4,486 research outputs found
Survey of financial statement analysis courses in Europe and the United States
The paper reports the results of a survey of the content and learning materials used in courses in financial statement analysis in Europe and the United States. Courses in Europe and undergraduate courses in the US exhibit similar characteristics with respect to course content (heavy emphasis on basic tools of analysis). Graduate courses in the US place heavier emphasis on coverage of generally accepted accounting principles and on applications of basic analytical tools. Differences in course content appear related to where the financial statement analysis course lodges within the accounting curriculum.Accounting education; financial statement analysis; Europe; US; graduate; undergraduate
On a link between a species survival time in an evolution model and the Bessel distributions
We consider a stochastic model for species evolution. A new species is born
at rate lambda and a species dies at rate mu. A random number, sampled from a
given distribution F, is associated with each new species at the time of birth.
Every time there is a death event, the species that is killed is the one with
the smallest fitness. We consider the (random) survival time of a species with
a given fitness f. We show that the survival time distribution depends
crucially on whether ff_c where f_c is a critical fitness that
is computed explicitly.Comment: 13 page
A stochastic model of evolution
We propose a stochastic model for evolution. Births and deaths of species
occur with constant probabilities. Each new species is associated with a
fitness sampled from the uniform distribution on [0,1]. Every time there is a
death event then the type that is killed is the one with the smallest fitness.
We show that there is a sharp phase transition when the birth probability is
larger than the death probability. The set of species with fitness higher than
a certain critical value approach an uniform distribution. On the other hand
all the species with fitness less than the critical disappear after a finite
(random) time.Comment: 6 pages, 1 figure, TeX, Added references, To appear in Markov
Processes and Related Field
Hot X-ray coronae around massive spiral galaxies: a unique probe of structure formation models
Luminous X-ray gas coronae in the dark matter halos of massive spiral
galaxies are a fundamental prediction of structure formation models, yet only a
few such coronae have been detected so far. In this paper, we study the hot
X-ray coronae beyond the optical disks of two normal massive spirals, NGC1961
and NGC6753. Based on XMM-Newton X-ray observations, hot gaseous emission is
detected to ~60 kpc - well beyond their optical radii. The hot gas has a
best-fit temperature of kT~0.6 keV and an abundance of ~0.1 Solar, and exhibits
a fairly uniform distribution, suggesting that the quasi-static gas resides in
hydrostatic equilibrium in the potential well of the galaxies. The bolometric
luminosity of the gas in the (0.05-0.15)r_200 region (r_200 is the virial
radius) is ~6e40 erg/s for both galaxies. The baryon mass fractions of NGC1961
and NGC6753 are f_b~0.1, which fall short of the cosmic baryon fraction. The
hot coronae around NGC1961 and NGC6753 offer an excellent basis to probe
structure formation simulations. To this end, the observations are confronted
with the moving mesh code Arepo and the smoothed particle hydrodynamics code
Gadget. Although neither model gives a perfect description, the observed
luminosities, gas masses, and abundances favor the Arepo code. Moreover, the
shape and the normalization of the observed density profiles are better
reproduced by Arepo within ~0.5r_200. However, neither model incorporates
efficient feedback from supermassive black holes or supernovae, which could
alter the simulated properties of the X-ray coronae. With the further advance
of numerical models, the present observations will be essential in constraining
the feedback effects in structure formation simulations.Comment: 19 pages, 13 figures, 6 tables, accepted for publication in Ap
CENP-A Is Dispensable for Mitotic Centromere Function after Initial Centromere/Kinetochore Assembly
Human centromeres are defined by chromatin containing the histone H3 variant CENP-A assembled onto repetitive alphoid DNA sequences. By inducing rapid, complete degradation of endogenous CENP-A, we now demonstrate that once the first steps of centromere assembly have been completed in G1/S, continued CENP-A binding is not required for maintaining kinetochore attachment to centromeres or for centromere function in the next mitosis. Degradation of CENP-A prior to kinetochore assembly is found to block deposition of CENP-C and CENP-N, but not CENP-T, thereby producing defective kinetochores and failure of chromosome segregation. Without the continuing presence of CENP-A, CENP-B binding to alphoid DNA sequences becomes essential to preserve anchoring of CENP-C and the kinetochore to each centromere. Thus, there is a reciprocal interdependency of CENP-A chromatin and the underlying repetitive centromere DNA sequences bound by CENP-B in the maintenance of human chromosome segregation
Visual speech fills in both discrimination and identification of non-intact auditory speech in children
