| 1. |
- Boström, Jannika, et al.
(författare)
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Autumn migratory fuelling : a response to simulated magnetic displacement in juvenile wheatears, Oenathe oenathe
- 2010
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Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 0340-5443 .- 1432-0762. ; 64:11, s. 1725-1732
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Tidskriftsartikel (refereegranskat)abstract
- Recent experiments exposing migratory birds to altered magnetic fields simulating geographical displacements have shown that the geomagnetic field acts as an external cue affecting migratory fuelling behaviour. This is the first study investigating fuel deposition in relation to geomagnetic cues in long-distance migrants using the western passage of the Mediterranean region. Juvenile wheatears (Oenanthe oenanthe) were exposed to a magnetically simulated autumn migration from southern Sweden to West Africa. Birds displaced parallel to the west of their natural migration route, simulating an unnatural flight over the Atlantic Ocean, increased their fuel deposition compared to birds experiencing a simulated migration along the natural route. These birds, on the other hand, showed relatively low fuel loads in agreement with earlier data on wheatears trapped during stopover. The experimental displacement to the west, corresponding to novel sites in the Atlantic Ocean, led to a simulated longer distance to the wintering area, probably explaining the observed larger fuel loads. Our data verify previous results suggesting that migratory birds use geomagnetic cues for fuelling decisions and, for the first time, show that birds, on their first migration, can use geomagnetic cues to compensate for a displacement outside their normal migratory route, by adjusting fuel deposition.
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| 2. |
- Fryland, Linda, et al.
(författare)
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Mapping of T-cell subsets in relation to disease course in experimental Borrelia burgdorferi infection
- 2012
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Resolution of Lyme borreliosis has previously been shown to be associated with a strong initial Th1 response, followed by a subsequent Th2 response, shutting off inflammation. We mapped markers for Th1, Th2, Th17, cytotoxic and T regulatory subsets in a murine model, where the outcome of Borrelia (B.) burgdorferi sensu stricto (s.s.) infection was altered by immune-deviation towards Th2 by exposure to a subtoxic dose of mercury. Twenty-one B. burgdorferi s.s.-infected (Bb), 21 immune-deviated B. burgdorferi s.s.-infected (BbId), and seven control C3H/HeN mice were sacrificed on days 15, 28 and 43 post-infection (p.i.) with B. burgdorferi s.s. BbId mice had increased joint swelling compared with Bb at the height of the disease (28 p.i.), and also showed a trend for increased spirochaetal load that became significant on day 43 p.i. BbId had an increased histopathology score on day 28 p.i. compared with both earlier and later time points. mRNA expression of IL-4 (p=0.018), IL-10 (p=0.018) and EBI-3 (p=0.009) decreased in Bb mice, but not in BbId, over the course of infection. A trend for higher expression of IL-12p40 mRNA in Bb mice compared with BbId was seen late in the disease course, while BbId showed trends for higher levels of Foxp3 and GM-CSF. At the protein level, BbId showed decreased levels of CXCL9 compared to the Bb group on day 15 p.i (p=0.007). Bb mice showed increases of CXCL9 and CXCL10 at all time points compared with day 0 p.i. (p≤0.014), whereas BbId mice showed an initial decrease in both chemokines at day 15 p.i. compared with day 0 (p≤0.008). In conclusion, both the clinical signs of infection and the trends for increased expression of pro-inflammatory GM-CSF and T-regulatory marker Foxp3 in BbId mice suggested ongoing inflammation. Although our findings support the need for a strong Th1 response followed by anti-inflammatory response for optimal resolution, the anti-inflammatory response seems to be more complex than only dampening the inflammation by a Th1-antagonistic Th2 response.
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| 3. |
- Henshaw, Ian, et al.
(författare)
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Geomagnetic field affects spring migratory direction in a long distance migrant
- 2010
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Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 0340-5443 .- 1432-0762. ; 64:8, s. 1317-1323
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Tidskriftsartikel (refereegranskat)abstract
- Night-migrating song birds travel to and from their wintering and breeding areas often separated thousands of kilometers apart and are clearly capable of finding intended goal areas from a distant location. Displacement experiments provide a useful way to highlight orientation and navigational skills in migrants. To investigate which cues birds actually use to compensate for displacement and the exact mechanism of each cue, experiments with manipulation of single cues are required. We conducted a simulated displacement of lesser whitethroats Sylvia curruca on spring migration. Birds were displaced not geographically but in geomagnetic space only, north and south of their breeding area to test whether they incorporate information from the geomagnetic field to find their breeding area. Lesser whitethroats held in southeast Sweden but experiencing a simulated displacement north of their breeding area (Norway) failed to show a consistent direction of orientation, whereas birds displaced south of their breeding area (Czech Republic) exhibited consistent northerly orientation, close to the expected seasonally appropriate direction, after displacement toward the trapping location. The absence of a clear compensatory direction in birds displaced north might be due to unfamiliar magnetic information or lack of sufficient information such as a magnetic gradient when moving around. By isolating one orientation cue, the geomagnetic field, we have been able to show that lesser whitethroats might incorporate geomagnetic field information to determine latitude during spring migration.
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| 4. |
- Jakobsson, Mattias, 1981-, et al.
