| 11. |
- Dencker, Magnus, et al.
(författare)
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Body fat, abdominal fat and body fat distribution related to VO(2PEAK) in young children.
- 2011
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Ingår i: International Journal of Pediatric Obesity. - : Informa UK Limited. - 1747-7174 .- 1747-7166. ; 6:2-2, s. 597-602
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Objective. Aerobic fitness, defined as maximum oxygen uptake (VO(2PEAK)), and body fat measurements represent two known risk factors for disease. The purpose of this study was to investigate the relationship between VO(2PEAK) and body fat measurements in young children at a population-based level. Methods. Cross-sectional study of 225 children (128 boys and 97 girls) aged 8-11 years, recruited from a population-based cohort. Total lean body mass (LBM), total fat mass (TBF), and abdominal fat mass (AFM) were measured by dual-energy x-ray absorptiometry. Body fat was also calculated as a percentage of body mass (BF%) and body fat distribution as AFM/TBF. VO(2PEAK) was assessed by indirect calorimetry during maximal exercise test. Results. Significant relationships existed between body fat measurements and VO(2PEAK) in both boys and girls, with Pearson correlation coefficients for absolute values of VO(2PEAK) (0.22-0.36, P< 0.05), and for VO(2PEAK) scaled by body mass (-0.38 - -0.70, P<0.05). No relationships were detected for VO(2PEAK) scaled to LBM (-0.17-0.04, all not significant). Boys and girls in the lowest quartile according to body fat measurements had higher absolute values of VO(2PEAK) and lower values of VO(2PEAK) scaled by body mass, compared with those in the highest quartile. No differences were found for VO(2PEAK) scaled to LBM. Conclusions. Our findings document the coexistence of two known risk factors for disease at a young age and confirms that VO(2PEAK) was scaled to LBM may be a better, body fat independent way of expressing fitness.
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| 12. |
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| 13. |
- Dencker, Magnus, et al.
(författare)
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Tracking of Physical Activity with Accelerometers Over a Two-year Time Period.
- 2013
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Ingår i: Journal of Physical Activity & Health. - 1543-5474. ; 10:2, s. 241-248
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Limited data exists of tracking and changes in accelerometer measured physical activity in children. METHODS: Physical activity was assessed by accelerometers for four days in 167 children (boys n=90, girls n=77), aged 9.8±0.6 years. Follow-up measurement was made 2.0±0.1 yrs later (range 1.9-2.1 yrs). General physical activity (GPA) was defined as mean count/minute. Minutes of inactivity, light- moderate- and vigorous physical activity (LMVPA), moderate and vigorous physical activity (MVPA) and vigorous physical activity (VPA) per day were calculated both as absolute values and as percentage of total registration time. RESULTS: Spearman rank order correlation indicated low tracking of MVPA and VPA in girls (r=0.25-0.33, P<0.05), and low-moderate tracking of GPA, inactivity, LMVPA, MVPA and VPA in boys (r=0.23-0.40, P<0.05). Time in inactivity increased at follow-up by 5-14%. Most of the assessed physical activity variables were decreased at follow-up by 6-30%. CONCLUSIONS: Physical activity tracks at a low-moderate degree from age 10 to age 12 years, which confirm previous investigations that have used self-report assessments. The low-moderate tracking of physical activity variables indicate that those who were most active initially remained most active. Increasing inactive behaviour was observed and that several other physical activity variables were decreased at follow-up.
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| 14. |
- Detter, Fredrik, et al.
(författare)
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A 5-Year Exercise Program in Pre- and Peripubertal Children Improves Bone Mass and Bone Size Without Affecting Fracture Risk.
- 2013
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Ingår i: Calcified Tissue International. - : Springer Science and Business Media LLC. - 1432-0827 .- 0171-967X. ; 92:4, s. 385-393
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Tidskriftsartikel (refereegranskat)abstract
- We studied the effect in children of an exercise intervention program on fracture rates and skeletal traits. Fractures were registered for 5 years in a population-based prospective controlled exercise intervention study that included children aged 6-9 years at study start, 446 boys and 362 girls in the intervention group and 807 boys and 780 girls in the control group. Intervention subjects received 40 min/school day of physical education and controls, 60 min/week. In 73 boys and 48 girls in the intervention group and 52 boys and 48 girls in the control group, bone mineral density (BMD, g/cm(2)) and bone area (mm(2)) were followed annually by dual-energy X-ray absorptiometry, after which annual changes were calculated. At follow-up we also assessed trabecular and cortical volumetric BMD (g/cm(3)) and bone structure by peripheral computed tomography in the tibia and radius. There were 20.0 fractures/1,000 person-years in the intervention group and 18.5 fractures/1,000 person-years in the control group, resulting in a rate ratio of 1.08 (0.79-1.47) (mean and 95 % CI). The gain in spine BMD was higher in both girls (difference 0.01 g/cm(2), 0.005-0.019) and boys (difference 0.01 g/cm(2), 0.001-0.008) in the intervention group. Intervention girls also had higher gain in femoral neck area (difference 0.04 mm(2), 0.005-0.083) and at follow-up larger tibial bone mineral content (difference 0.18 g, 0.015-0.35), larger tibial cortical area (difference 17 mm(2), 2.4-31.3), and larger radial cross-sectional area (difference 11.0 mm(2), 0.63-21.40). As increased exercise improves bone mass and in girls bone size without affecting fracture risk, society ought to encourage exercise during growth.
