TY - JOUR A1 - Huber, Albert T1 - The gravitational field of a massless particle on the horizon of a stationary black hole JF - Classical and Quantum Gravity N2 - In this work, the field of a gravitational shockwave generated by a massless point-like particle is calculated at the event horizon of a stationary Kerr–Newman black hole. Using the geometric framework of generalized Kerr–Schild deformations in combination with the spin-coefficient formalism of Newman and Penrose, it is shown that the field equations of the theory, at the event horizon of the black hole, can be reduced to a single linear ordinary differential equation for the so-called profile function of the geometry. This differential relation is solved exactly. Based on the results obtained, a physical interpretation is given for the found shockwave spacetime, and it is clarified how these results lead back to those of previous works on the subject, which deal with the much simpler cases of gravitational shockwaves in static black hole backgrounds. KW - Gravitation Y1 - ER - TY - JOUR A1 - Belkacem, Kévin A1 - Kupka, Friedrich A1 - Philidet, Jordan A1 - Samadi, Réza T1 - Surface effects and turbulent pressure. Assessing the Gas-Γ1 and Reduced-Γ1 empirical models. JF - Astronomy & Astrophysics KW - Surface KW - Pressure Y1 - ER - TY - JOUR A1 - Huber, Albert T1 - Junction Conditions and local Spacetimes in General Relativity JF - The European Physical Journal C N2 - In the present work, a theoretical framework focussing on local geometric deformations is introduced in order to cope with the problem of how to join spacetimes with different geometries and physical properties. This framework is used to show that two Lorentzian manifolds can be matched by considering local deformations of the associated spacetime metrics. Based on the fact that metrics can be suitably matched in this way, it is shown that the underlying geometric approach allows the characterization of local spacetimes in general relativity. Furthermore, it is shown that said approach not only extends the conventional thin shell formalism, but also allows the treatment of geometric problems that cannot be treated with standard gluing techniques. KW - Relativity Y1 - ER - TY - JOUR A1 - Kostogryz, Nadiia M. A1 - Kupka, Friedrich A1 - Piskunov, Nikolai A1 - Fabbian, Damian A1 - Krüger, Daniel A1 - Gizon, Laurent T1 - Accurate Short-Characteristics Radiative Transfer in A Numerical Tool for Astrophysical Research (ANTARES) JF - Solar Physics KW - Astrophysics Y1 - ER - TY - JOUR A1 - Krizek, Gerd Christian A1 - Hausleitner, Rene A1 - Böhme, Laura A1 - Olaverri-Monreal, Cristina T1 - Empirical Analysis of Safe Distance Calculation by the Stereoscopic Capturing and Processing of Images Through the Tailigator System JF - sensors N2 - Driver disregard for the minimum safety distance increases the probability of rear-end collisions. In order to contribute to active safety on the road, we propose in this work a low-cost Forward Collision Warning system that captures and processes images. Using cameras located in the rear section of a leading vehicle, this system serves the purpose of discouraging tailgating behavior from the vehicle driving behind. We perform in this paper the pertinent field tests to assess system performance, focusing on the calculated distance from the processing of images and the error margins in a straight line, as well as in a curve. Based on the evaluation results, the current version of the Tailigator can be used at speeds up to 50 km per hour without any restrictions. The measurements showed similar characteristics both on the straight line and in the curve. At close distances, between 3 and 5 m, the values deviated from the real value. At average distances, around 10 to 15 m, the Tailigator achieved the best results. From distances higher than 20 m, the deviations increased steadily with the distance. We contribute to the state of the art with an innovative low-cost system to identify tailgating behavior and raise awareness, which works independently of the rear vehicle's communication capabilities or equipment. KW - tailgating KW - stereoscopy Y1 - 2020 ER - TY - JOUR A1 - Kierspel, Thomas A1 - Kadek, Alan A1 - Barran, Perdita A1 - Bellina, Bruno A1 - Bijedic, Adi A1 - Brodmerkel, Maxim N. A1 - Commandeur, Jan A1 - Caleman, Carl A1 - Damjanovic, Tomislav A1 - Dawod, Ibrahim A1 - De Santis, Emiliano A1 - Lekkas, Alexandros A1 - Lorenzen, Kristina A1 - López Morillo, Luis A1 - Mandl, Thomas A1 - Marklund, Erik G. A1 - Papanastasiou, Dimitris A1 - Ramakers, Lennart A. I. A1 - Schweikhard, Lutz A1 - Simke, Florian A1 - Sinelnikova, Anna A1 - Smyrnakis, Athanasios A1 - Timneanu, Nicusor A1 - Uetrecht, Charlotte T1 - Coherent diffractive imaging of proteins and viral capsids: simulating MS SPIDOC JF - Analytical and Bioanalytical Chemistry N2 - MS SPIDOC is a novel sample delivery system designed for single (isolated) particle imaging at X-ray Free-Electron Lasers that is adaptable towards most large-scale facility beamlines. Biological samples can range from small proteins to MDa particles. Following nano-electrospray ionization, ionic samples can be m/z-filtered and structurally separated before being oriented at the interaction zone. Here, we present the simulation package developed alongside this prototype. The first part describes how the front-to-end ion trajectory simulations have been conducted. Highlighted is a quadrant lens; a simple but efficient device that steers the ion beam within the vicinity of the strong DC orientation field in the interaction zone to ensure spatial overlap with the X-rays. The second part focuses on protein orientation and discusses its potential with respect to diffractive imaging methods. Last, coherent diffractive imaging of prototypical T = 1 and T = 3 norovirus capsids is shown. We use realistic experimental parameters from the SPB/SFX instrument at the European XFEL to demonstrate that low- resolution diffractive imaging data (q < 0.3 nm −1 ) can be collected with only a few X-ray pulses. Such low-resolution data are sufficient to distinguish between both symmetries of the capsids, allowing to probe low abundant species in a beam if MS SPIDOC is used as sample delivery. KW - SPI KW - X-ray KW - Native MS KW - Protein complex structure KW - Simulation Y1 - U6 - http://dx.doi.org/https://doi.org/10.1007/s00216-023-04658-y VL - 2023 IS - 415 SP - 4209 EP - 4220 ER -