Following the Big Bang, structure in the Universe started collapsing under the force of gravity. This resulted in the formation of the first stars, galaxies and clusters of galaxies. The majority... Show moreFollowing the Big Bang, structure in the Universe started collapsing under the force of gravity. This resulted in the formation of the first stars, galaxies and clusters of galaxies. The majority of the baryonic mass in a galaxy cluster is part of the hot intracluster medium, which permeates the entire cluster As this medium cools down, it accretes onto the central galaxies where it triggers the formation of new stars. However, it also feeds the central supermassive black hole, creating an active galactic nucleus (AGN) that injects a large amount of energy into the intracluster medium again, resulting in a feedback cycle. This feedback cycle is an essential ingredient in the formation and evolution of galaxies. Using new high-resolution radio observations taken with the LOw Frequency ARray (LOFAR), we study AGN feedback in galaxy clusters in unprecedented detail, gaining insight into both the duty cycle of the AGN as well as the energy budget of the feedback cycle. Show less
Braun, J.; Blanco, R.; Marzo-Ortega, H.; Gensler, L.S.; Bosch, F. van den; Hall, S.; ... ; Deodhar, A. 2023
Background: Radiographic progression and course of inflammation over 2 years in patients with non-radiographic axial spondyloarthritis (nr-axSpA) from the phase 3, randomized, PREVENT study are... Show moreBackground: Radiographic progression and course of inflammation over 2 years in patients with non-radiographic axial spondyloarthritis (nr-axSpA) from the phase 3, randomized, PREVENT study are reported here. Methods: In the PREVENT study, adult patients fulfilling the Assessment of SpondyloArthritis International Society classification criteria for nr-axSpA with elevated CRP and/or MRI inflammation received secukinumab 150 mg or placebo. All patients received open-label secukinumab from week 52 onward. Sacroiliac (SI) joint and spinal radiographs were scored using the modified New York (mNY) grading (total sacroiliitis score; range, 0-8) and modified Stoke Ankylosing Spondylitis Spine Score (mSASSS; range, 0-72), respectively. SI joint bone marrow edema (BME) was assessed using the Berlin Active Inflammatory Lesions Scoring (0-24) and spinal MRI using the Berlin modification of the AS spine MRI (ASspiMRI) scoring (0-69). Results: Overall, 78.9% (438/555) of patients completed week 104 of the study. Over 2 years, minimal changes were observed in total radiographic SI joint scores (mean [SD] change, - 0.04 [0.49] and 0.04 [0.36]) and mSASSS scores (0.04 [0.47] and 0.07 [0.36]) in the secukinumab and placebo-secukinumab groups. Most of the patients showed no structural progression (increase <= smallest detectable change) in SI joint score (87.7% and 85.6%) and mSASSS score (97.5% and 97.1%) in the secukinumab and placebo-secukinumab groups. Only 3.3% (n = 7) and 2.9% (n = 3) of patients in the secukinumab and placebo-secukinumab groups, respectively, who were mNY-negative at baseline were scored as mNY-positive at week 104. Overall, 1.7% and 3.4% of patients with no syndesmophytes at baseline in the secukinumab and placebo-secukinumab group, respectively, developed >= 1 new syndesmophyte over 2 years. Reduction in SI joint BME observed at week 16 with secukinumab (mean [SD], - 1.23 [2.81] vs - 0.37 [1.90] with placebo) was sustained through week 104 (- 1.73 [3.49]). Spinal inflammation on MRI was low at baseline (mean score, 0.82 and 1.07 in the secukinumab and placebo groups, respectively) and remained low (mean score, 0.56 at week 104). Conclusion: Structural damage was low at baseline and most patients showed no radiographic progression in SI joints and spine over 2 years in the secukinumab and placebo-secukinumab groups. Secukinumab reduced SI joint inflammation, which was sustained over 2 years. Show less
This thesis examines silicon pore optics (SPO), a technology that exploits silicon wafers from the semiconductor industry to create extremely high quality X-ray optics, by studying its... Show moreThis thesis examines silicon pore optics (SPO), a technology that exploits silicon wafers from the semiconductor industry to create extremely high quality X-ray optics, by studying its manufacturing process, applications, and prospects. SPO technology has become very mature thanks to the continuous development efforts to prepare for the industrial production of Athena, the largest space-borne X-ray telescope yet to be launched. In effect, SPO is also a versatile technology that can be further developed for a wide range of applications, including radiation therapy. Show less
