| 1. |
- Algesten, Grete, et al.
(författare)
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Organic carbon budget for the Gulf of Bothnia
- 2006
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963 .- 1879-1573. ; 63:3-4, s. 155-161
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Tidskriftsartikel (refereegranskat)abstract
- We calculated input of organic carbon to the unproductive, brackish water basin of the Gulf of Bothnia from rivers, point sources and the atmosphere. We also calculated the net exchange of organic carbon between the Gulf of Bothnia and the adjacent marine system, the Baltic Proper. We compared the input with sinks for organic carbon; permanent incorporation in sediments and mineralization and subsequent evasion of CO2 to the atmosphere. The major fluxes were riverine input (1500 Gg C year(-1)), exchange with the Baltic Proper (depending on which of several possible DOC concentration differences between the basins that was used in the calculation, the flux varied between an outflow of 466 and an input of 950 Gg C year(-1)), sediment burial (1100 Gg C year) and evasion to the atmosphere (3610 Gg C year(-1)). The largest single net flux was the emission of CO2 to the atmosphere, mainly caused by bacterial mineralization of organic carbon. Input and output did not match in our budget which we ascribe uncertainties in the calculation of the exchange of organic carbon between the Gulf of Bothnia and the Baltic Proper, and the fact that CO2 emission, which in our calculation represented 1 year (2002) may have been overestimated in comparison with long-term means. We conclude that net heterotrophy of the Gulf of Bothnia was due to input of organic carbon from both the catchment and from the Baltic Proper and that the future degree of net heterotrophy will be sensible to both catchment export of organic carbon and to the ongoing eutrophication of the Baltic Proper.
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| 2. |
- Bresell, Anders, et al.
(författare)
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Bioinformatic and enzymatic characterization of the MAPEG superfamily
- 2005
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 272:7, s. 1688-1703
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Tidskriftsartikel (refereegranskat)abstract
- The membrane associated proteins in eicosanoid and glutathione metabolism (MAPEG) superfamily includes structurally related membrane proteins with diverse functions of widespread origin. A total of 136 proteins belonging to the MAPEG superfamily were found in database and genome screenings. The members were found in prokaryotes and eukaryotes, but not in any archaeal organism. Multiple sequence alignments and calculations of evolutionary trees revealed a clear subdivision of the eukaryotic MAPEG members, corresponding to the six families of microsomal glutathione transferases (MGST) 1, 2 and 3, leukotriene C4 synthase (LTC4), 5-lipoxygenase activating protein (FLAP), and prostaglandin E synthase. Prokaryotes contain at least two distinct potential ancestral subfamilies, of which one is unique, whereas the other most closely resembles enzymes that belong to the MGST2/FLAP/LTC4 synthase families. The insect members are most similar to MGST1/prostaglandin E synthase. With the new data available, we observe that fish enzymes are present in all six families, showing an early origin for MAPEG family differentiation. Thus, the evolutionary origins and relationships of the MAPEG superfamily can be defined, including distinct sequence patterns characteristic for each of the subfamilies. We have further investigated and functionally characterized representative gene products from Escherichia coli, Synechocystis sp., Arabidopsis thaliana and Drosophila melanogaster, and the fish liver enzyme, purified from pike (Esox lucius). Protein overexpression and enzyme activity analysis demonstrated that all proteins catalyzed the conjugation of 1-chloro-2,4-dinitrobenzene with reduced glutathione. The E. coli protein displayed glutathione transferase activity of 0.11 µmol·min−1·mg−1 in the membrane fraction from bacteria overexpressing the protein. Partial purification of the Synechocystis sp. protein yielded an enzyme of the expected molecular mass and an N-terminal amino acid sequence that was at least 50% pure, with a specific activity towards 1-chloro-2,4-dinitrobenzene of 11 µmol·min−1·mg−1. Yeast microsomes expressing the Arabidopsis enzyme showed an activity of 0.02 µmol·min−1·mg−1, whereas the Drosophila enzyme expressed in E. coli was highly active at 3.6 µmol·min−1·mg−1. The purified pike enzyme is the most active MGST described so far with a specific activity of 285 µmol·min−1·mg−1. Drosophila and pike enzymes also displayed glutathione peroxidase activity towards cumene hydroperoxide (0.4 and 2.2 µmol·min−1·mg−1, respectively). Glutathione transferase activity can thus be regarded as a common denominator for a majority of MAPEG members throughout the kingdoms of life whereas glutathione peroxidase activity occurs in representatives from the MGST1, 2 and 3 and PGES subfamilies.
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| 3. |
- Holmgren, Johan, 1977-, et al.
(författare)
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Public transport in towns : Inevitably on the decline?
