| 1. |
- Blennow, Mattias, et al.
(author)
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Day-night effect in solar neutrino oscillations with three flavors
- 2004
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In: Physical Review D. Particles and fields. - : The American Physical Society. - 0556-2821 .- 1089-4918. ; 69:7, s. 073006-1-073006-9
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Journal article (peer-reviewed)abstract
- We investigate the effects of a nonzero leptonic mixing angle theta(13) on the solar neutrino day-night asymmetry. Using a constant matter density profile for the Earth and well-motivated approximations, we derive analytical expressions for the nu(e) survival probabilities for solar neutrinos arriving directly at the detector and for solar neutrinos which have passed through the Earth. Furthermore, we numerically study the effects of a nonzero theta(13) on the day-night asymmetry at detectors and find that they are small. Finally, we show that if the uncertainties in the parameters theta(12) and Deltam(2) as well as the uncertainty in the day-night asymmetry itself were much smaller than they are today, this effect could, in principle, be used to determine theta(13).
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| 2. |
- Blennow, Mattias, et al.
(author)
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Solar Neutrino Day-Night Effect
- 2005
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In: NEUTRINO 2004. - : Elsevier Science B.V.. ; , s. 578-578
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Conference paper (peer-reviewed)abstract
- We summarize the results of Ref. [M. Blennow, T. Ohlsson and H. Snellman, Phys. Rev. D 69 (2004) 073006, hep-ph/0311098] in which we determine the effects of three flavor mixing on the day-night asymmetry in the flux of solar neutrinos. Analytic methods are used to determine the difference in the day and night solar electron neutrino survival probabilites and numerical methods are used to determine the effect of three flavor mixing at detectors.
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| 3. |
- Jacobsson, Björn, et al.
(author)
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Effects of random matter density fluctuations on the neutrino oscillation transition probabilities in the Earth
- 2002
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In: Physics Letters B. - 0370-2693 .- 1873-2445. ; 532:04-mar, s. 259-266
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Journal article (peer-reviewed)abstract
- In this Letter, we investigate the effects of random fluctuations of the Earth matter density for long baselines on the neutrino oscillation transition probabilities. We especially identify relevant parameters characterizing the matter density noise and calculate their effects by averaging over statistical ensembles of a large number of matter density profiles. For energies and baselines appropriate to neutrino factories, absolute errors on the relevant appearance probabilities are at the level of \DeltaP(alphabeta)\ similar to 10(-4) (with perhaps \P-mue similar to 1% for neutrinos), whereby a modest improvement in understanding of the geophysical data should render such effects unimportant.
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| 4. |
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| 5. |
- Linde, Johan, et al.
(author)
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Decuplet baryon magnetic moments in the chiral quark model
- 1998
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In: Physical Review D. Particles and fields. - : The American Physical Society. - 0556-2821 .- 1089-4918. ; 57:9, s. 5916-5919
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Journal article (peer-reviewed)abstract
- We present calculations of the decuplet baryon magnetic moments in the chiral quark model. As input we use parameters obtained in qualitatively accurate fits to the octet baryon magnetic moments studied previously. The values found for the magnetic moments of Delta(++) and Omega(-) are in good agreement with experiments. We finally calculate the total quark spin polarizations of the decuplet baryons and find that they are considerably smaller than what is expected from the non-relativistic quark model.
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| 6. |
- Linde, Johan, et al.
(author)
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Octet baryon magnetic moments in the chiral quark model with configuration mixing
- 1998
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In: Physical Review D. Particles and fields. - : The American Physical Society. - 0556-2821 .- 1089-4918. ; 57:1, s. 452-464
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Journal article (peer-reviewed)abstract
- The Coleman-Glashow sum-rule for magnetic moments is always fulfilled in the chiral quark model, independently of SU(3) symmetry breaking. This is due to the structure of the wave functions, coming from the non-relativistic quark model. Experimentally, the Coleman-Glashow sum-rule is violated by about ten standard deviations. To overcome this problem, two models of wave functions with configuration mixing are studied. One of these models violates the Coleman-Glashow sum-rule to the right degree and also reproduces the octet baryon magnetic moments rather accurately.