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| 15. |
- Detter, Fredrik, et al.
(författare)
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A Six-Year Exercise Program Improves Skeletal Traits without Affecting Fracture Risk - a Prospective Controlled Study in 2621 Children
- 2014
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Ingår i: Journal of bone and mineral research. - : Wiley. - 0884-0431 .- 1523-4681. ; 29:6, s. 1325-1336
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Tidskriftsartikel (refereegranskat)abstract
- Most pediatric exercise intervention studies, that evaluates the effect on skeletal traits include volunteers and follow bone mass for less than three years. We present a population-based six-year controlled exercise intervention study in children with also bone structure and incident fractures as endpoints. Fractures were registered in 417 girls and 500 boys in the intervention group (3969 person-years) and 835 girls and 869 boys in the control group (8245 person-years), all aged 6-9 years at study start, during the six-year study period. Children in the intervention group had 40 minutes daily school physical education (PE) and the control group 60 minutes per week. In a sub-cohort with 78 girls and 111 boys in the intervention group and 52 girls and 54 boys in the control group, bone mineral density (g/cm2 ) and bone area (mm2 ) were measured repeatedly by dual energy X-ray absorptiometry (DXA). Peripheral quantitative computed tomography (pQCT) measured bone mass and bone structure at follow-up. There were 21.7 low and moderate energy related fractures per 1000 person-years in the intervention group and 19.8 fractures in the control group, leading to a Rate Ratio (RR) of 1.12 (0.85, 1.46). Girls in the intervention group, in comparison with girls in the control group, had 0.009 g/cm2 (0.003, 0.015) larger gain annually in spine BMD, 0.07 g (0.014, 0.123) larger gain in femoral neck BMC and 4.0 mm2 (0.5, 7.8) larger gain in femoral neck area, and at follow-up 24.1 g (7.6, 40.6) higher tibial cortical BMC (g) and 23.9 mm2 (5.27, 42.6) larger tibial cross-sectional area. Boys with daily PE had 0.006 g/cm2 (0.002, 0.010) larger gain annually in spine BMD than control boys but at follow-up no higher pQCT values than boys in the control group. Daily PE for six years in at study start 6-9 year old improves bone mass and bone size in girls and bone mass in boys, without affecting the fracture risk. (c) 2014 American Society for Bone and Mineral Research.
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| 16. |
- Giesler, Reiner, et al.
(författare)
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Catchment-scale dissolved carbon concentrations and exportestimates across six subarctic streams in northern Sweden
- 2014
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 11:2, s. 525-537
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Tidskriftsartikel (refereegranskat)abstract
- Climatic change is currently enhancing permafrost thawing and the flow of water through the landscape in subarctic and arctic catchments, with major consequences for the carbon export to aquatic ecosystems. We studied stream water carbon export in several tundra-dominated catchments in northern Sweden. There were clear seasonal differences in both dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations. The highest DOC concentrations occurred during the spring freshet while the highest DIC concentrations were always observed during winter baseflow conditions for the six catchments considered in this study. Long-term trends for the period 1982 to 2010 for one of the streams showed that DIC concentrations has increased by 9% during the 28 yr of measurement while no clear trend was found for DOC. Similar increasing trends were also found for conductivity, Ca and Mg. When trends were discretized into individual months, we found a significant linear increase in DIC concentrations with time for September, November and December. In these subarctic catchments, the annual mass of C exported as DIC was in the same order of magnitude as DOC; the average proportion of DIC to the total dissolved C exported was 61% for the six streams. Furthermore, there was a direct relationship between total runoff and annual dissolved carbon fluxes for these six catchments. These relationships were more prevalent for annual DIC exports than annual DOC exports in this region. Our results also highlight that both DOC and DIC can be important in high-latitude ecosystems. This is particularly relevant in environments where thawing permafrost and changes to subsurface ice due to global warming can influence stream water fluxes of C. The large proportion of stream water DIC flux also has implications on regional C budgets and needs to be considered in order to understand climate-induced feedback mechanisms across the landscape.
