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1.
  • 2021
  • swepub:Mat__t
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2.
  • Bravo, L, et al. (author)
  • 2021
  • swepub:Mat__t
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3.
  • Tabiri, S, et al. (author)
  • 2021
  • swepub:Mat__t
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4.
  • Niemi, MEK, et al. (author)
  • 2021
  • swepub:Mat__t
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5.
  • Kanai, M, et al. (author)
  • 2023
  • swepub:Mat__t
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6.
  • Algaba, Juan-Carlos, et al. (author)
  • Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
  • 2021
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 911:1
  • Research review (peer-reviewed)abstract
    • In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M o˙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded.
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7.
  • Khatri, C, et al. (author)
  • Outcomes after perioperative SARS-CoV-2 infection in patients with proximal femoral fractures: an international cohort study
  • 2021
  • In: BMJ open. - : BMJ. - 2044-6055. ; 11:11, s. e050830-
  • Journal article (peer-reviewed)abstract
    • Studies have demonstrated high rates of mortality in people with proximal femoral fracture and SARS-CoV-2, but there is limited published data on the factors that influence mortality for clinicians to make informed treatment decisions. This study aims to report the 30-day mortality associated with perioperative infection of patients undergoing surgery for proximal femoral fractures and to examine the factors that influence mortality in a multivariate analysis.SettingProspective, international, multicentre, observational cohort study.ParticipantsPatients undergoing any operation for a proximal femoral fracture from 1 February to 30 April 2020 and with perioperative SARS-CoV-2 infection (either 7 days prior or 30-day postoperative).Primary outcome30-day mortality. Multivariate modelling was performed to identify factors associated with 30-day mortality.ResultsThis study reports included 1063 patients from 174 hospitals in 19 countries. Overall 30-day mortality was 29.4% (313/1063). In an adjusted model, 30-day mortality was associated with male gender (OR 2.29, 95% CI 1.68 to 3.13, p<0.001), age >80 years (OR 1.60, 95% CI 1.1 to 2.31, p=0.013), preoperative diagnosis of dementia (OR 1.57, 95% CI 1.15 to 2.16, p=0.005), kidney disease (OR 1.73, 95% CI 1.18 to 2.55, p=0.005) and congestive heart failure (OR 1.62, 95% CI 1.06 to 2.48, p=0.025). Mortality at 30 days was lower in patients with a preoperative diagnosis of SARS-CoV-2 (OR 0.6, 95% CI 0.6 (0.42 to 0.85), p=0.004). There was no difference in mortality in patients with an increase to delay in surgery (p=0.220) or type of anaesthetic given (p=0.787).ConclusionsPatients undergoing surgery for a proximal femoral fracture with a perioperative infection of SARS-CoV-2 have a high rate of mortality. This study would support the need for providing these patients with individualised medical and anaesthetic care, including medical optimisation before theatre. Careful preoperative counselling is needed for those with a proximal femoral fracture and SARS-CoV-2, especially those in the highest risk groups.Trial registration numberNCT04323644
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8.
  • Downey, Harriet, et al. (author)
  • Training future generations to deliver evidence-based conservation and ecosystem management
  • 2021
  • In: Ecological Solutions and Evidence. - : Wiley. - 2688-8319. ; 2:1
  • Research review (peer-reviewed)abstract
    • 1. To be effective, the next generation of conservation practitioners and managers need to be critical thinkers with a deep understanding of how to make evidence-based decisions and of the value of evidence synthesis.2. If, as educators, we do not make these priorities a core part of what we teach, we are failing to prepare our students to make an effective contribution to conservation practice.3. To help overcome this problem we have created open access online teaching materials in multiple languages that are stored in Applied Ecology Resources. So far, 117 educators from 23 countries have acknowledged the importance of this and are already teaching or about to teach skills in appraising or using evidence in conservation decision-making. This includes 145 undergraduate, postgraduate or professional development courses.4. We call for wider teaching of the tools and skills that facilitate evidence-based conservation and also suggest that providing online teaching materials in multiple languages could be beneficial for improving global understanding of other subject areas.
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9.
  • Janssen, Michael, et al. (author)
  • Event Horizon Telescope observations of the jet launching and collimation in Centaurus A
  • 2021
  • In: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 5:10, s. 1017-1028
  • Journal article (peer-reviewed)abstract
    • Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources1. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses5,6.
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10.
  • Power, M. J., et al. (author)
  • Changes in fire regimes since the Last Glacial Maximum : an assessment based on a global synthesis and analysis of charcoal data
  • 2008
  • In: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 30:7-8, s. 887-907
  • Journal article (peer-reviewed)abstract
    • Fire activity has varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesized sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In North America, Europe and southern South America, charcoal records indicate less-than-present fire activity during the deglacial period, from 21,000 to ∼11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greater-than-present fire activity from ∼19,000 to ∼17,000 cal yr BP and most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to ∼13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8,000 to ∼3,000 cal yr BP, Indonesia and Australia from 11,000 to 4,000 cal yr BP, and southern South America from 6,000 to 3,000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the post-glacial period. These complex patterns can largely be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load.
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11.
  • Akiyama, Kazunori, et al. (author)
  • First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
  • 2023
  • In: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 957:2
  • Journal article (peer-reviewed)abstract
    • Event Horizon Telescope (EHT) observations have revealed a bright ring of emission around the supermassive black hole at the center of the M87 galaxy. EHT images in linear polarization have further identified a coherent spiral pattern around the black hole, produced from ordered magnetic fields threading the emitting plasma. Here we present the first analysis of circular polarization using EHT data, acquired in 2017, which can potentially provide additional insights into the magnetic fields and plasma composition near the black hole. Interferometric closure quantities provide convincing evidence for the presence of circularly polarized emission on event-horizon scales. We produce images of the circular polarization using both traditional and newly developed methods. All methods find a moderate level of resolved circular polarization across the image (〈|v|〉 < 3.7%), consistent with the low image-integrated circular polarization fraction measured by the Atacama Large Millimeter/submillimeter Array (|vint| < 1%). Despite this broad agreement, the methods show substantial variation in the morphology of the circularly polarized emission, indicating that our conclusions are strongly dependent on the imaging assumptions because of the limited baseline coverage, uncertain telescope gain calibration, and weakly polarized signal. We include this upper limit in an updated comparison to general relativistic magnetohydrodynamic simulation models. This analysis reinforces the previously reported preference for magnetically arrested accretion flow models. We find that most simulations naturally produce a low level of circular polarization consistent with our upper limit and that Faraday conversion is likely the dominant production mechanism for circular polarization at 230 GHz in M87*
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12.
