1,054 research outputs found
Prey selection by an apex predator : the importance of sampling uncertainty.
The impact of predation on prey populations has long been a focus of ecologists, but a firm understanding of the factors influencing prey selection, a key predictor of that impact, remains elusive. High levels of variability observed in prey selection may reflect true differences in the ecology of different communities but might also reflect a failure to deal adequately with uncertainties in the underlying data. Indeed, our review showed that less than 10% of studies of European wolf predation accounted for sampling uncertainty. Here, we relate annual variability in wolf diet to prey availability and examine temporal patterns in prey selection; in particular, we identify how considering uncertainty alters conclusions regarding prey selection.
Over nine years, we collected 1,974 wolf scats and conducted drive censuses of ungulates in Alpe di Catenaia, Italy. We bootstrapped scat and census data within years to construct confidence intervals around estimates of prey use, availability and selection. Wolf diet was dominated by boar (61.5±3.90 [SE] % of biomass eaten) and roe deer (33.7±3.61%). Temporal patterns of prey densities revealed that the proportion of roe deer in wolf diet peaked when boar densities were low, not when roe deer densities were highest. Considering only the two dominant prey types, Manly's standardized selection index using all data across years indicated selection for boar (mean = 0.73±0.023). However, sampling error resulted in wide confidence intervals around estimates of prey selection. Thus, despite considerable variation in yearly estimates, confidence intervals for all years overlapped. Failing to consider such uncertainty could lead erroneously to the assumption of differences in prey selection among years. This study highlights the importance of considering temporal variation in relative prey availability and accounting for sampling uncertainty when interpreting the results of dietary studies
Cerebellar Atrophy Related To Chronic Exposure To Toluene. Case Report.
A 31-year-old woman presented slowly progressing ataxia and neurasthenic symptoms after 14-year occupational exposure to low concentration toluene vapour. Examination disclosed only cerebellar signs. Cognitive functions were normal except moderate visuo-spatial and constructive deficit. CT imaging showed severe pancerebellar atrophy without pathological signs in other brain structures. Two years after she was removed from workplace, CT imaging and ataxia showed no worsening, while visuo-constructive function improved. The authors warn against possible neurotoxic risk associated with this kind of exposure.5290-
Calculation of the heavy-hadron axial couplings g_1, g_2, and g_3 using lattice QCD
In a recent letter [Phys. Rev. Lett. 108, 172003 (2012), arXiv:1109.2480] we
have reported on a lattice QCD calculation of the heavy-hadron axial couplings
, , and . These quantities are low-energy constants of
heavy-hadron chiral perturbation theory (HHPT) and are related to the
, , and couplings.
In the following, we discuss important details of the calculation and give
further results. To determine the axial couplings, we explicitly match the
matrix elements of the axial current in QCD with the corresponding matrix
elements in HHPT. We construct the ratios of correlation functions used
to calculate the matrix elements in lattice QCD, and study the contributions
from excited states. We present the complete numerical results and discuss the
data analysis in depth. In particular, we demonstrate the convergence of
HHPT for the axial-current matrix elements at pion masses up to
about 400 MeV and show the impact of the nonanalytic loop contributions.
Finally, we present additional predictions for strong and radiative decay
widths of charm and bottom baryons.Comment: 42 pages, 20 figures, updated calculation of Xi_b^{*0} width using
mass measurement from CMS, published versio
Spectroscopy of HS: evidence of a new energy scale for superconductivity
The discovery of a superconducting phase in sulfur hydride under high
pressure with a critical temperature above 200 K has provided a new impetus to
the search for even higher . Theory predicted and experiment confirmed
that the phase involved is HS with Im-3m crystal structure. The observation
of a sharp drop in resistance to zero at , its downward shift with
magnetic field and a Meissner effect confirm superconductivity but the
mechanism involved remains to be determined. Here, we provide a first optical
spectroscopy study of this new superconductor. Experimental results for the
optical reflectivity of HS, under high pressure of 150 GPa, for several
temperatures and over the range 60 to 600 meV of photon energies, are compared
with theoretical calculations based on Eliashberg theory using DFT results for
the electron-phonon spectral density F(). Two significant
features stand out: some remarkably strong infrared active phonons at
160 meV and a band with a depressed reflectance in the superconducting state in
the region from 450 meV to 600 meV. In this energy range, as predicted by
theory, HS is found to become a better reflector with increasing
temperature. This temperature evolution is traced to superconductivity
originating from the electron-phonon interaction. The shape, magnitude, and
energy dependence of this band at 150 K agrees with our calculations. This
provides strong evidence of a conventional mechanism. However, the unusually
strong optical phonon suggests a contribution of electronic degrees of freedom.Comment: 10 pages, 8 figures. Main manuscript and supplementary informatio
Perturbative renormalization of bilinear quark and gluon operators
The renormalisation constants for local bilinear quark operators are
calculated using the Sheikholeslami-Wohlert improved action. In addition we
compute the renormalisation constant of the leading gluon operator for
different group representations and discuss the mixing of the operators E^2 and
B^2.Comment: 3 pages, poster contributed at Lattice96, St. Loui
Electrodynamics of superconducting pnictide superlattices
It has been recently reported (S. Lee et al., Nature Materials 12, 392, 2013)
that superlattices where layers of the 8% Co-doped BaFe2As2 superconducting
pnictide are intercalated with non superconducting ultrathin layers of either
SrTiO3 or of oxygen-rich BaFe2As2, can be used to control flux pinning, thereby
increasing critical fields and currents, without significantly affecting the
critical temperature of the pristine superconducting material. However, little
is known about the electron properties of these systems. Here we investigate
the electrodynamics of these superconducting pnictide superlattices in the
normal and superconducting state by using infrared reflectivity, from THz to
visible range. We find that multi-gap structure of these superlattices is
preserved, whereas some significant changes are observed in their electronic
structure with respect to those of the original pnictide. Our results suggest
that possible attempts to further increase the flux pinning may lead to a
breakdown of the pnictide superconducting properties.Comment: 4 pages, two figure
Lattice computation of structure functions
Recent lattice calculations of hadron structure functions are described.Comment: Plenary talk presented at LATTICE96, LaTeX, 7 pages, 5 figures,
espcrc2.sty and epsfig.sty include
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