| 1. |
- Lund Ohlsson, Marie
(författare)
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New methods for movement technique development in cross-country skiing using mathematical models and simulation
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This Licentiate Thesis is devoted to the presentation and discussion of some new contributions in applied mathematics directed towards scientific computing in sports engineering. It considers inverse problems of biomechanical simulations with rigid body musculoskeletal systems especially in cross-country skiing. This is a contrast to the main research on cross-country skiing biomechanics, which is based mainly on experimental testing alone. The thesis consists of an introduction and five papers. The introduction motivates the context of the papers and puts them into a more general framework. Two papers (D and E) consider studies of real questions in cross-country skiing, which are modelled and simulated. The results give some interesting indications, concerning these challenging questions, which can be used as a basis for further research. However, the measurements are not accurate enough to give the final answers. Paper C is a simulation study which is more extensive than paper D and E, and is compared to electromyography measurements in the literature. Validation in biomechanical simulations is difficult and reducing mathematical errors is one way of reaching closer to more realistic results. Paper A examines well-posedness for forward dynamics with full muscle dynamics. Moreover, paper B is a technical report which describes the problem formulation and mathematical models and simulation from paper A in more detail. Our new modelling together with the simulations enable new possibilities. This is similar to simulations of applications in other engineering fields, and need in the same way be handled with care in order to achieve reliable results. The results in this thesis indicate that it can be very useful to use mathematical modelling and numerical simulations when describing cross-country skiing biomechanics. Hence, this thesis contributes to the possibility of beginning to use and develop such modelling and simulation techniques also in this context.
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| 2. |
- Persson, Erik, 1972-, et al.
(författare)
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Utilization of the natural variation in wood properties–a comparison between pilot plant and mill scale trials
- 2003
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Ingår i: Proceedings of International Mechanical Pulping Conference, Quebec City. - 1896742866 ; , s. 83-90
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Konferensbidrag (refereegranskat)abstract
- Four different pulpwood classes of Norway spruce (Picea abies (L.) Karst). were tested in mill scale production of TMP at Hallsta Papermill. The objectives of the trial were to evaluate both rather extreme and more traditional roundwood classes in a full-scale TMP-plant with respect to pulp properties and energy requirements. The experiment was partly based on the results from the proceeding pilot plant trial within the EuroFiber project. The results generally confirmed the findings in the pilot plant trial. Young wood with a high proportion of juvenile wood gave a pulp with attractive optical properties, but somewhat lower tear index and higher energy consumption. The other extreme, sawmill chips from old trees of heavy dimensions, required lower energy input and gave higher tear index, but inferior optical properties. The two more traditional classes gave pulps with properties between the two extremes.
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| 3. |
- Persson, Erik, et al.
(författare)
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Utilization of the natural variations in wood properties in production of TMP : Comparison between pilot plant and mill scale trials using different assortments of Norway spruce pulpwood
- 2003
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Ingår i: 2003 International Mechanical Pulping Conference / Pulp and Paper Technical Association of Canada. - Montreal : PAPTAC. - 1896742866 ; , s. 485-
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Konferensbidrag (refereegranskat)abstract
- International Mechanical Pulping Conference, Québec City Canada x-y June 2003, Persson, Erik., Engstrand, Per, Karlsson, Lennart., Nilsson, Fredrik, Wahlgren, Mikael.
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| 4. |
- Svanedal, Ida, 1979-, et al.