  • Georgiev, Boris, et al. (author)
  • A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows
  • 2022
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Journal article (peer-reviewed)abstract
    • We present a framework for characterizing the spatiotemporal power spectrum of the variability expected from the horizon-scale emission structure around supermassive black holes, and we apply this framework to a library of general relativistic magnetohydrodynamic (GRMHD) simulations and associated general relativistic ray-traced images relevant for Event Horizon Telescope (EHT) observations of Sgr A*. We find that the variability power spectrum is generically a red-noise process in both the temporal and spatial dimensions, with the peak in power occurring on the longest timescales and largest spatial scales. When both the time-averaged source structure and the spatially integrated light-curve variability are removed, the residual power spectrum exhibits a universal broken power-law behavior. On small spatial frequencies, the residual power spectrum rises as the square of the spatial frequency and is proportional to the variance in the centroid of emission. Beyond some peak in variability power, the residual power spectrum falls as that of the time-averaged source structure, which is similar across simulations; this behavior can be naturally explained if the variability arises from a multiplicative random field that has a steeper high-frequency power-law index than that of the time-averaged source structure. We briefly explore the ability of power spectral variability studies to constrain physical parameters relevant for the GRMHD simulations, which can be scaled to provide predictions for black holes in a range of systems in the optically thin regime. We present specific expectations for the behavior of the M87* and Sgr A* accretion flows as observed by the EHT.
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13.
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14.
  • Roelofs, F., et al. (author)
  • Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes
  • 2023
  • In: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 957:2
  • Journal article (peer-reviewed)abstract
    • The Event Horizon Telescope (EHT) is a millimeter very long baseline interferometry (VLBI) array that has imaged the apparent shadows of the supermassive black holes M87* and Sagittarius A*. Polarimetric data from these observations contain a wealth of information on the black hole and accretion flow properties. In this work, we develop polarimetric geometric modeling methods for mm-VLBI data, focusing on approaches that fit data products with differing degrees of invariance to broad classes of calibration errors. We establish a fitting procedure using a polarimetric “m-ring” model to approximate the image structure near a black hole. By fitting this model to synthetic EHT data from general relativistic magnetohydrodynamic models, we show that the linear and circular polarization structure can be successfully approximated with relatively few model parameters. We then fit this model to EHT observations of M87* taken in 2017. In total intensity and linear polarization, the m-ring fits are consistent with previous results from imaging methods. In circular polarization, the m-ring fits indicate the presence of event-horizon-scale circular polarization structure, with a persistent dipolar asymmetry and orientation across several days. The same structure was recovered independently of observing band, used data products, and model assumptions. Despite this broad agreement, imaging methods do not produce similarly consistent results. Our circular polarization results, which imposed additional assumptions on the source structure, should thus be interpreted with some caution. Polarimetric geometric modeling provides a useful and powerful method to constrain the properties of horizon-scale polarized emission, particularly for sparse arrays like the EHT.
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15.
  • Akiyama, Kazunori, et al. (author)
  • First M87 Event Horizon Telescope Results. VII. Polarization of the Ring
  • 2021
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 910:1
  • Journal article (peer-reviewed)abstract
    • In 2017 April, the Event Horizon Telescope (EHT) observed the near-horizon region around the supermassive black hole at the core of the M87 galaxy. These 1.3 mm wavelength observations revealed a compact asymmetric ring-like source morphology. This structure originates from synchrotron emission produced by relativistic plasma located in the immediate vicinity of the black hole. Here we present the corresponding linear-polarimetric EHT images of the center of M87. We find that only a part of the ring is significantly polarized. The resolved fractional linear polarization has a maximum located in the southwest part of the ring, where it rises to the level of similar to 15%. The polarization position angles are arranged in a nearly azimuthal pattern. We perform quantitative measurements of relevant polarimetric properties of the compact emission and find evidence for the temporal evolution of the polarized source structure over one week of EHT observations. The details of the polarimetric data reduction and calibration methodology are provided. We carry out the data analysis using multiple independent imaging and modeling techniques, each of which is validated against a suite of synthetic data sets. The gross polarimetric structure and its apparent evolution with time are insensitive to the method used to reconstruct the image. These polarimetric images carry information about the structure of the magnetic fields responsible for the synchrotron emission. Their physical interpretation is discussed in an accompanying publication.
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16.
  • Akiyama, Kazunori, et al. (author)
  • First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon
  • 2021
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 910:1
  • Journal article (peer-reviewed)abstract
    • Event Horizon Telescope (EHT) observations at 230 GHz have now imaged polarized emission around the supermassive black hole in M87 on event-horizon scales. This polarized synchrotron radiation probes the structure of magnetic fields and the plasma properties near the black hole. Here we compare the resolved polarization structure observed by the EHT, along with simultaneous unresolved observations with the Atacama Large Millimeter/submillimeter Array, to expectations from theoretical models. The low fractional linear polarization in the resolved image suggests that the polarization is scrambled on scales smaller than the EHT beam, which we attribute to Faraday rotation internal to the emission region. We estimate the average density n(e) similar to 10(4-7) cm(-3), magnetic field strength B similar to 1-30 G, and electron temperature T-e similar to (1-12) x 10(10) K of the radiating plasma in a simple one-zone emission model. We show that the net azimuthal linear polarization pattern may result from organized, poloidal magnetic fields in the emission region. In a quantitative comparison with a large library of simulated polarimetric images from general relativistic magnetohydrodynamic (GRMHD) simulations, we identify a subset of physical models that can explain critical features of the polarimetric EHT observations while producing a relativistic jet of sufficient power. The consistent GRMHD models are all of magnetically arrested accretion disks, where near-horizon magnetic fields are dynamically important. We use the models to infer a mass accretion rate onto the black hole in M87 of (3-20) x 10(-4) M yr(-1).
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17.
  • Akiyama, Kazunori, et al. (author)
  • First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration
  • 2022
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Journal article (peer-reviewed)abstract
    • We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5-11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of similar to 50 mu as, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.
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18.
  • Akiyama, Kazunori, et al. (author)
  • First Sagittarius A* Event Horizon Telescope Results. III. Imaging of the Galactic Center Supermassive Black Hole
  • 2022
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Journal article (peer-reviewed)abstract
    • We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A* taken with the Event Horizon Telescope in 2017 April at a wavelength of 1.3 mm. Imaging of Sgr A* has been conducted through surveys over a wide range of imaging assumptions using the classical CLEAN algorithm, regularized maximum likelihood methods, and a Bayesian posterior sampling method. Different prescriptions have been used to account for scattering effects by the interstellar medium toward the Galactic center. Mitigation of the rapid intraday variability that characterizes Sgr A* has been carried out through the addition of a "variability noise budget" in the observed visibilities, facilitating the reconstruction of static full-track images. Our static reconstructions of Sgr A* can be clustered into four representative morphologies that correspond to ring images with three different azimuthal brightness distributions and a small cluster that contains diverse nonring morphologies. Based on our extensive analysis of the effects of sparse (u, v)-coverage, source variability, and interstellar scattering, as well as studies of simulated visibility data, we conclude that the Event Horizon Telescope Sgr A* data show compelling evidence for an image that is dominated by a bright ring of emission with a ring diameter of similar to 50 mu as, consistent with the expected "shadow" of a 4 x 10(6) M (circle dot) black hole in the Galactic center located at a distance of 8 kpc.
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19.
