| 11. |
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| 12. |
- Thompson, Paul M., et al.
(författare)
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The ENIGMA Consortium : large-scale collaborative analyses of neuroimaging and genetic data
- 2014
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Ingår i: BRAIN IMAGING BEHAV. - : Springer Science and Business Media LLC. - 1931-7557 .- 1931-7565. ; 8:2, s. 153-182
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Tidskriftsartikel (refereegranskat)abstract
- The Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Consortium is a collaborative network of researchers working together on a range of large-scale studies that integrate data from 70 institutions worldwide. Organized into Working Groups that tackle questions in neuroscience, genetics, and medicine, ENIGMA studies have analyzed neuroimaging data from over 12,826 subjects. In addition, data from 12,171 individuals were provided by the CHARGE consortium for replication of findings, in a total of 24,997 subjects. By meta-analyzing results from many sites, ENIGMA has detected factors that affect the brain that no individual site could detect on its own, and that require larger numbers of subjects than any individual neuroimaging study has currently collected. ENIGMA's first project was a genome-wide association study identifying common variants in the genome associated with hippocampal volume or intracranial volume. Continuing work is exploring genetic associations with subcortical volumes (ENIGMA2) and white matter microstructure (ENIGMA-DTI). Working groups also focus on understanding how schizophrenia, bipolar illness, major depression and attention deficit/hyperactivity disorder (ADHD) affect the brain. We review the current progress of the ENIGMA Consortium, along with challenges and unexpected discoveries made on the way.
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| 13. |
- van Ommen, Gert-Jan B, et al.
(författare)
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BBMRI-ERIC as a resource for pharmaceutical and life science industries : the development of biobank-based Expert Centres
- 2015
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Ingår i: European Journal of Human Genetics. - : Springer Science and Business Media LLC. - 1018-4813 .- 1476-5438. ; 23:7, s. 893-900
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Tidskriftsartikel (refereegranskat)abstract
- Biological resources (cells, tissues, bodily fluids or biomolecules) are considered essential raw material for the advancement of health-related biotechnology, for research and development in life sciences, and for ultimately improving human health. Stored in local biobanks, access to the human biological samples and related medical data for transnational research is often limited, in particular for the international life science industry. The recently established pan-European Biobanking and BioMolecular resources Research Infrastructure-European Research Infrastructure Consortium (BBMRI-ERIC) aims to improve accessibility and interoperability between academic and industrial parties to benefit personalized medicine, disease prevention to promote development of new diagnostics, devices and medicines. BBMRI-ERIC is developing the concept of Expert Centre as public-private partnerships in the precompetitive, not-for-profit field to provide a new structure to perform research projects that would face difficulties under currently established models of academic-industry collaboration. By definition, Expert Centres are key intermediaries between public and private sectors performing the analysis of biological samples under internationally standardized conditions. This paper presents the rationale behind the Expert Centres and illustrates the novel concept with model examples.
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| 14. |
- Yarmukhamedov, Sherzod, 1983-
(författare)
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A study of asymmetric information problems in vehicle insurance
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Insurance is an indispensable part of modern welfare systems. It provides financial protection against unexpected losses and facilitates security and efficiency. Despite these benefits, the insurance literature predicts distortive effects of insurance provision in the form of asymmetric information problems such as adverse selection and moral hazard. However, empirical evidence does not provide unambiguous support for this theoretical prediction.This dissertation empirically examines a theoretical prediction of the presence of asymmetric information problems in the case of vehicle insurance.Essay 1 analyzes the effects of a tax reform in Sweden that raised the price of vehicle insurance. The results indicate that the tax reform has increased the odds of switching to lower insurance coverage, in particular among older drivers. However, this switching behavior has not resulted in a significant change of driver behavior in terms of claims.Essay 2 uses a two-stage procedure to test for the presence of asymmetric information problems in the provision of vehicle insurance. In the first stage, we check for the presence of residual asymmetric information; in the second stage, we identify the source of the information problem, i.e. either adverse selection or moral hazard, or both. Our findings from the first stage estimation indicate the presence of residual asymmetric information in the choice of full insurance with a low deductible. The second stage estimation results reveal that the source of this information problem is moral hazard.Essay 3 analyzes the impact of insurance on the probability of accidents by investigating the accident risk of insured and uninsured drivers. The results show that uninsured drivers have a higher probability of causing an accident than insured drivers, and that uninsured drivers aged 25-34 pose a greater accident risk than uninsured drivers in other age categories.
