243 research outputs found
The impact of a correctional-based parenting program in strengthening parenting skills of incarcerated mothers
Despite a relative paucity of information on the impact that incarceration of a parent has on a child, most literature agrees that the effects are real and profound. Corrective Services NSW (CSNSW) in conjunction with Tresillian Family Care Centres introduced a parenting program, Mothering at a Distance (MAAD), across correctional facilities for female prisoners in New South Wales (NSW), Australia. The central aim of the Program was to provide early parenting education and support intervention to mothers in custody, with the aim of guarding against the intergenerational cycle of crime. The Program intended to enhance a prisoner's ability to provide appropriate and sensitive parenting and reduce the emotional and social impact of separation on their children. An evaluation of the Program's development, implementation, effectiveness, and sustainability was conducted on all groups run between October 2006 and December 2008. This article provides a summary of the evaluation findings
Eccentric double white dwarfs as LISA sources in globular clusters
We consider the formation of double white dwarfs (DWDs) through dynamical
interactions in globular clusters. Such interactions can give rise to eccentric
DWDs, in contrast to the exclusively circular population expected to form in
the Galactic disk. We show that for a 5-year Laser Interferometer Space Antenna
(LISA) mission and distances as far as the Large Magellanic Cloud, multiple
harmonics from eccentric DWDs can be detected at a signal-to-noise ratio higher
than 8 for at least a handful of eccentric DWDs, given their formation rate and
typical lifetimes estimated from current cluster simulations. Consequently the
association of eccentricity with stellar-mass LISA sources does not uniquely
involve neutron stars, as is usually assumed. Due to the difficulty of
detecting (eccentric) DWDs with present and planned electromagnetic
observatories, LISA could provide unique dynamical identifications of these
systems in globular clusters.Comment: Published in ApJ 665, L5
Atomic structure of dislocation kinks in silicon
We investigate the physics of the core reconstruction and associated
structural excitations (reconstruction defects and kinks) of dislocations in
silicon, using a linear-scaling density-matrix technique. The two predominant
dislocations (the 90-degree and 30-degree partials) are examined, focusing for
the 90-degree case on the single-period core reconstruction. In both cases, we
observe strongly reconstructed bonds at the dislocation cores, as suggested in
previous studies. As a consequence, relatively low formation energies and high
migration barriers are generally associated with reconstructed
(dangling-bond-free) kinks. Complexes formed of a kink plus a reconstruction
defect are found to be strongly bound in the 30-degree partial, while the
opposite is true in the case of 90-degree partial, where such complexes are
found to be only marginally stable at zero temperature with very low
dissociation barriers. For the 30-degree partial, our calculated formation
energies and migration barriers of kinks are seen to compare favorably with
experiment. Our results for the kink energies on the 90-degree partial are
consistent with a recently proposed alternative double-period structure for the
core of this dislocation.Comment: 12 pages, two-column style with 8 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#rn_di
Structure of Dark Matter Halos From Hierarchical Clustering
We investigate the structure of the dark matter halo formed in the cold dark
matter scenario using -body simulations. We simulated 12 halos with the mass
of to . In almost all
runs, the halos have density cusps proportional to developed at the
center, which is consistent with the results of recent high-resolution
calculations. The density structure evolves in a self-similar way, and is
universal in the sense that it is independent of the halo mass and initial
random realization of density fluctuation. The density profile is in good
agreement with the profile proposed by Moore et al. (1999), which has central
slope proportional to and outer slope proportional to . The
halo grows through repeated accretion of diffuse smaller halos. We argue that
the cusp is understood as a convergence slope for the accretion of tidally
disrupted matter.Comment: 34 including 23 figures, revised version, accepted for publication in
Ap
Electron spectroscopy of carbon materials: Experiment and theory
We present a comparative spectroscopic study of carbon as graphite, diamond and C60 using C1s K-edge electron energy-loss spectroscopy (EELS), X-ray emission spectroscopy, and theoretical modelling. The first principles calculations of these spectra are obtained in the local density approximation using a self-consistent Gaussian basis pseudo-potential method. Calculated spectra show excellent agreement with experiment and are able to discriminate not only between various carbon hybridisations but also local variation in environment. Core-hole effects on the calculated spectra are also investigated. For the first time, the EEL spectrum of carbyne is calculated
Thermodynamics of the self-gravitating ring model
We present the phase diagram, in both the microcanonical and the canonical