  • Akiyama, Kazunori, et al. (author)
  • First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass
  • 2022
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Journal article (peer-reviewed)abstract
    • In this paper we quantify the temporal variability and image morphology of the horizon-scale emission from Sgr A*, as observed by the EHT in 2017 April at a wavelength of 1.3 mm. We find that the Sgr A* data exhibit variability that exceeds what can be explained by the uncertainties in the data or by the effects of interstellar scattering. The magnitude of this variability can be a substantial fraction of the correlated flux density, reaching similar to 100% on some baselines. Through an exploration of simple geometric source models, we demonstrate that ring-like morphologies provide better fits to the Sgr A* data than do other morphologies with comparable complexity. We develop two strategies for fitting static geometric ring models to the time-variable Sgr A* data; one strategy fits models to short segments of data over which the source is static and averages these independent fits, while the other fits models to the full data set using a parametric model for the structural variability power spectrum around the average source structure. Both geometric modeling and image-domain feature extraction techniques determine the ring diameter to be 51.8 +/- 2.3 mu as (68% credible intervals), with the ring thickness constrained to have an FWHM between similar to 30% and 50% of the ring diameter. To bring the diameter measurements to a common physical scale, we calibrate them using synthetic data generated from GRMHD simulations. This calibration constrains the angular size of the gravitational radius to be 4.8(-0.7)(+1.4) mu as, which we combine with an independent distance measurement from maser parallaxes to determine the mass of Sgr A* to be 4.0(-0.6)(+1.1) x 10(6) M-circle dot.
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20.
  • Akiyama, Kazunori, et al. (author)
  • First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
  • 2022
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Journal article (peer-reviewed)abstract
    • In this paper we provide a first physical interpretation for the Event Horizon Telescope's (EHT) 2017 observations of Sgr A*. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT observations from radio to X-ray wavelengths to predictions from a library of models based on time-dependent general relativistic magnetohydrodynamics simulations, including aligned, tilted, and stellar-wind-fed simulations; radiative transfer is performed assuming both thermal and nonthermal electron distribution functions. We test the models against 11 constraints drawn from EHT 230 GHz data and observations at 86 GHz, 2.2 mu m, and in the X-ray. All models fail at least one constraint. Light-curve variability provides a particularly severe constraint, failing nearly all strongly magnetized (magnetically arrested disk (MAD)) models and a large fraction of weakly magnetized models. A number of models fail only the variability constraints. We identify a promising cluster of these models, which are MAD and have inclination i <= 30 degrees. They have accretion rate (5.2-9.5) x 10(-9) M (circle dot) yr(-1), bolometric luminosity (6.8-9.2) x 10(35) erg s(-1), and outflow power (1.3-4.8) x 10(38) erg s(-1). We also find that all models with i >= 70 degrees fail at least two constraints, as do all models with equal ion and electron temperature; exploratory, nonthermal model sets tend to have higher 2.2 mu m flux density; and the population of cold electrons is limited by X-ray constraints due to the risk of bremsstrahlung overproduction. Finally, we discuss physical and numerical limitations of the models, highlighting the possible importance of kinetic effects and duration of the simulations.
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21.
  • Akiyama, Kazunori, et al. (author)
  • First Sagittarius A* Event Horizon Telescope Results. VI. Testing the Black Hole Metric
  • 2022
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Journal article (peer-reviewed)abstract
    • Astrophysical black holes are expected to be described by the Kerr metric. This is the only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies Einstein's equations and does not have pathologies outside of the event horizon. We present new constraints on potential deviations from the Kerr prediction based on 2017 EHT observations of Sagittarius A* (Sgr A*). We calibrate the relationship between the geometrically defined black hole shadow and the observed size of the ring-like images using a library that includes both Kerr and non-Kerr simulations. We use the exquisite prior constraints on the mass-to-distance ratio for Sgr A* to show that the observed image size is within similar to 10% of the Kerr predictions. We use these bounds to constrain metrics that are parametrically different from Kerr, as well as the charges of several known spacetimes. To consider alternatives to the presence of an event horizon, we explore the possibility that Sgr A* is a compact object with a surface that either absorbs and thermally reemits incident radiation or partially reflects it. Using the observed image size and the broadband spectrum of Sgr A*, we conclude that a thermal surface can be ruled out and a fully reflective one is unlikely. We compare our results to the broader landscape of gravitational tests. Together with the bounds found for stellar-mass black holes and the M87 black hole, our observations provide further support that the external spacetimes of all black holes are described by the Kerr metric, independent of their mass.
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22.
  • Akiyama, Kazunori, et al. (author)
  • First Sagittarius A∗ Event Horizon Telescope Results. VII. Polarization of the Ring
  • 2024
  • In: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 964:2
  • Journal article (peer-reviewed)abstract
    • The Event Horizon Telescope observed the horizon-scale synchrotron emission region around the Galactic center supermassive black hole, Sagittarius A∗ (Sgr A∗), in 2017. These observations revealed a bright, thick ring morphology with a diameter of 51.8 ± 2.3 μas and modest azimuthal brightness asymmetry, consistent with the expected appearance of a black hole with mass M≈ 4 × 106 M⊙. From these observations, we present the first resolved linear and circular polarimetric images of Sgr A∗. The linear polarization images demonstrate that the emission ring is highly polarized, exhibiting a prominent spiral electric vector polarization angle pattern with a peak fractional polarization of ∼40% in the western portion of the ring. The circular polarization images feature a modestly (∼5%°-10%) polarized dipole structure along the emission ring, with negative circular polarization in the western region and positive circular polarization in the eastern region, although our methods exhibit stronger disagreement than for linear polarization. We analyze the data using multiple independent imaging and modeling methods, each of which is validated using a standardized suite of synthetic data sets. While the detailed spatial distribution of the linear polarization along the ring remains uncertain owing to the intrinsic variability of the source, the spiraling polarization structure is robust to methodological choices. The degree and orientation of the linear polarization provide stringent constraints for the black hole and its surrounding magnetic fields, which we discuss in an accompanying publication.
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23.
  • Akiyama, Kazunori, et al. (author)
  • First Sagittarius A∗ Event Horizon Telescope Results. VIII. Physical Interpretation of the Polarized Ring
  • 2024
  • In: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 964:2
  • Journal article (peer-reviewed)abstract
    • In a companion paper, we present the first spatially resolved polarized image of Sagittarius A∗ on event horizon scales, captured using the Event Horizon Telescope, a global very long baseline interferometric array operating at a wavelength of 1.3 mm. Here we interpret this image using both simple analytic models and numerical general relativistic magnetohydrodynamic (GRMHD) simulations. The large spatially resolved linear polarization fraction (24%-28%, peaking at ∼40%) is the most stringent constraint on parameter space, disfavoring models that are too Faraday depolarized. Similar to our studies of M87∗, polarimetric constraints reinforce a preference for GRMHD models with dynamically important magnetic fields. Although the spiral morphology of the polarization pattern is known to constrain the spin and inclination angle, the time-variable rotation measure (RM) of Sgr A∗ (equivalent to ≈ 46° ± 12° rotation at 228 GHz) limits its present utility as a constraint. If we attribute the RM to internal Faraday rotation, then the motion of accreting material is inferred to be counterclockwise, contrary to inferences based on historical polarized flares, and no model satisfies all polarimetric and total intensity constraints. On the other hand, if we attribute the mean RM to an external Faraday screen, then the motion of accreting material is inferred to be clockwise, and one model passes all applied total intensity and polarimetric constraints: a model with strong magnetic fields, a spin parameter of 0.94, and an inclination of 150°. We discuss how future 345 GHz and dynamical imaging will mitigate our present uncertainties and provide additional constraints on the black hole and its accretion flow.
