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Sökning: WFRF:(Andreasson Håkan)

  • Resultat 1-10 av 84
  • [1]234567...9Nästa
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  • Andréasson, Håkan, 1955-, et al. (författare)
  • Comments on the paper ‘Static solutions of the Vlasov–Einstein system’ by G. Wolansky
  • 2019
  • Ingår i: Archive for Rational Mechanics and Analysis. - 1432-0673 .- 0003-9527.
  • Tidskriftsartikel (refereegranskat)abstract
    • In this note we address the attempted proof of the existence of static solutions to the Einstein–Vlasov system as given in Wolansky (Arch Ration Mech Anal 156:205–230, 2001). We focus on a specific and central part of the proof which concerns a variational problem with an obstacle. We show that two important claims in Wolansky (2001) are incorrect and we question the validity of a third claim. We also discuss the variational problem and its difficulties with the aim of stimulating further investigation of this intriguing problem in particular answering the question of whether or not static solutions of the Einstein–Vlasov system can be found as local minimizers of an energy-Casimir functional.
  • Andreasson, Håkan, et al. (författare)
  • Proof of the cosmic no-hair conjecture in the T3-Gowdy symmetric Einstein-Vlasov setting
  • 2016
  • Ingår i: Journal of the European Mathematical Society (Print). - EMS Publishing House. - 1435-9855. ; 18:7, s. 1565-1650
  • Tidskriftsartikel (refereegranskat)abstract
    • The currently preferred models of the universe undergo accelerated expansion induced by dark energy. One model for dark energy is a positive cosmological constant. It is consequently of interest to study Einstein's equations with a positive cosmological constant coupled to matter satisfying the ordinary energy conditions: the dominant energy condition etc. Due to the difficulty of analysing the behaviour of solutions to Einstein's equations in general, it is common to either study situations with symmetry, or to prove stability results. In the present paper, we do both. In fact, we analyse, in detail, the future asymptotic behaviour of T-3-Gowdy symmetric solutions to the Einstein-Vlasov equations with a positive cosmological constant. In particular, we prove the cosmic no-hair conjecture in this setting. However, we also prove that the solutions are future stable (in the class of all solutions). Some of the results hold in a more general setting. In fact, we obtain conclusions concerning the causal structure of T-2-symmetric solutions, assuming only the presence of a positive cosmological constant, matter satisfying various energy conditions and future global existence. Adding the assumption of T-3-Gowdy symmetry to this list of requirements, we obtain C-0-estimates for all but one of the metric components. There is consequently reason to expect that many of the results presented in this paper can be generalised to other types of matter.
  • Petren-Mallmin, Marianne, et al. (författare)
  • Skeletal metastases from breast cancer : uptake of 18F-fluoride measured with positron emission tomography in correlation with CT
  • 1998
  • Ingår i: Skeletal Radiology. - 0364-2348 .- 1432-2161. ; 27:2, s. 72-76
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE:To characterise the uptake of 18F in skeletal metastases from breast cancer using positron emission tomography (PET) and to relate these findings to the appearance on CT.PATIENTS AND DESIGN:PET with 18F and CT were performed in five patients with multiple skeletal metastases from breast cancer. The CT characteristics were analysed in areas with high uptake on the PET study. Dynamic PET imaging of the skeletal kinetics of the 18F-fluoride ion were included.RESULTS:The areas of abnormal high accumulation of 18F correlated well with the pathological appearance on CT. Lytic as well as sclerotic lesions had markedly higher uptake than normal bone, with a 5-10 times higher transport rate constant for trapping of the tracer in the metastatic lesions than in normal bone.CONCLUSION:PET with 18F-fluoride demonstrates very high uptake in lytic and sclerotic breast cancer metastases.
  • Ciray, Ipek, et al. (författare)
  • Evaluation of new sclerotic bone metastases in breast cancer patients during treatment
  • 2000
  • Ingår i: Acta Radiologica. - 0284-1851 .- 1600-0455. ; 41:2, s. 178-182
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE:According to the World Health Organization (WHO) criteria for response of bone metastases to therapy, new lesions indicate progressive disease. We intended to prove that a new sclerotic lesion on conventional radiography may also be a sign of a positive therapeutic response in a previously undetectable lytic metastasis.MATERIAL AND METHODS:In a previous placebo-controlled clinical trial of clodronate (Ostac) therapy, 139 breast cancer patients with bone metastases underwent both conventional radiography and bone scan every 6 months for 2 years with 99mTc before and during clodronate treatment. WHO criteria were applied for therapy response evaluation.RESULTS:In 24 patients, 52 new sclerotic lesions observed during therapy were selected for re-evaluation of conventional radiographs and bone scans. In 8 of the 24 patients, 17 of 52 new sclerotic lesions (33%) had showed positive uptake on previous bone scans. These lesions were possibly misinterpreted as new when applying WHO criteria.CONCLUSION:For better assessment of new sclerotic lesions during treatment, more sensitive techniques, e.g. bone scan, are needed as a complement to conventional radiography.
  • Hall, Sara, et al. (författare)
  • Accuracy of a panel of 5 cerebrospinal fluid biomarkers in the differential diagnosis of patients with dementia and/or parkinsonian disorders.
