17,166 research outputs found
Modified evolution of stellar binaries from supermassive black hole binaries
The evolution of main sequence binaries resided in the galactic centre is
influenced a lot by the central super massive black hole (SMBH). Due to this
perturbation, the stars in a dense environment are likely to experience mergers
or collisions through secular or non-secular interactions. In this work, we
study the dynamics of the stellar binaries at galactic center, perturbed by
another distant SMBH. Geometrically, such a four-body system is supposed to be
decomposed into the inner triple (SMBH-star-star) and the outer triple
(SMBH-stellar binary-SMBH). We survey the parameter space and determine the
criteria analytically for the stellar mergers and the tidal disruption events
(TDEs). For a relative distant and equal masses SMBH binary, the stars have
more opportunities to merge as a result from the Lidov-Kozai(LK) oscillations
in the inner triple. With a sample of tight stellar binaries, our numerical
experiments reveal that a significant fraction of the binaries, ~70 per cent,
experience merger eventually. Whereas the majority of the stellar TDEs are
likely to occur at a close periapses to the SMBH, induced by the outer Kozai
effect. The tidal disruptions are found numerically as many as ~10 per cent for
a close SMBH binary that is enhanced significantly than the one without the
external SMBH. These effects require the outer perturber to have an inclined
orbit (>=40 degree) relatively to the inner orbital plane and may lead to a
burst of the extremely astronomical events associated with the detection of the
SMBH binary.Comment: 12 pages, 9 figures, MNRAS in pres
Towards a minimal order distributed observer for linear systems
In this paper we consider the distributed estimation problem for
continuous-time linear time-invariant (LTI) systems. A single linear plant is
observed by a network of local observers. Each local observer in the network
has access to only part of the output of the observed system, but can also
receive information on the state estimates of its neigbours. Each local
observer should in this way generate an estimate of the plant state. In this
paper we study the problem of existence of a reduced order distributed
observer. We show that if the observed system is observable and the network
graph is a strongly connected directed graph, then a distributed observer
exists with state space dimension equal to , where
is the number of network nodes, is the state space dimension of the
observed plant, and is the rank of the output matrix of the observed
output received by the th local observer. In the case of a single observer,
this result specializes to the well-known minimal order observer in classical
observer design.Comment: 12 pages, 1 figur
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Distinct cytokine profiles across trajectories of self-perceived cognitive impairment among early-stage breast cancer survivors.
The aim of the current study is to identify distinct cytokine profiles in relation to self-perceived cognitive trajectories. In our study cohort (n = 128), early-stage breast cancer patients were categorized into no impairment reported, acute, delayed, persistent and intermittent cognitive decline respectively. Pro-inflammatory cytokines were elevated compared to baseline; with TNF-Ξ± implicated in the acute cognitive trajectory while IL-6 and IL-8 were involved in the persistent cognitive trajectory. Our findings help to further our understanding of cytokine profiles implicated in cancer-related cognitive impairment (CRCI) and support the use of cytokine levels as biomarkers of cognitive decline over time
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