TY  - JOUR
A1  - Schleicher, Bernd
A1  - Arbet-Engels, Axel
A1  - Baack, Dominik
A1  - Balbo, Matteo
A1  - Biland, Adrian
A1  - Blank, Michael
A1  - Bretz, Thomas
A1  - Bruegge, Kai
A1  - Bulinski, Michael
A1  - Buss, Jens
A1  - Doerr, Manuel
A1  - Dorner, Daniela
A1  - Elsaesser, Dominik
A1  - Grischagin, Sergej
A1  - Hildebrand, Dorothee
A1  - Linhoff, Lena
A1  - Mannheim, Karl
A1  - Mueller, Sebastian Achim
A1  - Neise, Dominik
A1  - Neronov, Andrii
A1  - Noethe, Maximilian
A1  - Paravac, Aleksander
A1  - Rhode, Wolfgang
A1  - Schulz, Florian
A1  - Sedlaczek, Kevin
A1  - Shukla, Amit
A1  - Sliusar, Vitalii
A1  - Willert, Elan
A1  - Walter, Roland
T1  - Fractional Variability—A Tool to Study Blazar Variability
JF  - Galaxies
N2  - Active Galactic Nuclei emit radiation over the whole electromagnetic spectrum up to TeV energies. Blazars are one subtype with their jets pointing towards the observer. One of their typical features is extreme variability on timescales, from minutes to years. The fractional variability is an often used parameter for investigating the degree of variability of a light curve. Different detection methods and sensitivities of the instruments result in differently binned data and light curves with gaps. As they can influence the physics interpretation of the broadband variability, the effects of these differences on the fractional variability need to be studied. In this paper, we study the systematic effects of completeness in time coverage and the sampling rate. Using public data from instruments monitoring blazars in various energy ranges, we study the variability of the bright TeV blazars Mrk 421 and Mrk 501 over the electromagnetic spectrum, taking into account the systematic effects, and compare our findings with previous results. Especially in the TeV range, the fractional variability is higher than in previous studies, which can be explained by the much longer (seven years compared to few weeks) and more complete data sample.
KW  - blazars
KW  - variability
KW  - fractional variability
KW  - active galactic nuclei
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197348
SN  - 2075-4434
VL  - 7
IS  - 2
ER  - 
TY  - JOUR
A1  - Kleefeldt, Florian
A1  - Upcin, Berin
A1  - Bömmel, Heike
A1  - Schulz, Christian
A1  - Eckner, Georg
A1  - Allmanritter, Jan
A1  - Bauer, Jochen
A1  - Braunger, Barbara
A1  - Rueckschloss, Uwe
A1  - Ergün, Süleyman
T1  - Bone marrow-independent adventitial macrophage progenitor cells contribute to angiogenesis
JF  - Cell Death & Disease
N2  - Pathological angiogenesis promotes tumor growth, metastasis, and atherosclerotic plaque rupture. Macrophages are key players in these processes. However, whether these macrophages differentiate from bone marrow-derived monocytes or from local vascular wall-resident stem and progenitor cells (VW-SCs) is an unresolved issue of angiogenesis. To answer this question, we analyzed vascular sprouting and alterations in aortic cell populations in mouse aortic ring assays (ARA). ARA culture leads to the generation of large numbers of macrophages, especially within the aortic adventitia. Using immunohistochemical fate-mapping and genetic in vivo-labeling approaches we show that 60% of these macrophages differentiate from bone marrow-independent Ly6c\(^{+}\)/Sca-1\(^{+}\) adventitial progenitor cells. Analysis of the NCX\(^{−/-}\) mouse model that genetically lacks embryonic circulation and yolk sac perfusion indicates that at least some of those progenitor cells arise yolk sac-independent. Macrophages represent the main source of VEGF in ARA that vice versa promotes the generation of additional macrophages thereby creating a pro-angiogenetic feedforward loop. Additionally, macrophage-derived VEGF activates CD34\(^{+}\) progenitor cells within the adventitial vasculogenic zone to differentiate into CD31\(^{+}\) endothelial cells. Consequently, depletion of macrophages and VEGFR2 antagonism drastically reduce vascular sprouting activity in ARA. In summary, we show that angiogenic activation induces differentiation of macrophages from bone marrow-derived as well as from bone marrow-independent VW-SCs. The latter ones are at least partially yolk sac-independent, too. Those VW-SC-derived macrophages critically contribute to angiogenesis, making them an attractive target to interfere with pathological angiogenesis in cancer and atherosclerosis as well as with regenerative angiogenesis in ischemic cardiovascular disorders.
KW  - macrophages
KW  - angiogenesis
KW  - bone marrow-derived monocytes
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-299724
VL  - 13
IS  - 3
ER  -