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- Akiyama, Kazunori, et al.
(författare)
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First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
- 2019
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 875:1
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Tidskriftsartikel (refereegranskat)abstract
- The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. To this end, we construct a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by general relativistic ray tracing. We compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. The ring radius and ring asymmetry depend on black hole mass and spin, respectively, and both are therefore expected to be stable when observed in future EHT campaigns. Overall, the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity. If the black hole spin and M87's large scale jet are aligned, then the black hole spin vector is pointed away from Earth. Models in our library of non-spinning black holes are inconsistent with the observations as they do not produce sufficiently powerful jets. At the same time, in those models that produce a sufficiently powerful jet, the latter is powered by extraction of black hole spin energy through mechanisms akin to the Blandford-Znajek process. We briefly consider alternatives to a black hole for the central compact object. Analysis of existing EHT polarization data and data taken simultaneously at other wavelengths will soon enable new tests of the GRMHD models, as will future EHT campaigns at 230 and 345 GHz.
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- Travis, Ruth C., et al.
(författare)
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A Meta-analysis of Individual Participant Data Reveals an Association between Circulating Levels of IGF-I and Prostate Cancer Risk
- 2016
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Ingår i: Cancer Research. - 0008-5472 .- 1538-7445. ; 76:8, s. 2288-2300
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Tidskriftsartikel (refereegranskat)abstract
- The role of insulin-like growth factors (IGF) in prostate cancer development is not fully understood. To investigate the association between circulating concentrations of IGFs (IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3) and prostate cancer risk, we pooled individual participant data from 17 prospective and two cross-sectional studies, including up to 10,554 prostate cancer cases and 13,618 control participants. Conditional logistic regression was used to estimate the ORs for prostate cancer based on the study-specific fifth of each analyte. Overall, IGF-I, IGF-II, IGFBP-2, and IGFBP-3 concentrations were positively associated with prostate cancer risk (P-trend all <= 0.005), and IGFBP-1 was inversely associated weakly with risk (P-trend = 0.05). However, heterogeneity between the prospective and cross-sectional studies was evident (P-heterogeneity = 0.03), unless the analyses were restricted to prospective studies (with the exception of IGF-II, P-heterogeneity = 0.02). For prospective studies, the OR for men in the highest versus the lowest fifth of each analyte was 1.29 (95% confidence interval, 1.16-1.43) for IGF-I, 0.81 (0.68-0.96) for IGFBP-1, and 1.25 (1.12-1.40) for IGFBP-3. These associations did not differ significantly by time-to-diagnosis or tumor stage or grade. After mutual adjustment for each of the other analytes, only IGF-I remained associated with risk. Our collaborative study represents the largest pooled analysis of the relationship between prostate cancer risk and circulating concentrations of IGF-I, providing strong evidence that IGF-I is highly likely to be involved in prostate cancer development.
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- Akiyama, Kazunori, et al.
(författare)
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First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
- 2019
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 875:1
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Tidskriftsartikel (refereegranskat)abstract
- We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of similar to 40 mu as, consistent with the size and shape of the lensed photon orbit encircling the "shadow" of a supermassive black hole. The ring is persistent across four observing nights and shows enhanced brightness in the south. To assess the reliability of these results, we implemented a two-stage imaging procedure. In the first stage, four teams, each blind to the others' work, produced images of M87 using both an established method (CLEAN) and a newer technique (regularized maximum likelihood). This stage allowed us to avoid shared human bias and to assess common features among independent reconstructions. In the second stage, we reconstructed synthetic data from a large survey of imaging parameters and then compared the results with the corresponding ground truth images. This stage allowed us to select parameters objectively to use when reconstructing images of M87. Across all tests in both stages, the ring diameter and asymmetry remained stable, insensitive to the choice of imaging technique. We describe the EHT imaging procedures, the primary image features in M87, and the dependence of these features on imaging assumptions.
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- Akiyama, Kazunori, et al.
(författare)
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First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
- 2019
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 875:1
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of the properties of the central radio source in M87 using Event Horizon Telescope data obtained during the 2017 campaign. We develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) using two independent sampling algorithms that consider distinct representations of the visibility data. We show that the crescent family of models is statistically preferred over other comparably complex geometric models that we explore. We calibrate the geometric model parameters using general relativistic magnetohydrodynamic (GRMHD) models of the emission region and estimate physical properties of the source. We further fit images generated from GRMHD models directly to the data. We compare the derived emission region and black hole parameters from these analyses with those recovered from reconstructed images. There is a remarkable consistency among all methods and data sets. We find that >50% of the total flux at arcsecond scales comes from near the horizon, and that the emission is dramatically suppressed interior to this region by a factor >10, providing direct evidence of the predicted shadow of a black hole. Across all methods, we measure a crescent diameter of 42 +/- 3 mu as and constrain its fractional width to be
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- van Santen, Selveta Sanne, et al.
(författare)
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Diagnosing Metabolic Syndrome in Craniopharyngioma Patients: Body Composition versus BMI.
