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- 2019
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Tidskriftsartikel (refereegranskat)
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- Broms, Anna, et al.
(författare)
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A Method of Fundamental Solutions for Large-Scale 3D Elastance and Mobility Problems
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The method of fundamental solutions (MFS) is effective for the 3D Laplace and Stokes Dirichlet BVPs in the exterior of a collection of simple objects. Here, we present new formulations for the related elastance and mobility problems in the same geometries. The mobility problem computes rigid body velocities, given net forces and torques on the particles, while the elastance problem is the counterpart for Laplace and solves the problem of conductors with known net charges to determine unknown constant potentials. The new formulations allow for application of one-body preconditioning of the resulting systems, and for large suspensions with moderate lubrication forces, sources on inner proxy-surfaces give accuracy on par with a well-resolved boundary integral formulation. The performance of the well-conditioned mobility solver is demonstrated for a suspension of 10000 nearby ellipsoids. Using a discretization with $2.59\times 10^7$ total degrees of freedom in the preconditioned system, GMRES converges to five digits of accuracy in less than two hours on a workstation and the scaling is linear in the number of particles.
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| 11. |
- Broms, Anna, et al.
(författare)
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A reflection enhanced method of fundamental solutions for Laplace and Stokes boundary value problems in 2D
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Two elliptic PDEs with Dirichlet boundary conditions are considered in 2D for a collection of simple objects: the exterior Laplace and Stokes boundary value problems. We present a novel, cost-effective, accurate and singularity-free solution technique based on the method of fundamental solutions. For circular objects, controllable accuracy is obtained for close-to-touching neighbours, with sources on inner proxy-boundaries complemented as needed by a small set of extra singularities in near-contact regions. The locations of the extra sources are deduced from the fractal obtained by repeated inversion of circles in circles, sometimes referred to as Indra’s pearls. For Stokes, results for coarsely resolved closely interacting circular particles, undergoing rigid body motion, are compared to results from a well-resolved boundary integral equation equipped with a special quadrature method. A careful parameter study is made for the locations of the additional sources and their singularity types to reach a target accuracy of 10^{-6} for circles of unequal radii, down to particle separations of a thousandth of the particle radii. For well-separated objects, a one-body preconditioning strategy allows for acceleration with the fast multipole method.
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- Broms, Anna, et al.
(författare)
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Accurate close interactions of Stokes spheres using lubrication-adapted image systems
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Stokes flows with near-touching rigid particles induce near-singular lubrication forces under relative motion, making their accurate numerical treatment challenging. With the aim of controlling the accuracy with a computationally cheap method, we present a new technique that combines the method of fundamental solutions (MFS) with the method of images. For rigid spheres, we propose to represent the flow using Stokeslet sources on interior spheres, augmented by lines of sources adapted to each near-contact to resolve lubrication. The source strengths are found via a least-squares solve at contact-adapted boundary collocation nodes. Results for coarsely resolved spheres undergoing rigid body motion are compared to reference solutions determined with a well-resolved boundary integral formulation equipped with a special quadrature method. With less than 60 additional sources per particle per contact, we show controlled accuracy to three digits in the relative surface velocities for separations between the particles down to a thousandth of the particle radius. Computed forces and torques are more accurate than surface velocities, by a few orders of magnitude. For fixed spheres in a given background flow, the proxy-surface discretization alone gives controlled accuracy. A one-body preconditioning strategy allows for acceleration with the fast multipole method that combined yield close to linear scaling in the number of particles. This is demonstrated by solving problems of up to 2000 spheres on a workstation using 700 unknown proxy-sources per particle.
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| 13. |
- Aad, G., et al.
(författare)
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- 2015
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813 .- 1089-490X. ; 92:3
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Tidskriftsartikel (refereegranskat)
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| 14. |
- Aad, G., et al.
(författare)
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- 2015
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Ingår i: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; :8
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Tidskriftsartikel (refereegranskat)
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- Aad, G., et al.
(författare)
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- 2015
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Tidskriftsartikel (refereegranskat)
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| 16. |
- Anderson, Christopher J., et al.
