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| 3. |
- Arnason, T., et al.
(author)
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Long-term rearing of Arctic charr Salvelinus alpinus under different salinity regimes at constant temperature
- 2014
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In: Journal of Fish Biology. - : Wiley. - 0022-1112. ; 85:4, s. 1145-1162
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Journal article (peer-reviewed)abstract
- Arctic charr Salvelinus alpinus of the Holar strain (mean+/- s. e. body mass= 152.1+/-3.1g) were reared at four different salinity regimes at a constant temperature of 7.4 degrees C. Two groups were given a three-month acclimation in salinity 18 before the salinity was increased to either 25 or 29 (groups called A25 and A29), and two groups were reared in salinities 25 or 29 over the full experimental period of 409 days (groups called F25 and F29). In the first 3months, the A25 and A29 groups had the highest growth rates. By October 2011, there were no significant differences (two-way nested ANOVA, P> 0.05) in the mean body masses among A25, F25 and F29 (c. 1450 g), whereas A29 had a lower mean mass (1282 g). The growth in the last period from October 2011 to January 2012 was reduced by sexual maturation in the highest salinity regimes (A29 and F29), whereas fish in groups A25 and F25 showed high growth throughout the study. Males in all salinity groups had higher growth rates than females for the most part of the study, but the divergence between the sexes was most pronounced in the highest salinity regimes. All salinity groups showed distinct changes in Na+, K+-ATPase activity, with high activity in spring and summer, and lower activity in the autumn. Plasma sodium (Na+) levels were stable indicating that none of the experimental groups had problems in maintaining hydromineral balance during the study. While plasma leptin levels were not affected by salinity regimes, it was noted that these levels were 13-30% higher in fish with empty guts compared with those having food in their gut at the time of sampling. This suggests a link between leptin levels and food intake, indicating that this hormone may play a role in food intake and energy allocation in fishes.
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- Beylich, Achim, A., et al.
(author)
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Experimental weathering of selected non-calcareous rock types under wet/moist conditions
- 2007
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In: Zeitschrift für Geomorphologie. - 0372-8854. ; 51:1, s. 1-26
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Journal article (peer-reviewed)abstract
- This experiment outlines chemical and physical weathering of selected non-calcareous rock types during the time between November 2002 and February/March 2004. Parallel series of rock specimens were placed in boxes and half covered by water. One set was exposed to different temperature amplitudes in a freeze room, i.e., a simulated periglacial environment, another set was placed outdoor in a temperature environment with a mean annual temperature of c. +6°C, and four samples were placed in an office with a temperature of 21°C ± 3°C throughout. Electric conductivity, ion composition and pH values of the water together with the resulting amount of debris were determined for all samples at the termination of the experiment. In addition the electric conductivity and the debris were noted at intervals during the experiment. All samples experienced chemical weathering and the Freeze room and the Outdoor samples also underwent physical weathering to various extent. Generally speaking the highest degree of physical weathering was found in the Freeze room samples, but the pattern was not consistent. The relative importance of chemical weathering on the other hand seems more related to rock type than to environmental conditions. In single cases there are hints to suggest quantitative dominance of chemical over physical weathering in the Freeze room series. A tentative relationship between weathering of the respective rock types and the landforms in the areas of their origin could be noted. In spite of the low sample number and simple investigation methods the results suggest that rates of chemical and physical weathering as well as their mutual importance is more complex than traditionally believed.
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| 6. |
- Gunnarsson, S., et al.
(author)
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Effects of short-day treatment on long-term growth performance and maturation of farmed Arctic charr Salvelinus alpinus reared in brackish water
- 2014
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In: Journal of Fish Biology. - : Wiley. - 0022-1112. ; 85:4, s. 1211-1226
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Journal article (peer-reviewed)abstract
- The effects of a 6 week short-day photoperiod followed by continuous light, applied during the juvenile phase of Arctic charr Salvelinus alpinus in fresh water on smoltification and on the long-term growth andmaturity following transfer to brackish water (BW) (constant salinity of either 17 and 27 or increasing salinity in steps from 17 to 27) were investigated. Prior to salinity transfer, the juveniles were either reared at continuous light (C group) or reared for 6 weeks on a short day (8L: 16D, S group) followed by continuous light (24L: 0D). Increased salinity had negative effect on growth, with female fish reared at 17 salinity weighing 19 and 27% more than the salinity-step group (17-27) and the 27 salinity group, respectively. The stepwise acclimation to salinity had limited advantage in terms of growth rate. Short photoperiod for 6 weeks (November to January) followed by continuous light improved growth, but not seawater (SW) tolerance. Gill Na+, K+-ATPase activity and plasma Na+ levels changed with time, indicating some variation in osmoregulatory capacity during the experimental period. Overall, there appear to be interactive effects on maturation from applying short-day photoperiod followed by rearing at higher salinities. Plasma leptin varied with time and may be linked to stress caused by the observed variations in osmoregulatory ability. It is concluded that changes in growth rates observed in this study are mainly related to rearing salinity with higher growth rates at lower salinities. Short-day photoperiod has some growth-inducing effects but did not improve SW tolerance. Farmers of S. alpinus using BW for land-based rearing should keep salinity at moderate and stable levels according to these results to obtain best growth.
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| 7. |
- Gustavsson, Henrik, et al.
(author)
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Continuous assessment in software engineering project course using publicly available data from GitHub
- 2019
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In: Proceedings of the 15th International Symposium on Open Collaboration, OpenSym 2019. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450363198
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Conference paper (peer-reviewed)abstract
- This paper describes an approach for assessment in a large software engineering project course. We propose an approach for continuously collecting information from a source code repository and collaboration tool, and using this information for assessing student contributions and also for assessing the course as a whole from the teacher's standpoint. We present how we display metrics for how the students perform in relation to some of the requirements of the course. We argue that continuous summative assessment feedback to the students on how they are performing in the project is a suitable strategy for ensuring active participation from the students for the duration of the project course.
