| 1. |
- Jespersen, Naja Z., et al.
(författare)
-
Heterogeneity in the perirenal region of humans suggests presence of dormant brown adipose tissue that contains brown fat precursor cells
- 2019
-
Ingår i: Molecular Metabolism. - : Elsevier BV. - 2212-8778. ; 24, s. 30-43
-
Tidskriftsartikel (refereegranskat)abstract
- Objective:Increasing the amounts of functionally competent brown adipose tissue (BAT) in adult humans has the potential to restore dysfunctional metabolism and counteract obesity. In this study, we aimed to characterize the human perirenal fat depot, and we hypothesized that there would be regional, within-depot differences in the adipose signature depending on local sympathetic activity.Methods:We characterized fat specimens from four different perirenal regions of adult kidney donors, through a combination of qPCR mapping, immunohistochemical staining, RNA-sequencing, and pre-adipocyte isolation. Candidate gene signatures, separated by adipocyte morphology, were recapitulated in a murine model of unilocular brown fat induced by thermoneutrality and high fat diet.Results:We identified widespread amounts of dormant brown adipose tissue throughout the perirenal depot, which was contrasted by multilocular BAT, primarily found near the adrenal gland. Dormant BAT was characterized by a unilocular morphology and a distinct gene expression profile, which partly overlapped with that of subcutaneous white adipose tissue (WAT). Brown fat precursor cells, which differentiated into functional brown adipocytes were present in the entire perirenal fat depot, regardless of state. We identified SPARC as a candidate adipokine contributing to a dormant BAT state, and CLSTN3 as a novel marker for multilocular BAT.Conclusions:We propose that perirenal adipose tissue in adult humans consists mainly of dormant BAT and provide a data set for future research on factors which can reactivate dormant BAT into active BAT, a potential strategy for combatting obesity and metabolic disease.
|
|
| 2. |
- Madsen, Mads, et al.
(författare)
-
Well-Being, Physical Fitness, and Health Profile of 2,203 Danish Girls Aged 10-12 in Relation to Leisure-time Sports Club Activity-With Special Emphasis on the Five Most Popular Sports
- 2022
-
Ingår i: Strength and conditioning journal. - Philadelphia, PA : Lippincott Williams & Wilkins. - 1524-1602 .- 1533-4295. ; 36:8, s. 2283-2290
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigated the relationship between leisure-time sports club activities and well-being as well as physical health parameters in 10-12-year-old Danish girls. Two thousand two hundred three girls took part in the study, which included questionnaires on participation in leisure-time sports clubs, well-being, Yo-Yo intermittent recovery level 1 children's test, long jump, balance tests, body composition, blood pressure (BP), and resting heart rate (RHR). Data were analyzed according to whether the girls participated in leisure-time sport and according to the 5 most frequently reported sports. Girls enrolled in leisure-time sports had higher physical well-being (49.3 ± 8.6 vs. 45.2 ± 8.3), psychological well-being (50.4 ± 9.0 vs. 49.4 ± 9.8), experienced more peer and social support (50.2 ± 10.0 vs. 48.9 ± 10.7), and perceived a more positive school environment (52.5 ± 8.0 vs. 50.5 ± 9.3), as well as showing higher Yo-Yo (+39%), long jump (+10%), and balance performance (+15%) than girls not involved in sport clubs. The girls active in sports clubs had higher relative muscle mass (+5%), lower fat percentage (-11%), body mass index (-5%), RHR (-3.4 b·min-1), and diastolic BP (-1.4 mm Hg) compared with girls not involved in sport (p<0.05). Girls who played soccer showed higher aerobic fitness compared with inactive girls (+67%), dancers (+39%), swimmers (+38%), and gymnasts (+16%). Gymnasts had a lower fat percentage than inactive girls (-19%), team handballers (-10%), swimmers (-12%), and soccer players (-4%). Girls participating in club-based leisure-time sports showed higher well-being and better fitness and health profiles than girls not involved in any sports club activities. Girls involved in soccer had better aerobic fitness and gymnasts a lower fat percentage. Copyright © 2020 National Strength and Conditioning Association.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Dravins, Dainis, et al.