On the equivalence of N=1 brane worlds and geometric singularities with flux
We consider Kaluza Klein reductions of M-theory on the Z_N orbifold of the
spin bundle over S^3 along two different U(1) isometries. The first one gives
rise to the familiar ``large N duality'' of the N=1 SU(N) gauge theory in which
the UV is realized as the world-volume theory of N D6-branes wrapped on S^3,
whereas the IR involves N units of RR flux through an S^2. The second reduction
gives an equivalent version of this duality in which the UV is realized
geometrically in terms of an S^2 of A_{N-1} singularities, with one unit of RR
flux through the S^2. The IR is reached via a geometric transition and involves
a single D6 brane on a lens space S^3/Z_N or, alternatively, a singular
background (S^2\times R^4)/Z_N, with one unit of RR flux through S^2 and,
localized at the singularities, an action of their stabilizer group in the U(1)
RR gauge bundle, so that no massless twisted states occur. We also consider
linear sigma-model descriptions of these backgrounds.Comment: 25 pages, LaTeX; v2: one reference added, published versio
Simultaneous X-ray and optical spectroscopy of the Oef supergiant lambda Cep
Probing the structures of stellar winds is of prime importance for the
understanding of massive stars. Based on their optical spectral morphology and
variability, the stars of the Oef class have been suggested to feature
large-scale structures in their wind. High-resolution X-ray spectroscopy and
time-series of X-ray observations of presumably-single O-type stars can help us
understand the physics of their stellar winds. We have collected XMM-Newton
observations and coordinated optical spectroscopy of the O6Ief star lambda Cep
to study its X-ray and optical variability and to analyse its high-resolution
X-ray spectrum. We investigate the line profile variability of the He II 4686
and H-alpha emission lines in our time series of optical spectra, including a
search for periodicities. We further discuss the variability of the broadband
X-ray flux and analyse the high-resolution spectrum of lambda Cep using
line-by-line fits as well as a code designed to fit the full high-resolution
X-ray spectrum consistently. During our observing campaign, the He II 4686 line
varies on a timescale of ~18 hours. On the contrary, the H-alpha line profile
displays a modulation on a timescale of 4.1 days which is likely the rotation
period of the star. The X-ray flux varies on time-scales of days and could in
fact be modulated by the same 4.1 days period as H-alpha, although both
variations are shifted in phase. The high-resolution X-ray spectrum reveals
broad and skewed emission lines as expected for the X-ray emission from a
distribution of wind-embedded shocks. Most of the X-ray emission arises within
less than 2R* above the photosphere.Comment: Accepted for publication in Astronomy & Astrophysic
Three-dimensional simulation of river flood flows
This thesis describes the implementation of general Computational Fluid Dynamics (CFD) techniques to laboratory and natural channels under flood flow conditions. Two commercially available codes, TELEMAC and CFX4, have been used in this work.The assessment of CFD for the calculation of flooded channel flow dynamics is carried out by simulating one laboratory test case from the Flood Channel Facility (FCF) Series B. This test case is that of a meandering two-stage channel with a depth ratio of 25% on the flood plain. Results from a computer simulation of experiment B23 are presented with a detailed quantitative comparison of the measured velocity, turbulence and bed shear stress. It supports the conclusion that CFD is able to account for the different flow mechanisms arising from the interaction between inbank and overbank flows in meandering channels. The maximum error in the prediction of the velocity is 10% and the comparisons show the calculations of bed shear stress to be reasonably accurate as well. Numerical tests indicate that the numerical solution is relatively independent of the boundary conditions, and confirm that turbulence transport is of minor importance in the experiment simulated.Numerical results from the simulation of flood flow mechanisms in natural rivers are also presented. It is hoped that these are of value to practitioners. Two 1-km reaches on the River Severn and River Ribble are modelled. They permit the investigation of two-stage channel flow dynamics at a larger scale. The numerical verification process establishes that the scale and the complex nature of the geometry are limiting factors, particularly for the numerical discretization of the domain and the calculation of the variables at the walls. It is however possible to estimate a priori part of the error such constraints generate. Away from the walls, the flow main features seem well predicted. The parallel between the velocity fields observed in river flood flows and those observed in the FCF is evident. Validation against field data suggests that the models are able to reproduce the flow mechanisms and account for bed shear stress variations correctly. Yet a significant level of uncertainty remains when the model predictions are compared against measured point data; more validation work is therefore required
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