2,718 research outputs found
Hyperostotic tympanic bone spicules in domestic and wild animal species
Hyperostotic tympanic bone spicules (HTBS), or "mucoperiosteal exostoses" (ME, syn.) are small, globular (>= 1 mm in diameter), mostly stalked and drumstick-like, bony structures, which arise from the inner wall of the tympanic bulla and project into the middle ear cavity. HTBS present as mineral densities inside the tympanic bulla on radiographs or computed tomographic (CT) images. They have previously been referred to as "otoliths" and were thought to represent mineral concretions secondary to otitis media. Recently, it was shown that HTBS actually consist of regularly composed bone tissue, covered by normal middle ear mucosa. So far, HTBS have only extensively been described in dogs, where they occur with a prevalence of up to >45%. A recent study detected ME, most likely representing HTBS, in the tympanic cavities of skeletonised skull bones of African lions. To estimate the occurrence of HTBS in other mammal species, the middle ears of adult animals of 78 different domestic, wild, and zoo species undergoing routine necropsy at the Institute of Veterinary Pathology of the LMU Munich, Germany were examined in the present study. HTBS were found in the tympanic bullae of carnivorous species, such as canids (wolf, fox), and in several large felid species (lion, tiger, leopard, cheetah). In contrast, HTBS were not present in domestic cats (more than to 200 cases), small carnivorous species such as mustelids, nor in any primate, ungulate, ruminant, pig, insectivore, or rodent species. The detectability of HTBS by CT of the tympanic bullae of large felids was demonstrated in an African lion. Histologically, HTBS consisted of mature lamellar bone, covered by periosteum and a partially ciliated, flat epithelium, regularly without any apparent inflammatory alterations. The present study demonstrates that HTBS may frequently occur in large felids and in different canid species. These findings should be taken into account when examining the middle ear, or interpreting bulla radiographs/CT-images of the respective species. However, the factors triggering the development of HTBS remain to be identified
Far-infrared spectra of lateral quantum dot molecules
We study effects of electron-electron interactions and confinement potential
on the magneto-optical absorption spectrum in the far-infrared range of lateral
quantum dot molecules. We calculate far-infrared (FIR) spectra for three
different quantum dot molecule confinement potentials. We use accurate exact
diagonalization technique for two interacting electrons and calculate
dipole-transitions between two-body levels with perturbation theory. We
conclude that the two-electron FIR spectra directly reflect the symmetry of the
confinement potential and interactions cause only small shifts in the spectra.
These predictions could be tested in experiments with nonparabolic quantum dots
by changing the number of confined electrons. We also calculate FIR spectra for
up to six noninteracting electrons and observe some additional features in the
spectrum.Comment: For better quality Figs download manuscript from
http://www.fyslab.hut.fi/~mma/FIR/Helle_qdmfir.ps.g
The effects of compressible and incompressible states on the FIR-absorption of quantum wires and dots in a magnetic field
We investigate the effects of compressible and incompressible states on the
FIR-absorption of quantum wires and dots in a homogeneous perpendicular
magnetic field. The electron-electron interaction is treated in the Hartree
approximation at a finite low temperature. The calculated dispersion of the
collective excitations reproduces several experimental results.Comment: To be published by Physica Scripta in the proceedings of the 17NSM. 6
pages in LaTeX + 6 postscript figure
Are complete intersections complete intersections?
A commutative local ring is generally defined to be a complete intersection
if its completion is isomorphic to the quotient of a regular local ring by an
ideal generated by a regular sequence. It has not previously been determined
whether or not such a ring is necessarily itself the quotient of a regular ring
by an ideal generated by a regular sequence. In this article, it is shown that
if a complete intersection is a one dimensional integral domain, then it is
such a quotient. However, an example is produced of a three dimensional
complete intersection domain which is not a homomorphic image of a regular
local ring, and so the property does not hold in general
The Nonlinear Cosmological Matter Power Spectrum with Massive Neutrinos I: The Halo Model
Measurements of the linear power spectrum of galaxies have placed tight
constraints on neutrino masses. We extend the framework of the halo model of
cosmological nonlinear matter clustering to include the effect of massive
neutrino infall into cold dark matter (CDM) halos. The magnitude of the effect
of neutrino clustering for three degenerate mass neutrinos with m_nu=0.9 eV is
of order ~1%, within the potential sensitivity of upcoming weak lensing
surveys. In order to use these measurements to further constrain--or eventually
detect--neutrino masses, accurate theoretical predictions of the nonlinear
power spectrum in the presence of massive neutrinos will be needed, likely only
possible through high-resolution multiple particle (neutrino, CDM and baryon)
simulations.Comment: v2: matches PRD versio
PkANN - I. Non-linear matter power spectrum interpolation through artificial neural networks
We investigate the interpolation of power spectra of matter fluctuations
using Artificial Neural Network (PkANN). We present a new approach to confront
small-scale non-linearities in the power spectrum of matter fluctuations. This
ever-present and pernicious uncertainty is often the Achilles' heel in
cosmological studies and must be reduced if we are to see the advent of
precision cosmology in the late-time Universe. We show that an optimally
trained artificial neural network (ANN), when presented with a set of
cosmological parameters (Omega_m h^2, Omega_b h^2, n_s, w_0, sigma_8, m_nu and
redshift z), can provide a worst-case error <=1 per cent (for z<=2) fit to the
non-linear matter power spectrum deduced through N-body simulations, for modes
up to k<=0.7 h/Mpc. Our power spectrum interpolator is accurate over the entire
parameter space. This is a significant improvement over some of the current
matter power spectrum calculators. In this paper, we detail how an accurate
interpolation of the matter power spectrum is achievable with only a sparsely
sampled grid of cosmological parameters. Unlike large-scale N-body simulations
which are computationally expensive and/or infeasible, a well-trained ANN can
be an extremely quick and reliable tool in interpreting cosmological
observations and parameter estimation. This paper is the first in a series. In
this method paper, we generate the non-linear matter power spectra using
HaloFit and use them as mock observations to train the ANN. This work sets the
foundation for Paper II, where a suite of N-body simulations will be used to
compute the non-linear matter power spectra at sub-per cent accuracy, in the
quasi-non-linear regime 0.1 h/Mpc <= k <= 0.9 h/Mpc. A trained ANN based on
this N-body suite will be released for the scientific community.Comment: 12 pages, 9 figures, 2 tables, updated to match version accepted by
MNRA
Quantum Magnetic Properties in Perovskite with Anderson Localized Artificial Spin-1/2
Quantum magnetic properties in a geometrically frustrated lattice of spin-1/2
magnet, such as quantum spin liquid or solid and the associated spin
fractionalization, are considered key in developing a new phase of matter. The
feasibility of observing the quantum magnetic properties, usually found in
geometrically frustrated lattice of spin-1/2 magnet, in a perovskite material
with controlled disorder is demonstrated. It is found that the controlled
chemical disorder, due to the chemical substitution of Ru ions by Co-ions, in a
simple perovskite CaRuO3 creates a random prototype configuration of artificial
spin-1/2 that forms dimer pairs between the nearest and further away ions. The
localization of the Co impurity in the Ru matrix is analyzed using the Anderson
localization formulation. The dimers of artificial spin-1/2, due to the
localization of Co impurities, exhibit singlet-to-triplet excitation at low
temperature without any ordered spin correlation. The localized gapped
excitation evolves into a gapless quasi-continuum as dimer pairs break and
create freely fluctuating fractionalized spins at high temperature. Together,
these properties hint at a new quantum magnetic state with strong resemblance
to the resonance valence bond system.Comment: 8 pages, 6 figure
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