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| 7. |
- Melhus, Håkan, et al.
(author)
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Plasma 25-Hydroxyvitamin D Levels and Fracture Risk in a Community-Based Cohort of Elderly Men in Sweden
- 2010
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In: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 95:6, s. 2637-2645
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Journal article (peer-reviewed)abstract
- Context: Blood levels of 25-hydroxyvitamin D [25(OH)D] is the generally accepted indicator of vitamin D status, but no universal reference level has been reached. Objective: The objective of the study was to determine the threshold at which low plasma 25(OH)D levels are associated with fractures in elderly men and clarify the importance of low levels on total fracture burden. Design and Participants: In the Uppsala Longitudinal Study of Adult Men, a population-based cohort (mean age, 71 yr, n = 1194), we examined the relationship between 25(OH)D and risk for fracture. Plasma 25(OH)D levels were measured with high-pressure liquid chromatography-mass spectrometry. Setting: The study was conducted in the municipality of Uppsala in Sweden, a country with a high fracture incidence. Main Outcome Measure: Time to fracture was measured. Results: During follow-up (median 11 yr), 309 of the participants (26%) sustained a fracture. 25(OH)D levels below 40 nmol/liter, which corresponded to the fifth percentile of 25(OH)D, were associated with a modestly increased risk for fracture, multivariable-adjusted hazard ratio 1.65 (95% confidence interval 1.09-2.49). No risk difference was detected above this level. Approximately 3% of the fractures were attributable to low 25(OH)D levels in this population. Conclusions: Vitamin D insufficiency is not a major cause of fractures in community-dwelling elderly men in Sweden. Despite the fact that cutaneous synthesis of previtamin D during the winter season is undetectable at this northern latitude of 60 degrees , only one in 20 had 25(OH)D levels below 40 nmol/liter, the threshold at which the risk for fracture started to increase. Genetic adaptations to limited UV light may be an explanation for our findings.
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| 8. |
- Michaëlsson, Karl, et al.
(author)
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Plasma vitamin D and mortality in older men : a community-based prospective cohort study
- 2010
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In: American Journal of Clinical Nutrition. - : Elsevier BV. - 0002-9165 .- 1938-3207. ; 92:4, s. 841-848
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Journal article (peer-reviewed)abstract
- Background: Vitamin D status is known to be important for bone health but may also affect the development of several chronic diseases, including cancer and cardiovascular diseases, which are 2 major causes of death. Objective: We aimed to examine how vitamin D status relates to overall and cause-specific mortality. Design: The Uppsala Longitudinal Study of Adult Men, a community-based cohort of elderly men (mean age at baseline: 71 y; n = 1194), was used to investigate the association between plasma 25-hydroxyvitamin D [25(OH)D] and mortality. Total plasma 25(OH)D was determined with HPLC atmospheric pressure chemical ionization mass spectrometry. Proportional hazards regression was used to compute hazard ratios (HRs). Results: During follow-up (median: 12.7 y), 584 (49%) participants died. There was a U-shaped association between vitamin D concentrations and total mortality. An approximately 50% higher total mortality rate was observed among men in the lowest 10% (<46 nmol/L) and the highest 5% (>98 nmol/L) of plasma 25(OH)D concentrations compared with intermediate concentrations. Cancer mortality was also higher at low plasma concentrations (multivariable-adjusted HR: 2.20; 95% CI: 1.44, 3.38) and at high concentrations (HR: 2.64; 95% CI: 1.46, 4.78). For cardiovascular death, only low (HR: 1.89; 95% CI: 1.21, 2.96) but not high (HR: 1.33; 95% CI: 0.69, 2.54) concentrations indicated higher risk. Conclusions: Both high and low concentrations of plasma 25(OH)D are associated with elevated risks of overall and cancer mortality. Low concentrations are associated with cardiovascular mortality.
