| 1. |
- Berghauser Pont, Meta, 1972, et al.
(författare)
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PST
- 2019
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Annan publikation (mjukvara/multimedium) (övrigt vetenskapligt/konstnärligt)abstract
- PST is a tool for performing space syntax and regular accessibility analyses. It currently consists of two main parts - a C++ and Python library called Pstalgo and a plugin for the desktop application QGIS.PST is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. The GNU General Public License is intended to guarantee your freedom to share and change all versions of a program--to make sure it remains free software for all its users.For latest download visit either the Chalmers publication page, or find "Releases" on the Github page.
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| 2. |
- Brackmann, Christian, et al.
(författare)
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Structure of premixed ammonia plus air flames at atmospheric pressure: Laser diagnostics and kinetic modeling
- 2016
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 163, s. 370-381
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Tidskriftsartikel (refereegranskat)abstract
- The structure of premixed ammonia air flames, burning at atmospheric pressure under strain-stabilized conditions on a porous-plug burner, has been investigated using laser-diagnostic methods. Profiles of OH, NH, and NO were acquired by laser-induced fluorescence (LIF) and quantitative concentrations of OH and NO were retrieved using a concept for calibration versus absorption utilizing the LIF-signal itself, whereas NH concentrations were evaluated employing a saturated fluorescence signal. In addition, temperatures and relative oxygen concentrations were measured by rotational Coherent Anti-stokes Raman Spectroscopy (CARS). The new experimental data for flames with equivalence ratios of 0.9, 1.0, and 1.2 were used to validate and rank the performance of four contemporary detailed kinetic models. Simulations were carried out using experimental temperature profiles as well as by solving the energy equation. Two models of the same origin, developed by Mendiara and Glarborg (2009) and by Klippenstein et al. (2011), in most cases showed good agreement in terms of radical concentrations, however, the model of Mendiara and Glarborg had better prediction of temperatures and flame front positions. The model by Shmakov et al. (2010) had comparable performance concerning radical species, but significant discrepancies appeared in the prediction of flame front positions. The model of Duynslaegher et al. (2012), in addition to the flame front positions, deviated from experiments or other models in terms of NH and NO concentrations. A sensitivity analysis for the Mendiara-Glarborg mechanism indicated that remaining uncertainties of the rate constants implemented in the recent H/N/O models are difficult to scrutinize unambiguously due to experimental uncertainties. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 3. |
- Brondin, Anna, et al.
(författare)
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Open source step counter algorithm for wearable devices
- 2020
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Ingår i: Companion Proceedings of the 10th International Conference on the Internet of Things (IoT 2020). - New York, United States : ACM Digital Library. - 9781450388207
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Konferensbidrag (refereegranskat)abstract
- Commercial wearable devices and fitness trackers are commonly sold as black boxes of which little is known about their accuracy. This poses serious issues especially in health-related contexts such as clinical research, where transparency about accuracy and reliability are paramount.We present a validated algorithm for computing step counting that is optimised for use in constrained computing environments. Released as open source, the algorithm is based on the windowed peak detection approach, which has previously shown high accuracy on smartphones. The algorithm is optimised to run on a programmable smartwatch (Pine Time) and tested on 10 subjects in 8 scenarios, with varying varying positions of the wearable and walking paces.Our approach achieves a 89% average accuracy, with the highest average accuracy when walking outdoor (98%) and the lowest in a slow-walk scenario (77%). This result can be compared with the built-in step counter of the smartwatch (Bosch BMA421), which yielded a 94% average accuracy for the same use cases. Our work thus shows that an open-source approach for extracting physical activity data from wearable devices is possible and achieves an accuracy comparable to the one produced by proprietary embedded algorithms.
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| 4. |
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| 5. |
- Carlsson, Henning, et al.
