| 1. |
- Godhe, Anna, 1967, et al.
(författare)
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Seascape analysis reveals regional gene flow patterns among populations of a marine planktonic diatom
- 2013
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 280:1773
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the gene flow of the common marine diatom, Skeletonema marinoi, in Scandinavian waters and tested the null hypothesis of panmixia. Sediment samples were collected from the Danish Straits, Kattegat and Skagerrak. Individual strains were established from germinated resting stages. A total of 350 individuals were genotyped by eight microsatellite markers. Conventional F-statistics showed significant differentiation between the samples. We therefore investigated whether the genetic structure could be explained using genetic models based on isolation by distance (IBD) or by oceanographic connectivity. Patterns of oceanographic circulation are seasonally dependent and therefore we estimated how well local oceanographic connectivity explains gene flow month by month. We found no significant relationship between genetic differentiation and geographical distance. Instead, the genetic structure of this dominant marine primary producer is best explained by local oceanographic connectivity promoting gene flow in a primarily south to north direction throughout the year. Oceanographic data were consistent with the significant FST values between several pairs of samples. Because even a small amount of genetic exchange prevents the accumulation of genetic differences in F-statistics, we hypothesize that local retention at each sample site, possibly as resting stages, is an important component in explaining the observed genetic structure.
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| 2. |
- Jonsson, Per, 1981
(författare)
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Sheet metal trimming dies – characterisation methods of geometry and surface topography and the influence on wear
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, the life cycle of car models has decreased from 7 to 5 years and the volume sizes are becoming shorter in the automotive industry. The increasing number of car models introduced to the market means that a fewer number of parts must pay the costs for the tool/die design and manufacturing. In consequence, there is a need for reducing the manufacturing cost and lead time for the tool and die manufacturing. The higher product requirements (reduced weight, increased safety and lower emissions) have meant that a larger number of car body parts must be made in AHSS (Advanced High Strength Steels). This has led to a significantly larger abrasive and fatigue tool wear. The tool wear is therefore expected to increase even more in the future, if the issue is not addressed properly. Today the total maintenance cost of the trimming tools are approximately 70% of the total die maintenance cost in a press shop.The purpose of this thesis is to increase the knowledge of how surface topography and geometry on trimming dies influences tool wear, tool life and part quality. Methods to analyze wear, measure cutting edge radius on production dies and methods to analyze surface topography have been established.The cutting edge geometry has been evaluated with respect to the cutting edge radius and the angle of the upper tool. Experimental testing together with FE simulation has been used. Results show that by using a cutting edge radius of 80µm, rather than 20µm, the tool “wear in phase” can be more controlled.Sheet metal trimming when cutting at high angles (25° - 60°) has been evaluated. Two versions of the geometry on the lower cutting edge was tested, a traditional geometry and a 1.5mm shelf geometry. Results show that the shelf geometry reduces side force, especially for the higher angles. The shelf geometry also reduces the sharpness off the cut edge profile, thus increasing part quality, compared to the traditional geometry.Surfaces on both semi-industrial test dies and dies used in production were analyzed with different surface topography analysis methods. The result shows that the wear process is different on the different sides of the trimming edge. The texture direction of the surface is changed due to wear, with the strongest change on the clearance side of the edge. The roughness on sheet side of the edge is reduced due to a hammering effect from the sheet material. The result on the semiindustrial test dies and the production dies correlates well.Future research will be continued on surface topography and trimming edge geometry and its relationship to used manufacturing methods and tool wear.
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| 3. |
- Jonsson, Per, 1981, et al.
(författare)
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Surface Topography on trimming dies and the influence of wear
- 2010
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Ingår i: Proceedings of the International Deep Drawing Research Group. - 9783851251081 ; , s. 345-354
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Konferensbidrag (refereegranskat)abstract
- In this paper it is investigated how surface topography on trimming dies influences the wear process. Surfaces on both semi-industrial test dies and dies used in production were analyzed with different surface topography analysis methods. The result shows that the wear process is different on the different sides of the trimming edge. The texture direction of the surface is changed due to wear, with the strongest change on the clearance side of the edge. The roughness on sheet side of the edge is reduced due to a hammering effect from the sheet material. The result on the test dies and the production dies correlates well.