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| 15. |
- Ahlberg, Joakim, 1966-, et al.
(författare)
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Ad hoc-processen : hur används ledig kapacitet i järnvägsnätet?
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Efter Trafikverkets fastställelse av nästkommande års tågplan i mitten av hösten varje år vidtar den så kallade ad hoc-processen, det vill säga ansökningar om tåglägen som kan använda ledig kapacitet i järnvägsnätet. VTI fick i september 2015 Transportstyrelsens uppdrag att fördjupa förståelsen av ad hoc-processen. Detta notat avrapporterar uppdraget.Mot bakgrund av den beskrivning som görs har avsikten varit att också hitta mått på betydelsen av denna process i förhållande till den process som leder fram till att en färdig tidplan läggs fast. Det har emellertid visat sig att Trafikverkets olika system för informationshantering inte är utformade för att möjliggöra en sådan beskrivning. Tack vare ett nyligen offentliggjort statistikhjälpmedel är det emellertid möjligt att konstatera att närmare 97 procent av de persontåg som bokats i den ordinarie processen också faktiskt körs. Denna uppgift avser två tredjedelar av tidtabellåret 2015. Avsikten från Trafikverket/Trafikanalys är att inom en nära framtid också redovisa motsvarande information om godstrafiken.Bakom denna siffra döljer sig emellertid både ett utflöde från, och ett inflöde till den mängd trafik som ska bedrivas i enlighet med den tidtabell som fastställs under hösten varje år. Det saknas emellertid kunskap om när dessa förändringar genomförs, vilket är av stor betydelse för att bedöma graden av flexibilitet i ad hoc-processen. Denna situation kan komma att förändras som ett resultat av att Trafikverket från och med den tidtabell som avser 2016 inför avgifter för att avboka tilldelad kapacitet. Avgiften blir högre ju närmare det planerade tågets avgång som ansökan tas tillbaka. Detta kan bidra till en förbättrad flexibilitet i användningen av den spårkapacitet som inte reserveras i den ordinarie tidtabellsläggningsprocessen. Ytterligare en konsekvens kan bli att informationen om processen förbättras.
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| 16. |
- Ahlberg, Joakim, 1966-
(författare)
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Multi-unit common value auctions : theory and experiments
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Research on auctions that involve more than one identical item for sale was,almost non-existing in the 90’s, but has since then been getting increasing attention. External incentives for this research have come from the US spectrum, sales, the European 3G mobile-phone auctions, and Internet auctions. The policy relevance and the huge amount of money involved in many of them have helped the theory and experimental research advance. But in auctions where values are equal across bidders, common value auctions, that is, when the value depends on some outside parameter, equal to all bidders, the research is still embryonic.This thesis contributes to the topic with three studies. The first uses a Bayesian game to model a simple multi-unit common value auction, the task being to compare equilibrium strategies and the seller’s revenue from three auction formats; the discriminatory, the uniform and the Vickrey auction. The second study conducts an economic laboratory experiment on basis of the first study. The third study comprises an experiment on the multi-unit common value uniform auction and compares the dynamic and the static environments of this format.The most salient result in both experiments is that subjects overbid. They are victims of the winner’s curse and bid above the expected value, thus earning a negative profit. There is some learning, but most bidders continue to earn a negative profit also in later rounds. The competitive effect when participating in an auction seems to be stronger than the rationality concerns. In the first experiment, subjects in the Vickrey auction do somewhat better in small groups than subjects in the other auction types and, in the second experiment, subjects in the dynamic auction format perform much better than subjects in the static auction format; but still, they overbid.Due to this overbidding, the theoretical (but not the behavioral) prediction that the dynamic auction should render more revenue than the static fails inthe second experiment. Nonetheless, the higher revenue of the static auction comes at a cost; half of the auctions yield negative profits to the bidders, and the winner’s curse is more severely widespread in this format. Besides, only a minority of the bidders use the equilibrium bidding strategy.The bottom line is that the choice between the open and sealed-bid formats may be more important than the choice of price mechanism, especially in common value settings.
