2,432 research outputs found
Extraordinary Sex Ratios: Cultural Effects on Ecological Consequences
We model sex-structured population dynamics to analyze pairwise competition
between groups differing both genetically and culturally. A sex-ratio allele is
expressed in the heterogametic sex only, so that assumptions of Fisher's
analysis do not apply. Sex-ratio evolution drives cultural evolution of a
group-associated trait governing mortality in the homogametic sex. The two-sex
dynamics under resource limitation induces a strong Allee effect that depends
on both sex ratio and cultural trait values. We describe the resulting
threshold, separating extinction from positive growth, as a function of female
and male densities. When initial conditions avoid extinction due to the Allee
effect, different sex ratios cannot coexist; in our model, greater female
allocation always invades and excludes a lesser allocation. But the culturally
transmitted trait interacts with the sex ratio to determine the ecological
consequences of successful invasion. The invading female allocation may permit
population persistence at self-regulated equilibrium. For this case, the
resident culture may be excluded, or may coexist with the invader culture. That
is, a single sex-ratio allele in females and a cultural dimorphism in male
mortality can persist; a low-mortality resident trait is maintained by
father-to-son cultural transmission. Otherwise, the successfully invading
female allocation excludes the resident allele and culture, and then drives the
population to extinction via a shortage of males. Finally, we show that the
results obtained under homogeneous mixing hold, with caveats, in a spatially
explicit model with local mating and diffusive dispersal in both sexes.Comment: final version, reflecting changes in response to referees' comment
Magnetically-driven electronic phase separation in the semimetallic ferromagnet EuB
From measurements of fluctuation spectroscopy and weak nonlinear transport on
the semimetallic ferromagnet EuB we find direct evidence for
magnetically-driven electronic phase separation consistent with the picture of
percolation of magnetic polarons (MP), which form highly conducting
magnetically-ordered clusters in a paramagnetic and 'poorly conducting'
background. These different parts of the conducting network are probed
separately by the noise spectroscopy/nonlinear transport and the conventional
linear resistivity. We suggest a comprehensive and 'universal' scenario for the
MP percolation, which occurs at a critical magnetization either induced by
ferromagnetic order at zero field or externally applied magnetic fields in the
paramagentic region
Evaluation of color intensity enhanced by paprika as feed additive in goldfish and koi carp using computer-assisted image analysis
Body color intensity of red-colored koi carp Cyprinus carpio and goldfish Carassius auratus auratus varieties were measured to evaluate the effect of paprika used as a feed additive. Digital photos of the experimental fish were processed and analyzed by using special software. The red, green and blue (RGB) values of images were recorded and grayscale values of R, G and B were analyzed. The RGB values seem to play different roles in the development of the visible 'redness' of the two species. In most cases the B values decreased continuously during the administration of the paprika as a carotenoid feed additive, which seemed to have no effect on this process. The G values remained unchanged or decreased slightly as redness increased due to paprika feeding. The R values had a tendency to increase due to paprika feeding but significant differences can be expected only after 4 weeks at the feeding conditions applied here. Both the initial rate of redness and genetic background are thought to influence the rate of red color intensity change, which was observed to be different in the two fish species studied here
Finite hadronization time and unitarity in quark recombination model
The effect of finite hadronization time is considered in the recombination
model, and it is shown that the hadron multiplicity turns out to be
proportional to the initial quark density and unitarity is conserved in the
model. The baryon to meson ratio increases rapidly with the initial quark
density due to competition among different channels.Comment: 4 pages in RevTeX, 3 eps figures, to appear in J. Phys.G as a lette
Nonlinear asteroseismology of RR Lyrae
The observations of the Kepler space telescope revealed that fundamental-mode
RR Lyrae stars may show various radial overtones. The presence of multiple
radial modes may allow us to conduct nonlinear asteroseismology: comparison of
mode amplitudes and frequency shifts between observations and models. Here we
report the detection of three radial modes in the star RR Lyr, the eponym of
the class, using the Kepler short cadence data: besides the fundamental mode,
both the first and the ninth overtones can be derived from the data set. RR
Lyrae shows period doubling, but switches occasionally to a state where a
pattern of six pulsation cycles repeats instead of two. We found hydrodynamic
models that show the same three modes and the period-six state, allowing for
comparison with the observations.Comment: 5 pages, 4 figures, accepted for publication in ApJ Letter
Maps on density operators preserving quantum f-divergences
For an arbitrary strictly convex function f defined on the
non-negative real line we determine the structure of all transformations
on the set of density operators which preserve the quantum f-divergence
The fat and protein content of the sheep milk under different conditions
In Hungary the Hungarian Combing Merino has been and still is the most common sheep breed. In
order to increase the milk production traits, especially the milk components, several crossings were made. In an
experiment lasting three years the fat, protein and dry matter contents of the milk produced by ewes belonging to
different genotypes: Merino, (Merino x East-Friesian) F1, (Merino x Langhe) F1, (Merino x Sarda) F1, (Merino x
Pleven) F1 and (Merino x Awassi) F1 were studied. The test milkings of the ewes were carried out fortnightly,
twice a day. From the study the following conclusions could be drawn: (i) the East-Friesian F1 ewes produced
the largest amount of fat, protein and dry matter in their milk; followed by Langhe F1, Sarda F1, Pleven F1,
Awassi F1 and Merinos in the ranking; (ii) the improvement in conditions gave an increased yield of the studied
traits; and (iii) the pre-selection of Merinos on the basis of milk production should be made prior to the start of
crossbreeding considering to increase the milk production traits
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