104 research outputs found
How Starlings (<i>Sturnus vulgaris</i> L.) apportion their foraging in a virtual single-prey situation on a meadow
How Starlings (<i>Sturnus vulgaris</i> L.) apportion their foraging in a virtual single-prey situation on a meadow
Apparent annual survival of staging ruffs during a period of population decline: insights from sex and site-use related differences
The ruff Philomachus pugnax, a lekkingshorebird wintering in Africa and breeding across northernEurasia, declined severely in its western range. Based on acapture-mark-resighting programme (2004–2011) in thewesternmost staging area in Friesland (the Netherlands),we investigated changes in apparent annual survival inrelation to age and sex to explore potential causes ofdecline. We also related temporal variation in apparentsurvival to environmental factors. We used the Capture-Mark-Recapture multievent statistical framework to overcomebiases in survival estimates after testing for hiddenheterogeneity of detection. This enabled the estimation ofthe probability to belong to high or low detectabilityclasses. Apparent survival varied between years but wasnot related to weather patterns along the flyway, or to floodlevels in the Sahel. Over time, a decline in apparent survivalis suggested. Due to a short data series and flag loss inthe last period this cannot be verified. Nevertheless, thepatterns in sex-specific detectability and survival lead tonew biological insights. Among highly detectable birds,supposedly most reliant on Friesland, males survived betterthan females (?/HDmales = 0.74, range 0.51–0.93;?/HDfemales = 0.51, range 0.24–0.81). Among lowdetectable birds, the pattern is reversed (?/LDmales = 0.64,range 0.37–0.89; ?/LDfemales = 0.73, range 0.48–0.93).Probably the staging population contains a mixture of sexspecificmigration strategies. A loss of staging femalescould greatly affect the dynamics of the western ruffpopulation. Further unravelling of these population processesrequires geographically extended demographicmonitoring and the use of tracking devices
Electronic transport in EuB
EuB is a magnetic semiconductor in which defects introduce charge
carriers into the conduction band with the Fermi energy varying with
temperature and magnetic field. We present experimental and theoretical work on
the electronic magnetotransport in single-crystalline EuB. Magnetization,
magnetoresistance and Hall effect data were recorded at temperatures between 2
and 300 K and in magnetic fields up to 5.5 T. The negative magnetoresistance is
well reproduced by a model in which the spin disorder scattering is reduced by
the applied magnetic field. The Hall effect can be separated into an ordinary
and an anomalous part. At 20 K the latter accounts for half of the observed
Hall voltage, and its importance decreases rapidly with increasing temperature.
As for Gd and its compounds, where the rare-earth ion adopts the same Hund's
rule ground state as Eu in EuB, the standard antisymmetric
scattering mechanisms underestimate the of this contribution by several
orders of magnitude, while reproducing its almost perfectly. Well below
the bulk ferromagnetic ordering at = 12.5 K, a two-band model
successfully describes the magnetotransport. Our description is consistent with
published de Haas van Alphen, optical reflectivity, angular-resolved
photoemission, and soft X-ray emission as well as absorption data, but requires
a new interpretation for the gap feature deduced from the latter two
experiments.Comment: 35 pages, 12 figures, submitted to PR
Is the Sun Embedded in a Typical Interstellar Cloud?
The physical properties and kinematics of the partially ionized interstellar
material near the Sun are typical of warm diffuse clouds in the solar vicinity.
The interstellar magnetic field at the heliosphere and the kinematics of nearby
clouds are naturally explained in terms of the S1 superbubble shell. The
interstellar radiation field at the Sun appears to be harder than the field
ionizing ambient diffuse gas, which may be a consequence of the low opacity of
the tiny cloud surrounding the heliosphere. The spatial context of the Local
Bubble is consistent with our location in the Orion spur.Comment: "From the Outer Heliosphere to the Local Bubble", held at
International Space Sciences Institute, October 200
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