(författare)
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Numerical and experimental study of flame propagation and quenching of lean premixed turbulent low swirl flames at different Reynolds numbers
- 2015
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 162:6, s. 2582-2591
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a joint experimental and large eddy simulation (LES) study of lean premixed low swirl stabilized methane/air flames at different Reynolds numbers (Re similar to 20,000-100,000). The aims are to investigate the sensitivity of the structures and dynamics of low swirl flames to the inflow boundary conditions and to evaluate the capability of an LES flamelet model in predicting the stabilization and local extinction of the flames. Chemiluminescence measurements are carried out for Re - 20,000-50,000 and further detailed oxygen concentration and temperature fields are measured using rotational coherent anti-Stokes Raman spectroscopy (RCARS) for Re - 20,000 and 30,000 along the centerline of the burner and at various radial positions at different heights above the burner. The data are used first for validation of the combustion LES model employed in the numerical simulations, and then the RCARS and LES results are used to delineate the effect of ambient air entrainment on the flame structure at various burner exit velocities. A three-scalar flamelet model based on a level-set G-equation shows excellent predictions of the lift-off positions and the structures of the flames, including quenching at the trailing edge of the flame. The results show that the flame lift-off height varies only slightly when the burner exit velocity is increased, which is consistent with a shear-layer flame stabilization mechanism reported previously. The volume of the flame decreases substantially with increasing burner exit velocity at relatively low Reynolds numbers, as a result of flame quenching at the trailing edge of the flame caused by entrainment of the ambient air into the fuel/air stream and the flame itself. At high Reynolds numbers the flame structures become fairly self-similar with the flame volume nearly independent of the Reynolds number. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 6. |
- Edman, Sebastian, et al.
(författare)
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Pro-Brain-Derived Neurotrophic Factor (BDNF), but Not Mature BDNF, Is Expressed in Human Skeletal Muscle : Implications for Exercise-Induced Neuroplasticity.
- 2024
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Ingår i: Function. - : Oxford University Press. - 2633-8823. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Exercise promotes brain plasticity partly by stimulating increases in mature brain-derived neurotrophic factor (mBDNF), but the role of the pro-BDNF isoform in the regulation of BDNF metabolism in humans is unknown. We quantified the expression of pro-BDNF and mBDNF in human skeletal muscle and plasma at rest, after acute exercise (+/- lactate infusion), and after fasting. Pro-BDNF and mBDNF were analyzed with immunoblotting, enzyme-linked immunosorbent assay, immunohistochemistry, and quantitative polymerase chain reaction. Pro-BDNF was consistently and clearly detected in skeletal muscle (40-250 pg mg-1 dry muscle), whereas mBDNF was not. All methods showed a 4-fold greater pro-BDNF expression in type I muscle fibers compared to type II fibers. Exercise resulted in elevated plasma levels of mBDNF (55%) and pro-BDNF (20%), as well as muscle levels of pro-BDNF (∼10%, all P < 0.05). Lactate infusion during exercise induced a significantly greater increase in plasma mBDNF (115%, P < 0.05) compared to control (saline infusion), with no effect on pro-BDNF levels in plasma or muscle. A 3-day fast resulted in a small increase in plasma pro-BDNF (∼10%, P < 0.05), with no effect on mBDNF. Pro-BDNF is highly expressed in human skeletal muscle, particularly in type I fibers, and is increased after exercise. While exercising with higher lactate augmented levels of plasma mBDNF, exercise-mediated increases in circulating mBDNF likely derive partly from release and cleavage of pro-BDNF from skeletal muscle, and partly from neural and other tissues. These findings have implications for preclinical and clinical work related to a wide range of neurological disorders such as Alzheimer's, clinical depression, and amyotrophic lateral sclerosis.
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| 7. |
- Eliason, Marcus, et al.
(författare)
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Informella kontaktnäts betydelse för arbetssökande och företag på den svenska arbetsmarknaden
- 2017
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Rapport (refereegranskat)abstract
- Vi analyserar hur restaurangpriserna förändrades i samband med momssänkningar i Finland 2010 och Sverige 2012. Vi visar att prisförändringarna i samband med dessa skattesänkningar i stora drag kan karaktäriseras som ”allt” eller ”inget”. Vi lägger därför särskilt fokus på att förstå vilka restauranger som sänkte priserna och vilka som inte gjorde det. Det visar sig att nästan alla prisförändringar skedde genom att restauranger som tillhör någon form av kedja sänkte sina priser medan oberoende restauranger i de allra flesta fall lämnade sina priser opåverkade. Vi visar att mönstret ligger väl i linje med andra betydande skillnader i prissättningsaktivitet mellan de två typerna av restauranger. Detta tyder på att företagssammansättningen har en betydande direkt effekt på hur stort genomslag en momssänkning får på priser och, i förlängningen, ekonomisk aktivitet.