Introduction There are no consistently confirmed predictors of atrial fibrillation (AF) recurrence after catheter ablation. Therefore, we aimed to study whether left atrial appendage volume (LAAV)... Show moreIntroduction There are no consistently confirmed predictors of atrial fibrillation (AF) recurrence after catheter ablation. Therefore, we aimed to study whether left atrial appendage volume (LAAV) and function influence the long-term recurrence of AF after catheter ablation, depending on AF type. Methods AF patients who underwent point-by-point radiofrequency catheter ablation after cardiac computed tomography (CT) were included in this analysis. LAAV and LAA orifice area were measured by CT. Uni- and multivariable Cox proportional hazard regression models were performed to determine the predictors of AF recurrence. Results In total, 561 AF patients (61.9 +/- 10.2 years, 34.9% females) were included in the study. Recurrence of AF was detected in 40.8% of the cases (34.6% in patients with paroxysmal and 53.5% in those with persistent AF) with a median recurrence-free time of 22.7 (9.3-43.1) months. Patients with persistent AF had significantly higher body surface area-indexed LAV, LAAV, and LAA orifice area and lower LAA flow velocity, than those with paroxysmal AF. After adjustment left ventricular ejection fraction (LVEF) <50% (HR = 2.17; 95% CI = 1.38-3.43; p < .001) and LAAV (HR = 1.06; 95% CI = 1.01-1.12; p = .029) were independently associated with AF recurrence in persistent AF, while no independent predictors could be identified in paroxysmal AF. Conclusion The current study demonstrates that beyond left ventricular systolic dysfunction, LAA enlargement is associated with higher rate of AF recurrence after catheter ablation in persistent AF, but not in patients with paroxysmal AF. Show less
It has now been well established that shocks and turbulent motions in the intra-cluster medium (ICM) generated through cluster mergers can produce large-scale synchrotron emission. However, the... Show moreIt has now been well established that shocks and turbulent motions in the intra-cluster medium (ICM) generated through cluster mergers can produce large-scale synchrotron emission. However, the underlying particle acceleration mechanisms responsible for the origin of these faint diffuse radio sources are not well understood. With the advent of new generation low-frequency radio telescopes and better calibration techniques it has now become possible to unveil low-frequency radio sky with unprecedented depth and sensitivity, that is full of potential for new discoveries. The first part of this dissertation presents the study to better understand the nature of revived fossil (radio) plasma sources in galaxy cluster and establish them as a distinct class of radio sources. The complexity of objects, observed with these new instruments are just tip of the iceberg of the population, and will challenge the traditional taxonomy of diffuse radio sources. The last part of the dissertation focuses on deriving the deepest radio source-counts at 150 MHz. This is one of the several cosmological tests to check feasibility of new cosmological models and a sanity check for the data reduction. The derived source-counts are also compared with the other existing determinations, as well as with state-of-the-art evolutionary models. Show less
This thesis focuses on the X-ray spectral analysis of merging galaxy clusters and the plasma code development for future high-resolution X-ray spectroscopy observations. This work deepens in two... Show moreThis thesis focuses on the X-ray spectral analysis of merging galaxy clusters and the plasma code development for future high-resolution X-ray spectroscopy observations. This work deepens in two different aspects of these merging clusters still under debate: one, the study of the thermal (X-ray shocks) component and its correlation with the non-thermal (radio shocks/relics) component, and two, their metal enrichment history. The first one is crucial to understand how the shocks propagate and heat the ICM as well as to determine the physical association between these two components. The second one aims to contribute to a better knowledge of the metals origin, evolution and distribution in merging clusters, which can reveal important information on the dynamical history of the mergers. Show less