(författare)
-
Wavelength shifts in solar-type spectra
- 2005
-
Ingår i: European Space Agency, (Special Publication) ESA SP. - 1609-042X .- 0379-6566. ; 560, s. 113-119
-
Konferensbidrag (refereegranskat)abstract
- Spectral-line displacements away from the wavelengths naively expected from the Doppler shift caused by stellar radial motion may originate as convective shifts (correlated velocity and brightness patterns in the photosphere), as gravitational redshifts, or perhaps be induced by wave motions. Absolute lineshifts, in the past studied only for the Sun, are now accessible also for other stars thanks to astrometric determination of stellar radial motion, and spectrometers with accurate wavelength calibration. Comparisons between spectroscopic apparent radial velocities and astrometrically determined radial motions reveal greater spectral blueshifts in F-type stars than in the Sun (as theoretically expected from their more vigorous convection), further increasing in A-type stars (possibly due to atmospheric shockwaves). Work is in progress to survey the spectra of the Sun and several solar-type stars for "unblended" photospheric lines of most atomic species with accurate laboratory wavelengths available. One aim is to understand the ultimate information content of stellar spectra, and in what detail it will be feasible to verify models of stellar atmospheric hydrodynamics. These may predict bisectors and shifts for widely different classes of lines, but there will not result any comparison with observations if such lines do not exist in real spectra, or are too blended for meaningful measurement. An important near-future development to enable a further analysis of stellar surface structure will be the study of wavelength variations across spatially resolved stellar disks, e.g., the center-to-limb wavelength changes along a stellar diameter, and their spatially resolved time variability.
|
|
| 6. |
- Fellström, Bengt, et al.
(författare)
-
Effect of fluvastatin on renal end points in the Assessment of Lescol in Renal Transplant (ALERT) trial
- 2004
-
Ingår i: Kidney International. - : Elsevier BV. - 0085-2538 .- 1523-1755. ; 66:4, s. 1549-1555
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Hyperlipidemia is a risk factor for long-term renal transplant dysfunction, but no prospective clinical trials have investigated the effects of statin treatment on graft function in renal transplant recipients. The aim of the present study was to evaluate the effect of fluvastatin on long-term renal transplant function and development of chronic allograft nephropathy in the ALERT (Assessment of Lescol in Renal Transplantation) study. METHODS: ALERT was a randomized, double-blind, placebo-controlled study of the effect of fluvastatin, 40 mg and 80 mg daily, in renal transplant recipients. Patients were randomized to receive either fluvastatin (N= 1050) or placebo (N= 1052) and followed for five to six years. Renal end points included graft loss or doubling of serum creatinine or death; glomerular filtration rate (GFR) was also measured during follow-up in a subset of patients (N= 439). RESULTS: There were 283 patients (13.5%) with graft loss, mainly due to chronic rejection (82%), yielding an annual rate of 2.4%. Fluvastatin treatment significantly lowered mean low-density lipoprotein (LDL)-cholesterol levels by 32% (95% CI -33 to -30) compared with placebo, but had no significant effect on the incidence of renal graft loss or doubling of serum creatinine, or decline in GFR throughout follow-up in the whole study population. Neither was any treatment effect by fluvastatin found in any of the subgroups analyzed. CONCLUSION: Fluvastatin treatment significantly improves lipid values in renal transplant recipients but has no effect on graft loss or doubling of serum creatinine.
|
|
| 7. |
- Frisvad, Jeppe Revall, et al.
