| 1. |
- Ainegren, Mats, 1963-
(författare)
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The rolling resistances of roller skis and their effects on human performance during treadmill roller skiing
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern ski-treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical performance in a laboratory environment using classical and freestyle techniques on roller skis. For elite athletes the differences in performance between test occasions are quite small, thus emphasising the importance of knowing the roller skis’ rolling resistance coefficient, µR, in order to allow correct comparisons between the results, as well as providing the opportunity to study work economy between different athletes, test occasions and core techniques.Thus, one of the aims of this thesis was to evaluate how roller skis’ µR is related to warm-up, mass, velocity and inclination of the treadmill. It was also necessary to investigate the methodological variability of the rolling resistance measurement system, RRMS, specially produced for the experiments, with a reproducibility study in order to indicate the validity and reliability of the results.The aim was also to study physiological responses to different µR during roller skiing with freestyle and classical roller skis and techniques on the treadmill as a case in which all measurements were carried out in stationary and comparable conditions.Finally, the aim was also to investigate the work economy of amateurs and female and male junior and senior cross-country skiers during treadmill roller skiing, i.e. as a function of skill, age and gender, including whether differences in body mass causes significant differences in external power per kg due to differences in the roller skis’ µR.The experiments showed that during a warm-up period of 30 minutes, µR decreased to about 60-65% and 70-75% of its initial value for freestyle and classical roller skis respectively. For another 30 minutes of rolling no significant change was found. Simultaneous measurements of roller ski temperature and mR showed that stabilized mR corresponds to a certain running temperature for a given normal force on the roller ski. The study of the influence on mR of normal force, velocity and inclination produced a significant influence of normal force on mR, while different velocities and inclinations of the treadmill only resulted in small changes in mR. The reproducibility study of the RRMS showed no significant differences between paired measurements with either classical or the freestyle roller skis.The study of the effects on physiological variables of ~50% change in µR,showed that during submaximal steady state exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a significantly changed maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non significant or small.The final part of the thesis, which focused on work economy, found no significant difference between the four groups of elite competitors, i.e. between the two genders and between the junior and senior elite athletes. It was only the male amateurs who significantly differed among the five studied groups. The study also showed that the external power per kg was significantly different between the two genders due to differences in body mass and mR, i.e. the lighter female testing groups were roller skiing with a relatively heavier rolling resistance coefficient compared to the heavier testing groups of male participants.
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| 2. |
- Hägglund, Rickard, et al.
(författare)
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Measuring thickness changes of edge-wise compression loaded corrugated board panels using digital image correlation
- 2012
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Ingår i: Journal of Sandwich Structures and Materials. - : SAGE Publications. - 1099-6362 .- 1530-7972. ; 14:1, s. 75-94
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Tidskriftsartikel (refereegranskat)abstract
- This study examines thickness changes in web-core sandwich panels under edgewise compressive loading. Both undamaged and damaged panels were examined. Three-dimensional full-field digital image correlation systems were used to determine deflections on both sides of loaded panels. The change in thickness at any given point in the panel was obtained as the difference between the two displacement fields. It was observed that the thickness was reduced in the post-buckling regime. Damage introduced into the corrugated core by lateral compression proved to significantly reduce the load-carrying capability panels and elevate the thickness reduction of the panels.
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| 3. |
- Mattsson, Göran, et al.
(författare)
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Endothelial cells in endogenous and transplanted pancreatic islets : differences in the expression of angiogenic peptides and receptors
- 2006
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Ingår i: Pancreatology (Print). - : Elsevier BV. - 1424-3903 .- 1424-3911. ; 6:1-2, s. 86-95
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Tidskriftsartikel (refereegranskat)abstract
- Background/Aims: An important reason for the large amount of islets required for successful islet transplantation is likely to be inadequate engraftment of the transplanted islets. Thus, the revascularization is of major importance for graft survival. In order to study the expression of angiogenic peptides and receptors on islet endothelial cells (EC), we needed methods giving access to such endothelium. Therefore, we developed methods to isolate EC from islets transplanted intraportally or beneath the kidney capsule. Methods: Pancreatic islets were isolated, cultured and syngeneically transplanted into the liver or beneath the kidney capsule of C57BL/6 mice. One month post-transplantation, the islets were retrieved and EC from these islets were explanted. EC were also collected from freshly isolated and cultured non-transplanted islets. The EC were purified with Dynabeads and identified with immunocytochemistry. Angiogenesis GEArray technology was used to study angiogenic gene expression. Results: Several angiogenic genes were expressed in EC; e. g. endostatin, pigment-epithelial derived factor, vascular endothelial growth factor and angiopoietin-2, and their expression were affected by culture. Conclusion: The expression of angiogenesis-related genes in islet EC from non-transplanted islets is affected by culture. Moreover, we also describe a technique, which makes it possible to obtain EC from transplanted islets.