Pulsars were first discovered in 1967 and since then the population has grown and expanded over several wavelengths. In this thesis three different X-ray pulsars and three black widow radio pulsars... Show morePulsars were first discovered in 1967 and since then the population has grown and expanded over several wavelengths. In this thesis three different X-ray pulsars and three black widow radio pulsars and their evolution has been examined. The pulsars in this work all show variability that was not expected of their type of sources, e.g. the pulsar 2A 1822-371 is found to have an orbital period that is expanding over time more than what is expected. We suggest this to be due to the pulsar being a super Eddington source. Another part of the thesis uncovers that the magnetic field may have a significant influence in the behavior of the pulsars. Low magnetic field pulsars often show a correlation between their pulse phase and their flux, whereas we find that this correlation is not present in high magnetic field pulsars. This could mean that the hot spot, where the pulsations origin, is not moving in high magnetic field pulsars but could be moving in low magnetic field pulsars. The first black widow pulsars discovered had unstable timing solutions, whereas the black widow pulsars in this work all have stable timing solutions, and we look into possible explanations to this difference. Show less
Whereas the extreme conditions of the first minutes after the Big Bang have produced nearly all the hydrogen and helium in the Universe, heavier elements - or metals - are synthesised in the... Show moreWhereas the extreme conditions of the first minutes after the Big Bang have produced nearly all the hydrogen and helium in the Universe, heavier elements - or metals - are synthesised in the core of stars and in supernova explosions. Currently, however, the behaviour of supernovae (and their stellar progenitors) is not well understood, and could be better constrained by measuring accurately the relative amount of metals they produce. On the other hand, the very hot and diffuse gas - or intra-cluster medium (ICM), glowing in X-ray and detected in the large gravitational potential well of galaxy clusters and groups, is also rich in metals. This means that the building blocks of life, synthesised by billions of supernovae over cosmic times, are present even at the largest scales of the Universe, as they enrich the ICM. In this thesis, I show how measuring the abundances of O, Ne, Mg, Si, S, Ar, Ca, Cr, Mn, Fe, and Ni in a sample of nearby, relaxed galaxy clusters, groups, and ellipticals observed with XMM-Newton (the CHEmical Enrichment Rgs Sample) helps to better understand Type Ia and core-collapse supernovae, as well as the history and conditions of the ICM enrichment in general. Show less
Malan, D.F.; Walt, S.J. van der; Raidou, R.G.; Berg, B. van den; Stoel, B.C.; Botha, C.P.; ... ; Valstar, E.R. 2016
The main objective of this thesis is to develop new, accurate and reproducible automated methods for the detection and quantification of lesions in coronary and peripheral X-ray angiograms, which... Show moreThe main objective of this thesis is to develop new, accurate and reproducible automated methods for the detection and quantification of lesions in coronary and peripheral X-ray angiograms, which make it possible to extend the straight segment analysis to analyses of sidebranches and bifurcations. We introduce new methods for the detection of pathlines (Wavepath), the detection of arterial contours (Wavecontour) and the measurement of diameter sizes in straight segments, sidebranches and bifurcations. These methods are designed to increase reproducibility and decrease the influence of user interaction. These new methods are validated extensively in coronary and vascular angiograms, proving their accuracy and reproducibility. Furthermore we developed two new bifurcation models (Y-shape and T-shape) in order to accurately measure the diameters and lesion parameters of an entire bifurcation. The models, including their edge segment analyses, are validated extensively in a clinical validation study in order to assess the inter- and intra-observer variability on pre- and post-intervention data. Overall we can conclude that our goal of improving the QCA analysis and extend it towards the new morphologies and new intervention techniques has been met. Show less