(författare)
-
Survey of Models for Acquiring the Optical Properties of Translucent Materials
- 2020
-
Ingår i: Computer graphics forum (Print). - : Wiley. - 0167-7055 .- 1467-8659. ; 39, s. 729-755
-
Tidskriftsartikel (refereegranskat)abstract
- The outset of realistic rendering is a desire to reproduce the appearance of the real world. Rendering techniques therefore operate at a scale corresponding to the size of objects that we observe with our naked eyes. At the same time, rendering techniques must be able to deal with objects of nearly arbitrary shapes and materials. These requirements lead to techniques that oftentimes leave the task of setting the optical properties of the materials to the user. Matching the appearance of real objects by manual adjustment of optical properties is however nearly impossible. We can render objects with a plausible appearance in this way but cannot compare the appearance of a manufactured item to that of its digital twin. This is especially true in the case of translucent objects, where we need more than a goniometric measurement of the optical properties. In this survey, we provide an overview of forward and inverse models for acquiring the optical properties of translucent materials. We map out the efforts in graphics research in this area and describe techniques available in related fields. Our objective is to provide a better understanding of the tools currently available for appearance specification when it comes to digital representations of real translucent objects.
|
|
| 8. |
- Hamed, Tareq Abu, et al.
(författare)
-
Multiscale in modelling and validation for solar photovoltaics
- 2018
-
Ingår i: EPJ Photovoltaics. - : EDP Sciences. - 2105-0716. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Photovoltaics is amongst the most important technologies for renewable energy sources, and plays a key role in the development of a society with a smaller environmental footprint. Key parameters for solar cells are their energy conversion efficiency, their operating lifetime, and the cost of the energy obtained from a photovoltaic system compared to other sources. The optimization of these aspects involves the exploitation of new materials and development of novel solar cell concepts and designs. Both theoretical modeling and characterization of such devices require a comprehensive view including all scales from the atomic to the macroscopic and industrial scale. The different length scales of the electronic and optical degrees of freedoms specifically lead to an intrinsic need for multiscale simulation, which is accentuated in many advanced photovoltaics concepts including nanostructured regions. Therefore, multiscale modeling has found particular interest in the photovoltaics community, as a tool to advance the field beyond its current limits. In this article, we review the field of multiscale techniques applied to photovoltaics, and we discuss opportunities and remaining challenges.
|
|
| 9. |
- Holdaas, Hallvard, et al.
(författare)
-
Beneficial effect of early initiation of lipid-lowering therapy following renal transplantation
- 2005
-
Ingår i: Nephrology, Dialysis and Transplantation. - : Oxford University Press (OUP). - 0931-0509 .- 1460-2385. ; 20:5, s. 974-980
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Renal transplant recipients have a significantly reduced life expectancy, largely due to premature cardiovascular disease. The aim of the current analysis was to investigate the importance of time of initiation of therapy after transplantation, on the benefits of statin therapy. METHODS: 2102 renal transplant recipients with total cholesterol levels of 4.0-9.0 mmol/l were randomly assigned to treatment with fluvastatin (n = 1050) or placebo (n = 1052) and followed for a mean time of 5.1 years. The end-points were major cardiac events. The average median time from transplantation to randomization was 4.5 years (range: 0.5-29 years). RESULTS: In patients starting treatment with fluvastatin <4.5 years after renal transplantation, the incidence of cardiac events was 4.6% over 5.1 years vs 9.2% in those on placebo (P = 0.007). Fluvastatin significantly reduced the risk of cardiac death and non-fatal myocardial infarction by 56% [risk ratio (RR): 0.44; 95% confidence interval (95% CI): 0.26-0.74; P = 0.002]. In a more detailed analysis patients were grouped into 2-year intervals (since the last transplantation). The frequency of cardiac death and non-fatal myocardial infarction was reduced by 3.2%, 5.1%, 9.6% and 8.2% with fluvastatin treatment as compared to 6%, 10.4%, 13.4% and 9.6% with placebo when treatment was initiated at 0-2, 2-4, 4-6 and >6 years, respectively. The risk reduction for patients initiating therapy with fluvastatin at years 0-2 (compared with >6 years) following transplantation was 59% (RR: 0.41; 95% CI: 0.18-0.92; P = 0.0328). This is also reflected in total time on renal replacement therapy: in patients in the first quartile (<47 months) fluvastatin use was associated with a risk reduction of 64% compared with 19% for patients in the fourth quartile (>120 months) (P = 0.033). CONCLUSIONS: Our data support an early introduction of fluvastatin therapy in a population of transplant recipients at high risk of premature coronary heart disease.