  • 2012
  • Ingår i: Archives of neurology. - 1538-3687. ; 69:11, s. 1445-52
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: To assess the ability of 5 cerebrospinal fluid (CSF) biomarkers to differentiate between common dementia and parkinsonian disorders. Design: A cross-sectional, clinic-based study. Participants: Cerebrospinal fluid samples (N=453) were obtained from healthy individuals serving as controls and from patients with Parkinson disease (PD), PD with dementia (PDD), dementia with Lewy bodies (DLB), Alzheimer disease (AD), progressive supranuclear palsy (PSP), multiple system atrophy (MSA), or corticobasal degeneration (CBD). Setting: Neurology and memory disorder clinics. Main Outcome Measures: Cerebrospinal fluid biomarker levels in relation to clinical diagnosis. Results: Cerebrospinal fluid levels of alpha-synuclein were decreased in patients with PD, PDD, DLB, and MSA but increased in patients with AD. Cerebrospinal fluid levels of beta-amyloid 1-42 were decreased in DLB and even further decreased in AD. Cerebrospinal fluid levels of total tau and hyperphosphorylated tau were increased in AD. Multivariate analysis revealed that these biomarkers could differentiate AD from DLB and PDD with an area under the curve of 0.90, with alpha-synuclein and total tau contributing most to the model. Cerebrospinal fluid levels of neurofilament light chain were substantially increased in atypical parkinsonian disorders (ie, PSP, MSA, and CBD), and multivariate analysis revealed that the level of neurofilament light chain alone could differentiate PD from atypical parkinsonian disorders, with an area under the curve of 0.93. Conclusions: Ascertainment of the alpha-synuclein level in CSF somewhat improves the differential diagnosis of AD vs DLB and PDD when combined with established AD biomarkers. The level of neurofilament light chain alone may differentiate PD from atypical parkinsonian disorders.
  • Nilsson, Tony, et al. (författare)
  • Effects on Alcohol Consumption and Alcohol Related Harm of a Community-Based Prevention Intervention With National Support in Sweden
  • 2018
  • Ingår i: Substance Use & Misuse. - 1082-6084. ; 53:3, s. 412-419
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: In order to strengthen local alcohol prevention work in Sweden the Swedish government has for the past almost 15years commissioned the Public Health Agency of Sweden to initiate a series of community-based alcohol prevention projects. The latest of these, labeled local development with ambitions (LUMA), included 25 municipalities in Sweden. Objectives: Aim of this study is to examine if LUMA municipalities that received financial support, with requirements, increased local alcohol prevention and if alcohol consumption and harm declined. Methods: Twenty-five Swedish municipalities that received financial support aiming to strengthen local alcohol preventing activities (intervention group) were compared to municipalities that did not receive such support (control group, N = 224), before, during, and after the intervention period. Two composite measures of policy and activity were created and used. The composite activity measure includes seven activity indicators and the composite policy measure includes six policy indicators. Harm measures have been selected based on several recommended indicators for monitoring alcohol, tobacco, and other drugs in Sweden. A fixed effects model was used to analyze data. Results: The results reveal that prevention activities increased and several alcohol-related harm indicators were reduced in intervention municipalities (LUMA) compared with in control municipalities. Conclusions: It seems as if financial support, combined with specific requirements and support from the regional and national level, can stimulate local alcohol prevention activities and have a significant effect on alcohol consumption and alcohol-related harm. Similar evaluations in other countries would be of great value for assessing the generalizability of findings.
  • Ames, E., et al. (författare)
  • Cosmic string and black hole limits of toroidal Vlasov bodies in general relativity
  • 2019
  • Ingår i: Physical Review D. - 2470-0010. ; 99:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We numerically investigate limits of a two-parameter family of stationary solutions to the Einstein-Vlasov system. The solutions are toroidal and have nonvanishing angular momentum. As the parameters are tuned to more relativistic solutions (measured e.g., by an increasing redshift) we provide evidence for a sequence of solutions which approaches the extreme Kerr black hole family. Solutions with angular momentum larger than the square of the mass are also investigated, and in the relativistic limit the near-field geometry of such solutions is observed to become locally rotationally symmetric about the matter density. The existence of a deficit angle in these regions is investigated.
  • Ames, Ellery, et al. (författare)
  • On axisymmetric and stationary solutions of the self-gravitating Vlasov system
  • 2016
  • Ingår i: Classical and Quantum Gravity. - 0264-9381. ; 33:15
  • Tidskriftsartikel (refereegranskat)abstract
    • Axisymmetric and stationary solutions are constructed to the Einstein-Vlasov and Vlasov-Poisson systems. These solutions are constructed numerically, using finite element methods and a fixed-point iteration in which the total mass is fixed at each step. A variety of axisymmetric stationary solutions are exhibited, including solutions with toroidal, disk-like, spindle-like, and composite spatial density configurations, as are solutions with non-vanishing net angular momentum. In the case of toroidal solutions, we show for the first time, solutions of the Einstein-Vlasov system which contain ergoregions.
  • Andreasson, Bengt Håkan, 1955- (författare)
  • Bilens minskade attraktionskraft
  • 2006
  • Ingår i: Vardagslivets fronter. - Göteborg : Arkipelag. - 91-85838-70-5
  • Bokkapitel (övrigt vetenskapligt)
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