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| 8. |
- Eliason, Marcus, et al.
(författare)
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Social Connections and the Sorting of Workers to Firms
- 2019
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Ingår i: SSRN Electronic Journal. - : Institute of Labor Economics (IZA). - 1556-5068.
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The literature on social networks often presumes that job search through (strong) social ties leads to increased inequality by providing privileged individuals with access to more attractive labor market opportunities. We assess this presumption in the context of sorting between AKM-style person and establishment fixed effects. Our rich Swedish register data allow us to measure connections between agents – workers to workers and workers to firms – through parents, children, siblings, spouses, former co-workers and classmates from high school/college, and current neighbors. In clear contrast with the above presumption, there is less sorting inequality among the workers hired through social networks. This outcome results from opposing factors. On the one hand, reinforcing positive sorting, high-wage job seekers are shown to have social connections to high-wage workers, and therefore to high-wage firms (because of sorting of workers over firms). Furthermore, connections have a causal impact on the allocation of workers across workplaces – employers are much more likely to hire displaced workers to whom they are connected through their employees, in particular if their social ties are strong. On the other hand, attenuating positive sorting, the (causal) impact is much stronger for low-wage firms than it is for high-wage firms, irrespective of the type of worker involved, even conditional on worker fixed effects. The lower degree of sorting among connected hires thus arises because low-wage firms use their (relatively few) connections to high-wage workers to hire workers of a type that they are unable to attract through market channels.
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| 9. |
- Eliason, Marcus, et al.
(författare)
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Social connections and the sorting of workers to firms
- 2023
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Ingår i: Journal of Econometrics. - : Elsevier. - 0304-4076 .- 1872-6895. ; 233:2, s. 468-506
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Tidskriftsartikel (refereegranskat)abstract
- We assess the presumption that social networks reinforce inequality by providing high -wage workers' with preferential access to high-wage establishments. Our results based on very detailed Swedish register data contradict this view. We do show that high -wage job seekers tend to be connected to high-wage workers employed in high-wage establishments. Furthermore, social connections appear to directly cause the allocation of workers to jobs. But the sorting resulting from hires within social networks is less unequal than the sorting resulting from market hires, essentially because low-wage firms rely on social connections to hire high-wage workers.
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| 10. |
- Horwath, Oscar, 1991-, et al.
(författare)
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Acute hypoxia attenuates resistance exercise-induced ribosome signaling but does not impact satellite cell pool expansion in human skeletal muscle.
- 2023
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Ingår i: The FASEB Journal. - : John Wiley & Sons. - 0892-6638 .- 1530-6860. ; 37:3
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Tidskriftsartikel (refereegranskat)abstract
- Cumulative evidence supports the hypothesis that hypoxia acts as a regulator of muscle mass. However, the underlying molecular mechanisms remain incompletely understood, particularly in human muscle. Here we examined the effect of hypoxia on signaling pathways related to ribosome biogenesis and myogenic activity following an acute bout of resistance exercise. We also investigated whether hypoxia influenced the satellite cell response to resistance exercise. Employing a randomized, crossover design, eight men performed resistance exercise in normoxia (FiO2 21%) or normobaric hypoxia (FiO2 12%). Muscle biopsies were collected in a time-course manner (before, 0, 90, 180 min and 24 h after exercise) and were analyzed with respect to cell signaling, gene expression and satellite cell content using immunoblotting, RT-qPCR and immunofluorescence, respectively. In normoxia, resistance exercise increased the phosphorylation of RPS6, TIF-1A and UBF above resting levels. Hypoxia reduced the phosphorylation of these targets by ~37%, ~43% and ~ 67% throughout the recovery period, respectively (p < .05 vs. normoxia). Resistance exercise also increased 45 S pre-rRNA expression and mRNA expression of c-Myc, Pol I and TAF-1A above resting levels, but no differences were observed between conditions. Similarly, resistance exercise increased mRNA expression of myogenic regulatory factors throughout the recovery period and Pax7+ cells were elevated 24 h following exercise in mixed and type II muscle fibers, with no differences observed between normoxia and hypoxia. In conclusion, acute hypoxia attenuates ribosome signaling, but does not impact satellite cell pool expansion and myogenic gene expression following a bout of resistance exercise in human skeletal muscle.
