468 research outputs found
Repeatable and heritable behavioural variation in a wild cooperative breeder
Quantifying consistent differences in behaviour among individuals is vital to understanding the ecological and evolutionary significance of animal personality. To quantify personality, the phenotypic variation of a behavioural trait is partitioned to assess how it varies among individuals, which is also known as repeatability. If pedigree data are available, the phenotypic variation can then be further partitioned to estimate the additive genetic variance and heritability. Assessing the repeatability and heritability of personality traits therefore allows for a better understanding of what natural selection can act upon, enabling evolution. In a natural population of facultative cooperatively breeding Seychelles warbler (Acrocephalus sechellensis) on Cousin Island, a lack of breeding vacancies forces individuals into different life-history strategies, and these differences in reproductive state could generate behavioural differences among individuals in the population. We used this population to estimate the repeatability of 4 behavioural traits (novel environment exploration, novel object exploration, obstinacy/struggle rate, and escape response), and narrow-sense heritability (of behavior, h2B; behavior minus observer variance; and personality), and evolvability, of the repeatable behavioural traits. We also tested for an among-individual correlation between the repeatable traits. We found that, compared to estimates in other study species, the exploratory behaviours were moderately repeatable (0.23â0.37), there was a positive among-individual correlation (0.51) between novel environment and novel object exploration, and that novel environment exploration was moderately heritable (0.17; h2B was low as it includes observer variance). This study further clarifies the additive genetic variance available for selection to act upon in this cooperatively breeding bird
Quantitative assessment of the effects of space allowance, group size and floor characteristics on the lying behaviour of growing-finishing pigs
To obtain quantitative information that can be later used in animal welfare modelling, the relationship between the lying behaviour of growing-finishing pigs (initial body weight (BW) between 19 and 87 kg) and different factors related to the housing conditions, with a potential negative effect on their welfare, was studied by means of a meta-analytical approach. Data from 22 experiments reported in 21 scientific publications were collected. The space allowance, expressed on an allometric basis by means of a k-value (m2/BW0.667), the group size (n) and the floor characteristics (fully and partly slatted v. non-slatted floor), as well as their significant two-way interactions were used as fixed effects, and the experiment was used as a random factor to take into account the interexperiment effect. Further regression analyses were performed on the predicted values of observations in order to improve the adjustment of data. A significant quadratic relationship was established between space allowance (k-value, P <0.05; squared k-value, P <0.01) and the percentage of time spent lying. A significant interaction between the k-value and the floor type was also found (P <0.05), showing that the relationship between space allowance and lying behaviour is affected by the presence or absence of slats. Threshold k-values were obtained using broken-line analyses, being about 0.039 for slatted floors and almost double for non-slatted floors. Compared to other studies, these values suggest that the ability to rest as space availability decreases may be compromised before a reduced performance becomes apparent. Group size did not show a significant effect. Additional information should be added to the model, as further data become available, to adjust the proposed parameters as well as to try to include the effect of other important aspects such as that of ambient temperature
Ecology and Evolution of Drosophila ambochila, A Rare Picture-Winged Species Endemic to the Wai'anae Range of O'ahu, Hawaiian Islands
The rare O'ahu picture-winged fly Drosophila ambochila Hardy
& Kaneshiro is endemic to two windward ravines in the Wai'anae Mountains
that harbor its host plant. Drosophila ambochila is an ecological specialist that
breeds on Pisonia stems and trunks in an intermediate stage of decay. By providing
field-collected females with suitable substrate material, we have been
able to observe the oviposition behavior of this species in the laboratory and
obtain F 1 larvae. In nature, females oviposit each batch of mature eggs ("'4050)
in a single cluster, by repeatedly inserting their long ovipositor into the
same crack or beetle hole in the decaying Pisonia bark. Ovipositor, ovary, and
egg morphology are characteristic of bark-breeding Hawaiian Drosophila, but
SEM studies revealed a distinctive chorionic ultrastructure for the eggs of this