(författare)
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Metal Ion Coordination, Conditional Stability Constants and Solution Behavior of Chelating Surfactant Metal Complexes
- 2014
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:16, s. 4605-4612
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Tidskriftsartikel (refereegranskat)abstract
- Coordination complexes of some divalent metal ions with the DTPA (diethylenetriaminepentaacetic acid)-based chelating surfactant 2-dodecyldiethylenetriaminepentaacetic acid (4-C12-DTPA) have been examined in terms of chelation and solution behavior. The headgroup of 4-C 12-DTPA contains eight donor atoms that can participate in the coordination of a metal ion. Conditional stability constants for five transition metal complexes with 4-C12-DTPA were determined by competition measurements between 4-C12-DTPA and DTPA, using electrospray ionization mass spectrometry (ESI-MS). Small differences in the relative strength between the coordination complexes of DTPA and 4-C12-DTPA indicated that the hydrocarbon tail only affected the chelating ability of the headgroup to a limited extent. The coordination of Cu2+ ions was investigated in particular, using UV-visible spectroscopy. By constructing Job's plots, it was found that 4-C12-DTPA could coordinate up to two Cu2+ ions. Surface tension measurements and NMR diffusometry showed that the coordination of metal ions affected the solution behavior of 4-C 12-DTPA, but there were no specific trends between the studied divalent metal complexes. Generally, the effects of the metal ion coordination could be linked to the neutralization of the headgroup charge of 4-C 12-DTPA, and the resulting reduced electrostatic repulsions between adjacent surfactants in micelles and monolayers. The pH vs concentration plots, on the other hand, showed a distinct difference between 4-C12-DTPA complexes of the alkaline earth metals and the transition metals. This was explained by the difference in coordination between the two groups of metal ions, as predicted by the hard and soft acid and base (HSAB) theory.
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| 5. |
- Weis, Jan, 1956-, et al.
(författare)
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GABA quantification in human anterior cingulate cortex
- 2021
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Ingår i: PLOS ONE. - : PLOS. - 1932-6203. ; 16:1
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Tidskriftsartikel (refereegranskat)abstract
- γ-Aminobutyric acid (GABA) is a primary inhibitory neurotransmitter in the human brain. It has been shown that altered GABA concentration plays an important role in a variety of psychiatric and neurological disorders. The main purpose of this study was to propose a combination of PRESS and MEGA-PRESS acquisitions for absolute GABA quantification and to compare GABA estimations obtained using total choline (tCho), total creatine (tCr), and total N-acetyl aspartate (tNAA) as the internal concentration references with water referenced quantification. The second aim was to demonstrate the fitting approach of MEGA-PRESS spectra with QuasarX algorithm using a basis set of GABA, glutamate, glutamine, and NAA in vitro spectra. Thirteen volunteers were scanned with the MEGA-PRESS sequence at 3T. Interleaved water referencing was used for quantification, B0 drift correction and to update the carrier frequency of RF pulses in real time. Reference metabolite concentrations were acquired using a PRESS sequence with short TE (30 ms) and long TR (5000 ms). Absolute concentration were corrected for cerebrospinal fluid, gray and white matter water fractions and relaxation effects. Water referenced GABA estimations were significantly higher compared to the values obtained by metabolite references. We conclude that QuasarX algorithm together with the basis set of in vitro spectra improves reliability of GABA+ fitting. The proposed GABA quantification method with PRESS and MEGA-PRESS acquisitions enables the utilization of tCho, tCr, and tNAA as internal concentration references. The use of different concentration references have a good potential to improve the reliability of GABA estimation.
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| 6. |
- Åhs, Fredrik, et al.
(författare)
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Medial temporal lobe resection attenuates superior temporal sulcus response to faces
- 2014
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Ingår i: Neuropsychologia. - : Elsevier BV. - 0028-3932 .- 1873-3514. ; 61, s. 291-298
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Tidskriftsartikel (refereegranskat)abstract
- Face perception depends on activation of a core face processing network including the fusiform face area, the occipital face area and the superior temporal sulcus (STS). The medial temporal lobe (MTL) is also involved in decoding facial expression and damage to the anterior MTL, including the amygdala, generally interferes with emotion recognition. The impairment in emotion recognition following anterior MTL injury can be a direct result from injured MTL circuitry, as well as an indirect result from decreased MTL modulation of areas in the core face network. To test whether the MTL modulates activity in the core face network, we used functional magnetic resonance imaging to investigate activation in the core face processing network in patients with right or left anterior temporal lobe resections (ATR) due to intractable epilepsy. We found reductions of face-related activation in the right STS after both right and left ATR together with impaired recognition of facial expressions. Reduced activity in the fusiform and the occipital face areas was also observed in patients after right ATR suggesting widespread effects on activity in the core face network in this group. The reduction in face-related STS activity after both right and left ATR suggests that MTL modulation of the STS may facilitate recognition of facial expression.
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