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| 11. |
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| 12. |
- Kelsen, Jesper, et al.
(författare)
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Copenhagen Head Injury Ciclosporin Study : A Phase IIa Safety, Pharmacokinetics, and Biomarker Study of Ciclosporin in Severe Traumatic Brain Injury Patients
- 2019
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Ingår i: Journal of Neurotrauma. - : Mary Ann Liebert Inc. - 0897-7151 .- 1557-9042. ; 36:23, s. 3253-3263
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Tidskriftsartikel (refereegranskat)abstract
- Traumatic brain injury (TBI) contributes to almost one third of all trauma-related deaths, and those that survive often suffer from long-term physical and cognitive deficits. Ciclosporin (cyclosporine, cyclosporin A) has shown promising neuroprotective properties in pre-clinical TBI models. The Copenhagen Head Injury Ciclosporin (CHIC) study was initiated to establish the safety profile and pharmacokinetics of ciclosporin in patients with severe TBI, using a novel parenteral lipid emulsion formulation. Exploratory pharmacodynamic study measures included microdialysis in brain parenchyma and protein biomarkers of brain injury in the cerebrospinal fluid (CSF). Sixteen adult patients with severe TBI (Glasgow Coma Scale 4-8) were included, and all patients received an initial loading dose of 2.5 mg/kg followed by a continuous infusion for 5 days. The first 10 patients received an infusion dosage of 5 mg/kg/day whereas the subsequent 6 patients received 10 mg/kg/day. No mortality was registered within the study duration, and the distribution of adverse events was similar between the two treatment groups. Pharmacokinetic analysis of CSF confirmed dose-dependent brain exposure. Between- and within-patient variability in blood concentrations was limited, whereas CSF concentrations were more variable. The four biomarkers, glial fibrillary acidic protein, neurofilament light, tau, and ubiquitin carboxy-terminal hydrolase L1, showed consistent trends to decrease during the 5-day treatment period, whereas the samples taken on the days after the treatment period showed higher values in the majority of patients. In conclusion, ciclosporin, as administered in this study, is safe and well tolerated. The study confirmed that ciclosporin is able to pass the blood-brain barrier in a TBI population and provided an initial biomarker-based signal of efficacy.
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| 13. |
- Kristensson, Elias, et al.
(författare)
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Stray light suppression in spectroscopy using periodic shadowing
- 2014
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Ingår i: Optics Express. - 1094-4087. ; 22:7, s. 7711-7721
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that spectroscopic measurements suffer from an interference known as stray light, causing spectral distortion that reduces measurement accuracy. In severe situations, stray light may even obscure the existence of spectral lines. Here a novel general method is presented, named Periodic Shadowing, that enables effective stray light elimination in spectroscopy and experimental results are provided to demonstrate its capabilities and versatility. Besides its efficiency, implementing it in a spectroscopic arrangement comes at virtually no added experimental complexity. (C) 2014 Optical Society of America
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| 14. |
- Kristensson, Elias, et al.
(författare)
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Stray light suppression in spectroscopy using periodic shadowing
- 2014
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 22:7, s. 7711-7711
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that spectroscopic measurements suffer from an interference known as stray light, causing spectral distortion that reduces measurement accuracy. In severe situations, stray light may even obscure the existence of spectral lines. Here a novel general method is presented, named Periodic Shadowing, that enables effective stray light elimination in spectroscopy and experimental results are provided to demonstrate its capabilities and versatility. Besides its efficiency, implementing it in a spectroscopic arrangement comes at virtually no added experimental complexity.
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| 15. |
- Larsson [Nordström], Susanna, 1983-, et al.
