3,416 research outputs found
Equation of state for neutron star matter with NJL model and Dirac-Brueckner-Hartree-Fock approximation
As the interior density of a neutron star can become very high, it has been
expected and discussed that quark matter may exist inside it. To describe the
transition from hadron to quark phases (and vice versa), there are mainly two
methods; one is the first-order phase transition, and the other is the
crossover phenomenon. In the present study, using the flavor-SU (3) NJL model
with the vector coupling interaction, we have calculated the equation of state
for the quark phase at high density. Furthermore, for the hadron phase at low
density, we have used two kinds of the equations of state; one is a relatively
soft one by the QHD model, and the other is a stiff one calculated with
relativistic Brueckner-Hartree-Fock approximation. Using those equations of
state for the two phases, we have investigated the influence of various choices
of parameters concerning the crossover region on the mass and radius of a
neutron star.Comment: 3 pages, 2 figures, conference proceedings: NIC Symposium, 19-24 June
2016, Niigata, Japa
Crosstalk Between Brain-Derived Neurotrophic Factor And N-Methyl-D-Aspartate Receptor Signaling In Neurons
Glutamate is the major excitatory neurotransmitter in brain exerting prosurvival effect on neurons via N-methyl-D-aspartate receptor (NMDAR) signaling under physiological conditions. However in pathological circumstances such as ischemia, NMDARs might have proapoptotic excitotoxic activity. In contrast brain-derived neurotrophic factor (BDNF) signaling via TrkB receptors has been largely considered to promote neuronal differentiation, plasticity and survival during normal development, and protect neurons in pathophysiological conditions antagonizing the NMDAR-mediated excitotoxic cell death. In this review we summarize recent evidence for the existent crosstalk and positive feedback loops between the BDNF and NMDAR signaling and point out some of the important specific features of each signaling pathway
Oscillations in the G-type Giants
The precise radial-velocity measurements of 4 G-type giants, 11Com,
Hya, Tau, and Her were carried out. The short-term variations
with amplitudes, 1-7m/s and periods, 3-10 hours were detected. A period
analysis shows that the individual power distribution is in a Gaussian shape
and their peak frequencies () are in a good agreement with the
prediction by the scaling law. With using a pre-whitening procedure,
significant frequency peaks more than 3 are extracted for these
giants. From these peaks, we determined the large frequency separation by
constructing highest peak distribution of collapsed power spectrum, which is
also in good agreement with what the scaling law for the large separation
predicts. Echelle diagrams of oscillation frequency were created based on the
extracted large separations, which is very useful to clarify the properties of
oscillation modes. In these echelle diagrams, odd-even mode sequences are
clearly seen. Therefore, it is certain that in these G-type giants, non-radial
modes are detected in addition to radial mode. As a consequence, these
properties of oscillation modes are shown to follow what Dzymbowski et
al.(2001) and Dupret et al.(2009) theoretically predicted. Damping times for
these giants were estimated with the same method as that developed by Stello et
al.(2004). The relation of Q value (ratio of damping time to period) to the
period was discussed by adding the data of the other stars ranging from dwarfs
to giants.Comment: 28 pages, 16 figures, accepted for publication in PASJ 62, No.4, 201
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