| 2731. |
- Helgesson, Peter, 1985, et al.
(författare)
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The N-Player War of Attrition in the Limit of Infinitely Many Players
- 2015
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Ingår i: Dynamic Games and Applications. - : Springer Science and Business Media LLC. - 2153-0785 .- 2153-0793. ; 5:1, s. 65-93
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Tidskriftsartikel (refereegranskat)abstract
- The War of Attrition is a classical game theoretic model that was first introduced to mathematically describe certain non-violent animal behavior. The original setup considers two participating players in a one-shot game competing for a given prize by waiting. This model has later been extended to several different models allowing more than two players. One of the first of these N -player generalizations was due to Haigh and Cannings (Acta Appl Math 14:59–74, 1989) where two possible models are mainly discussed; one in which the game starts afresh with new strategies each time a player leaves the game, and one where the players have to stick with the strategy they chose initially. The first case is well understood whereas, for the second case, much is still left open. There are two main results in this paper. The first concerns the asymptotic behavior of the models as the number of players tend to infinity. In particular, we prove that the time evolution of the models coincide in the limit, thus providing a link between the two in the regime of infinitely many players. Secondly we prove, under certain conditions, existence and uniqueness of an ESS in the second model for any given number of players.
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| 2732. |
- Hellberg, Sofie, 1979, et al.
(författare)
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Det finns inga enkla lösningar
- 2009
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Ingår i: Göteborgs-Posten 090623.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Det är välkommet att Bo Rothstein i två artiklar i GP tar sig an de gamla klassiska diskussionerna om teorins roll i samhällsvetenskaplig forskningen samt om vad forskningen egentligen är till för. Det är viktigt att dessa diskussioner förs även i det offentliga rummet. Rothsteins lägesbeskrivning av en samhällsvetenskaplig forskning i kris är dock i behov av nyansering. Teorins roll diskuteras ständigt, såväl inom discipliner som tvärvetenskapligt. Den stereotypa bild Rothstein målar upp representerar i liten grad det arbete som bedrivs. Forskningen är betydligt mer nyanserad och sammansatt idag. Bland annat är korruption och dysfunktionella samhällsinstitutioner frågor som utvecklingsforskning ägnat sig åt länge. Tidigare endimensionella perspektiv har kompletterats med och berikats av mångdimensionella angreppssätt som till exempel länkar postkoloniala strukturer med interna maktrelationer. Frågan om vad vår forskning syftar till är en avgörande politiskt fråga, och vi instämmer i värdet av problemorienterad forskning. Utvecklingsforskning och genusstudier, som Rothstein speciellt pekar ut som problematiska, är områden som i stor utsträckning uppmärksammat behovet av samhällsrelevant forskning, och många forskare engagerar sig i dialog med samhällets aktörer för att bidra till lösningar på angelägna problem. Det här engagemanget har bidragit till såväl misslyckanden som förbättringar. Samhällsvetenskaplig forskning visar på komplexiteten i de problem som finns, policy däremot måste bygga på något förenklade bilder av den komplexiteten. Förutom att den reflekterar olika maktintressen. Det finns inga enkla lösningar på relationen mellan forskning och policy, diskussionen måste hållas ständigt levande. Den är också nödvändig i det tvärvetenskapliga forskningssamarbete som pågår på GU men som Rothstein mycket riktigt påpekar måste stärkas ytterligare. Forskare bidrar med kunskap men hur den ska användas bör vara upp till den demokratiska processen att avgöra. Sofie Hellberg Stina Hansson Doktorander på Institutionen för globala studier
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| 2733. |
- Hellerer, Thomas, 1973, et al.
(författare)
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Monitoring of lipid storage in Caenorhabditis elegans using coherent anti-Stokes Raman scattering (CARS) microscopy
- 2007
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 104:37, s. 14658-14663
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Tidskriftsartikel (refereegranskat)abstract
- Better understanding of the fundamental mechanisms behind metabolic diseases requires methods to monitor lipid stores on single-cell level in vivo. We have used Caenorhabditis elegans as a model organism to demonstrate the limitations of fluorescence microscopy for imaging of lipids compared with coherent anti-Stokes Raman scattering (CARS) microscopy, the latter allowing chemically specific and label-free imaging in living organisms. CARS microscopy was used to quantitatively monitor the impact of genetic variations in metabolic pathways on lipid storage in 60 specimens of C. elegans. We found that the feeding-defective mutant pha-3 contained a lipid volume fraction one-third of that found in control worms. In contrast, mutants (daf-2, daf-4 dauer) with deficiencies in the insulin and transforming growth factors (IGF and TGF-beta) signaling pathways had lipid volume fractions that were 1.4 and 2 times larger than controls, respectively. This was observed as an accumulation of small-sized lipid droplets in the hypodermal cells, hosting as much as 40% of the total lipid volume in contrast to the 9% for the wild-type larvae. Spectral CARS microscopy measurements indicated that this is accompanied by a shift in the ordering of the lipids from gel to liquid phase. We conclude that the degree of hypodermal lipid storage and the lipid phase can be used as a marker of lipid metabolism shift. This study shows that CARS microscopy has the potential to become a sensitive and important tool for studies of lipid storage mechanisms, improving our understanding of phenomena underlying metabolic disorders.