(författare)
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It’s a matter of eating or being eaten : gender positioning and difference making in the heavy metal subculture
- 2013
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Ingår i: European Journal of Cultural Studies. - London, UK : Sage Publications. - 1367-5494 .- 1460-3551. ; 16, s. 453-467
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this article is to study how gender difference and ultimately female gender positioning are created and manifested in the heavy metal culture. The empirical material consists of single interviews and focus group interviews with heavy metal fans between the ages of 18 and 26. The overall finding is that, while gender is a movable position in general, women move their gender position to a greater extent than men as they are constantly forced to adhere to the male values of the heavy metal culture. Three dualities in the positioning of heavy metal women illustrate to this phenomenon: a whore-goddess paradigm based on the knowledge of the female heavy metal fan; the balancing act of “acting male” and “looking female”; and the gender “twilight zone” of being insufficiently male for heavy metal culture while being insufficiently female for the mainstream world.
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| 16. |
- Manum, B., et al.
(författare)
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Modelling bikeability; Space syntax based measures applied in examining speeds and flows of bicycling in Gothenburg
- 2017
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Ingår i: 11th International Space Syntax Symposium, SSS 2017, Lisbon, Portugal, 3-7 July 2017. - 9789729899447 ; , s. 89.1-89.16
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Konferensbidrag (refereegranskat)abstract
- For numerous reasons related to energy demand, emissions, public health as well as liveable and attractive cities, a frequently stated aim in contemporary discussions on urban development is to increase amount and modal share of bicycling. In recent years, space syntax based methods have shown to be useful for providing informed premises for these discussions. Combining space syntax analyses with data on locations of residents, workplaces and destinations opens the door not only for predictive modelling of route choice preferences but also the potential amount of bicycling along routes. Building on previous research, the research presented in this paper develops space syntax based measures expected to capture bicycling and evaluates these measures by comparing the analyses with empirical data from studies carried out in cooperation with the City of Gothenburg. Among the variables considered essential for bicycling and included in our GIS model are: the slope and curvature of routes, the width and surface type of bicycle lanes and the kind and amount of traffic along the route. For modelling bicycling flow potentials, a measure termed Origin-Destination Betweenness (OD-betweenness) is used and tested, examining different combinations of variables and threshold distances. The empirical data consists of gate counts of bicycle traffic and detailed GPS-tracks mapping actual bicycling speeds of ca. 900 trips along a selection of bicycle routes. Using multiple regression analysis to model speed data, eight variables were found significant. In addition to slope and curvature of routes, the significant variables relate to proximity to traffic signals, degree of separation from pedestrians, density of entrances along the routes and quality of paving of the cycle lane. Concerning bicycling flow potentials, the most significant variables in the multiple regression model were: OD-betweenness within 5 km, segment angular integration within 10 km, density of residents and people at work (students included) within 1 km and network betweenness within 3km. Based on the results of the current project, a proposal for further research is to elaborate on the OD-betweenness analyses by including speeds and preferably traffic safety in the betweenness measure. By using time along segments instead of metric length for defining the analysis threshold (radius), it should be possible to have a new and improved generation of space syntax based accessibility analyses for bicycling studies. A working name for such a measure is "least impedance origin destination betweenness".
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| 17. |
- Marcus, Lars, 1962-, et al.
(författare)
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Developing the spatial capital at the Stockholm Central Station
- 2012
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Ingår i: The Future of Cities and Regions. - : Springer Science+Business Media B.V.. - 9789400725188 ; , s. 297-322
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Bokkapitel (refereegranskat)abstract
- This project concerns the most centrally located and spatially complex area in central Stockholm. It is located directly to the west of the internationally well-known Stockholm City area developed in the 1950s and 1960s. Presently significant reconstruction of the central station and its track areas is under way which will also open up a large new development area in one of the most attractive locations in Stockholm. For this project Spacescape, an architectural office specializing in analysis of urban space and urban development projects in relation to urban life qualities such as, attractiveness, public safety and retail support formed an integrated consultancy group together with architects and landscape architects, delivering evaluation and design support to the project. This concerned both an analysis of the current status of the area, including the spatially complex interior of the central station, as well as support and evaluation of the different stages in the proposal. The themes analysed included spatial capital (accessibility to the rest of the city, especially for people working and living in the city), pedestrian flows, wayfinding, recreational qualities and public safety. Through continuous analyses during the design process Spacescape were able to support the project in a direction providing greater benefits in these areas and telling images show how the new proposal could create a much better outcome than the current one.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
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| 26. |
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| 27. |
- Marcus, Lars, 1962-, et al.