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| 9. |
- Ohlsson, Tommy, 1973-, et al.
(author)
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Chiral quark model analysis of nucleon quark sea isospin asymmetry and spin polarization
- 1999
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In: European Physical Journal C. - : Springer-Verlag. - 1434-6044 .- 1434-6052. ; 7:3, s. 501-506
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Journal article (peer-reviewed)abstract
- We analyze recent measurements of the nucleon quark sea isospin asymmetry in terms of the chiral quark model. The new measurements indicate that the SU(3) model with modest symmetry breaking and no eta' Goldstone boson gives a satisfactory description of data. We also discuss the matching parameter for the axial-vector current. Finally, we analyze the nucleon quark spin polarization measurements directly in the chiral quark model without using any SU(3) symmetry assumption on the hyperon axial-vector form factors. The new data indicate that the chiral quark model gives a remarkably good and consistent description of all low energy baryon measurements.
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| 10. |
- Ohlsson, Tommy, 1973-, et al.
(author)
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Neutrino oscillations and mixings with three flavors
- 1999
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In: Physical Review D. Particles and fields. - : The American Physical Society. - 0556-2821 .- 1089-4918. ; 60:9, s. 093007-1-093007-8
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Journal article (peer-reviewed)abstract
- Global fits to all data of candidates for neutrino oscillations are presented in the framework of a three-flavor model. The analysis excludes mass regions where the MSW effect is important for the solar neutrino problem. The best fit gives theta(1) approximate to 28.9 degrees, theta(2) approximate to 4.2 degrees, theta(3) approximate to 45.0 degrees, m(2)(2) - m(1)(2) approximate to 2.87 X 10(-4) eV(2), and m(3)(2) - m(2)(2) approximate to 1.11 eV(2) indicating essentially maximal mixing between the two lightest neutrino mass eigenstates.
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| 11. |
- Ohlsson, Tommy, 1973-, et al.
(author)
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Neutrino oscillations with three flavors in matter : Applications to neutrinos traversing the earth
- 2000
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In: Physics Letters B. - : Elsevier Science B.V.. - 0370-2693 .- 1873-2445. ; 474:1-2, s. 153-162
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Journal article (peer-reviewed)abstract
- Analytic formulas are presented for three flavor neutrino oscillations in matter in the plane wave approximation. We calculate in particular the time evolution operator in both mass and flavor bases. We also find the transition probabilities expressed as functions of the vacuum mass squared differences, the vacuum mixing angles, and the matter density parameter. The application of this to neutrino oscillations for both atmospheric and long baseline neutrinos in a mantle-core-mantle step function model of the Earth's matter density profile is discussed.
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| 12. |
- Ohlsson, Tommy, 1973-, et al.
(author)
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Neutrino oscillations with three flavors in matter of varying density
- 2001
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In: European Physical Journal C. - : Springer-Verlag / Società Italiana di Fisica. - 1434-6044 .- 1434-6052. ; 20:3, s. 507-515
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Journal article (peer-reviewed)abstract
- In this paper, we discuss the evolution operator and the transition probabilities expressed as functions of the vacuum mass squared differences, the vacuum mixing angles, and the matter density parameter for three flavor neutrino oscillations in matter of varying density in the plane wave approximation. The applications of this to neutrino oscillations in a model of the earth's matter density profile, step function matter density profiles, constant matter density profiles. linear matter density profiles, and finally in a model of the sun's matter density profile are discussed. We show that for matter density profiles which do not fluctuate too much, the total evolution operator consisting of n operators can be replaced by one single evolution operator in the semi-classical approximation.
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| 13. |
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| 14. |
- Ohlsson, Tommy, 1973-, et al.