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| 4. |
- Lind, Ulrika, et al.
(författare)
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Molecular Characterization of the alpha-Subunit of Na+/K+ ATPase from the Euryhaline Barnacle Balanus improvisus Reveals Multiple Genes and Differential Expression of Alternative Splice Variants
- 2013
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 8:10
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Tidskriftsartikel (refereegranskat)abstract
- The euryhaline bay barnacle Balanus improvisus has one of the broadest salinity tolerances of any barnacle species. It is able to complete its life cycle in salinities close to freshwater (3 PSU) up to fully marine conditions (35 PSU) and is regarded as one of few truly brackish-water species. Na+/K+ ATPase (NAK) has been shown to be important for osmoregulation when marine organisms are challenged by changing salinities, and we therefore cloned and examined the expression of different NAKs from B. improvisus. We found two main gene variants, NAK1 and NAK2, which were approximately 70% identical at the protein level. The NAK1 mRNA existed in a long and short variant with the encoded proteins differing only by 27 N-terminal amino acids. This N-terminal stretch was coded for by a separate exon, and the two variants of NAK1 mRNAs appeared to be created by alternative splicing. We furthermore showed that the two NAK1 isoforms were differentially expressed in different life stages and in various tissues of adult barnacle, i.e the long isoform was predominant in cyprids and in adult cirri. In barnacle cyprid larvae that were exposed to a combination of different salinities and pCO(2) levels, the expression of the long NAK1 mRNA increased relative to the short in low salinities. We suggest that the alternatively spliced long variant of the Nak1 protein might be of importance for osmoregulation in B. improvisus in low salinity conditions.
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| 5. |
- Wrange, Anna-Lisa, 1981, et al.
(författare)
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Importance of plasticity and local adaptation for coping with changing salinity in coastal areas: a test case with barnacles in the Baltic Sea
- 2014
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Salinity plays an important role in shaping coastal marine communities. Near-future climate predictions indicate that salinity will decrease in many shallow coastal areas due to increased precipitation; however, few studies have addressed this issue. The ability of ecosystems to cope with future changes will depend on species’ capacities to acclimatise or adapt to new environmental conditions. Here, we investigated the effects of a strong salinity gradient (the Baltic Sea system – Baltic, Kattegat, Skagerrak) on plasticity and adaptations in the euryhaline barnacle Balanus improvisus. We used a common-garden approach, where multiple batches of newly settled barnacles from each of three different geographical areas along the Skagerrak-Baltic salinity gradient were exposed to corresponding native salinities (6, 15 and 30 PSU), and phenotypic traits including mortality, growth, shell strength, condition index and reproductive maturity were recorded. Results We found that B. improvisus was highly euryhaline, but had highest growth and reproductive maturity at intermediate salinities. We also found that low salinity had negative effects on other fitness-related traits including initial growth and shell strength, although mortality was also lowest in low salinity. Overall, differences between populations in most measured traits were weak, indicating little local adaptation to salinity. Nonetheless, we observed some population-specific responses – notably that populations from high salinity grew stronger shells in their native salinity compared to the other populations, possibly indicating adaptation to differences in local predation pressure. Conclusions Our study shows that B. improvisus is an example of a true brackish-water species, and that plastic responses are more likely than evolutionary tracking in coping with future changes in coastal salinity.
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| 6. |
- Yang, Jian, 1960, et al.
(författare)
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Development of the cryogenic 2-14 GHz eleven feed system for VLBI2010
- 2012
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Ingår i: 6th European Conference on Antennas and Propagation, EuCAP 2012; Prague; Czech Republic; 26 March 2012 through 30 March 2012. - 9781457709180 ; , s. 621-625
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Konferensbidrag (refereegranskat)abstract
- We present an overview of the recent developments of a cryogenic 2-14 GHz feed system for the Very Long Baseline Interferometry 2010 (VLBL2010) project. The developments include a new balun feeding network, a new circular Eleven feed, system noise temperature modeling and testing, integration with different low noise amplifiers (LNAs), and cryostat design and integration.
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