464 research outputs found
Mixed Map Labeling
Point feature map labeling is a geometric problem, in which a set of input
points must be labeled with a set of disjoint rectangles (the bounding boxes of
the label texts). Typically, labeling models either use internal labels, which
must touch their feature point, or external (boundary) labels, which are placed
on one of the four sides of the input points' bounding box and which are
connected to their feature points by crossing-free leader lines. In this paper
we study polynomial-time algorithms for maximizing the number of internal
labels in a mixed labeling model that combines internal and external labels.
The model requires that all leaders are parallel to a given orientation , whose value influences the geometric properties and hence the
running times of our algorithms.Comment: Full version for the paper accepted at CIAC 201
Numerical simulations of neutron star - black hole mergers
Collisions of black holes and neutron stars, named mixed binaries in the following, are interesting because of at least two reasons. Firstly, it is expected that they emit a large amount of energy as gravitational waves, which could be measured by new detectors. The form of those waves is expected to carry information about the internal structure of such systems. Secondly, collisions of such objects are the prime suspects of short gamma ray bursts. The exact mechanism for the energy emission is unknown so far...thesi
Neutron Star instabilities in full General Relativity using a ideal fluid
We present results about the effect of the use of a stiffer equation of
state, namely the ideal-fluid ones, on the dynamical bar-mode
instability in rapidly rotating polytropic models of neutron stars in full
General Relativity. We determine the change on the critical value of the
instability parameter for the emergence of the instability when the
adiabatic index is changed from 2 to 2.75 in order to mimic the
behavior of a realistic equation of state. In particular, we show that the
threshold for the onset of the bar-mode instability is reduced by this change
in the stiffness and give a precise quantification of the change in value of
the critical parameter . We also extend the analysis to lower values
of and show that low-beta shear instabilities are present also in the
case of matter described by a simple polytropic equation of state.Comment: 16 pages, 16 figure
Cactus: Issues for Sustainable Simulation Software
The Cactus Framework is an open-source, modular, portable programming
environment for the collaborative development and deployment of scientific
applications using high-performance computing. Its roots reach back to 1996 at
the National Center for Supercomputer Applications and the Albert Einstein
Institute in Germany, where its development jumpstarted. Since then, the Cactus
framework has witnessed major changes in hardware infrastructure as well as its
own community. This paper describes its endurance through these past changes
and, drawing upon lessons from its past, also discusses futureComment: submitted to the Workshop on Sustainable Software for Science:
Practice and Experiences 201
Modeling Mergers of Known Galactic Systems of Binary Neutron Stars
We present a study of the merger of six different known galactic systems of
binary neutron stars (BNS) of unequal mass with a mass ratio between and
. Specifically, these systems are J1756-2251, J0737-3039A, J1906+0746,
B1534+12, J0453+1559 and B1913+16. We follow the dynamics of the merger from
the late stage of the inspiral process up to 20 ms after the system has
merged, either to form a hyper-massive neutron star (NS) or a rotating black
hole (BH), using a semi-realistic equation of state (EOS), namely the
seven-segment piece-wise polytropic SLy with a thermal component. For the most
extreme of these systems (, J0453+1559), we also investigate the
effects of different EOSs: APR4, H4, and MS1. Our numerical simulations are
performed using only publicly available open source code such as, the Einstein
Toolkit code deployed for the dynamical evolution and the LORENE code for the
generation of the initial models. We show results on the gravitational wave
signals, spectrogram and frequencies of the BNS after the merger and the BH
properties in the two cases in which the system collapse within the simulated
time.Comment: 13 pages, 10 figure
Spectral analysis of gravitational waves from binary neutron star merger remnants
In this work we analyze the gravitational wave signal from hypermassive
neutron stars formed after the merger of binary neutron star systems, focusing
on its spectral features. The gravitational wave signals are extracted from
numerical relativity simulations of models already considered by De Pietri et
al. [Phys. Rev. D 93, 064047 (2016)], Maione et al. [Classical Quantum Gravity
33, 175009 (2016)], and Feo et al. [Classical Quantum Gravity 34, 034001
(2017)], and allow us to study the effect of the total baryonic mass of such
systems (from to ), the mass ratio (up to ), and the neutron star equation of state, both in equal and highly
unequal mass binaries. We use the peaks we find in the gravitational spectrum
as an independent test of already published hypotheses of their physical origin
and empirical relations linking them with the characteristics of the merging
neutron stars. In particular, we highlight the effects of the mass ratio, which
in the past was often neglected. We also analyze the temporal evolution of the
emission frequencies. Finally, we introduce a modern variant of Prony's method
to analyze the gravitational wave postmerger emission as a sum of complex
exponentials, trying to overcome some drawbacks of both Fourier spectra and
least-squares fitting. Overall, the spectral properties of the postmerger
signal observed in our simulation are in agreement with those proposed by other
groups. More specifically, we find that the analysis of Bauswein and
Stergioulas [Phys. Rev. D 91, 124056 (2015)] is particularly effective for
binaries with very low masses or with a small mass ratio and that the
mechanical toy model of Takami et al. [Phys. Rev. D 91, 064001 (2015)] provides
a comprehensive and accurate description of the early stages of the postmerger.Comment: 19 pages, 6 figure
Identification of 4-chlorobenzoyl-coenzyme A as intermediate in the dehalogenation catalysed by 4-chlorobenzoate dehalogenase from Pseudomonas sp. CBS3
AbstractThe intermediate in the reaction catalysed by 4-chlorobenzoate dehalogenase from Pseudomonas sp. CBS3 was identified as 4-chlorobenzoyl-CoA. One component of 4-chlorobenzoate debalogenase worked as a a 4-chlorobenzoyl-CoA ligase catalysing the formation of 4-chlorobenzoyl-CoA from 4-chlorobenzoate, coenzyme A and ATP. This intermediate was detected spectrophotometrically and by HPLC. 4-chlorobenzoyl-CoA was the substrate for the dehalogenase component, which catalysed the conversion to 4-hydroxybenzoate with concomitant release or coenzyme A
Stiffness effects on the dynamics of the bar-mode instability of Neutron Stars in full General Relativity
We present results on the effect of the stiffness of the equation of state on
the dynamical bar-mode instability in rapidly rotating polytropic models of
neutron stars in full General Relativity. We determine the change in the
threshold for the emergence of the instability for a range of the adiabatic
index from 2.0 to 3.0, including two values chosen to mimic more
realistic equations of state at high densities.Comment: 12 pages, 5 figures. arXiv admin note: substantial text overlap with
arXiv:1403.806
Развитие финансово-кредитной инфраструктуры национальной экономики
We introduce a variation of unit-distance graphs which we call emph clear unit-distance graphs. They require the pairwise distances of the representing points to be either exactly 1 or not close to 1. We discuss properties and applications of clear unit-distance graphs
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