(författare)
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Monte Carlo simulations of charge transport in organic systems with true off-diagonal disorder
- 2012
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 137:11
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a novel method to model off-diagonal disorder in organic materials has been developed. The off-diagonal disorder is taken directly from the geometry of the system, which includes both a distance and an orientational dependence on the constituent molecules, and does not rely on a parametric random distribution. To study this method, a system is generated by running molecular dynamics simulations on phenylene-vinylene oligomers packed into boxes. The impact of the model is then investigated by means of Monte Carlo simulations of the charge transport in these boxes and a comparison is made to the commonly used model of off-diagonal disorder, where only the distance dependence is properly accounted for. It is shown that this new model has a significant impact on the charge transport, while still being compliant with previously published and confirmed results.
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| 5. |
- Jakobsson, Mattias, 1981-
(författare)
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Monte Carlo Studies of Charge Transport Below the Mobility Edge
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Charge transport below the mobility edge, where the charge carriers are hopping between localized electronic states, is the dominant charge transport mechanism in a wide range of disordered materials. This type of incoherent charge transport is fundamentally different from the coherent charge transport in ordered crystalline materials. With the advent of organic electronics, where small organic molecules or polymers replace traditional inorganic semiconductors, the interest for this type of hopping charge transport has increased greatly. The work documented in this thesis has been dedicated to the understanding of this charge transport below the mobility edge.While analytical solutions exist for the transport coefficients in several simplified models of hopping charge transport, no analytical solutions yet exist that can describe these coefficients in most real systems. Due to this, Monte Carlo simulations, sometimes described as ideal experiments performed by computers, have been extensively used in this work.A particularly interesting organic system is deoxyribonucleic acid (DNA). Besides its overwhelming biological importance, DNA’s recognition and self-assembly properties have made it an interesting candidate as a molecular wire in the field of molecular electronics. In this work, it is shown that incoherent hopping and the Nobel prize-awarded Marcus theory can be used to describe the results of experimental studies on DNA. Furthermore, using this experimentally verified model, predictions of the bottlenecks in DNA conduction are made.The second part of this work concerns charge transport in conjugated polymers, the flagship of organic materials with respect to processability. It is shown that polaronic effects, accounted for by Marcus theory but not by the more commonly used Miller-Abrahams theory, can be very important for the charge transport process. A significant step is also taken in the modeling of the off-diagonal disorder in organic systems. By taking the geometry of the system from large-scale molecular dynamics simulations and calculating the electronic transfer integrals using Mulliken theory, the off-diagonal disorder is for the first time modeled directly from theory without the need for an assumed parametric random distribution.
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| 6. |
- Jakobsson, Mattias, et al.
(författare)
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Polaron effects and electric field dependence of the charge carrier mobility in conjugated polymers
- 2011
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 135:13, s. 134902-
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Tidskriftsartikel (refereegranskat)abstract
- Charge transport in conjugated polymers has been investigated using Monte Carlo simulations implemented on top of the Marcus theory for donor-acceptor transition rates. In particular, polaron effects and the dependency of the mobility on the temperature and the applied electric field have been studied. The conclusions are that while the qualitative temperature dependence is similar to that predicted by Miller-Abrahams theory in the Gaussian disorder model (GDM), the electric field dependence is characterized by a crossover into the Marcus inverted region, not present in the GDM. Furthermore, available analytical approximations to describe the electric field dependence of the mobility in Marcus theory fail to fit the simulation data and hence cannot be used to directly draw conclusions about the importance of polaron effects for charge transport in conjugated polymers.
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| 7. |
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| 8. |
- Jakobsson, Niklas, et al.
(författare)
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Does immigration affect welfare state generosity? Quasi-experimental evidence
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This note studies the impact of immigration on welfare state generosity in 12 Western European countries. In estimations not coping with the possible endogeneity problem, there are indications of a negative relationship between immigration and welfare state generosity. However, when the distance to the Balkan wars are used as a source of exogenous variation in the immigrant share, as to overcome potential endogeneity in mobility across countries, our findings suggest that an increase in the immigrant share does not decrease welfare state generosity.
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| 9. |
- Jakobsson, Sven, 1951-
(författare)
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Tovetorps Forskningsstation
- 2011
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Ingår i: Sörmlandsbygden 2012. - Nyköping : Österbergs & Sörmlandstryck. ; , s. 49-66
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Bokkapitel (populärvet., debatt m.m.)
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| 10. |
- Laikre, Linda, et al.
(författare)
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Hunting Effects on Favourable Conservation Status of Highly Inbred Swedish Wolves
- 2013
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Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 27:2, s. 248-253
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Tidskriftsartikel (refereegranskat)abstract
- The wolf (Canis lupus) is classified as endangered in Sweden by the Swedish Species Information Centre, which is the official authority for threat classification. The present population, which was founded in the early 1980s, descends from 5 individuals. It is isolated and highly inbred, and on average individuals are more related than siblings. Hunts have been used by Swedish authorities during 2010 and 2011 to reduce the population size to its upper tolerable level of 210 wolves. European Union (EU) biodiversity legislation requires all member states to promote a concept called “favourable conservation status” (FCS) for a series of species including the wolf. Swedish national policy stipulates maintenance of viable populations with sufficient levels of genetic variation of all naturally occurring species. Hunting to reduce wolf numbers in Sweden is currently not in line with national and EU policy agreements and will make genetically based FCS criteria less achievable for this species. We suggest that to reach FCS for the wolf in Sweden the following criteria need to be met: (1) a well-connected, large, subdivided wolf population over Scandinavia, Finland, and the Russian Karelia-Kola region should be reestablished, (2) genetically effective size (Ne) of this population is in the minimum range of Ne = 500–1000, (3) Sweden harbors a part of this total population that substantially contributes to the total Ne and that is large enough to not be classified as threatened genetically or according to IUCN criteria, and (4) average inbreeding levels in the Swedish population are <0.1.
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