Nesting behaviour influences species-specific gas exchange across avian eggshells

Carefully controlled gas exchange across the eggshell is essential for the development of the avian embryo. Water vapour conductance (GH2O) across the shell, typically measured as mass loss during incubation, has been demonstrated to optimally ensure the healthy development of the embryo while avoiding desiccation. Accordingly, eggs exposed to sub-optimal gas exchange have reduced hatching success. We tested the association between eggshell GH2O and putative life-history correlates of adult birds, ecological nest parameters and physical characteristics of the egg itself to investigate how variation in GH2O has evolved to maintain optimal water loss across a diverse set of nest environments. We measured gas exchange through eggshell fragments in 151 British breeding bird species and fitted phylogenetically controlled, general linear models to test the relationship between GH2O and potential predictor parameters of each species. Of our 17 life-history traits, only two were retained in the final model: wet-incubating parent and nest type. Eggs of species where the parent habitually returned to the nest with wet plumage had significantly higher GH2O than those of parents that returned to the nest with dry plumage. Eggs of species nesting in ground burrows, cliffs and arboreal cups had significantly higher GH2O than those of species nesting on the ground in open nests or cups, in tree cavities and in shallow arboreal nests. Phylogenetic signal (measured as Pagel's λ) was intermediate in magnitude, suggesting that differences observed in the GH2O are dependent upon a combination of shared ancestry and species-specific life history and ecological traits. Although these data are correlational by nature, they are consistent with the hypothesis that parents constrained to return to the nest with wet plumage will increase the humidity of the nest environment, and the eggs of these species have evolved a higher GH2O to overcome this constraint and still achieve optimal water loss during incubation. We also suggest that eggs laid in cup nests and burrows may require a higher GH2O to overcome the increased humidity as a result from the confined nest microclimate lacking air movements through the nest. Taken together, these comparative data imply that species-specific levels of gas exchange across avian eggshells are variable and evolve in response to ecological and physical variation resulting from parental and nesting behaviours

Factorization of correlations in two-dimensional percolation on the plane and torus

Recently, Delfino and Viti have examined the factorization of the three-point density correlation function P_3 at the percolation point in terms of the two-point density correlation functions P_2. According to conformal invariance, this factorization is exact on the infinite plane, such that the ratio R(z_1, z_2, z_3) = P_3(z_1, z_2, z_3) [P_2(z_1, z_2) P_2(z_1, z_3) P_2(z_2, z_3)]^{1/2} is not only universal but also a constant, independent of the z_i, and in fact an operator product expansion (OPE) coefficient. Delfino and Viti analytically calculate its value (1.022013...) for percolation, in agreement with the numerical value 1.022 found previously in a study of R on the conformally equivalent cylinder. In this paper we confirm the factorization on the plane numerically using periodic lattices (tori) of very large size, which locally approximate a plane. We also investigate the general behavior of R on the torus, and find a minimum value of R approx. 1.0132 when the three points are maximally separated. In addition, we present a simplified expression for R on the plane as a function of the SLE parameter kappa.Comment: Small corrections (final version). In press, J. Phys.

Fern spore extracts can damage DNA

The carcinogenicity of the vegetative tissues of bracken fern (Pteridium) has long been established. More recently, the carcinogenic effects of the spores of bracken have also been recognized. Both vegetative tissues and spores of bracken can induce adducts in DNA in animal tissues, but the possible genotoxic or carcinogenic effects of spores from fern species other than bracken are unknown. The single-cell gel electrophoresis (‘comet’) assay was used to investigate whether fern spores can cause DNA damage in vitro. Extracts of spores from six fern species were administered to cultured human premyeloid leukaemia (K562) cells. Spore extracts of five fern species: Anemia phyllitidis, Dicksonia antarctica, Pteridium aquilinum, Pteris vittata and Sadleria pallida, induced significantly more DNA strand breaks than those in the control groups. Only in one species, Osmunda regalis, was the effect no different from that in the control groups. Using extracts from A. phyllitidis and P. vittata, the extent of DNA damage was increased by increasing the original dose 10 times, whereas an experiment in which exposure times were varied suggested that the highest levels of strand breaks appear after 2 h exposure. Simultaneous incubation with human S9 liver enzyme mix ablated the damaging effect of the extracts. Our data show that fern spore extracts can cause DNA damage in human cells in vitro. Considering the strong correlation between DNA damage and carcinogenic events, the observations made in this report may well have some implications for human health. © 2000 Cancer Research Campaig