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24.
  • Akiyama, Kazunori, et al. (author)
  • The persistent shadow of the supermassive black hole of M 87: I. Observations, calibration, imaging, and analysis*
  • 2024
  • In: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 681
  • Journal article (peer-reviewed)abstract
    • In April 2019, the Event Horizon Telescope (EHT) Collaboration reported the first-ever event-horizon-scale images of a black hole, resolving the central compact radio source in the giant elliptical galaxy M 87. These images reveal a ring with a southerly brightness distribution and a diameter of ∼42 μas, consistent with the predicted size and shape of a shadow produced by the gravitationally lensed emission around a supermassive black hole. These results were obtained as part of the April 2017 EHT observation campaign, using a global very long baseline interferometric radio array operating at a wavelength of 1.3 mm. Here, we present results based on the second EHT observing campaign, taking place in April 2018 with an improved array, wider frequency coverage, and increased bandwidth. In particular, the additional baselines provided by the Greenland telescope improved the coverage of the array. Multiyear EHT observations provide independent snapshots of the horizon-scale emission, allowing us to confirm the persistence, size, and shape of the black hole shadow, and constrain the intrinsic structural variability of the accretion flow. We have confirmed the presence of an asymmetric ring structure, brighter in the southwest, with a median diameter of 43.3-3.1+1.5 μas. The diameter of the 2018 ring is remarkably consistent with the diameter obtained from the previous 2017 observations. On the other hand, the position angle of the brightness asymmetry in 2018 is shifted by about 30 relative to 2017. The perennial persistence of the ring and its diameter robustly support the interpretation that the ring is formed by lensed emission surrounding a Kerr black hole with a mass ∼6.5× 109M. The significant change in the ring brightness asymmetry implies a spin axis that is more consistent with the position angle of the large-scale jet.
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25.
  • Broderick, Avery E., et al. (author)
  • Characterizing and Mitigating Intraday Variability: Reconstructing Source Structure in Accreting Black Holes with mm-VLBI
  • 2022
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Journal article (peer-reviewed)abstract
    • The extraordinary physical resolution afforded by the Event Horizon Telescope has opened a window onto the astrophysical phenomena unfolding on horizon scales in two known black holes, M87* and Sgr A*. However, with this leap in resolution has come a new set of practical complications. Sgr A* exhibits intraday variability that violates the assumptions underlying Earth aperture synthesis, limiting traditional image reconstruction methods to short timescales and data sets with very sparse (u, v) coverage. We present a new set of tools to detect and mitigate this variability. We develop a data-driven, model-agnostic procedure to detect and characterize the spatial structure of intraday variability. This method is calibrated against a large set of mock data sets, producing an empirical estimator of the spatial power spectrum of the brightness fluctuations. We present a novel Bayesian noise modeling algorithm that simultaneously reconstructs an average image and statistical measure of the fluctuations about it using a parameterized form for the excess variance in the complex visibilities not otherwise explained by the statistical errors. These methods are validated using a variety of simulated data, including general relativistic magnetohydrodynamic simulations appropriate for Sgr A* and M87*. We find that the reconstructed source structure and variability are robust to changes in the underlying image model. We apply these methods to the 2017 EHT observations of M87*, finding evidence for variability across the EHT observing campaign. The variability mitigation strategies presented are widely applicable to very long baseline interferometry observations of variable sources generally, for which they provide a data-informed averaging procedure and natural characterization of inter-epoch image consistency.
  •  
26.
  • Farah, Joseph, et al. (author)
  • Selective Dynamical Imaging of Interferometric Data
  • 2022
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Journal article (peer-reviewed)abstract
    • Recent developments in very long baseline interferometry (VLBI) have made it possible for the Event Horizon Telescope (EHT) to resolve the innermost accretion flows of the largest supermassive black holes on the sky. The sparse nature of the EHT's (u, v)-coverage presents a challenge when attempting to resolve highly time-variable sources. We demonstrate that the changing (u, v)-coverage of the EHT can contain regions of time over the course of a single observation that facilitate dynamical imaging. These optimal time regions typically have projected baseline distributions that are approximately angularly isotropic and radially homogeneous. We derive a metric of coverage quality based on baseline isotropy and density that is capable of ranking array configurations by their ability to produce accurate dynamical reconstructions. We compare this metric to existing metrics in the literature and investigate their utility by performing dynamical reconstructions on synthetic data from simulated EHT observations of sources with simple orbital variability. We then use these results to make recommendations for imaging the 2017 EHT Sgr A* data set.
  •  
27.
  • Goddi, Ciriaco, et al. (author)
  • Polarimetric Properties of Event Horizon Telescope Targets from ALMA
  • 2021
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 910:1
  • Journal article (peer-reviewed)abstract
    • We present the results from a full polarization study carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) during the first Very Long Baseline Interferometry (VLBI) campaign, which was conducted in 2017 April in the lambda 3 mm and lambda 1.3 mm bands, in concert with the Global mm-VLBI Array (GMVA) and the Event Horizon Telescope (EHT), respectively. We determine the polarization and Faraday properties of all VLBI targets, including Sgr A*, M87, and a dozen radio-loud active galactic nuclei (AGNs), in the two bands at several epochs in a time window of 10 days. We detect high linear polarization fractions (2%-15%) and large rotation measures (RM > 10(3.3)-10(5.5) rad m(-2)), confirming the trends of previous AGN studies at millimeter wavelengths. We find that blazars are more strongly polarized than other AGNs in the sample, while exhibiting (on average) order-of-magnitude lower RM values, consistent with the AGN viewing angle unification scheme. For Sgr A* we report a mean RM of (-4.2 0.3) x 10(5) rad m(-2) at 1.3 mm, consistent with measurements over the past decade and, for the first time, an RM of (-2.1 0.1) x 10(5) rad m(-2) at 3 mm, suggesting that about half of the Faraday rotation at 1.3 mm may occur between the 3 mm photosphere and the 1.3 mm source. We also report the first unambiguous measurement of RM toward the M87 nucleus at millimeter wavelengths, which undergoes significant changes in magnitude and sign reversals on a one year timescale, spanning the range from -1.2 to 0.3 x 10(5) rad m(-2) at 3 mm and -4.1 to 1.5 x 10(5) rad m(-2) at 1.3 mm. Given this time variability, we argue that, unlike the case of Sgr A*, the RM in M87 does not provide an accurate estimate of the mass accretion rate onto the black hole. We put forward a two-component model, comprised of a variable compact region and a static extended region, that can simultaneously explain the polarimetric properties observed by both the EHT (on horizon scales) and ALMA (which observes the combined emission from both components). These measurements provide critical constraints for the calibration, analysis, and interpretation of simultaneously obtained VLBI data with the EHT and GMVA.