species. Larval salivary chromosome analyses indicated that the O'ahu D. ambochila
is most closely related to D. alsophila from the island of Hawai'i and
have helped to resolve the phylogenetic relationships among six of the nine species
belonging to the vesciseta subgroup of the glabriapex species group
Effect of Interband Transitions on the c axis Penetration Depth of Layered Superconductors
The electromagnetic response of a system with two planes per unit cell
involves, in addition to the usual intraband contribution, an added interband
term. These transitions affect the temperature dependence and the magnitude of
the zero temperature c-axis penetration depth. When the interplane hopping is
sufficiently small, the interband transitions dominate the low temperature
behaviour of the penetration depth which then does not reflect the linear
temperature dependence of the intraband term and in comparison becomes quite
flat even for a d-wave gap. It is in this regime that the pseudogap was found
in our previous normal state calculations of the c-axis conductivity, and the
effects are connected.Comment: 8 pages, 5 figure
Inherent Inhomogeneities in Tunneling Spectra of BSCCO Crystals in the Superconducting State
Scanning Tunneling Spectroscopy on cleaved BSCCO(2212) single crystals reveal
inhomogeneities on length-scales of 30 . While most of the surface
yields spectra consistent with a d-wave superconductor, small regions show a
doubly gapped structure with both gaps lacking coherence peaks and the larger
gap having a size typical of the respective pseudo-gap for the same sample.Comment: 4 pages, 4 figure
Friedel oscillations in a two-band Hubbard model for CuO chains
Friedel oscillations induced by open boundary conditions in a two-band
Hubbard model for CuO chains are numerically studied. We find that for
physically realistic parameters and close to quarter filling, these
oscillations have a 2k_F modulation according with experimental results on
YBa_2Cu_3O_{7-delta}. In addition, we predict that, for the same parameters, as
hole doping is reduced from quarter filling to half filling, Friedel
oscillations would acquire a 4k_F modulation, typical of a strongly correlated
electrons regime. The 4k_F modulation dominates also in the electron doped
region. The range of parameters varied is very broad, and hence the results
reported could apply to other cuprates and other strongly correlated compounds
with quasi-one dimensional structures. On a more theoretical side, we stress
the fact that the copper and oxygen subsystems should be described by two
different Luttinger liquid exponents.Comment: 7 pages, 7 eps figure
Tuning the superconducting state in the magnetic MoSr2YCu2O8 materials
The properties of the MoSr2YCu2O8 materials are found to systematically
change with the oxygen concentration determined by the sintering and annealing
conditions. The as-prepared (asp) sample is anti-ferromagnetically (AFM)
ordered at 16 K. The magnetic features are related to the Mo5+ sublattice.
Annealing under an oxygen atmosphere induces superconductivity (SC) in the Cu-O
planes, and the TC and the shielding fraction values obtained depend strongly
on the oxygen concentration. Annealing the asp material at 1030 C under ambient
oxygen atmosphere yields TC of 18 K, whereas further annealing at 650 C under
92 atm. of oxygen, shifts TC to 32 K. The AFM ordering, which coexists with SC
state through effectively decoupled subsystems, is not affected by the presence
or absence of the SC state. In all samples studied, TN < TC. This behavior
resembles most of the inter-metallic magneto-superconductors, but is in sharp
contrast to the iso-structural RuSr2GdCu2O8 system where TN > TC.Comment: 7 pages, 8 Figure
Explicit formulae in probability and in statistical physics
We consider two aspects of Marc Yor's work that have had an impact in
statistical physics: firstly, his results on the windings of planar Brownian
motion and their implications for the study of polymers; secondly, his theory
of exponential functionals of Levy processes and its connections with
disordered systems. Particular emphasis is placed on techniques leading to
explicit calculations.Comment: 14 pages, 2 figures. To appear in Seminaire de Probabilites, Special
Issue Marc Yo
Ground state and elementary excitations of single and binary Bose-Einstein condensates of trapped dipolar gases
We analyze the ground-state properties and the excitation spectrum of
Bose-Einstein condensates of trapped dipolar particles. First, we consider the
case of a single-component polarized dipolar gas. For this case we discuss the
influence of the trapping geometry on the stability of the condensate as well
as the effects of the dipole-dipole interaction on the excitation spectrum. We
discuss also the ground state and excitations of a gas composed of two
antiparallel dipolar components.Comment: 12 pages, 9 eps figures, final versio
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