(författare)
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Stockholm central station : Creating spatial capital through urban design
- 2012
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Ingår i: The Future of Cities and Regions: Simulation, Scenario and Visioning, Governance and Scale. - Dordrecht : Springer Netherlands. - 9789400725188 - 9789400725171 ; , s. 297-321
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This project concerns the most centrally located and spatially complex area in central Stockholm. It is located directly to the west of the internationally well-known Stockholm City area developed in the 1950s and 1960s. Presently significant reconstruction of the central station and its track areas is under way which will also open up a large new development area in one of the most attractive locations in Stockholm. For this project Spacescape, an architectural office specializing in analysis of urban space and urban development projects in relation to urban life qualities such as, attractiveness, public safety and retail support formed an integrated consultancy group together with architects and landscape architects, delivering evaluation and design support to the project. This concerned both an analysis of the current status of the area, including the spatially complex interior of the central station, as well as support and evaluation of the different stages in the proposal. The themes analysed included spatial capital (accessibility to the rest of the city, especially for people working and living in the city), pedestrian flows, wayfinding, recreational qualities and public safety. Through continuous analyses during the design process Spacescape were able to support the project in a direction providing greater benefits in these areas and telling images show how the new proposal could create a much better outcome than the current one.
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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
- Mukkattukavil, Deepak John, 1993-, et al.
(författare)
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Resonant inelastic soft x-ray scattering on LaPt2Si2
- 2022
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 34:32
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption and resonant inelastic x-ray scattering spectra of LaPt2Si2 single crystal at the Si 2p and La 4d edges are presented. The data are interpreted in terms of density functional theory, showing that the Si spectra can be described in terms of Si s and d local partial density of states (LPDOS), and the La spectra are due to quasi-atomic local 4f excitations. Calculations show that Pt d-LPDOS dominates the occupied states, and a sharp localized La f state is found in the unoccupied states, in line with the observations.
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| 33. |
- Nordström, Erik, et al.
(författare)
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Field investigations on the risk for ASR when using potentially reactive aggregates and low alkali cements : Results after 50 years in Sweden
- 2013
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Ingår i: ICOLD 2013 International Symposium — Seattle USA. - 9781884575631 ; , s. 393-402
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Konferensbidrag (refereegranskat)abstract
- The adverse effects from reactions of reactive aggregates in concrete dams are well known worldwide. The mechanisms ruling alkali silica reactions (ASR) are partly but not fully understood. A majority of the Swedish concrete dams are so far considered to be protected from ASR due to the common use during the 50:s, 60:s and 70:s of the Swedish low alkali cement Limhamn LH. Today there is a discussion if it still is possible to develop ASR after very long time in dams with reactive aggregates and use of low alkali cement. Via selection of seven facilities in the Swedish alpine area, where reactive aggregates are common, the current paper is aiming to compile experiences from almost 50 years of exposure. In the paper two examples on ASR in spite of use of low alkali cement are shown.
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| 34. |
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| 35. |
- Nordström, Fabian, et al.
(författare)
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The lactate receptor GPR81 is predominantly expressed in type II human skeletal muscle fibers : potential for lactate autocrine signaling.
- 2023
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Ingår i: American Journal of Physiology - Cell Physiology. - : American Physiological Society. - 0363-6143 .- 1522-1563. ; 324:2, s. C477-C487
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Tidskriftsartikel (refereegranskat)abstract
- GPR81 was first identified in adipocytes as a receptor for L-lactate, which upon binding inhibits cAMP-PKA-CREB signaling. Moreover, incubation of myotubes with lactate augments expression of GPR81 and genes and proteins involved in lactate- and energy metabolism. However, characterization of GPR81 expression and investigation of related signaling in human skeletal muscle under conditions of elevated circulating lactate levels are lacking. Muscle biopsies were obtained from healthy men and women at rest, after leg extension exercise, with or without venous infusion of sodium lactate, and 90 and 180 min after exercise (8 men and 8 women). Analyses included protein and mRNA levels of GPR81, as well as GPR81-dependent signaling molecules. GPR81 expression was 2.5-fold higher in type II glycolytic compared with type I oxidative muscle fibers, and the expression was inversely related to the percentage of type I muscle fibers. Muscle from women expressed about 25% more GPR81 protein than from men. Global PKA-activity increased by 5-8% after exercise, with no differences between trials. CREBS133 phosphorylation was reduced by 30% after exercise and remained repressed during the entire trials, with no influence of the lactate infusion. The mRNA expression of VEGF and PGC-1α were increased by 2.5 - 6-fold during recovery, and that of LDH reduced by 15% with no differences between trials for any gene at any time point. The high expression of GPR81-protein in type II fibers suggests that lactate functions as an autocrine signaling molecule in muscle; however, lactate does not appear to regulate CREB signaling during exercise.