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28.
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29.
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30.
  • Issaoun, Sara, et al. (author)
  • Resolving the Inner Parsec of the Blazar J1924-2914 with the Event Horizon Telescope
  • 2022
  • In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 934:2
  • Journal article (peer-reviewed)abstract
    • The blazar J1924-2914 is a primary Event Horizon Telescope (EHT) calibrator for the Galactic center's black hole Sagittarius A*. Here we present the first total and linearly polarized intensity images of this source obtained with the unprecedented 20 mu as resolution of the EHT. J1924-2914 is a very compact flat-spectrum radio source with strong optical variability and polarization. In April 2017 the source was observed quasi-simultaneously with the EHT (April 5-11), the Global Millimeter VLBI Array (April 3), and the Very Long Baseline Array (April 28), giving a novel view of the source at four observing frequencies, 230, 86, 8.7, and 2.3 GHz. These observations probe jet properties from the subparsec to 100 pc scales. We combine the multifrequency images of J1924-2914 to study the source morphology. We find that the jet exhibits a characteristic bending, with a gradual clockwise rotation of the jet projected position angle of about 90 degrees between 2.3 and 230 GHz. Linearly polarized intensity images of J1924-2914 with the extremely fine resolution of the EHT provide evidence for ordered toroidal magnetic fields in the blazar compact core.
  •  
31.
  • Jorstad, S.G., et al. (author)
  • The Event Horizon Telescope Image of the Quasar NRAO 530
  • 2023
  • In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 943:2
  • Journal article (peer-reviewed)abstract
    • We report on the observations of the quasar NRAO 530 with the Event Horizon Telescope (EHT) on 2017 April 5-7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*. At z = 0.902, this is the most distant object imaged by the EHT so far. We reconstruct the first images of the source at 230 GHz, at an unprecedented angular resolution of similar to 20 mu as, both in total intensity and in linear polarization (LP). We do not detect source variability, allowing us to represent the whole data set with static images. The images reveal a bright feature located on the southern end of the jet, which we associate with the core. The feature is linearly polarized, with a fractional polarization of similar to 5%-8%, and it has a substructure consisting of two components. Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. The jet extends over 60 mu as along a position angle similar to -28 degrees. It includes two features with orthogonal directions of polarization (electric vector position angle), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. The outermost feature has a particularly high degree of LP, suggestive of a nearly uniform magnetic field. Future EHT observations will probe the variability of the jet structure on microarcsecond scales, while simultaneous multiwavelength monitoring will provide insight into the high-energy emission origin.
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32.
  • Narayan, Ramesh, et al. (author)
  • The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole
  • 2021
  • In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 912:1
  • Journal article (peer-reviewed)abstract
    • Synchrotron radiation from hot gas near a black hole results in a polarized image. The image polarization is determined by effects including the orientation of the magnetic field in the emitting region, relativistic motion of the gas, strong gravitational lensing by the black hole, and parallel transport in the curved spacetime. We explore these effects using a simple model of an axisymmetric, equatorial accretion disk around a Schwarzschild black hole. By using an approximate expression for the null geodesics derived by Beloborodov and conservation of the Walker-Penrose constant, we provide analytic estimates for the image polarization. We test this model using currently favored general relativistic magnetohydrodynamic simulations of M87*, using ring parameters given by the simulations. For a subset of these with modest Faraday effects, we show that the ring model broadly reproduces the polarimetric image morphology. Our model also predicts the polarization evolution for compact flaring regions, such as those observed from Sgr A* with GRAVITY. With suitably chosen parameters, our simple model can reproduce the EVPA pattern and relative polarized intensity in Event Horizon Telescope images of M87*. Under the physically motivated assumption that the magnetic field trails the fluid velocity, this comparison is consistent with the clockwise rotation inferred from total intensity images.
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33.
  • Satapathy, Kaushik, et al. (author)
  • The Variability of the Black Hole Image in M87 at the Dynamical Timescale
  • 2022
  • In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 925:1
  • Journal article (peer-reviewed)abstract
    • The black hole images obtained with the Event Horizon Telescope (EHT) are expected to be variable at the dynamical timescale near their horizons. For the black hole at the center of the M87 galaxy, this timescale (5-61 days) is comparable to the 6 day extent of the 2017 EHT observations. Closure phases along baseline triangles are robust interferometric observables that are sensitive to the expected structural changes of the images but are free of station-based atmospheric and instrumental errors. We explored the day-to-day variability in closure-phase measurements on all six linearly independent nontrivial baseline triangles that can be formed from the 2017 observations. We showed that three triangles exhibit very low day-to-day variability, with a dispersion of similar to 3 degrees-5 degrees. The only triangles that exhibit substantially higher variability (similar to 90 degrees-180 degrees) are the ones with baselines that cross the visibility amplitude minima on the u-v plane, as expected from theoretical modeling. We used two sets of general relativistic magnetohydrodynamic simulations to explore the dependence of the predicted variability on various black hole and accretion-flow parameters. We found that changing the magnetic field configuration, electron temperature model, or black hole spin has a marginal effect on the model consistency with the observed level of variability. On the other hand, the most discriminating image characteristic of models is the fractional width of the bright ring of emission. Models that best reproduce the observed small level of variability are characterized by thin ring-like images with structures dominated by gravitational lensing effects and thus least affected by turbulence in the accreting plasmas.
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34.
  • Torne, Pablo, et al. (author)
  • A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set
  • 2023
  • In: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 959:1
  • Journal article (peer-reviewed)abstract
    • In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz (lambda = 1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT data sets. The high observing frequency means that pulsars-which typically exhibit steep emission spectra-are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope, and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the fast folding algorithm, and single-pulse searches targeting both pulsars and burst-like transient emission. We use the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction (less than or similar to 2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region.
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35.