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| 4. |
- Roback, Kerstin, et al.
(författare)
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Evaluation of health research : measuring costs and socioeconomic effects.
- 2011
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Ingår i: International Journal of Preventive Medicine. - India : Medknow Publications. - 2008-7802 .- 2008-8213. ; 2:4, s. 203-15
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Forskningsöversikt (refereegranskat)abstract
- Objectives: The topic of this work is health research evaluation including basic and clinical medical research, as well as healthcare research. The main objects are to explore possible approaches for valuing research in economic terms and to prepare an analytical model for evaluation of health research using the Swedish context. The study also aims to identify potential effects and their significance, and to provide a basis for discussions about the effects of research investments.Methods: The study has reviewed ten articles indicating positive effects, in the form of improved health and economic growth. The study also developed a model applied to Swedish health research.Results: The review indicates that positive effects, in the form of improved health and economic growth, have a value that greatly exceeds the costs of the research investments. The tentative model applied to Swedish health research also indicates predominantly positive returns, but in a lower range than the review would imply. Methodological problems, however, entail major uncertainty in the cited results.Conclusions: Accurate determination of the economic value of research would require significantly better basic data and better knowledge of relationships between research, implementation of new knowledge, and health effects. Information in support of decisions about future allocation of research resources is preferably produced by a combination of general analyses and strategically selected case studies.
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| 5. |
- Åslund, Pär, et al.
(författare)
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An analysis of strain localization and formation of face wrinkles in edge-wise loaded corrugated sandwich panels using a continuum damage model
- 2015
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 56-57, s. 248-257
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Tidskriftsartikel (refereegranskat)abstract
- This paper examines the compressive failure mechanism in edge-to-edge loaded corrugated sandwich panels. The formation of face wrinkles is specifically considered. A detailed finite element model of face sheets and web core of a sandwich panel was developed to provide insight on the failure mechanism. A gradient enhanced continuum damage theory was implemented to capture length effects caused by the material microstructure including formation of damage in the face sheets and core. Distributions of strains in the face sheets determined from finite element analysis (FEA) are compared to experimentally measured strains. The predicted location and orientation of the face wrinkle, as indicated by high values of the second principal strain, agrees well with experimental observations. Load vs. out-of-plane deflection curves obtained from FEA with the gradient enhanced damage material model are compared to those obtained from a linear-elastic material model and experimentally determined curves. The gradient enhanced solution gives qualitatively better agreement with experimental results, although the magnitudes of strains are less than those determined experimentally.
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| 6. |
- Åslund, Pär, et al.
(författare)
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Modeling of global and local buckling of corrugated board panels loaded in edge-to-edge compression
- 2014
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Ingår i: Journal of Sandwich Structures and Materials. - : SAGE Publications. - 1099-6362 .- 1530-7972. ; 16:3, s. 272-292
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Tidskriftsartikel (refereegranskat)abstract
- Detailed structural nonlinear finite element modeling of a sandwich panel with corrugated core is performed in this study. A simply supported panel is loaded in uniaxial compression well into the regimes of global panel buckling and local face sheet buckling. The highly nonlinear load versus in-plane and out-of-plane displacement responses obtained from finite element analysis agree reasonably well with experimental results, but the model slightly overpredicts the maximum load. The difference between experiments and predictions is attributed to damage of the corrugated paper web introduced during manufacture of the core and corrugated board. Computations of the buckling also results in a slight thickness reduction of the panel for a large range of face and web thicknesses identify lower thickness limits when the web loses its ability to contribute to the compressive strength of the panel. The highly nonlinear response associated with local and global buckling also results in thickness reduction of the panel.
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