- 2008
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Ingår i: Research in Transportation Economics. - : Elsevier BV. - 0739-8859 .- 1875-7979. ; 23:1, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- In this article the post war development of public transport demand in the town of Linköping is explained using time series analysis. It is found that the dramatic increase in public transport demand between 1946 and 1983, at least in part, can be explained by the rapid increase in female labour force participation and the expansion of the city’s outer areas. After that, female labour force participation decreased slightly and the town expansion has stopped. Without these positive forces to counterbalance the rising levels of car ownership public transport demand has fallen by 71%. The effects of a policy change, including peak-load pricing, straighter bus routes, smaller bus size and staggered school hours, is analysed. It is found that the proposed package would increase public transport travel by 42 % compared to present policy.
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| 4. |
- Holmgren, Johan, 1977-
(författare)
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Studies in Local Public Transport Demand
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of four papers where the overall purpose is to contribute to the understanding of how local public transport demand is affected by different factors. An underlying theme running trough the thesis is the two-way relationship between public transport demand and the service level caused by the fact that capacity and quality are joint products.In Paper I the relationship between public transport demand and the service level (in terms of vehicle-kilometres) is investigated using panel data from Swedish counties. A Granger causality test is performed in order to test if the level of service cause public transport demand or if demand cause service level, or if they cause each other. It is found that demand and service cause each other, which is to say that there is a two-way relationship between them.In Paper II elasticity estimates for local public transport demand from previous research are summarised and the variation in results is analysed using meta-regression. The variation is explained by model specification, type of data used and origin of data.In Paper III a demand function for local public transport is estimated using panel data from Swedish counties. Instrument variable estimation is used in order to avoid the problem of a two-way relationship between demand and service level (vehicle-kilometres). Demand elasticities with respect to public transport fare, price of petrol, vehicle-kilometres and car ownership are found to be -0.4, 0.34, 0.55, and -1.37. After also taking the effects of income on car ownership into account, it is found that the total effect of income on public transport demand is close to zero.In Paper IV it is found that the strong increase in public transport demand in the town of Linköping between 1946 and 1983, in addition to fare, vehicle-kilometres and car ownership, can be explained by the rapid increase in female labour force participation and the expansion of the city’s outer areas. The city expansion is thought to have increased average trip distance and thereby reduced the number of trips that could be made walking or by bicycle. After 1983, female labour force participation decreased slightly and the expansion of the areas in question has stopped. Without these positive forces to counterbalance the rising levels of car ownership bus trips per capita has fallen by 71%. The effects of a policy change, including peak-load pricing, straighter bus routes, smaller bus size and staggered school hours, is analysed. It is found that the proposed changes would increase public transport travel by 42 % compared to present policy.
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| 5. |
- Olstam, Johan, 1979-
(författare)
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Simulation of Surrounding Vehicles in Driving Simulators
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Driving simulators and microscopic traffic simulation are important tools for making evaluations of driving and traffic. A driving simulator is de-signed to imitate real driving and is used to conduct experiments on driver behavior. Traffic simulation is commonly used to evaluate the quality of service of different infrastructure designs. This thesis considers a different application of traffic simulation, namely the simulation of surrounding vehicles in driving simulators.The surrounding traffic is one of several factors that influence a driver's mental load and ability to drive a vehicle. The representation of the surrounding vehicles in a driving simulator plays an important role in the striving to create an illusion of real driving. If the illusion of real driving is not good enough, there is an risk that drivers will behave differently than in real world driving, implying that the results and conclusions reached from simulations may not be transferable to real driving.This thesis has two main objectives. The first objective is to develop a model for generating and simulating autonomous surrounding vehicles in a driving simulator. The approach used by the model developed is to only simulate the closest area of the driving simulator vehicle. This area is divided into one inner region and two outer regions. Vehicles in the inner region are simulated according to a microscopic model which includes sub-models for driving behavior, while vehicles in the outer regions are updated according to a less time-consuming mesoscopic model.The second objective is to develop an algorithm for combining autonomous vehicles and controlled events. Driving simulators are often used to study situations that rarely occur in the real traffic system. In order to create the same situations for each subject, the behavior of the surrounding vehicles has traditionally been strictly controlled. This often leads to less realistic surrounding traffic. The algorithm developed makes it possible to use autonomous traffic between the predefined controlled situations, and thereby get both realistic traffc and controlled events. The model and the algorithm developed have been implemented and tested in the VTI driving simulator with promising results.
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| 6. |
- Starkhammar, Josefin, et al.
(författare)
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Editorial: 47-channel burst-mode recording hydrophone system enabling measurements of the dynamic echolocation behavior of free-swimming dolphins
- 2009
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Ingår i: Journal of the Acoustical Society of America. - : A I P Publishing LLC. - 0001-4966 .- 1520-8524. ; 126:3, s. 959-962
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Detailed echolocation behavior studies on free-swimming dolphins require a measurement system that incorporates multiple hydrophones (often andgt; 16). However, the high data flow rate of previous systems has limited their usefulness since only minute long recordings have been manageable. To address this problem, this report describes a 47-channel burst-mode recording hydrophone system that enables highly resolved full beamwidth measurements on multiple free-swimming dolphins during prolonged recording periods. The system facilitates a wide range of biosonar studies since it eliminates the need to restrict the movement of animals in order to study the fine details of their sonar beams.
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