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| 2734. |
- Hellman, Anders, 1974, et al.
(författare)
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Hydrogen-Induced Reconstruction of Cu(100): Two-Dimensional and One-Dimensional Structures of Surface Hydride
- 2014
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Ingår i: Journal of Physical Chemistry C. - Washington : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:29, s. 15773-15778
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption of atomic hydrogen has a remarkable influence on the structure and morphology of the Cu(I00) surface. We have examined two specific situations; the well-known reconstructed p(2 x 2)-H surface and a one-dimensional (6 X 1)-H surface resembling the stripe reconstruction observed in an electrochemical environment. High resolution electron energy loss spectroscopy and density functional calculations show that the H atoms occupy only surface sites and that H bonding in induced 3-fold Cu surface hollow sites is a structural key element. The calculations support a transient scenario in which H absorption in subsurface sites is a critical intermediate step in the reconstruction of the Cu surface. We find clear evidence in terms of characteristic properties, like the H-Cu bond lengths and the dipole excited vibrational mode spectra, that these structures consist of two-dimensional and one-dimensional structures of surface hydride.
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| 2735. |
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| 2736. |
- Hellman, Fredrik, 1985, et al.
(författare)
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Numerical Homogenization of Elliptic PDEs with Similar Coefficients
- 2019
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Ingår i: Multiscale Modeling and Simulation. - : SIAM PUBLICATIONS. - 1540-3467 .- 1540-3459. ; 17:2, s. 650-674
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Tidskriftsartikel (refereegranskat)abstract
- We consider a sequence of elliptic partial differential equations (PDEs) with different but similar rapidly varying coefficients. Such sequences appear, for example, in splitting schemes for time-dependent problems (with one coefficient per time step) and in sample based stochastic integration of outputs from an elliptic PDE (with one coefficient per sample member). We propose a parallelizable algorithm based on Petrov-Galerkin localized orthogonal decomposition that adaptively (using computable and theoretically derived error indicators) recomputes the local corrector problems only where it improves accuracy. The method is illustrated in detail by an example of a time-dependent two-pase Darcy flow problem in three dimensions.
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| 2737. |
- Hellman, Fredrik, et al.
(författare)
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Numerical upscaling for heterogeneous materials in fractured domains
- 2021
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Ingår i: Esaim - Mathematical Modelling and Numerical Analysis - Modelisation Mathematique Et Analyse Numerique. - : EDP Sciences. - 0764-583X .- 2822-7840 .- 1290-3841. ; 55
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Tidskriftsartikel (refereegranskat)abstract
- We consider numerical solution of elliptic problems with heterogeneous diffusion coefficients containing thin highly conductive structures. Such problems arise e.g. in fractured porous media, reinforced materials, and electric circuits. The main computational challenge is the high resolution needed to resolve the data variation. We propose a multiscale method that models the thin structures as interfaces and incorporate heterogeneities in corrected shape functions. The construction results in an accurate upscaled representation of the system that can be used to solve for several forcing functions or to simulate evolution problems in an efficient way. By introducing a novel interpolation operator, defining the fine scale of the problem, we prove exponential decay of the shape functions which allows for a sparse approximation of the upscaled representation. An a priori error bound is also derived for the proposed method together with numerical examples that verify the theoretical findings. Finally we present a numerical example to show how the technique can be applied to evolution problems.
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| 2738. |
- Hellman, Fredrik, et al.
(författare)
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Well-posedness and finite element approximation of mixed dimensional partial differential equations
- 2024
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Ingår i: BIT NUMERICAL MATHEMATICS. - 0006-3835 .- 1572-9125. ; 64:1
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Tidskriftsartikel (refereegranskat)abstract
- In this article, a mixed dimensional elliptic partial differential equation is considered, posed in a bulk domain with a large number of embedded interfaces. In particular, well-posedness of the problem and regularity of the solution are studied. A fitted finite element approximation is also proposed and an a priori error bound is proved. For the solution of the arising linear system, an iterative method based on subspace decomposition is proposed and analyzed. Finally, numerical experiments are presented and rapid convergence using the proposed preconditioner is achieved, confirming the theoretical findings.