|
|
| 10. |
|
|
| 11. |
- Holst, Bjørn, et al.
(författare)
-
Molecular switch controlling expression of the mannose-specific adhesin, Msa, in Lactobacillus plantarum
- 2019
-
Ingår i: Applied and Environmental Microbiology. - 0099-2240. ; 85:10
-
Tidskriftsartikel (refereegranskat)abstract
- Some lactic acid bacteria, especially Lactobacillus spp., possess adhesive properties enabling colonization of the human gastrointestinal tract. Two probiotic Lactobacillus plantarum strains, WCSF1 and 299v, display highly different mannose-specific adhesion, with L. plantarum 299v being superior to L. plantarum WCFS1 based on a yeast agglutination assay. A straightforward correlation between the mannose adhesion capacity and domain composition of the mannose-specific adhesin (Msa) in the two strains has not been demonstrated previously. In this study, we analyzed the promoter regions upstream of the msa gene encoding a mannose-specific adhesin in these two strains. The promoter region was mapped by primer extension and DNA sequence analysis, and only a single nucleotide change was identified between the two strains. However, Northern blot analysis showed a stronger msa transcript band in 299v than in WCFS1 correlating with the different adhesion capacities. During the establishment of a high-throughput yeast agglutination assay, we isolated variants of WCFS1 that displayed a very strong mannose-specific adhesion phenotype. The region upstream of the msa gene in these variants showed an inversion of a 104-bp fragment located between two perfectly inverted repeats present in the untranslated leader region. The inversion disrupts a strong hairpin structure that otherwise most likely would terminate the msa transcript. In addition, the ribosome binding site upstream of the msa gene, which is also masked within this hairpin structure, becomes accessible upon inversion, thereby increasing the frequency of translation initiation in the variant strains. Furthermore, Northern blot analysis showed a higher abundance of the msa transcript in the variants than in the wild type, correlating with a strong-Msa phenotype.
|
|
| 12. |
- Jardine, Alan G., et al.
(författare)
-
Cardiovascular risk and renal transplantation : post hoc analyses of the Assessment of Lescol in Renal Transplantation (ALERT) Study
- 2005
-
Ingår i: American Journal of Kidney Diseases. - : Elsevier BV. - 0272-6386 .- 1523-6838. ; 46:3, s. 529-36
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Renal transplantation is associated with an increased risk for premature cardiovascular disease. We analyzed the data in the placebo arm of Assessment of Lescol in Renal Transplantation (ALERT) to improve our understanding of the relationship between cardiovascular risk factors and outcomes in this unique population. METHODS: We performed Cox survival analysis for myocardial infarction, cardiac death, and noncardiac death in 1,052 patients recruited to the placebo arm of ALERT. These subjects were aged 30 to 75 years, had stable graft function at least 6 months after transplantation, had a serum total cholesterol level between 155 and 348 mg/dL (4 and 9 mmol/L), and were receiving cyclosporine-based immunosuppression. RESULTS: The results confirm previous studies. In multivariate analysis, preexisting coronary heart disease (hazard ratio [HR], 3.69; P < 0.001), total cholesterol level (HR, 1.55 per 50 mg/dL; P = 0.0045), and prior acute rejection (HR, 2.36; P = 0.0023) were independent risk factors. Conversely, independent risk factors for cardiac death were age (HR, 1.58 per decade; P = 0.0033), diabetes (HR, 3.35; P = 0.0002), ST-T changes on the ECG (HR, 3.17; P = 0.0004), and serum creatinine level (HR, 2.65 per milligram per deciliter; P < 0.0001). CONCLUSION: This analysis confirms that renal transplant recipients share risk factors for myocardial infarction and cardiac death with the general population. However, the pattern of risk factors and their relationship with outcomes is atypical, highlighting the unique nature of cardiovascular risk in transplant recipients.
|
|
| 13. |
- Jardine, Alan G., et al.