(författare)
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Response to Comment on "Estimating the reproducibility of psychological science"
- 2016
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 351:6277
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Gilbert et al. conclude that evidence from the Open Science Collaboration's Reproducibility Project: Psychology indicates high reproducibility, given the study methodology. Their very optimistic assessment is limited by statistical misconceptions and by causal inferences from selectively interpreted, correlational data. Using the Reproducibility Project: Psychology data, both optimistic and pessimistic conclusions about reproducibility are possible, and neither are yet warranted.
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| 17. |
- Blank, Rainer, et al.
(författare)
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International clinical practice recommendations on the definition, diagnosis, assessment, intervention, and psychosocial aspects of developmental coordination disorder
- 2019
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Ingår i: Developmental Medicine & Child Neurology. - : John Wiley & Sons. - 0012-1622 .- 1469-8749. ; 61:3, s. 242-285
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Tidskriftsartikel (refereegranskat)abstract
- AIM: These international clinical practice recommendations (CPR) for developmental coordination disorder (DCD), initiated by the European Academy of Childhood Disability (EACD), aim to address key questions on the definition, diagnosis, assessment, intervention, and psychosocial aspects of DCD relevant for clinical practice.METHOD: Key questions in five areas were considered through literature reviews and formal expert consensus. For recommendations based on evidence, literature searches on 'mechanisms', 'assessment', and 'intervention' were updated since the last recommendations in 2012. New searches were conducted for 'psychosocial issues' and 'adolescents/adults'. Evidence was rated according to the Oxford Centre for Evidence-Based Medicine (level of evidence [LOE] 1-4) and transferred into recommendations. For recommendations based on formal consensus, two meetings of an international, multidisciplinary expert panel were conducted with a further five Delphi rounds to develop good clinical practice (GCP) recommendations.RESULTS: Thirty-five recommendations were made. Eight were based on the evidence from literature reviews (three on 'assessment', five on 'intervention'). Twenty-two were updated from the 2012 recommendations. New recommendations relate to diagnosis and assessment (two GCPs) and psychosocial issues (three GCPs). Additionally, one new recommendation (LOE) reflects active video games as adjuncts to more traditional activity-oriented and participation-oriented interventions, and two new recommendations (one GCP, one LOE) were made for adolescents and adults with DCD.INTERPRETATION: The CPR-DCD is a comprehensive overview of DCD and current understanding based on research evidence and expert consensus. It reflects the state of the art for clinicians and scientists of varied disciplines. The international CPR-DCD may serve as a basis for national guidelines.WHAT THIS PAPER ADDS:Updated international clinical practice guidelines on developmental coordination disorder (DCD).Refined and extended recommendations on clinical assessment and intervention for DCD.A critical synopsis of current research on mechanisms of DCD.A critical synopsis of psychosocial issues in DCD, with implications for clinical practice.The first international recommendations to consider adolescents and adults with DCD.
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- Falkmer, Torbjörn, et al.
(författare)
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Usability of the SAFEWAY2SCHOOL system in children with cognitive disabilities
- 2014
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Ingår i: European Transport Research Review. - : Springer Berlin/Heidelberg. - 1867-0717 .- 1866-8887. ; 6:2, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- SAFEWAY2SCHOOL is a programme based on several systems for the enhancement of school transportation safety for children. The aim of the study was to explore whether children with cognitive disabilities will notice, realise, understand, trust and accept the SAFEWAY2SCHOOL system and act in accordance with its instructions. Methods: Fourteen children with cognitive disabilities and a control group of 23 children were shown five videos of scenarios involving journeys to and from school. During the first viewing visual scanning patterns were recorded with an eye tracking device. After a second viewing the participant was asked ten questions per scenario. Five questions addressed what the children saw on the video, and the remaining five what they would need to know and/or do within the scenario. Additional ratings of trust, likability, acceptability and usability were also collected. Results: Very few differences were found in the visual scanning patterns of children with disabilities compared to children who participated in the control group. Of the 50 questions regarding what children saw or needed to know and/or do, only one significant difference between groups was found. No significant differences were found regarding self-reported ratings of trust, acceptability or usability of the system. Despite some significant differences across five of the 11 likability aspects, ratings were consistently high for both groups. Conclusions: Children with cognitive disabilities proved that the SAFEWAY2SCHOOL system is as useful for them as it was for children in the control group. However, a valid estimation of the full utility of SAFEWAY2SCHOOL requires in situ testing of the system with these children. © 2013 The Author(s).