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| 17. |
- Jonsson, Joakim H, et al.
(författare)
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Treatment planning using MRI data: an analysis of the dose calculation accuracy for different treatment regions
- 2010
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Ingår i: Radiation Oncology. - 1748-717X. ; 5, s. 62-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Because of superior soft tissue contrast, the use of magnetic resonance imaging (MRI) as a complement to computed tomography (CT) in the target definition procedure for radiotherapy is increasing. To keep the workflow simple and cost effective and to reduce patient dose, it is natural to strive for a treatment planning procedure based entirely on MRI. In the present study, we investigate the dose calculation accuracy for different treatment regions when using bulk density assignments on MRI data and compare it to treatment planning that uses CT data.METHODS: MR and CT data were collected retrospectively for 40 patients with prostate, lung, head and neck, or brain cancers. Comparisons were made between calculations on CT data with and without inhomogeneity corrections and on MRI or CT data with bulk density assignments. The bulk densities were assigned using manual segmentation of tissue, bone, lung, and air cavities.RESULTS: The deviations between calculations on CT data with inhomogeneity correction and on bulk density assigned MR data were small. The maximum difference in the number of monitor units required to reach the prescribed dose was 1.6%. This result also includes effects of possible geometrical distortions.CONCLUSIONS: The dose calculation accuracy at the investigated treatment sites is not significantly compromised when using MRI data when adequate bulk density assignments are made. With respect to treatment planning, MRI can replace CT in all steps of the treatment workflow, reducing the radiation exposure to the patient, removing any systematic registration errors that may occur when combining MR and CT, and decreasing time and cost for the extra CT investigation.
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| 18. |
- Jonsson, Joakim, 1984-
(författare)
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Integration of MRI into the radiotherapy workflow
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The modern day radiotherapy treatments are almost exclusively based on computed tomography (CT) images. The CT images are acquired using x-rays, and therefore reflect the radiation interaction properties of the material. This information is used to perform accurate dose calculation by the treatment planning system, and the data is also well suited for creating digitally reconstructed radiographs for comparing patient set up at the treatment machine where x-ray images are routinely acquired for this purpose.The magnetic resonance (MR) scanner has many attractive features for radiotherapy purposes. The soft tissue contrast as compared to CT is far superior, and it is possible to vary the sequences in order to visualize different anatomical and physiological properties of an organ. Both of these properties may contribute to an increase in accuracy of radiotherapy treatment.Using the MR images by themselves for treatment planning is, however, problematic. MR data reflects the magnetic properties of protons, and thus have no connection to the radiointeraction properties of the material. MRI also has inherent difficulty in imaging bone, which will appear in images as areas of no signal similar to air. This makes both dose calculation and patient positioning at the treatment machine troublesome.There are several clinics that use MR images together with CT images to perform treatment planning. The images are registered to a common coordinate system, a process often described as image fusion. In these cases, the MR images are primarily used for target definition and the CT images are used for dose calculations. This method is now not ideal, however, since the image fusion may introduce systematic uncertainties into the treatment due to the fact that the tumor is often able to move relatively freely with respect to the patients’ bony anatomy and outer contour, especially when the image registration algorithms take the entire patient anatomy in the volume of interest into account.The work presented in the thesis “Integration of MRI into the radiotherapy workflow” aim towards investigating the possibilities of workflows based entirely on MRI without using image registration, as well as workflows using image registration methods that are better suited for targets that can move with respect to surrounding bony anatomy, such as the prostate.
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| 19. |
- Karlberg, Magnus, et al.
(författare)
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Dynamics of rotor systems with clearance and weak pedestals in full contact
- 2010
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Ingår i: 13th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery 2010 (ISROMAC-13). - Red Hook, NY : Curran Associates, Inc.. - 9781617388484 ; , s. 531-536
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Konferensbidrag (refereegranskat)abstract
- Many rotating machineries are supported by bearings with clearance, which are further clamped in, compared to the bearing stiffness, weak pedestals. As have been reported in several studies, it is essential to choose a proper clearance in order to avoid unwanted vibrations. When rotating machineries supported by bearings with clearance are subjected to stationary loads (gravity, magnetic pull etc.), it may not loose contact between the shaft and the bearing (i.e. full contact). However, even in full contact unwanted dynamics can occur which is of interest in this paper. It is found that the clearance give raise to anisotropic pedestal stiffness. It is further shown that some of the resonance frequencies decrease with the clearance.
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| 20. |
- Karlsson, Lennart, et al.
(författare)
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Editorial
- 2013
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Ingår i: International Journal of Product Development. - 1477-9056 .- 1741-8178. ; 18:1, s. 1-2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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