(författare)
-
Fluvastatin prevents cardiac death and myocardial infarction in renal transplant recipients : post-hoc subgroup analyses of the ALERT Study
- 2004
-
Ingår i: American Journal of Transplantation. - : Elsevier BV. - 1600-6135 .- 1600-6143. ; 4:6, s. 988-995
-
Tidskriftsartikel (refereegranskat)abstract
- Renal transplant recipients have a greatly increased risk of premature cardiovascular disease. The ALERT study was a multicenter, randomized, double-blind, placebo-controlled trial of fluvastatin (40-80 mg/day) in 2102 renal transplant recipients followed for 5-6 years. The main study used a composite cardiac end-point including myocardial infarction, cardiac death and cardiac interventions. Although reduced by fluvastatin, this primary end-point failed to achieve statistical significance thus precluding analysis of predefined subgroups. Therefore, in the present survival analysis, we used an alternative primary end-point of cardiac death or definite nonfatal myocardial infarction (as used in other cardiac outcome trials) which was significantly reduced by Fluvastatin therapy and permits subgroup analysis. Fluvastatin reduced LDL-cholesterol by 1 mmol/L compared with placebo, and the incidence of cardiac death or definite myocardial infarction was reduced from 104 to 70 events (RR 0.65; 95% CI 0.48, 0.88; p = 0.005). Fluvastatin use was associated with reduction in cardiac death or nonfatal myocardial infarction, which achieved statistical significance in many subgroups. The subgroups included patients at lower cardiovascular risk, who were younger, nondiabetic, nonsmokers and without pre-existing CVD. These data support the early introduction of statins following renal transplantation.
|
|
| 14. |
- Ledri, Marco, et al.
(författare)
-
Differential Effect of Neuropeptides on Excitatory Synaptic Transmission in Human Epileptic Hippocampus.
- 2015
-
Ingår i: The Journal of Neuroscience. - 1529-2401. ; 35:26, s. 9622-9631
-
Tidskriftsartikel (refereegranskat)abstract
- Development of novel disease-modifying treatment strategies for neurological disorders, which at present have no cure, represents a major challenge for today's neurology. Translation of findings from animal models to humans represents an unresolved gap in most of the preclinical studies. Gene therapy is an evolving innovative approach that may prove useful for clinical applications. In animal models of temporal lobe epilepsy (TLE), gene therapy treatments based on viral vectors encoding NPY or galanin have been shown to effectively suppress seizures. However, how this translates to human TLE remains unknown. A unique possibility to validate these animal studies is provided by a surgical therapeutic approach, whereby resected epileptic tissue from temporal lobes of pharmacoresistant patients are available for neurophysiological studies in vitro. To test whether NPY and galanin have antiepileptic actions in human epileptic tissue as well, we applied these neuropeptides directly to human hippocampal slices in vitro. NPY strongly decreased stimulation-induced EPSPs in dentate gyrus and CA1 (up to 30 and 55%, respectively) via Y2 receptors, while galanin had no significant effect. Receptor autoradiographic binding revealed the presence of both NPY and galanin receptors, while functional receptor binding was only detected for NPY, suggesting that galanin receptor signaling may be impaired. These results underline the importance of validating findings from animal studies in human brain tissue, and advocate for NPY as a more appropriate candidate than galanin for future gene therapy trials in pharmacoresistant TLE patients.
|
|
| 15. |
|
|
| 16. |
- Linz, Dominik, et al.