  • Weissler, E. Hope, et al. (author)
  • Understanding Study Drug Discontinuation Through EUCLID
  • 2022
  • In: Frontiers in Cardiovascular Medicine. - : Frontiers Media S.A.. - 2297-055X. ; 9
  • Journal article (peer-reviewed)abstract
    • Introduction: Disparities in the care and outcomes of peripheral artery disease (PAD) have been well-established. In part this is due to disparities in enrollment of PAD trial cohorts. However, less attention has been paid to non-random protocol non-adherence after enrollment, which may lead to inaccurate estimates of treatment effects and reduce generalizability of study results. We aimed to ascertain characteristics associated with premature study drug discontinuation in a PAD cohort.Methods: Using data from EUCLID (Examining Use of Ticagrelor in Peripheral Artery Disease), factors associated with study drug discontinuation were assessed using univariable and multivariable Cox proportional hazards models with time to study drug discontinuation as the outcome of interest. Relationships between study drug discontinuation and major adverse cardiovascular events (MACE; cardiovascular death, myocardial infarction, ischemic stroke), major adverse limb events (MALE; acute limb ischemia, major amputation, and lower extremity revascularization), and all-cause hospitalization were assessed.Results: Of 13,842 eligible EUCLID participants, 3,886 (28.1%) prematurely and permanently discontinued study drug over a maximum follow-up of 42 months (annualized rate of 13.2 discontinuations per 100 patient-years). In a multivariable model, premature study drug discontinuation was associated with older age (aHR 1.16, 95%CI 1.14-1.19), eligibility based on prior lower extremity revascularization rather than ABI/TBI criteria (aHR 1.14, 95%CI 1.06-1.23), CLI status (aHR 1.23, 95%CI 1.06-1.42), COPD (aHR 1.36, 95%CI 1.24-1.49), and geographic region. In a multivariable analysis, study drug discontinuation was significantly associated with MACE (aHR 3.27, 95%CI 2.90-3.67, p < 0.001), MALE (aHR 1.84, 95%CI 1.63-2.07, p < 0.001), and all-cause hospitalization (aHR 2.37, 95%CI 2.21-2.54) following study drug discontinuation.Conclusions: This analysis of EUCLID demonstrates that premature, permanent discontinuation of study drug is relatively common in more than a quarter of PAD patients, is unevenly distributed based on geography and other baseline characteristics, and is associated with worse outcomes in a clinical trial context. Study teams leading future PAD trials may want to address the possibility of study drug discontinuation prospectively, as a proactive approach may help investigators to maintain study cohort diversity and representativeness without sacrificing power and precision.
  •  
36.
  • Wielgus, Maciek, et al. (author)
  • Millimeter Light Curves of Sagittarius A* Observed during the 2017 Event Horizon Telescope Campaign
  • 2022
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Journal article (peer-reviewed)abstract
    • The Event Horizon Telescope (EHT) observed the compact radio source, Sagittarius A* (Sgr A*), in the Galactic Center on 2017 April 5-11 in the 1.3 mm wavelength band. At the same time, interferometric array data from the Atacama Large Millimeter/submillimeter Array and the Submillimeter Array were collected, providing Sgr A* light curves simultaneous with the EHT observations. These data sets, complementing the EHT very long baseline interferometry, are characterized by a cadence and signal-to-noise ratio previously unattainable for Sgr A* at millimeter wavelengths, and they allow for the investigation of source variability on timescales as short as a minute. While most of the light curves correspond to a low variability state of Sgr A*, the April 11 observations follow an X-ray flare and exhibit strongly enhanced variability. All of the light curves are consistent with a red-noise process, with a power spectral density (PSD) slope measured to be between -2 and -3 on timescales between 1 minute and several hours. Our results indicate a steepening of the PSD slope for timescales shorter than 0.3 hr. The spectral energy distribution is flat at 220 GHz, and there are no time lags between the 213 and 229 GHz frequency bands, suggesting low optical depth for the event horizon scale source. We characterize Sgr A*'s variability, highlighting the different behavior observed just after the X-ray flare, and use Gaussian process modeling to extract a decorrelation timescale and a PSD slope. We also investigate the systematic calibration uncertainties by analyzing data from independent data reduction pipelines.
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37.
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38.
  • Bissell, Malenka M., et al. (author)
  • 4D Flow cardiovascular magnetic resonance consensus statement : 2023 update
  • 2023
  • In: Journal of Cardiovascular Magnetic Resonance. - : BMC. - 1097-6647 .- 1532-429X. ; 25:1
  • Research review (peer-reviewed)abstract
    • Hemodynamic assessment is an integral part of the diagnosis and management of cardiovascular disease. Four-dimensional cardiovascular magnetic resonance flow imaging (4D Flow CMR) allows comprehensive and accurate assessment of flow in a single acquisition. This consensus paper is an update from the 2015 ‘4D Flow CMR Consensus Statement’. We elaborate on 4D Flow CMR sequence options and imaging considerations. The document aims to assist centers starting out with 4D Flow CMR of the heart and great vessels with advice on acquisition parameters, post-processing workflows and integration into clinical practice. Furthermore, we define minimum quality assurance and validation standards for clinical centers. We also address the challenges faced in quality assurance and validation in the research setting. We also include a checklist for recommended publication standards, specifically for 4D Flow CMR. Finally, we discuss the current limitations and the future of 4D Flow CMR. This updated consensus paper will further facilitate widespread adoption of 4D Flow CMR in the clinical workflow across the globe and aid consistently high-quality publication standards.
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39.
  • Bowman, John L, et al. (author)
  • Insights into Land Plant Evolution Garnered from the Marchantia polymorpha Genome
  • 2017
  • In: Cell. - : Elsevier BV. - 0092-8674 .- 1097-4172. ; 171:2, s. 287-304.15
  • Journal article (peer-reviewed)abstract
    • The evolution of land flora transformed the terrestrial environment. Land plants evolved from an ancestral charophycean alga from which they inherited developmental, biochemical, and cell biological attributes. Additional biochemical and physiological adaptations to land, and a life cycle with an alternation between multicellular haploid and diploid generations that facilitated efficient dispersal of desiccation tolerant spores, evolved in the ancestral land plant. We analyzed the genome of the liverwort Marchantia polymorpha, a member of a basal land plant lineage. Relative to charophycean algae, land plant genomes are characterized by genes encoding novel biochemical pathways, new phytohormone signaling pathways (notably auxin), expanded repertoires of signaling pathways, and increased diversity in some transcription factor families. Compared with other sequenced land plants, M. polymorpha exhibits low genetic redundancy in most regulatory pathways, with this portion of its genome resembling that predicted for the ancestral land plant. PAPERCLIP.
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40.
  • Bruno, Raphael Romano, et al. (author)
  • The Clinical Frailty Scale for mortality prediction of old acutely admitted intensive care patients: a meta-analysis of individual patient-level data
  • 2023
  • In: Annals of Intensive Care. - : SPRINGER. - 2110-5820. ; 13:1
  • Journal article (peer-reviewed)abstract
    • Background This large-scale analysis pools individual data about the Clinical Frailty Scale (CFS) to predict outcome in the intensive care unit (ICU). Methods A systematic search identified all clinical trials that used the CFS in the ICU (PubMed searched until 24th June 2020). All patients who were electively admitted were excluded. The primary outcome was ICU mortality. Regression models were estimated on the complete data set, and for missing data, multiple imputations were utilised. Cox models were adjusted for age, sex, and illness acuity score (SOFA, SAPS II or APACHE II). Results 12 studies from 30 countries with anonymised individualised patient data were included (n = 23,989 patients). In the univariate analysis for all patients, being frail (CFS >= 5) was associated with an increased risk of ICU mortality, but not after adjustment. In older patients (>= 65 years) there was an independent association with ICU mortality both in the complete case analysis (HR 1.34 (95% CI 1.25-1.44), p < 0.0001) and in the multiple imputation analysis (HR 1.35 (95% CI 1.26-1.45), p < 0.0001, adjusted for SOFA). In older patients, being vulnerable (CFS 4) alone did not significantly differ from being frail. After adjustment, a CFS of 4-5, 6, and >= 7 was associated with a significantly worse outcome compared to CFS of 1-3. Conclusions Being frail is associated with a significantly increased risk for ICU mortality in older patients, while being vulnerable alone did not significantly differ. New Frailty categories might reflect its "continuum" better and predict ICU outcome more accurately.
