557 research outputs found
AZEuS: An Adaptive Zone Eulerian Scheme for Computational MHD
A new adaptive mesh refinement (AMR) version of the ZEUS-3D astrophysical
magnetohydrodynamical (MHD) fluid code, AZEuS, is described. The AMR module in
AZEuS has been completely adapted to the staggered mesh that characterises the
ZEUS family of codes, on which scalar quantities are zone-centred and vector
components are face-centred. In addition, for applications using static grids,
it is necessary to use higher-order interpolations for prolongation to minimise
the errors caused by waves crossing from a grid of one resolution to another.
Finally, solutions to test problems in 1-, 2-, and 3-dimensions in both
Cartesian and spherical coordinates are presented.Comment: 52 pages, 17 figures; Accepted for publication in ApJ
Gender Differences in Pro-Environmental Behavior Intentions
Previous research has found gender differences in pro-environmental behavior (PEB) performance. Women typically score higher on environmental concern and show stronger inclination to engage in private or domestic PEBs (Tindall et al., 2003) and Allen et al. (2015) found that women are more likely to engage in efficiency upgrade PEBs. However, men show higher prevalence towards performing public PEB (Hunter et al., 2004). The present study recruited 313 Mturk participants. They were randomly assigned to one of six different norm levels. After exposure to a norm level, the experimental groups were provided the opportunity to perform the PEB. Participants then completed measures of environmental attitudes and were asked questions relating to their intention to partake in a list of PEBs in the coming six months. These related to efficiency upgrades, political PEB, home PEB, and travel PEB. We hypothesized that women would be more likely to engage in PEBs relating to home, travel, and efficiency upgrades when compared to men; and that men will be more likely to engage in political PEBs. Results yielded women scoring significantly higher on intention to engage in home PEBs (p \u3c .001) and travel PEBs (p = .016), but no significant difference was found for efficiency upgrades (p = .972) or political PEBs (p = .898). Knowing the tendencies and intentions behind different gendersâ PEB performance allows us the opportunity to intervene based on both genders. While recognizing the nature of engagement on specific PEB, we can efficiently promote specific PEB engagement within groups
Protostellar collapse: A comparison between SPH and AMR calculations
The development of parallel supercomputers allows today the detailed study of
the collapse and the fragmentation of prestellar cores with increasingly
accurate numerical simulations. Thanks to the advances in sub-millimeter
observations, a wide range of observed initial conditions enable us to study
the different modes of low-mass star formation. The challenge for the
simulations is to reproduce the observational results. Two main numerical
methods, namely AMR and SPH, are widely used to simulate the collapse and the
fragmentation of prestellar cores. We compare thoroughly these two methods
within their standard framework. We use the AMR code RAMSES and the SPH code
DRAGON. Our physical model is as simple as possible and consists of an
isothermal sphere rotating around the z-axis. We first study the conservation
of angular momentum as a function of the resolution. Then, we explore a wide
range of simulation parameters to study the fragmentation of prestellar cores.
There seems to be a convergence between the two methods, provided resolution in
each case is sufficient. Resolution criteria adapted to our physical cases, in
terms of resolution per Jeans mass, for an accurate description of the
formation of protostellar cores are deduced from the present study. This
convergence is encouraging for future work in simulations of low-mass star
formation, providing the aforementioned criteria are fulfilled.
Higher resolution figures can be downloaded at
http://www-dapnia.cea.fr/Projets/COAST/paper_amrvssph.pdfComment: 16 pages, 16 figures, accepted for publication in A&
A Multi-dimensional Code for Isothermal Magnetohydrodynamic Flows in Astrophysics
We present a multi-dimensional numerical code to solve isothermal
magnetohydrodynamic (IMHD) equations for use in modeling astrophysical flows.
First, we have built a one-dimensional code which is based on an explicit
finite-difference method on an Eulerian grid, called the total variation
diminishing (TVD) scheme. Recipes for building the one-dimensional IMHD code,
including the normalized right and left eigenvectors of the IMHD Jacobian
matrix, are presented. Then, we have extended the one-dimensional code to a
multi-dimensional IMHD code through a Strang-type dimensional splitting. In the
multi-dimensional code, an explicit cleaning step has been included to
eliminate non-zero at every time step. To estimate the
proformance of the code, one- and two-dimensional IMHD shock tube tests, and
the decay test of a two-dimensional Alfv\'{e}n wave have been done. As an
example of astrophysical applications, we have simulated the nonlinear
evolution of the two-dimensional Parker instability under a uniform gravity.Comment: Accepted for publication in ApJ, using aaspp4.sty, 22 text pages with
10 figure
A Chandra Observation of Supernova Remnant G350.1-0.3 and Its Central Compact Object
We present a new Chandra observation of supernova remnant (SNR) G350.1-0.3.
The high resolution X-ray data reveal previously unresolved filamentary
structures and allow us to perform detailed spectroscopy in the diffuse regions
of this SNR. Spectral analysis demonstrates that the region of brightest
emission is dominated by hot, metal-rich ejecta while the ambient material
along the perimeter of the ejecta region and throughout the remnant's western
half is mostly low-temperature, shocked interstellar/circumstellar medium
(ISM/CSM) with solar-type composition. The data reveal that the emission
extends far to the west of the ejecta region and imply a lower limit of 6.6 pc
on the diameter of the source (at a distance of 4.5 kpc). We show that
G350.1-0.3 is likely in the free expansion (ejecta-dominated) stage and
calculate an age of 600-1200 years. The derived relationship between the shock
velocity and the electron/proton temperature ratio is found to be entirely
consistent with that of other SNRs. We perform spectral fits on the X-ray
source XMMU J172054.5-372652, a candidate central compact object (CCO), and
find that its spectral properties fall within the typical range of other CCOs.