(författare)
-
Longer and better lives for patients with atrial fibrillation : the 9th AFNET/EHRA consensus conference
- 2024
-
Ingår i: Europace. - : Oxford University Press. - 1099-5129 .- 1532-2092. ; 26:4
-
Tidskriftsartikel (refereegranskat)abstract
- Aims: Recent trial data demonstrate beneficial effects of active rhythm management in patients with atrial fibrillation (AF) and support the concept that a low arrhythmia burden is associated with a low risk of AF-related complications. The aim of this document is to summarize the key outcomes of the 9th AFNET/EHRA Consensus Conference of the Atrial Fibrillation NETwork (AFNET) and the European Heart Rhythm Association (EHRA).Methods and results: Eighty-three international experts met in Munster for 2 days in September 2023. Key findings are as follows: (i) Active rhythm management should be part of the default initial treatment for all suitable patients with AF. (ii) Patients with device-detected AF have a low burden of AF and a low risk of stroke. Anticoagulation prevents some strokes and also increases major but non-lethal bleeding. (iii) More research is needed to improve stroke risk prediction in patients with AF, especially in those with a low AF burden. Biomolecules, genetics, and imaging can support this. (iv) The presence of AF should trigger systematic workup and comprehensive treatment of concomitant cardiovascular conditions. (v) Machine learning algorithms have been used to improve detection or likely development of AF. Cooperation between clinicians and data scientists is needed to leverage the potential of data science applications for patients with AF.Conclusions: Patients with AF and a low arrhythmia burden have a lower risk of stroke and other cardiovascular events than those with a high arrhythmia burden. Combining active rhythm control, anticoagulation, rate control, and therapy of concomitant cardiovascular conditions can improve the lives of patients with AF. Graphical Abstract
|
|
| 17. |
- Madsen, Søren
(författare)
-
An N-Body Model of the Hyades
- 2003
-
Ingår i: Dynamics and Evolution of Dense Stellar Systems. ; 11
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 18. |
- Madsen, Søren, et al.
(författare)
-
Astrometric radial velocities. III. Hipparcos measurements of nearby star clusters and associations
- 2002
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 381, s. 446-463
-
Tidskriftsartikel (refereegranskat)abstract
- Radial motions of stars in nearby moving clusters are determined fromaccurate proper motions and trigonometric parallaxes, without any use ofspectroscopy. Assuming that cluster members share the same velocityvector (apart from a random dispersion), we apply a maximum-likelihoodmethod on astrometric data from Hipparcos to compute radial and spacevelocities (and their dispersions) in the Ursa Major, Hyades, ComaBerenices, Pleiades, and Praesepe clusters, and for theScorpius-Centaurus, alpha Persei, and ``HIP 98321'' associations. Theradial motion of the Hyades cluster is determined to within 0.4 kms-1 (standard error), and that of its individual stars towithin 0.6 km s-1. For other clusters, Hipparcos data yieldastrometric radial velocities with typical accuracies of a few kms-1. A comparison of these astrometric values withspectroscopic radial velocities in the literature shows a good generalagreement and, in the case of the best-determined Hyades cluster, alsopermits searches for subtle astrophysical differences, such as evidencefor enhanced convective blueshifts of F-dwarf spectra, and decreasedgravitational redshifts in giants. Similar comparisons for the ScorpiusOB2 complex indicate some expansion of its associations, albeit slowerthan expected from their ages. As a by-product from the radial-velocitysolutions, kinematically improved parallaxes for individual stars areobtained, enabling Hertzsprung-Russell diagrams with unprecedentedaccuracy