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| 8. |
- Gustavsson, Marcus, et al.
(author)
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A new symbol- and GIS-based detailed geomorphological mapping system: renewal of a scientific discipline for understanding landscape development
- 2006
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In: Geomorphology. - : Elsevier BV. - 0169-555X .- 1872-695X. ; 77:1-2, s. 90-111
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Journal article (peer-reviewed)abstract
- This paper presents a comprehensive and flexible new geomorphological combination legend that expands the possibilities of current geomorphological mapping concepts. The new legend is presented here at scale of 1:10,000 and it combines symbols for hydrography, morphometry/morphography, lithology and structure with colour variations for process/genesis and geologic age. The piece-by-piece legend forms a “geomorphological alphabet” that offers a high diversity of geomorphological information and a possibility for numerous combinations of information. This results in a scientific map that is rich in data and which is more informative than most previous maps but is based on a simple legend. The system is developed to also be used as a basis for applications in GIS. The symbol-based information in the geomorphological maps can be digitally stored as a powerful database with thematic layers and attribute tables. By combining and further developing aspects of different classical mapping systems and techniques into expanded data combinations, new possibilities of presentation and storage are developed and thus a strong scientific tool is provided for landscape configuration and the reconstruction of its development; in turn the combination paves the way for specific thematic applications. The new system is illustrated for two contrasting landscape types: the first is located on the border of Vorarlberg, western Austria, and Liechtenstein in a glacially influenced, high altitude alpine setting that is strongly modified by various degradation processes; the second area represents a formerly glaciated region in Dalarna, central Sweden near Mora, an area that is characterized by a variety of aeolian, fluvial, glaciofluvial and lacustrine depositional and erosional landforms and also reflects isostatic uplift. The new method functions well for both areas and results in detailed scientific outlines of both landscape types.
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| 9. |
- Gustavsson, Marcus, et al.
(author)
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Adsorption Efficiency of Respirator Filter Cartridges for Isocyanates
- 2010
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In: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 0003-4878 .- 1475-3162. ; 54:4, s. 377-390
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Journal article (peer-reviewed)abstract
- In some industries, the temperature and the humidity will vary greatly between different work places, such as outdoor work in arctic or tropical climates. There is therefore a need to test respirator filters at conditions that simulate conditions that are relevant for the industries that they are used in. Filter cartridges were exposed to controlled atmospheres of varying isocyanate concentration, air humidity, and temperature in an exposure chamber. For isocyanic acid (ICA) and methyl isocyanate (MIC), the exposure concentrations were between 100 and 200 p.p.b., monitored using a proton transfer reaction mass spectrometer. ICA and MIC were generated by continuous thermal degradation of urea and dimethylurea. The breakthrough was studied by collecting air samples at the outlet of the filter cartridges using impinger flasks or dry samplers with di-n-butylamine as derivatization reagent for isocyanates followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. For hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), the exposure concentrations were between 4 and 20 p.p.b. and were generated by wet membrane permeation. To reveal the profile of adsorption in different layers of the respirator filters, representative samples from each of the layers were hydrolyzed. The hydrolysis products hexamethylene diamine and isophorone diamine were determined after derivatization with pentafluoropropionic anhydride (PFPA) followed by LC-MS/MS analysis. The two filter types studied efficiently absorbed both ICA and MIC. There was no trend of impaired performance throughout 48-h exposure tests. Even when the filters were exposed to high concentrations (similar to 200 p.p.b.) of ICA and MIC for 96 h, the isocyanates were efficiently absorbed with only a limited breakthrough. The majority of the HDI and IPDI (> 90%) were absorbed in the top layers of the absorbant, but HDI and IPDI penetrated farther down into the respirator filters during 120 h of exposure as compared to 16 h exposure.
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| 10. |
- Gustavsson, Marcus, 1972-
(author)
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Development of a Detailed Geomorphological Mapping System and GIS Geodatabase in Sweden
- 2006
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Doctoral thesis (other academic/artistic)abstract
- This thesis presents a method for detailed landscape presentation. The method incorporates both fieldwork-based comprehensive geomorphological description and digital data handling and thus contributes in filling the gap between traditional geomorphological mapping and modern geomorphological studies performed in Geographic Information Systems (GIS).The main part of the thesis relates to development of a new detailed geomorphological mapping system, constructed to be easy to use and yet present a large amount of geomorphological information. The legend of the mapping system has successfully been applied to various types of landscapes, mapped at various scales between 1:5,000 and 1:50,000 without any modifications needed. The information presented in the map is based on simple descriptive criteria and thus the subjectivity is kept low, which enables a broad field of usage. In parallel with the mapping system a GIS-based geomorphological database has been developed. The structure and data presentation of the new mapping system allows for easy transformation of the data to form part of this database. The selected format of the GIS database is the ESRI ArcGIS®, Personal geodatabase.In the development of the geomorphological mapping system four field areas have been mapped in central (Bonäs, Risa and Liden) and northern Sweden (Tarfala). In addition the new legend has been adapted to a field area situated in Vorarlberg, Austria (Upper Gamperdona valley).In relation to the Tarfala field area an added issue of the project has been to give insights in the effects of physical and chemical weathering on various rock types to see if this can be detected in materials and landforms. The results from this study point at that resistance towards weathering vary among rocks even though they are of same rock type.
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