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| 2739. |
- Hellsing, Marie, 1983, et al.
(författare)
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An Experimental Field Study of the Effects of Listening to Self-selected Music on Emotions, Stress, and Cortisol Levels
- 2016
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Ingår i: Music and Medicine. - 1943-8621 .- 1943-863X. ; 8:4, s. 187-198
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Tidskriftsartikel (refereegranskat)abstract
- Music listening may evoke meaningful emotions in listeners and may enhance certain health benefits. At the same time, it is important to consider individual differences, such as musical taste, when examining musical emotions and in considering their possible health effects. In a field experiment, 21 women listened to their own preferred music on mp3-players daily for 30 minutes during a two week time period in their own homes. One week they listened to their own chosen relaxing music and the other their own chosen energizing music. Self-reported stress, emotions and health were measured by a questionnaire each day and salivary cortisol was measured with 6 samples two consecutive days every week. The experiment group was compared to a control group (N = 20) who were instructed to relax for 30 minutes everyday for three weeks, and with a baseline week when they relaxed without music for one week (before the music intervention weeks). The results showed that when participants in the experiment group listened to their own chosen music they reported to have experienced significantly higher intensity positive emotions and less stress than when they relaxed without music. There was also a significant decrease in cortisol from the baseline week to the second music intervention week. The control group’s reported stress levels, perceived emotions and cortisol levels remain stable during all three weeks of the study. Together these results suggest that listening to preferred music may be a more effective way of reducing feelings of stress and cortisol levels and increasing positive emotions than relaxing without music.
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| 2740. |
- Hellstrand Tang, Ulla, 1956, et al.
(författare)
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Comparison of plantar pressure in three types of insole given to patients with diabetes at risk of developing foot ulcers – A two-year, randomized trial
- 2014
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Ingår i: Journal of Clinical and Translational Endocrinology. - : Elsevier BV. - 2214-6237. ; 1:4, s. 121-132
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Tidskriftsartikel (refereegranskat)abstract
- Background: Special insoles and shoes designed to prevent foot ulcers caused by repetitive high pressures are recommended for patients with diabetes who have any of the following risk factors: neuropathy; peripheral vascular disease; foot deformities; previous ulcers; amputation; and skin pathologies. However, there is a need for increased knowledge regarding: a) differences in the peak pressure (PP) and pressure time integral (PTI) for different types of insoles; and b) the properties of the pressure distribution for insoles used over a period of several months. We present the results of a randomized trial to compare the plantar pressures of three commonly used insoles. Objectives: The primary objective was to compare the PP and PTI between three types of insoles. The secondary objective was to explore the long-term pattern of peak plantar pressure distribution and variations in specific regions of interest (ROI). The tertiary objective was to investigate the impacts of insole adjustments, how much the insoles were used, and the levels of patient satisfaction. Methods In a 2-year trial, 114 patients with type 1 (N = 31) or type 2 (N = 83) diabetes (62 men and 52 women; mean age, 57.7 ± 15.4 years; duration of diabetes, 12.3 ± 11.2 years; neuropathy, 38%), were randomized to be supplied with one of three different insoles. The ethylene vinyl acetate (EVA) insoles were used in outdoor walking shoes. The 35 EVA group (N = 39) received soft custom-made insoles composed of EVA of 35 shore A hardness, the 55 EVA group (N = 37) received custom-made insoles composed of EVA of 55 shore hardness, and the control group (N = 38) received prefabricated insoles composed of a hard core with a top layer of soft 12 shore hardness microfiber. Using F-Scan®, the in-shoe plantar pressures were measured at seven ROI (hallux, metatarsal head 1, metatarsal head 2, metatarsal head 4, metatarsal head 5, lateral aspect of the mid-foot, heel) on five occasions during the study period. The plantar-pressure variables used were PP (main outcome) and PTI. The plantar patterns of load were explored, satisfaction and usage of the insoles were rated by the participants, and insole adjustments were recorded. Results:A mixed model analysis estimated lower PP values in the heel regions for the 35 EVA and 55 EVA insoles (171 ± 13 and 161 ± 13 kPa, respectively) than for the prefabricated insoles (234 ± 10 kPa) (p
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