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- Frantz, Laurent A. F., et al.
(författare)
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Ancient pigs reveal a near-complete genomic turnover following their introduction to Europe
- 2019
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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. ; 116:35, s. 17231-17238
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Tidskriftsartikel (refereegranskat)abstract
- Archaeological evidence indicates that pig domestication had begun by similar to 10,500 y before the present ( BP) in the Near East, and mitochondrial DNA ( mtDNA) suggests that pigs arrived in Europe alongside farmers similar to 8,500 y BP. A few thousand years after the introduction of Near Eastern pigs into Europe, however, their characteristic mtDNA signature disappeared and was replaced by haplotypes associated with European wild boars. This turnover could be accounted for by substantial gene flow from local European wild boars, although it is also possible that European wild boars were domesticated independently without any genetic contribution from the Near East. To test these hypotheses, we obtained mtDNA sequences from 2,099 modern and ancient pig samples and 63 nuclear ancient genomes from Near Eastern and European pigs. Our analyses revealed that European domestic pigs dating from 7,100 to 6,000 y BP possessed both Near Eastern and European nuclear ancestry, while later pigs possessed no more than 4% Near Eastern ancestry, indicating that gene flow from European wild boars resulted in a near-complete disappearance of Near East ancestry. In addition, we demonstrate that a variant at a locus encoding black coat color likely originated in the Near East and persisted in European pigs. Altogether, our results indicate that while pigs were not independently domesticated in Europe, the vast majority of human-mediated selection over the past 5,000 y focused on the genomic fraction derived from the European wild boars, and not on the fraction that was selected by early Neolithic farmers over the first 2,500 y of the domestication process.
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- Fryklund, Fredrik, 1988-
(författare)
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Integral equations and function extension techniques for numerical solution of PDEs
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today many phenomena from science and engineering can be simulated accurately thanks to computational methods. Still, many challenges remain, one of them being close interface interactions when simulating e.g. the dynamics of a substance concentration in multiphase flows at the micro level. The challenge is to maintain high accuracy and efficiency as drops, vesicles, etc. are very close to each other, which many numerical methods struggle with. Also, the drops' geometries undergo changes over time. Thus far there is no standardized method for solving the equation modeling a concentration on time-dependent geometries efficiently and accurately. Boundary integral methods are powerful in handling moving and complex geometries, and maintaining high accuracy throughout the domain, even for close interactions. However, they are only efficient for a limited class of problems, and thus do not apply to our problem at hand.The focus of this dissertation is to expand the class of problems boundary integral methods are applicable to, without sacrificing their most attractive properties, plus presenting how the resulting equations time-dependent geometries can be solved on time-dependent geometries. This is achieved by the development of the algorithm partition of unity extension (PUX). It smoothly extends data from its domain of definition, with compact support, which allows for application of established fast methods.With our PUX method and state-of-the-art computational algorithms new problems could be studied, and to new levels of accuracy. In the process new underlying dynamics that were previously obscured by large errors appeared. These findings spurred a new set of questions, leading to the design of accurate algorithms for a class of problems that appear when applying boundary integral methods in conjunction with discretizing the governing equations first in time.In sum, we are now closer to a complete solver for the evolution of the substance concentration on time-dependent geometries. In this endeavor, methods have been development and studied that have applications outside our scope, and have already been applied successfully in other researchers' work. The work with PUX has thus been fruitful and will be developed and investigated further in the future, with adaptivity as the goal.
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| 24. |
- Kappos, Ludwig, et al.
