Incorporating a radiative hydrodynamics scheme in the numerical-relativity code BAM

To study binary neutron star systems and to interpret observational data such as gravitational-wave and kilonova signals, one needs an accurate description of the processes that take place during the final stages of the coalescence, e.g., through numerical-relativity simulations. In this work, we present an updated version of the numerical-relativity code BAM in order to incorporate nuclear-theory based Equations of State and a simple description of neutrino interactions through a Neutrino Leakage Scheme. Different test simulations, for stars undergoing a neutrino-induced gravitational collapse and for binary neutron stars systems, validate our new implementation. For the binary neutron stars systems, we show that we can evolve stably and accurately distinct microphysical models employing the different equations of state: SFHo, DD2, and the hyperonic BHB$\Lambda \phi$. Overall, our test simulations have good agreement with those reported in the literature

High-accuracy high-mass ratio simulations for binary neutron stars and their comparison to existing waveform models

The subsequent observing runs of the advanced gravitational-wave detector network will likely provide us with various gravitational-wave observations of binary neutron star systems. For an accurate interpretation of these detections, we need reliable gravitational-wave models. To test and to point out how existing models could be improved, we perform a set of high-resolution numerical-relativity simulations for four different physical setups with mass ratios $q$ = $1.25$, $1.50$, $1.75$, $2.00$, and total gravitational mass $M = 2.7M_\odot$ . Each configuration is simulated with five different resolutions to allow a proper error assessment. Overall, we find approximately 2nd order converging results for the dominant $(2,2)$, but also subdominant $(2,1)$, $(3,3)$, $(4,4)$ modes, while, generally, the convergence order reduces slightly for an increasing mass ratio. Our simulations allow us to validate waveform models, where we find generally good agreement between state-of-the-art models and our data, and to prove that scaling relations for higher modes currently employed for binary black hole waveform modeling also apply for the tidal contribution. Finally, we also test if the current NRTidal model to describe tidal effects is a valid description for high-mass ratio systems. We hope that our simulation results can be used to further improve and test waveform models in preparation for the next observing runs

Back and Forth: Reverse Phase Transitions in Numerical Relativity Simulations

Multi-messenger observations of binary neutron star mergers provide a uniqueopportunity to constrain the dense-matter equation of state. Although it isknown from quantum chromodynamics that hadronic matter will undergo a phasetransition to exotic forms of matter, e.g., quark matter, the onset density ofsuch a phase transition cannot be computed from first principles. Hence, itremains an open question if such phase transitions occur inside isolatedneutron stars or during binary neutron star mergers, or if they appear at evenhigher densities that are not realized in the Cosmos. In this article, weperform numerical-relativity simulations of neutron-star mergers andinvestigate scenarios in which the onset density of such a phase transition isexceeded in at least one inspiralling binary component. Our simulations revealthat shortly before the merger it is possible that such stars undergo a"reverse phase transition", i.e., densities decrease and the quark core insidethe star disappears leaving a purely hadronic star at merger. After the merger,when densities increase once more, the phase transition occurs again and leads,in the cases considered in this work, to a rapid formation of a black hole. Wecompute the gravitational-wave signal and the mass ejection for our simulationsof such scenarios and find clear signatures that are related to the postmergerphase transition, e.g., smaller ejecta masses due to the softening of theequation of state through the quark core formation. Unfortunately, we do notfind measurable imprints of the reverse phase transition.<br

Glucopiericidin C: a cytotoxic pieridin glucoside antibiotic produced by a marine Streptomyces isolate.

More than 35 naturally occurring piericidins1 and closely related antibiotics have been reported. They are derived from prenylated polyoxypyridines and exhibit interesting biological activitie

A domain in the N-terminal extension of class IIb eukaryotic aminoacyl-tRNA synthetases is important for tRNA binding

Cytoplasmic aspartyl-tRNA synthetase (AspRS) from Saccharomyces cerevisiae is a homodimer of 64 kDa subunits. Previous studies have emphasized the high sensitivity of the N-terminal region to proteolytic cleavage, leading to truncated species that have lost the first 20–70 residues but that retain enzymatic activity and dimeric structure. In this work, we demonstrate that the N-terminal extension in yeast AspRS participates in tRNA binding and we generalize this finding to eukaryotic class IIb aminoacyl-tRNA synthetases. By gel retardation studies and footprinting experiments on yeast tRNA(Asp), we show that the extension, connected to the anticodon-binding module of the synthetase, contacts tRNA on the minor groove side of its anticodon stem. Sequence comparison of eukaryotic class IIb synthetases identifies a lysine-rich 11 residue sequence ((29)LSKKALKKLQK(39) in yeast AspRS with the consensus xSKxxLKKxxK in class IIb synthetases) that is important for this binding. Direct proof of the role of this sequence comes from a mutagenesis analysis and from binding studies using the isolated peptide