(author)
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Three flavor neutrino oscillations in matter
- 2000
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In: Journal of Mathematical Physics. - : American Institute of Physics. - 0022-2488 .- 1089-7658. ; 41:5, s. 2768-2788
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Journal article (peer-reviewed)abstract
- We derive analytic expressions for three flavor neutrino oscillations in the presence of matter in the plane wave approximation using the Cayley-Hamilton formalism. Especially, we calculate the time evolution operator in both flavor and mass bases. Furthermore, we find the transition probabilities, matter mass squared differences, and matter mixing angles all expressed in terms of the vacuum mass squared differences, the vacuum mixing angles, and the matter density. The conditions for resonance in the presence of matter are also studied in some examples.
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| 15. |
- Ohlsson, Tommy, 1973-, et al.
(author)
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Weak form factors for semileptonic octet baryon decays in the chiral quark model
- 1999
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In: European Physical Journal C. - : Springer-Verlag. - 1434-6044 .- 1434-6052. ; 6:2, s. 285-296
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Journal article (peer-reviewed)abstract
- We study the weak vector and axial-vector form factors of first- and second-class currents for the semileptonic octet baryon decays in the spirit of the chiral quark model. Our results for the weak magnetism form factors are consistent with the conserved vector current (CVC) results. The induced pseudotensor form factors, which are highly model dependent. are small. The overall performance of the chiral quark model is quite good and in general agreement with existing experimental data.
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| 16. |
- Ohlsson, Tommy, 1973-, et al.
(author)
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Weak magnetism in chiral quark models
- 2000
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In: European Physical Journal C. - : Springer-Verlag. - 1434-6044 .- 1434-6052. ; 12:2, s. 271-276
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Journal article (peer-reviewed)abstract
- We discuss symmetry breaking in the weak magnetism form factors for the semileptonic octet baryon decays. In the chiral quark model, the symmetry breaking can be accounted for in the masses and the quark spin polarizations can take on more general values due to Goldstone boson depolarization. Here we clarify some features of the chiral quark model prediction for the weak magnetism and compare to the corresponding result of the chiral quark soliton model.
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| 17. |
- Snellman, Greta, et al.
(author)
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Determining Vitamin D Status : A Comparison between Commercially Available Assays
- 2010
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:7, s. e11555-
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Journal article (peer-reviewed)abstract
- Background: Vitamin D is not only important for bone health but can also affect the development of several non-bone diseases. The definition of vitamin D insufficiency by serum levels of 25-hydroxyvitamin D depends on the clinical outcome but might also be a consequence of analytical methods used for the definition. Although numerous 25-hydroxyvitamin D assays are available, their comparability is uncertain. We therefore aim to investigate the precision, accuracy and clinical consequences of differences in performance between three common commercially available assays. Methodology/Principal Findings: Serum 25-hydroxyvitamin D levels from 204 twins from the Swedish Twin Registry were determined with high-pressure liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (HPLCAPCI-MS), a radioimmunoassay (RIA) and a chemiluminescent immunoassay (CLIA). High inter-assay disagreement was found. Mean 25-hydroxyvitamin D levels were highest for the HPLC-APCI-MS technique (85 nmol/L, 95% CI 81-89), intermediate for RIA (70 nmol/L, 95% CI 66-74) and lowest with CLIA (60 nmol/L, 95% CI 56-64). Using a 50-nmol/L cut-off, 8% of the subjects were insufficient using HPLC-APCI-MS, 22% with RIA and 43% by CLIA. Because of the heritable component of 25-hydroxyvitamin D status, the accuracy of each method could indirectly be assessed by comparison of within-twin pair correlations. The strongest correlation was found for HPLC-APCI-MS (r = 0.7), intermediate for RIA (r = 0.5) and lowest for CLIA (r = 0.4). Regression analyses between the methods revealed a non-uniform variance (p<0.0001) depending on level of 25-hydroxyvitamin D. Conclusions/Significance: There are substantial inter-assay differences in performance. The most valid method was HPLCAPCI-MS. Calibration between 25-hydroxyvitamin D assays is intricate.
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| 18. |
- Snellman, Greta, 1978-, et al.