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| 36. |
- Nordström, Marcus, et al.
(författare)
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Calibrated Surrogate Maximization of Dice
- 2020
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Ingår i: Medical Image Computing and Computer Assisted Intervention – MICCAI 2020. - Cham : Springer Nature. ; , s. 269-278
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Konferensbidrag (refereegranskat)abstract
- In the medical imaging community, it is increasingly popular to train machine learning models for segmentation problems with objectives based on the soft-Dice surrogate. While experimental studies have showed good performance with respect to Dice, there have also been reports of some issues related to stability. In parallel with these developments, direct optimization of evaluation metrics has also been studied in the context of binary classification. Recently, in this setting, a quasi-concave, lower-bounded and calibrated surrogate for the F1-score has been proposed. In this work, we show how to use this surrogate in the context of segmentation. We then show that it has some better theoretical properties than soft-Dice. Finally, we experimentally compare the new surrogate with soft-Dice on a 3D-segmentation problem and get results indicating that stability is improved. We conclude that the new surrogate, for theoretical and experimental reasons, can be considered a promising alternative to the soft-Dice surrogate.
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| 37. |
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| 38. |
- Nordström, Marcus, et al.
(författare)
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Marginal Thresholding in Noisy Image Segmentation
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This work presents a study on label noise in medical image segmentation by considering a noise model based onGaussian field deformations. Such noise is of interest because it yields realistic looking segmentations and because itis unbiased in the sense that the expected deformation is theidentity mapping. Efficient methods for sampling and closedform solutions for the marginal probabilities are provided.Moreover, theoretically optimal solutions to the loss functions cross-entropy and soft-Dice are studied and it is shownhow they diverge as the level of noise increases. Based on recent work on loss function characterization, it is shown thatoptimal solutions to soft-Dice can be recovered by thresholding solutions to cross-entropy with a particular a prioriunknown threshold that efficiently can be computed. Thisraises the question whether the decrease in performanceseen when using cross-entropy as compared to soft-Dice iscaused by using the wrong threshold. The hypothesis is validated in 5-fold studies on three organ segmentation problemsfrom the TotalSegmentor data set, using 4 different strengthsof noise. The results show that changing the threshold leadsthe performance of cross entropy to go from systematicallyworse than soft-Dice to similar or better results than soft-Dice.
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| 39. |
- Nordström, Marcus, et al.
(författare)
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Noisy Image Segmentation With Soft-Dice
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a study on the soft-Dice loss, one ofthe most popular loss functions in medical image segmentation, for situations where noise is present in target labels. In particular, the set of optimal solutions are characterizedand sharp bounds on the volume bias of these solutions areprovided. It is further shown that a sequence of soft segmentations converging to optimal soft-Dice also converges tooptimal Dice when converted to hard segmentations usingthresholding. This is an important result because soft-Diceis often used as a proxy for maximizing the Dice metric.Finally, experiments confirming the theoretical results areprovided.
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| 40. |
- Nordström, Marcus, et al.
(författare)
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On image segmentation with noisy labels : characterization and volume properties of the optimal solutions to accuracy and dice.
- 2022
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Ingår i: Advances in Neural Information Processing Systems 35 - 36th Conference on Neural Information Processing Systems, NeurIPS 2022. - : Neural information processing systems foundation.
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Konferensbidrag (refereegranskat)abstract
- We study two of the most popular performance metrics in medical image segmentation, Accuracy and Dice, when the target labels are noisy. For both metrics,several statements related to characterization and volume properties of the set ofoptimal segmentations are proved, and associated experiments are provided. Ourmain insights are: (i) the volume of the solutions to both metrics may deviatesignificantly from the expected volume of the target, (ii) the volume of a solutionto Accuracy is always less than or equal to the volume of a solution to Dice and(iii) the optimal solutions to both of these metrics coincide when the set of feasiblesegmentations is constrained to the set of segmentations with the volume equal tothe expected volume of the target.