in luminosity. For the Hyades (parallax accuracy 0.3 mas), itsmain sequence resembles a thin line, possibly with wiggles in it.Although this main sequence has underpopulated regions at certaincolours (previously suggested to be ``Böhm-Vitense gaps''), suchare not visible for other clusters, and are probably spurious. Futurespace astrometry missions carry a great potential for absoluteradial-velocity determinations, insensitive to the complexities ofstellar spectra. Based on observations by the ESA Hipparcos satellite.Extended versions of Tables ef{tab1} and ef{tab2} are available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.125.8) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/446
|
|
| 19. |
- Madsen, Søren
(författare)
-
Hyades dynamics from N-body simulations: Accuracy of astrometric radial velocities from Hipparcos
- 2003
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 401:2, s. 565-576
-
Tidskriftsartikel (refereegranskat)abstract
- The internal velocity structure in the Hyades cluster as seen byHipparcos is compared with realistic N-body simulations using the NBODY6code, which includes binary interaction, stellar evolution and theGalactic tidal field. The model allows to estimate reliably the accuracyof astrometric radial velocities in the Hyades as derived by Lindegrenet al. (cite{lindegren00}) and Madsen et al. (cite{madsen02}) fromHipparcos data, by applying the same estimation procedure on thesimulated data. The simulations indicate that the current clustervelocity dispersion decreases from 0.35 km s-1 at the clustercentre to a minimum of 0.20 km s-1 at 8 pc radius (2-3 coreradii), from where it slightly increases outwards. A clear negativecorrelation between dispersion and stellar mass is seen in the centralpart of the cluster but is almost absent beyond a radius of 3 pc. Itfollows that the (internal) standard error of the astrometric radialvelocities relative to the cluster centroid may be as small as 0.2 kms-1 for a suitable selection of stars, while a total(external) standard error of 0.6 km s-1 is found when theuncertainty of the bulk motion of the cluster is included. Attempts tosee structure in the velocity dispersion using observational data fromHipparcos and Tycho-2 are inconclusive.Based on observations by the ESA Hipparcos satellite, and on the N-bodycode NBODY6 by Sverre Aarseth, publicly available atftp://ftp.ast.cam.ac.uk/pub/sverre/
|
|
| 20. |
- Madsen, Søren, et al.
(författare)
-
Intrinsic spectral blueshifts in rapidly rotating stars?
- 2003
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 411:3, s. 581-586
-
Tidskriftsartikel (refereegranskat)abstract
- Spectroscopic radial velocities for several nearby open clusters suggestthat spectra of (especially earlier-type) rapidly rotating stars aresystematically blueshifted by 3 km s-1 or more, relative tothe spectra of slowly rotating ones. Comparisons with astrometricallydetermined radial motions in the Hyades suggests this to be an absoluteblueshift, relative to wavelengths naively expected from stellar radialmotion and gravitational redshift. Analogous trends are seen also inmost other clusters studied (Pleiades, Coma Berenices, Praesepe, alphaPersei, IC 2391, NGC 6475, IC 4665, NGC 1976 and NGC 2516). Possiblemechanisms are discussed, including photospheric convection, stellarpulsation, meridional circulation, and shock-wave propagation, as wellas effects caused by template mismatch in determining wavelengthdisplacements. For early-type stars, a plausible mechanism is shock-wavepropagation upward through the photospheric line-forming regions. Suchwavelength shifts thus permit studies of certain types of stellaratmospheric dynamics and - irrespective of their cause - may influencededuced open-cluster membership (when selected from common velocity) anddeduced cluster dynamics (some types of stars might show fortuitousvelocity patterns).