- 2019
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Ingår i: European journal of endocrinology. - 1479-683X. ; 181:2, s. 173-183
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Tidskriftsartikel (refereegranskat)abstract
- Craniopharyngioma patients often have poor metabolic profiles due to hypothalamic-pituitary damage. Previously, using body mass index (BMI) as obesity marker, the occurrence of the metabolic syndrome in these patients was estimated at 46%. Our aim was to determine if Dual X-ray Absorptiometry (DXA-) scan in evaluation of obesity and metabolic syndrome would be superior.Retrospective study of craniopharyngioma patients for whom DXA-scan results were available.BMI, fat percentage and fat mass index were used to evaluate obesity and as components for obesity in metabolic syndrome.Ninety-five craniopharyngioma patients were included (51% female, 49% childhood-onset disease). Metabolic syndrome occurred in 34-53 (45-51%) subjects (depending on the definition of obesity, although all definitions occurred in higher frequency than in the general population). Metabolic syndrome frequency was higher if obesity was defined by fat percentage (52% vs. 42%) or fat mass index (51% vs. 43%) compared to BMI. Misclassification appeared in 9% (fat percentage vs. BMI) and 7% (fat mass index vs. BMI) for metabolic syndrome and 29% and 13% for obesity itself, respectively. For metabolic syndrome, almost perfect agreement was found for BMI compared with fat percentage or fat mass index. For obesity, agreement was fair to moderate (BMI vs. fat percentage).Using BMI to evaluate obesity underestimates the true prevalence of metabolic syndrome in patients with craniopharyngioma. Furthermore, fat percentage contributes to a better evaluation of obesity than BMI. The contribution of DXA-scan might be limited for identification of the metabolic syndrome.
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- Wijnen, Mark, et al.
(författare)
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Excess morbidity and mortality in patients with craniopharyngioma: a hospital-based retrospective cohort study.
- 2018
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Ingår i: European journal of endocrinology. - 1479-683X. ; 178:1, s. 95-104
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Tidskriftsartikel (refereegranskat)abstract
- Most studies in patients with craniopharyngioma did not investigate morbidity and mortality relative to the general population nor evaluated risk factors for excess morbidity and mortality. Therefore, the objective of this study was to examine excess morbidity and mortality, as well as their determinants in patients with craniopharyngioma.Hospital-based retrospective cohort study conducted between 1987 and 2014.We included 144 Dutch and 80 Swedish patients with craniopharyngioma identified by a computer-based search in the medical records (105 females (47%), 112 patients with childhood-onset craniopharyngioma (50%), 3153 person-years of follow-up). Excess morbidity and mortality were analysed using standardized incidence and mortality ratios (SIRs and SMRs). Risk factors were evaluated univariably by comparing SIRs and SMRs between non-overlapping subgroups.Patients with craniopharyngioma experienced excess morbidity due to type 2 diabetes mellitus (T2DM) (SIR: 4.4, 95% confidence interval (CI): 2.8-6.8) and cerebral infarction (SIR: 4.9, 95% CI: 3.1-8.0) compared to the general population. Risks for malignant neoplasms, myocardial infarctions and fractures were not increased. Patients with craniopharyngioma also had excessive total mortality (SMR: 2.7, 95% CI: 2.0-3.8), and mortality due to circulatory (SMR: 2.3, 95% CI: 1.1-4.5) and respiratory (SMR: 6.0, 95% CI: 2.5-14.5) diseases. Female sex, childhood-onset craniopharyngioma, hydrocephalus and tumour recurrence were identified as risk factors for excess T2DM, cerebral infarction and total mortality.Patients with craniopharyngioma are at an increased risk for T2DM, cerebral infarction, total mortality and mortality due to circulatory and respiratory diseases. Female sex, childhood-onset craniopharyngioma, hydrocephalus and tumour recurrence are important risk factors.
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- Wijnen, Mark, et al.
(författare)
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The metabolic syndrome and its components in 178 patients treated for craniopharyngioma after 16 years of follow-up.
- 2018
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Ingår i: European journal of endocrinology. - 1479-683X. ; 178:1, s. 11-22
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Tidskriftsartikel (refereegranskat)abstract
- Patients with craniopharyngioma are at an increased risk for cardio- and cerebrovascular mortality. The metabolic syndrome (MetS) is an important cardiometabolic risk factor, but barely studied in patients with craniopharyngioma. We aimed to investigate the prevalence of and risk factors for the MetS and its components in patients with craniopharyngioma.Cross-sectional study with retrospective data.We studied the prevalence of and risk factors for the MetS and its components in 110 Dutch (median age 47 years, range 18-92) and 68 Swedish (median age 50 years, range 20-81) patients with craniopharyngioma with ≥3 years of follow-up (90 females (51%); 83 patients with childhood-onset craniopharyngioma (47%); median follow-up after craniopharyngioma diagnosis 16 years (range 3-62)). In Dutch patients aged 30-70 years and Swedish patients aged 45-69 years, we examined the prevalence of the MetS and its components relative to the general population.Sixty-nine (46%) of 149 patients with complete data demonstrated the MetS. Prevalence of the MetS was significantly higher in patients with craniopharyngioma compared with the general population (40% vs 26% (P<0.05) for Dutch patients; 52% vs 15% (P<0.05) for Swedish patients). Multivariable logistic regression analysis identified visual impairment as a borderline significant predictor of the MetS (OR 2.54, 95% CI 0.95-6.81; P=0.06) after adjustment for glucocorticoid replacement therapy and follow-up duration. Age, female sex, tumor location, radiological hypothalamic damage, 90Yttrium brachytherapy, glucocorticoid replacement therapy and follow-up duration significantly predicted components of the MetS.Patients with craniopharyngioma are at an increased risk for the MetS, especially patients with visual impairment.
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