(author)
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Long-term dietary vitamin D intake and risk of fracture and osteoporosis : a longitudinal cohort study of Swedish middle-aged and elderly women
- 2012
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In: Bone. - : Elsevier BV. - 8756-3282 .- 1873-2763. ; 50:Suppl 1, s. S65-S65
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Journal article (other academic/artistic)abstract
- Context: Vitamin D deficiency may lead to osteoporosis and fracture but the importance of dietary vitamin D intake for skeletal health in adults is uncertain.Objective: To investigate associations between long-term dietary intake of vitamin D with risk of fractures and osteoporosis.Design: A prospective longitudinal cohort study.Setting: The population-based Swedish Mammography Cohort and the subcohort SMC Clinical.Participants: 61,433 women (age range 38 to 76 years) were followed for 19 years. Of these, 5,022 participated in the subcohort. Diet was assessed by repeated food frequency questionnaires. Main outcome measures: Incident fractures of any type and hip fractures, which were identified from registry data. Secondary outcome was osteoporosis diagnosed by dual energy x ray absorptiometry in the subcohort.Results: 14,738 women experienced any type of first fracture during follow-up, with 3,871 of these being hip fractures. Twenty percent of the women in the subcohort were classified as osteoporotic. A multivariable-adjusted hazard ratio (HR) and 95% confidence interval (CI) for any first fracture was 0.96 (95% CI 0.92-1.01) for the lowest and 1.02 (95% CI 0.96-1.07) for the highest quintile when compared with the third quintile of vitamin D intake. The corresponding HR for a first hip fracture was 1.02 (95% CI, 0.96-1.08) for the lowest and 1.14 (95% CI, 1.03-1.26) for the highest quintile. The odds ratio of osteoporosis by quintiles of vitamin D intake was 1.20 (95% CI, 0.85-1.71) for the lowest and 0.99 (95% CI, 0.78-1.25) for the highest quintile. Bone mineral density, however, were 2% higher at the lumbar spine and 0.3% higher at the total hip in women with highest vs. women with lowest intake of vitamin D (p<0.0001). Conclusions: Dietary intake of vitamin D seems to be of minor importance for the occurrence of fractures and osteoporosis in community-dwelling Swedish middle-aged and elderly women.
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| 19. |
- Snellman, Greta, et al.
(author)
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Long-Term Dietary Vitamin D Intake and Risk of Fracture and Osteoporosis : A Longitudinal Cohort Study of Swedish Middle-aged and Elderly Women
- 2014
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In: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 99:3, s. 781-790
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Journal article (peer-reviewed)abstract
- Context: The importance of dietary vitamin D for osteoporotic fracture prevention is uncertain. Objective: Our objective was to investigate associations between dietary vitamin D intake with risk of fracture and osteoporosis. Design and Participants: In the population-based Swedish Mammography Cohort (including 61 433 women followed for 19 years), diet was assessed by repeated food frequency questionnaires. Setting: The study was conducted in 2 municipalities in central Sweden. Main Outcome Measure: Incident fractures were identified from registry data. In a subcohort (n = 5022), bone mineral density was determined by dual-energy x-ray absorptiometry and serum 25-hydroxyvitamin D was measured using HPLC-tandem mass spectrometry. Results: A total of 14 738 women experienced any type of first fracture during follow-up, and 3871 had a hip fracture. Multivariable-adjusted hazard ratio (HR) for any first fracture was 0.96 (95% confidence interval, 0.92-1.01) for the lowest (mean, 3.1 mu g/d) and 1.02 (0.96-1.07) for the highest (mean, 6.9 mu g/d) quintile compared with the third quintile of vitamin D intake. The corresponding HR for a first hip fracture was 1.02 (0.96-1.08) for the lowest and 1.14 (1.03-1.26) for the highest quintile. Intakes >10 mu g/d, compared with <5 mu g/d, conferred an HR of 1.02 (0.92-1.13) for any fracture and an HR of 1.27 (1.03-1.57) for hip fracture. The intake of vitamin D did not affect the odds for osteoporosis, although higher levels were associated with higher bone mineral density (0.3%-2%, P < .0001). A positive association was observed between vitamin D intake and serum 25-hydroxyvitamin D. Conclusions: Dietary intakes of vitamin D seem of minor importance for the occurrence of fractures and osteoporosis in community-dwelling Swedish women.