|
|
| 21. |
- Madsen, Søren
(författare)
-
Radial Velocities Without Spectroscopy -Astrometric determination of stellar radial motion
- 2002
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work demonstrates the determination of absolute stellar radial velocities from geometrical principles, i.e. using astrometry. Such `astrometric radial velocities' are obtained independently of spectroscopic information. While spectroscopic radial velocities are affected by line shifts from astrophysical processes on the stellar surfaces, by gravitational redshift and various other effects, astrometric radial velocities are not. Comparison between these two types of radial velocities therefore makes it possible to study certain stellar phenomena if the accuracies are good enough. Astrometric radial velocities of sufficient accuracy have indeed come within reach for stars in the Hyades cluster and a few more moving clusters, thanks to the space astrometry mission Hipparcos. The thesis consists of two parts. The first gives a brief background and explanation of the method used to derive astrometric radial velocities, and highlights some of the results. The second part consists of six research papers briefly summarised below. In Papers I and II some early results and expectations are outlined. It is demonstrated that the parallaxes for the cluster stars are considerable improved by the method. The expected effects when comparing astrometric and spectroscopic radial velocities are described. Papers III, IV and V give a systematic exploration of the concept of astrometric radial velocities and their determination in practice. In Paper III, various possibilities for their current and future determination are discussed. Only in nearby open clusters OB associations is it possible to reach accuracies at the sub-km/s level with available astrometric data. In Paper IV the kinematic cluster modelling is further developed and described in detail. Possible biases are investigated using Monte Carlo simulations. The Hyades is used as an example in applying the method. Paper V presents results in the form of astrometric radial velocities and improved parallaxes for stars in five open clusters and five OB associations. In Paper VI, extensive Monte Carlo modelling of the Hyades cluster and its observation by Hipparcos is used to study the internal velocity dispersion and how it affects the accuracy of astrometric radial velocities obtained in Paper V. For the dynamic modelling of the cluster, the N-body code NBODY6 is used, including stellar evolution. The minimum internal standard error of the astrometric radial velocities is set by the velocity dispersion at around 0.2 km/s, while the total standard error, including the uncertainty of the bulk cluster motion, is around 0.6 km/s.
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
- Strøm Rönnquist, Sebastian, et al.
(författare)
-
Frailty and osteoporosis in patients with hip fractures under the age of 60-a prospective cohort of 218 individuals
- 2022
-
Ingår i: Osteoporosis International. - : Springer Science and Business Media LLC. - 1433-2965 .- 0937-941X. ; 33:5, s. 1037-1055
-
Tidskriftsartikel (refereegranskat)abstract
- Research on younger patients with hip fractures is limited. This study adds knowledge on patient and injury characteristics, and DXA was investigated at the time of the fracture. Risk factors for osteoporosis and fractures were numerous among young patients, and osteoporosis was markedly more prevalent than in the general population.INTRODUCTION: Knowledge on younger patients with hip fractures is limited. Common preconceptions are that they suffer fractures due to high-energy trauma, alcohol or substance use disorder but not associated to osteoporosis. We aimed to descriptively analyze the characteristics of young and middle-aged patients with hip fractures and examine bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA) at the time of the fracture.METHODS: A prospective multicenter cohort study on adult patients with hip fractures below age 60 collected detailed information on patient characteristics regarding demographics, trauma mechanism, previous fractures, comorbidity and medication, and lifestyle factors. DXA results were compared to population-based reference data.RESULTS: The cohort contains 91 women and 127 men, median age 53 (IQR 47-57). Most fractures, 83%, occurred in patients aged 45-59. Two-thirds of all fractures resulted from low-energy trauma. Half of the patients had prior fractures after age 20. Thirty-four percent were healthy, 31% had one previous disease, and 35% had multiple comorbidities. Use of medication associated with increased fracture risk was 32%. Smoking was prevalent in 42%, harmful alcohol use reported by 29%, and signs of drug-related problems by 8%. Osteoporosis according to WHO criteria was found in 31%, osteopenia in 57%, and normal BMD in 12%.CONCLUSION: In patients with hip fractures below age 60, risk factors for osteoporosis and fractures were numerous. Moreover, the prevalence of osteoporosis was markedly higher than in the general population. We suggest that young and middle-aged patients with hip fractures undergo a thorough health investigation including DXA, regardless of trauma mechanism.
|
|