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| 41. |
- Nordström, Marcus
(författare)
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On Medical Image Segmentation With Noisy Labels
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that data sets used for training and testing automatic medical image segmentation methods often contain a lot of label noise. Such noise affects the performance of the methods and has been subject to a lot of research. One way to approach the topic of label noise that largely has been overlooked in the literature is to investigate how it affects the theoretically optimal segmentations. This thesis consist of four papers related to such investigations for the two most popular choices of loss functions in the field, cross-entropy and soft-Dice, and the most popular metric, Dice.In paper A, the loss functions cross-entropy and soft-Dice are investigated. Inspired by work from binary classification, the properties of calibration and convexity are proposed to explain the experimental observations of good stability associated with cross-entropy and good performance associated with soft-Dice. It is then shown that soft-Dice neither is convex nor quasi-convex and it is conjectured that soft-Dice is calibrated to Dice. Finally, an alternative quasi-convex loss function is experimentally compared to soft-Dice on a kidney segmentation problem.In paper B, the optimal segmentations to the metrics Accuracy and Dice are characterized when noise is present. This characterization is then used to give a detailed account of the volume bias associated with the metrics. In particular, sharp bounds for volume bias is provided, it is shown that the volume of an optimizer to Accuracy always is less than or equal to the volume of an optimizer to Dice and that the set of optimizers to the two metrics coincide when the optimization is constrained to the segmentations without volume bias. Finally, experimental results supporting the observations are presented on a set of segmentation problems.In paper C, the effect label noise has on soft-Dice is studied. In particular, the optimal solutions are characterized and sharp bounds for the volume biasis provided. Moreover the conjecture of soft-Dice being calibrated to Dice is proved under a compactness assumption that always holds in practice. Finally, experimental results supporting the observations are presented on a set of organ segmentation problems and a set of synthetic segmentation problems.In paper D, a noise model based on Gaussian field deformations is proposed. Several theoretical properties for labels with this sort of noise is proved, including a closed form expression for marginal probabilities and a representation that can be used for efficient sampling. The noise model is then used to study 1/2-thresholded optimal solutions to the loss functions cross-entropyand soft-Dice, and it is shown how they diverge as the noise level is increased. Finally, by using the characterization of the optimal solutions to soft-Dice it is shown how cross-entropy can be used in conjunction with an a priori unknown but computable threshold to recover optimal solutions to soft-Dice. The theoretical observations are validated on three organ segmentation problems with various levels of noise.
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| 42. |
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| 43. |
- Selart, Marcus, et al.
(författare)
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Effects of Reward on Self-regulation, Intrinsic Motivation and Creativity
- 2008
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Ingår i: Scandinavian Journal of Educational Research. - 0031-3831 .- 1470-1170. ; 52:5, s. 439-458
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Tidskriftsartikel (refereegranskat)abstract
- This article evaluates the effects of two types of rewards (performance-contingent versus engagement-contingent) on self-regulation, intrinsic motivation and creativity. Forty-two undergraduate students were randomly assigned to three conditions; i.e. a performance-contingent reward group, an engagement-contingent reward group and a control group. Results provide little support for the negative effects of performance rewards on motivational components. However, they do indicate that participants in the engagement-contingent reward group and the control group achieved higher rated creativity than participants in the performance-contingent reward group. Alternative explanations for this finding are discussed. Keywords: Rewards; Self-Regulation; Creativity; Intrinsic Motivation
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| 44. |
- Westerlund, Joakim, et al.
(författare)
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Breaks in persistence in fixed-T panel data
- 2021
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Ingår i: Economics Letters. - : Elsevier BV. - 0165-1765. ; 205
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers an autoregressive panel data model in which the autoregressive coefficient has undergone a structural break. The object of interest is the unknown breakpoint. A least squares-based estimator is proposed that is shown to be consistent when only the number of cross-section units, N, is large and the number of time periods, T, is small, thereby enabling quick detection of the onset of a new regime.
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