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41.
  • Daniau, A. -L, et al. (author)
  • predictability of biomass burning in response to climate changes
  • 2012
  • In: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 26, s. GB4007-
  • Journal article (peer-reviewed)abstract
    • Climate is an important control on biomass burning, but the sensitivity of fire to changes in temperature and moisture balance has not been quantified. We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates. Analyses of paleo-fire data show that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels, and that temperature is quantitatively the most important driver of changes in biomass burning over the past 21,000 yrs. Given that a similar relationship between climate drivers and fire emerges from analyses of the interannual variability in biomass burning shown by remote-sensing observations of month-by-month burnt area between 1996 and 2008, our results signal a serious cause for concern in the face of continuing global warming.
  •  
42.
  • Davis, Hope C., et al. (author)
  • Time between anterior cruciate ligament injury and reconstruction and cartilage metabolism six-months following reconstruction
  • 2018
  • In: Knee. - : Elsevier BV. - 0968-0160. ; 25:2, s. 296-305
  • Journal article (peer-reviewed)abstract
    • Background: To determine the association between time from injury to ACL reconstruction (TimeInjury-ACLR) and biochemical markers of cartilage metabolism and inflammation six months following ACL reconstruction (ACLR). Methods: Individuals with a unilateral ACL injury were enrolled at initial presentation in the orthopedic clinic; blood was collected six months following ACLR. Enzyme-linked immunosorbent assays were used to analyze the ratio of serum concentrations of type-II collagen breakdown (C2C) to synthesis (CPII), plasma matrix metalloproteinase-3 (MMP-3), interleukin-6 (IL-6), and serum aggrecan neoepitope (ARGS). We used separate linear regressions to assess associations between biochemical markers and TimeInjury-ACLR. Results: Twenty-two participants (50% females, mean [SD], age 21.9 [4.5] years old; BMI 23.8 [2.6] kg/m2) completed the study. TimeInjury-ACLR ranged from nine to 67days (31.0 [14.4days]). Greater TimeInjury-ACLR predicted greater serum C2C:CPII ratios six months following ACLR (C2C:CPII=0.15 [0.02], R2 =0.213, P=0.030). Males (R2 =0.733, P=0.001) but not females (R2 =0.030, P=0.609) demonstrated a significant association between greater C2C:CPII and TimeInjury-ACLR at the six-month follow-up exam. TimeInjury-ACLR did not associate with IL-6, MMP-3, or ARGS at six months. Conclusions: Greater time between injury and ACL reconstruction was associated with greater serum C2C:CPII six months following ACLR in males but not females, and IL-6, MMP-3, and ARGS levels were not associated with TimeInjury-ACLR in males or females. The time between ACL injury and ACLR may affect collagen metabolism in males and should be further investigated in a larger study along with other patient-relevant outcomes.
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43.
  • Eisen, DP, et al. (author)
  • Urine D-arabinitol/L-arabinitol ratio in diagnosing Candida infection in patients with haematological malignancy and HIV infection
  • 2002
  • In: Diagnostic Microbiology and Infectious Disease. - 1879-0070. ; 42:1, s. 39-42
  • Journal article (peer-reviewed)abstract
    • Adult patients with hematologic malignancies along with HIV infected patients were prospectively studied to determine the performance of urine D-arabinitol/L-arabinitol (DA/LA) ratio in diagnosing invasive candidiasis. Ten evaluable febrile neutropenic patients had proven invasive candidiasis and elevated DA/LA ratios were found in 5. Invasive candidiasis with normal DA/LA ratios was most frequently due to Candida krusei infection. This Candida species is a non-producer of arabinitol. Only 4 of 81 febrile neutropenic patients given either antifungal prophylaxis or empiric antifungal treatment had elevated DA/LA ratios. Only 1 of 15 HIV positive patients with either oropharyngeal or esophageal candidiasis had elevated DA/LA ratios. Widespread use of fluconazole prophylaxis in bone marrow transplantation patients at the study hospital has led to an increased prevalence of C. krusei infection. This is the likely reason for the low sensitivity of the test in proven and suspected invasive Candida infections reported here. (C) 2002 Elsevier Science Inc. All rights reserved.
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44.
  • Henriksen, N. A., et al. (author)
  • EHS and AHS guidelines for treatment of primary ventral hernias in rare locations or special circumstances
  • 2020
  • In: BJS Open. - : Oxford University Press (OUP). - 2474-9842. ; 4:2, s. 342-353
  • Research review (peer-reviewed)abstract
    • BACKGROUND: Rare locations of hernias, as well as primary ventral hernias under certain circumstances (cirrhosis, dialysis, rectus diastasis, subsequent pregnancy), might be technically challenging. The aim was to identify situations where the treatment strategy might deviate from routine management. METHODS: The guideline group consisted of surgeons from the European and Americas Hernia Societies. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used in formulating the recommendations. The Scottish Intercollegiate Guidelines Network (SIGN) critical appraisal checklists were used to evaluate the quality of full-text papers. A systematic literature search was performed on 1 May 2018 and updated 1 February 2019. The Appraisal of Guidelines for Research and Evaluation (AGREE) instrument was followed. RESULTS: Literature was limited in quantity and quality. A majority of the recommendations were graded as weak, based on low quality of evidence. In patients with cirrhosis or on dialysis, a preperitoneal mesh repair is suggested. Subsequent pregnancy is a risk factor for recurrence. Repair should be postponed until after the last pregnancy. For patients with a concomitant rectus diastasis or those with a Spigelian or lumbar hernia, no recommendation could be made for treatment strategy owing to lack of evidence. CONCLUSION: This is the first European and American guideline on the treatment of umbilical and epigastric hernias in patients with special conditions, including Spigelian and lumbar hernias. All recommendations were weak owing to a lack of evidence. Further studies are needed on patients with rectus diastasis, Spigelian and lumbar hernias.
  •  
45.
