42 research outputs found
Traveling waves and pattern formation for spatially discrete bistable reaction-diffusion equations (survey)
Analysis and Stochastic
First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by
gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have
assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of
1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center
of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission
ring with a diameter of 42 ± 3 μas, which is circular and encompasses a central depression in brightness with a flux
ratio 10:1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and
width remaining stable over four different observations carried out in different days. Overall, the observed image is
consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in
brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to
the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic
magnetohydrodynamic simulations of black holes and derive a central mass of M = (6.5 ± 0.7) × 109 Me. Our radiowave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies
and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme
limit and on a mass scale that was so far not accessible
Actin acting at the Golgi
The organization, assembly and remodeling of the actin cytoskeleton provide force and tracks for a variety of (endo)membrane-associated events such as membrane trafficking. This review illustrates in different cellular models how actin and many of its numerous binding and regulatory proteins (actin and co-workers) participate in the structural organization of the Golgi apparatus and in traf- ficking-associated processes such as sorting, biogenesis and motion of Golgi-derived transport carriers