproduction and long-term costs in the form of reduced life span and future reproduction. This indicates that immune system activation can be an important agent in life history trade-offs. In this review, we evaluate the importance of four currencies generally considered as potential mediators of the costs of immune responses in ecological studies: (1) energetic costs, (2) nutrient costs, (3) autoimmunity and (4) oxidative stress, which may be responsible for these trade-offs. A meta-analysis revealed significant elevation of energy consumption during an immune response; however, the magnitude of this energetic cost was only 5-15%. In a direct comparison using similar immune system activation in tits, energetic savings in terms of lowered feeding rate was seven times higher than energetic costs of mounting an immune response. These results do not support the hypothesis that energy is the key proximate currency mediating the costs of immunity. Nutrient savings from immunosuppression seem to be even less beneficial as this constitutes only a minor part of the daily nutrient turnover in the body. In our view, there are some indications that oxidative stress can be an important currency that could mediate both short-term and long-term costs of immune system activation, although direct evidence is so far limited. The importance of autoimmune responses is at this point hard to evaluate owing to limited empirical studies in wild animals. (c) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
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| 6. |
- Hedlund, Maria, et al.
(författare)
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Sphingomyelin, glycosphingolipids, and ceramide signalling in cells exposed to p-fimbriated Escherichia coli
- 1998
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Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 29:5, s. 1297-1306
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Forskningsöversikt (refereegranskat)abstract
- Uropathogenic Escherichia coli attach to epithelial cells through P fimbriae that bind Galα1‐4Galβ‐oligosaccharide sequences in cell surface glycosphingolipids. The binding of P‐fimbriated E. coli to uroepithelial cells causes the release of ceramide, activation of the ceramide signalling pathway and a cytokine response in the epithelial cells. The present study examined the molecular source of ceramide in human kidney A498 cells exposed to P‐fimbriated E. coli. Agonists such as TNF‐α and IL‐1β released ceramide from sphingomyelin by the activation of endogenous sphingomyelinases and hydrolysis of sphingomyelin, and triggered an IL‐6 response. P‐fimbriated E. coli caused a slight increase in endogenous sphingomyelinase activity, but there was no associated sphingomyelin hydrolysis. Instead, the concentration of galactose‐containing glycolipids decreased. We propose that P‐fimbriated E. coli differ from other activators of the ceramide pathway, in that release of ceramide is from receptor glycolipids and not from sphingomyelin. Receptor breakdown may be an efficient host defence strategy, as it reduces the concentration of cell surface receptors, releases soluble receptor analogues and activates an inflammatory response.
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| 7. |
- Hegemann, Arne, et al.
(författare)
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A physiological perspective on the ecology and evolution of partial migration
- 2019
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Ingår i: Journal of Ornithology. - : Springer Science and Business Media LLC. - 2193-7192 .- 2193-7206. ; 160:3, s. 893-905
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Forskningsöversikt (refereegranskat)abstract
- Billions of animals migrate between breeding and non-breeding areas worldwide. Partial migration, where both migrants and residents coexist within a population, occurs in most animal taxa, including fish, insects, birds and mammals. Partial migration has been hypothesised to be the most common form of migration and to be an evolutionary precursor to full migration. Despite extensive theoretical models about partial migration and its potential to provide insight into the ecology and evolution of migration, the physiological mechanisms that shape partial migration remain poorly understood. Here, we review current knowledge on how physiological processes mediate the causes and consequences of avian partial migration, and how they may help us understand why some individuals migrate and others remain resident. When information from birds is missing, we highlight examples from other taxa. In particular, we focus on temperature regulation, metabolic rate, immune function, oxidative stress, telomeres, and neuroendocrine and endocrine systems. We argue that these traits provide physiological pathways that regulate the ecological and behavioural causes and/or consequences of partial migration, and may provide insight into the mechanistic basis of wintering decisions. They may, thus, also help us to explain why individuals switch strategies among winters. We also highlight current gaps in our knowledge and suggest promising future research opportunities. A deeper understanding of the physiological mechanisms mediating the causes and consequences of partial migration will not only provide novel insights into the ecology and evolution of migration in general, but will also be vital to precisely modelling population trends and predicting range shifts under global change.
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| 8. |
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| 9. |
- Johansson, Jacob, et al.
(författare)
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The eco-evolutionary consequences of interspecific phenological asynchrony - a theoretical perspective
- 2015
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 124:1, s. 102-112
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Forskningsöversikt (refereegranskat)abstract
- The timing of biological events (phenology) is an important aspect of both a species' life cycle and how it interacts with other species and its environment. Patterns of phenological change have been given much scientific attention, particularly recently in relation to climate change. For pairs of interacting species, if their rates of phenological change differ, then this may lead to asynchrony between them and disruption of their ecological interactions. However it is often difficult to interpret differential rates of phenological change and to predict their ecological and evolutionary consequences. We review theoretical results regarding this topic, with special emphasis on those arising from life history theory, evolutionary game theory and population dynamic models. Much ecological research on phenological change builds upon the concept of match/mismatch, so we start by putting forward a simple but general model that captures essential elements of this concept. We then systematically compare the predictions of this baseline model with expectations from theory in which additional ecological mechanisms and features of species life cycles are taken into account. We discuss the ways in which the fitness consequences of interspecific phenological asynchrony may be weak, strong, or idiosyncratic. We discuss theory showing that synchrony is not necessarily an expected evolutionary outcome, and how population densities are not necessarily maximized by adaptation, and the implications of these findings. By bringing together theoretical developments regarding the eco-evolutionary consequences of phenological asynchrony, we provide an overview of available alternative hypotheses for interpreting empirical patterns as well as the starting point for the next generation of theory in this field.
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| 10. |
- Liljebäck, Niklas, et al.
(författare)
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Learning from long time series of harvest and population data : Swedish lessons for European goose management
- 2021
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Ingår i: Wildlife Biology. - : Wiley. - 0909-6396 .- 1903-220X. ; 2021:1
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Forskningsöversikt (refereegranskat)abstract
- Goose management in Europe is faced by multiple challenges, as some species are declining and in need of conservation actions, while other populations have become very abundant, resulting in calls for increased harvest. Sweden has long-Term series of harvest data and counts of breeding and autumn-staging geese. We used national data (indices) for greylag goose, bean goose and Canada goose to study shifts in temporal trends and correlative patterns, and to infer possible causal links between harvest and population trends. Our study provides an opportunity to guide management given the data collected within the present monitoring, as well as to suggest improvements for future data collection. The populations of greylag and Canada geese increased in Sweden 1979-2018, but this long-Term trend included a recent decrease in the latter species. Bean goose breeding index decreased, whilst staging numbers and harvest varied with no clear long-Term trend. For Canada goose, our analysis suggests that harvest may affect population growth negatively. For bean goose and greylag goose we could not detect any effect of harvest on autumn counts the following year. We find that the present data and analysis of coherence may suffice as basis for decisions for the current management situation in Sweden with its rather unspecific goals for greylag (very abundant) and Canada goose (invasive species) populations. However, for management of bean geese, with international concerns of over harvest, data lack crucial information. For future management challenges, with more explicit goals, for all goose species we advocate information that is more precise. Data such as hunting effort, age-structure of goose populations and mark-recapture data to estimate survival and population size, is needed to feed predictive population models guiding future Swedish and European goose management.
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