  • Henriksen, N. A., et al. (author)
  • Guidelines for treatment of umbilical and epigastric hernias from the European Hernia Society and Americas Hernia Society
  • 2020
  • In: British Journal of Surgery. - : Oxford University Press (OUP). - 0007-1323 .- 1365-2168. ; 107:3, s. 171-190
  • Research review (peer-reviewed)abstract
    • Background: Umbilical and epigastric hernia repairs are frequently performed surgical procedures with an expected low complication rate. Nevertheless, the optimal method of repair with best short- and long-term outcomes remains debatable. The aim was to develop guidelines for the treatment of umbilical and epigastric hernias. Methods: The guideline group consisted of surgeons from Europe and North America including members from the European Hernia Society and the Americas Hernia Society. The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach, the Scottish Intercollegiate Guidelines Network (SIGN) critical appraisal checklists, and the Appraisal of Guidelines for Research and Evaluation (AGREE) instrument were used. A systematic literature search was done on 1 May 2018, and updated on 1 February 2019. Results: Literature reporting specifically on umbilical and epigastric hernias was limited in quantity and quality, resulting in a majority of the recommendations being graded as weak, based on low-quality evidence. The main recommendation was to use mesh for repair of umbilical and epigastric hernias to reduce the recurrence rate. Most umbilical and epigastric hernias may be repaired by an open approach with a preperitoneal flat mesh. A laparoscopic approach may be considered if the hernia defect is large, or if the patient has an increased risk of wound morbidity. Conclusion: This is the first European and American guideline on the treatment of umbilical and epigastric hernias. It is recommended that symptomatic umbilical and epigastric hernias are repaired by an open approach with a preperitoneal flat mesh.
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46.
  • Jha, Abhishek, et al. (author)
  • High-Specific-Activity-131I-MIBG versus 177Lu-DOTATATE Targeted Radionuclide Therapy for Metastatic Pheochromocytoma and Paraganglioma
  • 2021
  • In: Clinical Cancer Research. - : American Association For Cancer Research (AACR). - 1078-0432 .- 1557-3265. ; 27:11, s. 2989-2995
  • Journal article (peer-reviewed)abstract
    • Targeted radionuclide therapies (TRT) using 131I-metaiodobenzylguanidine (131I-MIBG) and peptide receptor radionuclide therapy (177Lu or 90Y) represent several of the therapeutic options in the management of metastatic/inoperable pheochromocytoma/paraganglioma. Recently, high-specific-activity-131I-MIBG therapy was approved by the FDA and both 177Lu-DOTATATE and 131I-MIBG therapy were recommended by the National Comprehensive Cancer Network guidelines for the treatment of metastatic pheochromocytoma/paraganglioma. However, a clinical dilemma often arises in the selection of TRT, especially when a patient can be treated with either type of therapy based on eligibility by MIBG and somatostatin receptor imaging. To address this problem, we assembled a group of international experts, including oncologists, endocrinologists, and nuclear medicine physicians, with substantial experience in treating neuroendocrine tumors with TRTs to develop consensus and provide expert recommendations and perspectives on how to select between these two therapeutic options for metastatic/inoperable pheochromocytoma/paraganglioma. This article aims to summarize the survival outcomes of the available TRTs; discuss personalized treatment strategies based on functional imaging scans; address practical issues, including regulatory approvals; and compare toxicities and risk factors across treatments. Furthermore, it discusses the emerging TRTs.
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47.
  • Kyle-Leinhase, I., et al. (author)
  • Comparison of hernia registries : the CORE project
  • 2018
  • In: Hernia. - : Springer Science and Business Media LLC. - 1265-4906 .- 1248-9204. ; 22:4, s. 561-575
  • Research review (peer-reviewed)abstract
    • Introduction: The aim of the international CORE project was to explore the databases of the existing hernia registries and compare them in content and outcome variables. Methods: The CORE project was initiated with representatives from all established hernia registries (Danish Hernia Database, Swedish Hernia Registry, Herniamed, EuraHS, Club Hernie, EVEREG, AHSQC) in March 2015 in Berlin. The following categories were used to compare the registries: initiation and funding, data collection and use for certification of hernia centers, patient data and data protection, operative data, registration of complications and follow-up data. Results: The Danish Hernia Database is the only one to qualify as a genuine national registry where participation is compulsory for entry of all procedures by all surgeons performing a hernia operation. All other registries have to be considered as voluntary and completeness of data depends upon the participating hospitals and surgeons. Only the Danish Hernia Database and the Swedish Hernia Registry are publicly funded. All other registries are reliant on financial support from the medical technology industry. As an incentive for voluntary participation in a hernia registry, hospitals or surgeons are issued a certificate confirming that they are taking part in a quality assurance study for hernia surgery. Due to data protection and privacy regulations, most registries are obliged or have chosen to enter their patient data anonymously or coded. The Danish Hernia Database and Swedish Hernia Registry utilize a national personal patient code. In the Herniamed Registry, patient data are saved in a coded and anonymous format after obtaining the patient’s informed consent. Conclusion: Despite the differences in the way data are collected for each of the listed hernia registries, the data are indispensable in clinical research.
  •  
48.
  • LeBlanc, K, et al. (author)
  • Quality of Life after Hernia Surgery
  • 2015
  • In: Hernia : the journal of hernias and abdominal wall surgery. - 1248-9204. ; 19 Suppl 1, s. S127-31
  • Journal article (peer-reviewed)
  •  
49.
  • Lee, Cheng-Ruei, et al. (author)
  • Young inversion with multiple linked QTLs under selection in a hybrid zone
  • 2017
  • In: NATURE ECOLOGY & EVOLUTION. - : Springer Science and Business Media LLC. - 2397-334X. ; 1:5
  • Journal article (peer-reviewed)abstract
    • Fixed chromosomal inversions can reduce gene flow and promote speciation in two ways: by suppressing recombination and by carrying locally favoured alleles at multiple loci. However, it is unknown whether favoured mutations slowly accumulate on older inversions or if young inversions spread because they capture pre-existing adaptive quantitative trait loci (QTLs). By genetic mapping, chromosome painting and genome sequencing, we have identified a major inversion controlling ecologically important traits in Boechera stricta. The inversion arose since the last glaciation and subsequently reached local high frequency in a hybrid speciation zone. Furthermore, the inversion shows signs of positive directional selection. To test whether the inversion could have captured existing, linked QTLs, we crossed standard, collinear haplotypes from the hybrid zone and found multiple linked phenology QTLs within the inversion region. These findings provide the first direct evidence that linked, locally adapted QTLs may be captured by young inversions during incipient speciation.
  •  
50.
  • Martson, A-G, et al. (author)
  • How to design a study to evaluate therapeutic drug monitoring in infectious diseases?
  • 2020
  • In: Clinical Microbiology and Infection. - : Elsevier BV. - 1198-743X .- 1469-0691. ; 26:8, s. 1008-1016
  • Research review (peer-reviewed)abstract
    • Background: Therapeutic drug monitoring (TDM) is a tool to personalize and optimize dosing by measuring the drug concentration and subsequently adjusting the dose to reach a target concentration or exposure. The evidence to support TDM is however often ranked as expert opinion. Limitations in study design and sample size have hampered definitive conclusions of the potential added value of TDM.Objectives: We aim to give expert opinion and discuss the main points and limitations of available data from antibiotic TDM trials and emphasize key elements for consideration in design of future clinical studies to quantify the benefits of TDM.Sources: The sources were peer-reviewed publications, guidelines and expert opinions from the field of TDM.Content: This review focuses on key aspects of antimicrobial TDM study design: describing the rationale for a TDM study, assessing the exposure of a drug, assessing susceptibility of pathogens and selecting appropriate clinical endpoints. Moreover we provide guidance on appropriate study design.
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