224 research outputs found
Abnormal Fees and Timely Loss Recognition - A Long-Term Perspective
This is the author accepted manuscript. The final version is available from the American Accounting Association via the DOI in this recordWe examine the relation between timely loss recognition and abnormal audit, non-audit, and total fees over a long period (2001â2007 and 2010â2015). We use positive abnormal audit fees as a measure of abnormal audit effort, and positive abnormal non-audit fees as a measure of economic bond between the auditor and the auditee. Using the Ball and Shivakumar (2006) model, we report some evidence suggesting audit effort is associated with slower loss recognition in accruals before the SarbanesâOxley Act (SOX) became effective. However, we find stronger evidence that audit effort is associated with slower loss recognition post-SOX when clients raise substantial external funds or when the auditor is not an industry specialist. Using C_Score, we find a negative association between changes in abnormal audit fees and total fees, and changes in C_Score post-SOX, but not pre-SOX. We find no sample-wide evidence that abnormal non-audit fees are associated with the speed of loss recognition. Collectively, the results suggest post-SOX auditors exert more effort when losses are delayed and that non-audit services do not compromise auditor independence
Navier-Stokes hydrodynamics of thermal collapse in a freely cooling granular gas
We employ Navier-Stokes granular hydrodynamics to investigate the long-time
behavior of clustering instability in a freely cooling dilute granular gas in
two dimensions. We find that, in circular containers, the homogeneous cooling
state (HCS) of the gas loses its stability via a sub-critical pitchfork
bifurcation. There are no time-independent solutions for the gas density in the
supercritical region, and we present analytical and numerical evidence that the
gas develops thermal collapse unarrested by heat diffusion. To get more
insight, we switch to a simpler geometry of a narrow-sector-shaped container.
Here the HCS loses its stability via a transcritical bifurcation. For some
initial conditions a time-independent inhomogeneous density profile sets in,
qualitatively similar to that previously found in a narrow-channel geometry.
For other initial conditions, however, the dilute gas develops thermal collapse
unarrested by heat diffusion. We determine the dynamic scalings of the flow
close to collapse analytically and verify them in hydrodynamic simulations. The
results of this work imply that, in dimension higher than one, Navier-Stokes
hydrodynamics of a dilute granular gas is prone to finite-time density blowups.
This provides a natural explanation to the formation of densely packed clusters
of particles in a variety of initially dilute granular flows.Comment: 18 pages, 19 figure
Multi-Dimensional Simulations of the Accretion-Induced Collapse of White Dwarfs to Neutron Stars
We present 2.5D radiation-hydrodynamics simulations of the accretion-induced
collapse (AIC) of white dwarfs, starting from 2D rotational equilibrium
configurations of a 1.46-Msun and a 1.92-Msun model. Electron capture leads to
the collapse to nuclear densities of these cores within a few tens of
milliseconds. The shock generated at bounce moves slowly, but steadily,
outwards. Within 50-100ms, the stalled shock breaks out of the white dwarf
along the poles. The blast is followed by a neutrino-driven wind that develops
within the white dwarf, in a cone of ~40deg opening angle about the poles, with
a mass loss rate of 5-8 x 10^{-3} Msun/yr. The ejecta have an entropy on the
order of 20-50 k_B/baryon, and an electron fraction distribution that is
bimodal. By the end of the simulations, at >600ms after bounce, the explosion
energy has reached 3-4 x 10^{49}erg and the total ejecta mass has reached a few
times 0.001Msun. We estimate the asymptotic explosion energies to be lower than
10^{50}erg, significantly lower than those inferred for standard core collapse.
The AIC of white dwarfs thus represents one instance where a neutrino mechanism
leads undoubtedly to a successful, albeit weak, explosion.
We document in detail the numerous effects of the fast rotation of the
progenitors: The neutron stars are aspherical; the ``nu_mu'' and anti-nu_e
neutrino luminosities are reduced compared to the nu_e neutrino luminosity; the
deleptonized region has a butterfly shape; the neutrino flux and electron
fraction depend strongly upon latitude (a la von Zeipel); and a quasi-Keplerian
0.1-0.5-Msun accretion disk is formed.Comment: 25 pages, 19 figures, accpeted to ApJ, high resolution of the paper
and movies available at http://hermes.as.arizona.edu/~luc/aic/aic.htm
Gravitational Waves from Axisymmetric, Rotational Stellar Core Collapse
We have carried out an extensive set of two-dimensional, axisymmetric,
purely-hydrodynamic calculations of rotational stellar core collapse with a
realistic, finite-temperature nuclear equation of state and realistic massive
star progenitor models. For each of the total number of 72 different
simulations we performed, the gravitational wave signature was extracted via
the quadrupole formula in the slow-motion, weak-field approximation. We
investigate the consequences of variation in the initial ratio of rotational
kinetic energy to gravitational potential energy and in the initial degree of
differential rotation. Furthermore, we include in our model suite progenitors
from recent evolutionary calculations that take into account the effects of
rotation and magnetic torques. For each model, we calculate gravitational
radiation wave forms, characteristic wave strain spectra, energy spectra, final
rotational profiles, and total radiated energy. In addition, we compare our
model signals with the anticipated sensitivities of the 1st- and 2nd-generation
LIGO detectors coming on line. We find that most of our models are detectable
by LIGO from anywhere in the Milky Way.Comment: 13 pages, 22 figures, accepted for publication in ApJ (v600, Jan.