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| 17. |
- Ait Ali, Abderrahman, 1991-, et al.
(författare)
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A disaggregate bundle method for train timetabling problems
- 2020
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Ingår i: Journal of Rail Transport Planning & Management. - : Elsevier BV. - 2210-9706 .- 2210-9714. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- The train timetabling problem (TTP) consists of finding a feasible timetable for a number of trains which minimises some objective function, e.g., sum of running times or deviations from ideal departure times. One solution approach is to solve the dual problem of the TTP using so-called bundle methods. This paper presents a new bundle method that uses disaggregate data, as opposed to the standard bundle method which in a certain sense relies on aggregate data. We compare the disaggregate and aggregate methods on realistic train timetabling scenarios from the Iron Ore line in Northern Sweden. Numerical results indicate that the proposed disaggregate method reaches better solutions faster than the standard aggregate approach.
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| 18. |
- Ait Ali, Abderrahman, 1991-, et al.
(författare)
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Disaggregation in Bundle Methods : Application to the Train Timetabling Problem
- 2017
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Konferensbidrag (refereegranskat)abstract
- Bundle methods are often used to solve dual problems that arise from Lagrangian relaxations of large scale optimization problems. An example of such problems is the train timetabling problem. This paper focuses on solving a dual problem that arises from Lagrangian relaxation of a train timetabling optimization program. The dual problem is solved using bundle methods. We formulate and compare the performances of two different bundle methods: the aggregate method, which is a standard method, and a new, disaggregate, method which is proposed here. The two methods were tested on realistic train timetabling scenarios from the Iron Ore railway line. The numerical results show that the new disaggregate approach generally yields faster convergence than the standard aggregate approach.
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| 19. |
- Akhiani, Aliasghar, 1957, et al.
(författare)
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Interaction of cholera toxin with three life-cycle stages of Schistosoma mansoni: adult worm, egg and cercaria
- 2007
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Ingår i: Scand J Immunol. ; 65:1, s. 48-53
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Tidskriftsartikel (refereegranskat)abstract
- We have previously reported that there is an immunological cross-reactivity between Schistosoma mansoni and cholera toxin (CT). In this study, using an immunofluorescence technique with anti-CT antibody, we provide further evidence for this cross-reactivity by demonstrating an antigen, localized in the tegument of S. mansoni adult worms which is cross-reactive with a CT antigen. Anti-CT antibodies also reacted with structures in S. mansoni cercariae and eggs. Additionally, CT itself was found to bind strongly to the gut of the adult worm, gut cells of cercaria and the egg shell. The binding of CT to the parasite was blocked when parasite sections were incubated with CT which had been incubated with the ganglioside GM1. Lipid extraction and isolation of gangliosides demonstrated the presence of GM1 in adult worms. For further analysis of CT-binding structures, the possible interaction of CT with two major schistosome gut antigens, circulating cathodic antigen (CCA) and circulating anodic antigen (CAA), was studied. We found that CT blocked the binding of anti-CCA antibody to the gut of adult worms and that anti-CCA blocked the binding of CT to the worm gut. These findings indicate that CT binds to CCA present in the gut of the parasite and thus has, in addition to GM1, a second binding specificity.
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| 20. |
- Alexandersson, Gunnar, et al.
(författare)
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The liberalization of railway passenger transport in Sweden : outstanding regulatory challenges
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this paper is to describe Sweden’s recent reforms to open the railway passenger markets to entry, and to addresses four critical issues for the success of the reforms; the allocation of infrastructure capacity, the provision of maintenance and terminal facilities, the access to rolling stock and the provision of information and ticketing to travelers. The analysis shows that the legislation and regulatory tools that are needed to handle these challenges to a large extent remain to be developed.
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