We also present archival 24 um data of G350.1-0.3 taken with the Spitzer Space
Telescope during the MIPSGAL galactic survey and find that the infrared and
X-ray morphologies are well-correlated. These results help to explain this
remnant's peculiar asymmetries and shed new light on its dynamics and
evolution
ć·ăźäžăźæè«ăăĄ
There is provided a novel derivative of 2-acetoxybenzoic acid, i.e., 1-O-(2\u27-acetoxy)benzoyl-α-D-2-deoxyglucopyranose, which is suitable for the attainment of high 2-acetoxybenzoic acid blood levels without irritation of the gastrointestinal lining
The Outer Shock of the Oxygen-Rich Supernova Remnant G292.0+1.8: Evidence for the Interaction with the Stellar Winds from its Massive Progenitor
We study the outer-shock structure of the oxygen-rich supernova remnant
G292.0+1.8, using a deep observation with the Chandra X-ray Observatory. We
measure radial variations of the electron temperature and emission measure that
we identify as the outer shock propagating into a medium with a radially
decreasing density profile. The inferred ambient density structure is
consistent with models for the circumstellar wind of a massive progenitor star
rather than for a uniform interstellar medium. The estimated wind density n_H =
0.1 ~ 0.3 cm^-3) at the current outer radius (~7.7 pc) of the remnant is
consistent with a slow wind from a red supergiant (RSG) star. The total mass of
the wind is estimated to be ~ 15 - 40 solar mass (depending on the estimated
density range), assuming that the wind extended down to near the surface of the
progenitor. The overall kinematics of G292.0+1.8 are consistent with the
remnant expanding through the RSG wind.Comment: 9 pages (2-column), 5 figures, accepted for Ap
Ionization front-driven turbulence in the clumpy interstellar medium
We present 3D radiation-gasdynamical simulations of an ionization front
running into a dense clump. In our setup, a B0 star irradiates an overdensity
which is at a distance of 10 pc and modelled as a supercritical 100 M_sol
Bonnor-Ebert sphere. The radiation from the star heats up the gas and creates a
shock front that expands into the interstellar medium. The shock compresses the
clump material while the ionizing radiation heats it up. The outcome of this
"cloud-crushing" process is a fully turbulent gas in the wake of the clump. In
the end, the clump entirely dissolves. We propose that this mechanism is very
efficient in creating short-living supersonic turbulence in the vicinity of
massive stars
Parentsâ Attitudes Regarding Their Childrenâs Play and Sport During COVID-19
The COVID-19 pandemic and associated public health measures have interrupted the daily routines of parents and children. The purpose of this study was to explore parentsâ attitudes regarding their childrenâs play/sport during COVID-19. A secondary objective was to explore the influence of parent demographics and parent-reported physical activity levels and risk tolerance on these attitudes. Ontario parents of children aged 12 and younger completed an online survey (AugustâDecember 2020) that assessed their attitudes (grouped by support, safety and socialization-related attitudes; n = 14 items) regarding their child(ren)âs play/sport, their physical activity levels (n = 2 items), and demographic details (n = 16 items). Two open-ended items were used to gather a deeper understanding of attitudes. Parentsâ tolerance for risk was measured via the validated Tolerance of Risk in Play Scale. Descriptive statistics were calculated to describe attitudes and risk tolerance. Least Absolute Shrinkage and Selection Operator regressions were conducted to examine factors influencing parentsâ attitudes. Multiple linear models were computed using the identified predictors for each attitude category. Deductive content analysis was undertaken on open-ended responses. Participants (n = 819) reported the highest scores for safety-related attitude items (M = 3.54, SD = .63) followed by socialization and support, which all influenced attitudes regarding childrenâs play/sport (p \u3c .05). Demographics and parentsâ physical activity levels were identified as important predictors of parentsâ attitudes. Qualitative data revealed that parents had mixed levels of comfort with respect to their childrenâs return to play/sport. Findings from this study reveal that increased support is needed to guide future play/sport decision-making
Fall-back crust around a quark-nova compact remnant I: The degenerate shell case with applications to SGRs, AXPs and XDINs
We explore the formation and evolution of debris ejected around quark stars
in the Quark Nova scenario, and the application to Soft Gamma-ray Repeaters
(SGRs) and Anomolous X-ray Pulsars (AXPs). If an isolated neutron star explodes
as a Quark Nova, an Iron-rich shell of degenerate matter forms out of the
fall-back (crust) material. Our model can account for many of the observed
features of SGRs and AXPs such as: (i) the two types of bursts (giant and
regular); (ii) the spin-up and spin-down episodes during and following the
bursts with associated persistant increases in ; (iii) the energetics
of the boxing day burst, SGR180620; (iv) the presence of an Iron line as
observed in SGR190014; (v) the correlation between the far-Infrared and the
X-ray fluxes during the bursting episode and the quiescent phase; (vi) the hard
X-ray component observed in SGRs during the giant bursts, and (vii) the
discrepancy between the ages of SGRs/AXPs and their supernova remnants. We also
find a natural evolutionary relationship between SGRs and AXPs in our model
which predicts that only the youngest SGRs/AXPs are most likely to exhibit
strong bursting. Many features of X-ray Dim Isolated Neutron stars (XDINs) are
also accounted for in our model such as, (i) the two-component blackbody
spectra; (ii) the absorption lines around 300 eV; and (iii) the excess optical
emission.Comment: submitted to Ap
- âŠ