86 research outputs found
Imprints of Nuclear Symmetry Energy on Properties of Neutron Stars
Significant progress has been made in recent years in constraining the
density dependence of nuclear symmetry energy using terrestrial nuclear
laboratory data. Around and below the nuclear matter saturation density, the
experimental constraints start to merge in a relatively narrow region. At
supra-saturation densities, there are, however, still large uncertainties.
After summarizing the latest experimental constraints on the density dependence
of nuclear symmetry energy, we highlight a few recent studies examining
imprints of nuclear symmetry energy on the binding energy, energy release
during hadron-quark phase transitions as well as the -mode frequency and
damping time of gravitational wave emission of neutron stars.Comment: 10 pages. Invited talk given in the Nuclear Astrophysics session of
INPC2010, July 4-9, 2010, Vancouver, Canada; Journal of Physics: Conference
Series (2011
Constraining the physics of the r-mode instability in neutron stars with X-ray and UV observations
Rapidly rotating Neutron Stars in Low Mass X-ray Binaries (LMXBs) may be an
interesting source of Gravitational Waves (GWs). In particular, several modes
of stellar oscillation may be driven unstable by GW emission, and this can lead
to a detectable signal. Here we illustrate how current X-ray and ultra-violet
(UV) observations can constrain the physics of the r-mode instability. We show
that the core temperatures inferred from the data would place many systems well
inside the unstable region predicted by standard physical models. However, this
is at odds with theoretical expectations. We discuss different mechanisms that
could be at work in the stellar interior, and we show how they can modify the
instability window and make it consistent with the inferred temperatures.Comment: Submitted to MNRA
The âHauntâ project: An attempt to build a âhauntedâ room by manipulating complex electromagnetic fields and infrasound
Recent research has suggested that a number of environmental factors may be associated with a tendency for susceptible individuals to report mildly anomalous sensations typically associated with âhauntedâ locations, including a sense of presence, feeling dizzy, inexplicable smells, and so on. Factors that may be associated with such sensations include fluctuations in the electromagnetic field and the presence of infrasound. A review of such work is presented, followed by the results of the âHauntâ project in which an attempt was made to construct an artificial âhauntedâ room by systematically varying such environmental factors. Participants (N = 79) were required to spend 50 minutes in a specially constructed chamber, within which they were exposed to infrasound, complex electromagnetic fields, both or neither. They were informed in advance that during this period they might experience anomalous sensations and asked to record on a floor-plan their location at the time occurrence of any such sensations, along with a note of the time of occurrence and a brief description of the sensation. Upon completing the session in the experimental chamber, they were asked to complete three questionnaires. The first was an EXIT scale asking respondents to indicate whether or not they had experienced particular anomalous sensations. The second was the Australian Sheep-Goat Scale, a widely used measure of belief in and experience of the paranormal. The third was Persingerâs Personal Philosophy Inventory, although only the items that constitute the Temporal Lobe Signs Inventory (TLS) sub-scale were scored. These items deal with psychological experiences typically associated with temporal lobe epilepsy but normally distributed throughout the general population. Although many participants reported anomalous sensations of various kinds, the number reported was unrelated to experimental condition but was related to TLS scores. The most parsimonious explanation for our findings is in terms of suggestibility
Gravitational waves from single neutron stars: an advanced detector era survey
With the doors beginning to swing open on the new gravitational wave
astronomy, this review provides an up-to-date survey of the most important
physical mechanisms that could lead to emission of potentially detectable
gravitational radiation from isolated and accreting neutron stars. In
particular we discuss the gravitational wave-driven instability and
asteroseismology formalism of the f- and r-modes, the different ways that a
neutron star could form and sustain a non-axisymmetric quadrupolar "mountain"
deformation, the excitation of oscillations during magnetar flares and the
possible gravitational wave signature of pulsar glitches. We focus on progress
made in the recent years in each topic, make a fresh assessment of the
gravitational wave detectability of each mechanism and, finally, highlight key
problems and desiderata for future work.Comment: 39 pages, 12 figures, 2 tables. Chapter of the book "Physics and
Astrophysics of Neutron Stars", NewCompStar COST Action 1304. Minor
corrections to match published versio
Collecting Comet Samples by ER-2 Aircraft: Cosmic Dust Collection During the Draconid Meteor Shower in October 2012
Many tons of dust grains, including samples of asteroids and comets, fall from space into the Earth's atmosphere each day. NASA periodically collects some of these particles from the Earth's stratosphere using sticky collectors mounted on NASA's high-flying aircraft. Sometimes, especially when the Earth experiences a known meteor shower, a special opportunity is presented to associate cosmic dust particles with a known source. NASA JSC's Cosmic Dust Collection Program has made special attempts to collect dust from particular meteor showers and asteroid families when flights can be planned well in advance. However, it has rarely been possible to make collections on very short notice. In 2012, the Draconid meteor shower presented that opportunity. The Draconid meteor shower, originating from Comet 21P/Giacobini-Zinner, has produced both outbursts and storms several times during the last century, but the 2012 event was not predicted to be much of a show. Because of these predictions, the Cosmic Dust team had not targeted a stratospheric collection effort for the Draconids, despite the fact that they have one of the slowest atmospheric entry velocities (23 km/s) of any comet shower, and thus offer significant possibilities of successful dust capture. However, radar measurements obtained by the Canadian Meteor Orbit Radar during the 2012 Draconids shower indicated a meteor storm did occur October 8 with a peak at 16:38 (+/-5 min) UTC for a total duration of approximately 2 hours
Increased genetic gains in sheep, beef and dairy breeding programs from using female reproductive technologies combined with optimal contribution selection and genomic breeding values
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