ensemble, of the Self-Gravitating-Ring (SGR) model, which describes the motion
of equal point masses constrained on a ring and subject to 3D gravitational
attraction. If the interaction is regularized at short distances by the
introduction of a softening parameter, a global entropy maximum always exists,
and thermodynamics is well defined in the mean-field limit. However, ensembles
are not equivalent and a phase of negative specific heat in the microcanonical
ensemble appears in a wide intermediate energy region, if the softening
parameter is small enough. The phase transition changes from second to first
order at a tricritical point, whose location is not the same in the two
ensembles. All these features make of the SGR model the best prototype of a
self-gravitating system in one dimension. In order to obtain the stable
stationary mass distribution, we apply a new iterative method, inspired by a
previous one used in 2D turbulence, which ensures entropy increase and, hence,
convergence towards an equilibrium state
Probing Electron-Capture Supernovae: X-Ray Binaries in Starbursts
Presenting population models of high-mass X-ray binaries (HMXBs) formed after
bursts of star formation, we investigate the effect of electron-capture
supernovae (ECS) of massive ONeMg white dwarfs and the hypothesis that ECS
events are associated with typically low supernova kicks imparted to the
nascent neutron stars. We identify an interesting ECS bump in the time
evolution of HMXB numbers; this bump is caused by significantly increased
production of wind-fed HMXBs 20-60 Myr post starburst. The amplitude and age
extent of the ECS bump depend on the strength of ECS kicks and the mass range
of ECS progenitors. We also find that ECS-HMXBs form through a specific
evolutionary channel that is expected to lead to binaries with Be donors in
wide orbits. These characteristics, along with their sensitivity to ECS
properties, provide us with an intriguing opportunity to probe ECS physics and
progenitors through studies of starbursts of different ages. Specifically, the
case of the Small Magellanic Cloud, with a significant observed population of
Be HMXBs and starburst activity 30-60 Myr ago, arises as a promising laboratory
for understanding the role of electron-capture supernovae in neutron star
formation.Comment: 5 pages, 3 figures, Published by ApJ in 07/0
On the Origin of X-ray Emission From Millisecond Pulsars in 47 Tuc
The observed spectra and X-ray luminosities of millisecond pulsars in 47 Tuc
can be interpreted in the context of theoretical models based on strong, small
scale multipole fields on the neutron star surface. For multipole fields that
are relatively strong as compared to the large scale dipole field, the emitted
X-rays are thermal and likely result from polar cap heating associated with the
return current from the polar gap. On the other hand, for weak multipole
fields, the emission is nonthermal and results from synchrotron radiation of
pairs created by curvature radiation. The X-ray luminosity, , is
related to the spin down power, , expressed in the form with and for strong and weak
multipole fields respectively. If the polar cap size is of the order of the
length scale of the multipole field, and , the polar cap
temperature is .
A comparison of the X-ray properties of millisecond pulsars in globular
clusters and in the Galactic field suggests that the emergence of relatively
strong small scale multipole fields from the neutron star interior may be
correlated with the age and evolutionary history of the underlying neutron
star.Comment: 25 pages, 2 figures, accepted for publication in Ap
Separated before birth: pulsars B2020+28 and B2021+51 as the remnants of runaway stars
Astrometric data on the pulsars B2020+28 and B2021+51 suggest that they
originated within several parsecs of each other in the direction of the Cyg OB2
association. It was proposed that the pulsars share their origin in a common
massive binary and were separated at the birth of the second pulsar following
the asymmetric supernova explosion. We consider a different scenario for the
origin of the pulsar pair based on a possibility that the pulsars were
separated before their birth and that they are the remnants of runaway stars
ejected (with velocities similar to those of the pulsars) from the core of Cyg
OB2 due to strong three- or four-body dynamical encounters. Our scenario does
not require any asymmetry in supernova explosions.Comment: 4 pages, 2 figures, accepted for publication in A&A Letter
Star cluster dynamics
Dynamical evolution plays a key role in shaping the current properties of
star clusters and star cluster systems. A detailed understanding of the effects
of evolutionary processes is essential to be able to disentangle the properties
which result from dynamical evolution from those imprinted at the time of
cluster formation. In this review, we focus our attention on globular clusters
and review the main physical ingredients driving their early and long-term
evolution, describe the possible evolutionary routes and show how cluster
structure and stellar content are affected by dynamical evolution.Comment: 20 pages, 2 figures. To appear as invited review article in a special
issue of the Phil. Trans. Royal Soc. A: Ch. 7 "Star clusters as tracers of
galactic star-formation histories" (ed. R. de Grijs). Fully peer reviewed.
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