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| 20. |
- Snellman, Greta, et al.
(author)
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Seasonal genetic influence on serum 25-hydroxyvitamin D levels : a twin study
- 2009
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In: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 4:11, s. e7747-
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Journal article (peer-reviewed)abstract
- BACKGROUND: Although environmental factors, mainly nutrition and UV-B radiation, have been considered major determinants of vitamin D status, they have only explained a modest proportion of the variation in serum 25-hydroxyvitamin D. We aimed to study the seasonal impact of genetic factors on serum 25-hydroxyvitamin D concentrations. METHODOLOGY/PRINCIPAL FINDINGS: 204 same-sex twins, aged 39-85 years and living at northern latitude 60 degrees, were recruited from the Swedish Twin Registry. Serum 25-hydroxyvitamin D was analysed by high-pressure liquid chromatography and mass spectrometry. Genetic modelling techniques estimated the relative contributions of genetic, shared and individual-specific environmental factors to the variation in serum vitamin D. The average serum 25-hydroxyvitamin D concentration was 84.8 nmol/l (95% CI 81.0-88.6) but the seasonal variation was substantial, with 24.2 nmol/l (95% CI 16.3-32.2) lower values during the winter as compared to the summer season. Half of the variability in 25-hydroxyvitamin D during the summer season was attributed to genetic factors. In contrast, the winter season variation was largely attributable to shared environmental influences (72%; 95% CI 48-86%), i.e., solar altitude. Individual-specific environmental influences were found to explain one fourth of the variation in serum 25-hydroxyvitamin D independent of season. CONCLUSIONS/SIGNIFICANCE: There exists a moderate genetic impact on serum vitamin D status during the summer season, probably through the skin synthesis of vitamin D. Further studies are warranted to identify the genes impacting on vitamin D status.
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| 21. |
- Snellman, Greta, 1978-, et al.
(author)
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Serum 25-hydroxyvitamin D in relation to BMD and fractures in a Swedish cohort of women and men
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Other publication (other academic/artistic)abstract
- Background/aimVitamin D insufficiency has been suggested to be common and to cause osteoporotic fractures. Results from previous studies are inconsistent. The aim of our study was to assess if circulating vitamin D is associated with incident fractures and bone mineral density (BMD) among elderly Swedish men and women.MethodA population-based cohort consisting of 1002 Swedish men and women, aged 70-years at baseline with a setting at latitude 60o north, was followed for 7 years. Serum vitamin D (25(OH)D) at baseline was analysed by an immunoassay. Fractures during follow-up were identified from registry data and BMD was measured with DXA. Association between 25(OH)D levels and time to fracture was our primary endpoint and BMD our secondary outcome.ResultMean S-25(OH)Dlevel was 58 (SD 20) nmol/L and 38% of the participants had levels <50 nmol/L. After multivariable adjustment, S-25(OH)D was only associated with total body BMD among men (P=0.03) but the relation was weak. Each SD increase in S-25(OH)D (approximately 20 nmol/L) conferred a 1% increase in total body BMD. Low vitamin D levels were not associated with lower BMD at the total hip or the lumbar spine in men or women. During follow-up, 155 (15%) of the participants sustained a fracture. No association between 25(OH)D and the rate of fracture was evident. The lowest quintile compared to highest quintile of 25(OH)D conferred a HR of 1.13 (95% CI 0.65-1.94).ConclusionIn a general population of elderly Swedish men and women, serum vitamin D is not a strong determinant of fractures or of low bone mineral density.
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| 22. |
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