(författare)
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Siponimod versus placebo in secondary progressive multiple sclerosis (EXPAND): a double-blind, randomised, phase 3 study
- 2018
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Ingår i: The Lancet. - 0140-6736 .- 1474-547X. ; 391, s. 1263-1273
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Elsevier Ltd Background: No treatment has consistently shown efficacy in slowing disability progression in patients with secondary progressive multiple sclerosis (SPMS). We assessed the effect of siponimod, a selective sphingosine 1-phosphate (S1P) receptor 1,5 modulator, on disability progression in patients with SPMS. Methods: This event-driven and exposure-driven, double-blind, phase 3 trial was done at 292 hospital clinics and specialised multiple sclerosis centres in 31 countries. Using interactive response technology to assign numbers linked to treatme nt arms, patients (age 18–60 years) with SPMS and an Expanded Disability Status Scale score of 3·0–6·5 were randomly assigned (2:1) to once daily oral siponimod 2 mg or placebo for up to 3 years or until the occurrence of a prespecified number of confirmed disability progression (CDP) events. The primary endpoint was time to 3-month CDP. Efficacy was assessed for the full analysis set (ie, all randomly assigned and treated patients); safety was assessed for the safety set. This trial is registered with ClinicalTrials.gov, number NCT01665144. Findings: 1651 patients were randomly assigned between Feb 5, 2013, and June 2, 2015 (1105 to the siponimod group, and 546 to the placebo group). One patient did not sign the consent form, and five patients did not receive study drug, all of whom were in the siponimod group. 1645 patients were included in the analyses (1099 in the siponimod group and 546 in the placebo). At baseline, the mean time since first multiple sclerosis symptoms was 16·8 years (SD 8·3), and the mean time since conversion to SPMS was 3·8 years (SD 3·5); 1055 (64%) patients had not relapsed in the previous 2 years, and 918 (56%) of 1651 needed walking assistance. 903 (82%) patients receiving siponimod and 424 (78%) patients receiving placebo completed the study. 288 (26%) of 1096 patients receiving siponimod and 173 (32%) of 545 patients receiving placebo had 3-month CDP (hazard ratio 0·79, 95% CI 0·65–0·95; relative risk reduction 21%; p=0·013). Adverse events occurred in 975 (89%) of 1099 patients receiving siponimod versus 445 (82%) of 546 patients receiving placebo; serious adverse events were reported for 197 (18%) patients in the siponimod group versus 83 (15%) patients in the placebo group. Lymphopenia, increased liver transaminase concentration, bradycardia and bradyarrhythmia at treatment initiation, macular oedema, hypertension, varicella zoster reactivation, and convulsions occurred more frequently with siponimod than with placebo. Initial dose titration mitigated cardiac first-dose effects. Frequencies of infections, malignancies, and fatalities did not differ between groups. Interpretation: Siponimod reduced the risk of disability progression with a safety profile similar to that of other S1P modulators and is likely to be a useful treatment for SPMS. Funding: Novartis Pharma AG.
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- Koivula, Robert, et al.
(författare)
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Discovery of biomarkers for glycaemic deterioration before and after the onset of type 2 diabetes : rationale and design of the epidemiological studies within the IMI DIRECT Consortium
- 2014
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 57:6, s. 1132-1142
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Tidskriftsartikel (refereegranskat)abstract
- AIMS/HYPOTHESIS:The DIRECT (Diabetes Research on Patient Stratification) Study is part of a European Union Framework 7 Innovative Medicines Initiative project, a joint undertaking between four industry and 21 academic partners throughout Europe. The Consortium aims to discover and validate biomarkers that: (1) predict the rate of glycaemic deterioration before and after type 2 diabetes onset; (2) predict the response to diabetes therapies; and (3) help stratify type 2 diabetes into clearly definable disease subclasses that can be treated more effectively than without stratification. This paper describes two new prospective cohort studies conducted as part of DIRECT.METHODS:Prediabetic participants (target sample size 2,200-2,700) and patients with newly diagnosed type 2 diabetes (target sample size ~1,000) are undergoing detailed metabolic phenotyping at baseline and 18 months and 36 months later. Abdominal, pancreatic and liver fat is assessed using MRI. Insulin secretion and action are assessed using frequently sampled OGTTs in non-diabetic participants, and frequently sampled mixed-meal tolerance tests in patients with type 2 diabetes. Biosamples include venous blood, faeces, urine and nail clippings, which, among other biochemical analyses, will be characterised at genetic, transcriptomic, metabolomic, proteomic and metagenomic levels. Lifestyle is assessed using high-resolution triaxial accelerometry, 24 h diet record, and food habit questionnaires.CONCLUSIONS/INTERPRETATION:DIRECT will yield an unprecedented array of biomaterials and data. This resource, available through managed access to scientists within and outside the Consortium, will facilitate the development of new treatments and therapeutic strategies for the prevention and management of type 2 diabetes
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