2004). Revised version: Corrected typos and minor mistakes in text and
references. Minor additions to the text according to the referee's
suggestions, conclusions unchange
Model Flames in the Boussinesq Limit: The Effects of Feedback
We have studied the fully nonlinear behavior of pre-mixed flames in a
gravitationally stratified medium, subject to the Boussinesq approximation. Key
results include the establishment of criterion for when such flames propagate
as simple planar flames; elucidation of scaling laws for the effective flame
speed; and a study of the stability properties of these flames. The simplicity
of some of our scalings results suggests that analytical work may further
advance our understandings of buoyant flames.Comment: 11 pages, 14 figures, RevTex, gzipped tar fil
Hydrodynamics of thermal granular convection
A hydrodynamic theory is formulated for buoyancy-driven ("thermal") granular
convection, recently predicted in molecular dynamic simulations and observed in
experiment. The limit of a dilute flow is considered. The problem is fully
described by three scaled parameters. The convection occurs via a supercritical
bifurcation, the inelasticity of the collisions being the control parameter.
The theory is expected to be valid for small Knudsen numbers and nearly elastic
grain collisions.Comment: 4 pages, 4 EPS figures, some details adde
Nucleosynthesis in Type Ia Supernovae
Among the major uncertainties involved in the Chandrasekhar mass models for
Type Ia supernovae are the companion star of the accreting white dwarf (or the
accretion rate that determines the carbon ignition density) and the flame speed
after ignition. We present nucleosynthesis results from relatively slow
deflagration (1.5 - 3 % of the sound speed) to constrain the rate of accretion
from the companion star. Because of electron capture, a significant amount of
neutron-rich species such as ^{54}Cr, ^{50}Ti, ^{58}Fe, ^{62}Ni, etc. are
synthesized in the central region. To avoid the too large ratios of
^{54}Cr/^{56}Fe and ^{50}Ti/^{56}Fe, the central density of the white dwarf at
thermonuclear runaway must be as low as \ltsim 2 \e9 \gmc. Such a low central
density can be realized by the accretion as fast as \dot M \gtsim 1 \times
10^{-7} M_\odot yr^{-1}. These rapidly accreting white dwarfs might correspond
to the super-soft X-ray sources.Comment: 10 page LaTeX, 7 PostScript figures, to appear in Nuclear Physics A,
Vol. A621 (1997
Symmetry-breaking instability in a prototypical driven granular gas
Symmetry-breaking instability of a laterally uniform granular cluster (strip
state) in a prototypical driven granular gas is investigated. The system
consists of smooth hard disks in a two-dimensional box, colliding inelastically
with each other and driven, at zero gravity, by a "thermal" wall. The limit of
nearly elastic particle collisions is considered, and granular hydrodynamics
with the Jenkins-Richman constitutive relations is employed. The hydrodynamic
problem is completely described by two scaled parameters and the aspect ratio
of the box. Marginal stability analysis predicts a spontaneous symmetry
breaking instability of the strip state, similar to that predicted recently for
a different set of constitutive relations. If the system is big enough, the
marginal stability curve becomes independent of the details of the boundary
condition at the driving wall. In this regime, the density perturbation is
exponentially localized at the elastic wall opposite to the thermal wall. The
short- and long-wavelength asymptotics of the marginal stability curves are
obtained analytically in the dilute limit. The physics of the symmetry-breaking
instability is discussed.Comment: 11 pages, 14 figure
The rate of the founder Jewish mutations in BRCA1 and BRCA2 in prostate cancer patients in Israel
Inherited predisposition occurs in 5â10% of all prostate cancer (CaP) patients, but the genes involved in conferring genetic susceptibility remain largely unknown. Several lines of evidence indicate that germline mutations in BRCA1 and BRCA2 might be associated with an increased risk for CaP. Three mutations in these two genes (185delAG and 5382InsC (BRCA1) and 6174delT (BRCA2) occur in about 2.5% of the general Ashkenazi population, and the 185delAG BRCA1 mutation, in up to 1% of non-Ashkenazi Jews. In order to assess the contribution of these germline mutations to prostate cancer in Jewish Israeli patients, we tested 174 unselected prostate cancer patients (95 of Ashkenazi origin) for these mutations by PCR amplification and modified restriction enzyme digests. Patientâs age range was 45â81 years (median 66), and in 24 (14.4%) the disease was diagnosed prior to 55 years of age. Nineteen (11%) and 12 (6.9%) patients had a first or second degree relative with CaP or breast cancer, respectively. Overall, five mutation carriers were detected: 2/152 (1.3%) 185delAG, 2/104 (2%) 5382InsC, and 1/158 (0.6%) 6174delT. In all carriers, the disease was diagnosed after the age of 55, and only one of them had a family history of breast and CaP. In addition, no allelic losses at the BRCA1 locus were demonstrated in 17 patients with a family history of CaP, using seven microsatellite markers. We conclude that the rate of the predominant Jewish BRCA1 and BRCA2 mutations in CaP patients does not significantly differ from that of the general population, and that mutational inactivation of the BRCA1 is rare in familial CaP. Thus, germline BRCA1 and BRCA2 mutations probably contribute little to CaP occurrence, to inherited predisposition, and to early onset disease in Jewish individuals. © 2000 Cancer Research Campaig
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