Rigorous confidence intervals for critical probabilities

We use the method of Balister, Bollobas and Walters to give rigorous 99.9999% confidence intervals for the critical probabilities for site and bond percolation on the 11 Archimedean lattices. In our computer calculations, the emphasis is on simplicity and ease of verification, rather than obtaining the best possible results. Nevertheless, we obtain intervals of width at most 0.0005 in all cases

Fluctuations for the Ginzburg-Landau ∇ϕ\nabla \phi Interface Model on a Bounded Domain

We study the massless field on $D_n = D \cap \tfrac{1}{n} \Z^2$, where $D \subseteq \R^2$ is a bounded domain with smooth boundary, with Hamiltonian \CH(h) = \sum_{x \sim y} \CV(h(x) - h(y)). The interaction \CV is assumed to be symmetric and uniformly convex. This is a general model for a $(2+1)$-dimensional effective interface where $h$ represents the height. We take our boundary conditions to be a continuous perturbation of a macroscopic tilt: $h(x) = n x \cdot u + f(x)$ for $x \in \partial D_n$, $u \in \R^2$, and $f \colon \R^2 \to \R$ continuous. We prove that the fluctuations of linear functionals of $h(x)$ about the tilt converge in the limit to a Gaussian free field on $D$, the standard Gaussian with respect to the weighted Dirichlet inner product $(f,g)_\nabla^\beta = \int_D \sum_i \beta_i \partial_i f_i \partial_i g_i$ for some explicit $\beta = \beta(u)$. In a subsequent article, we will employ the tools developed here to resolve a conjecture of Sheffield that the zero contour lines of $h$ are asymptotically described by $SLE(4)$, a conformally invariant random curve.Comment: 58 page

Associations between teacher-reported school climate and depressive symptoms in Australian adolescents : a 5-year longitudinal study.

Adolescent depression is serious and common. As adolescents spend approximately 15,000 h in school, this setting is a logical place to seek etiological factors. Research suggests there are negative associations between school climate and adolescent depressive symptoms. However, such studies typically use student reports of both climate and depressive symptoms; this is problematic because common method variance results when the same individual provides information on all variables, contributing to overestimations of associations between depressive symptoms and school climate. Therefore, the purpose of this study is to examine the association between teacher-reported school climate and adolescent-reported depressive symptoms. Thus, 2545 Australian high school students participated in this 5-year longitudinal study. Students completed a measure of depressive symptoms annually; their teachers (N = 882) completed a questionnaire to evaluate the quality of the school environment (i.e., safe/orderly and supportive relationships). Multi-group latent growth models revealed that more positive teacher-reported school climate was cross-sectionally associated with fewer student-reported depressive symptoms in both boys and girls, although this association was significantly stronger for girls. Longitudinally, positive school climate was associated with lower depressive symptoms but a higher rate of change of symptoms for both boys and girls. The overall findings are consistent with previous findings with student-reported school climate. However, the gender difference and the directionality of the longitudinal association between school climate and depressive symptoms over time demonstrate that additional studies of mechanisms by which school climate is connected to adolescents’ depressive symptoms are needed

Associations between teacher-reported school climate and depressive symptoms in Australian adolescents : a 5-year longitudinal study.

Adolescent depression is serious and common. As adolescents spend approximately 15,000 h in school, this setting is a logical place to seek etiological factors. Research suggests there are negative associations between school climate and adolescent depressive symptoms. However, such studies typically use student reports of both climate and depressive symptoms; this is problematic because common method variance results when the same individual provides information on all variables, contributing to overestimations of associations between depressive symptoms and school climate. Therefore, the purpose of this study is to examine the association between teacher-reported school climate and adolescent-reported depressive symptoms. Thus, 2545 Australian high school students participated in this 5-year longitudinal study. Students completed a measure of depressive symptoms annually; their teachers (N = 882) completed a questionnaire to evaluate the quality of the school environment (i.e., safe/orderly and supportive relationships). Multi-group latent growth models revealed that more positive teacher-reported school climate was cross-sectionally associated with fewer student-reported depressive symptoms in both boys and girls, although this association was significantly stronger for girls. Longitudinally, positive school climate was associated with lower depressive symptoms but a higher rate of change of symptoms for both boys and girls. The overall findings are consistent with previous findings with student-reported school climate. However, the gender difference and the directionality of the longitudinal association between school climate and depressive symptoms over time demonstrate that additional studies of mechanisms by which school climate is connected to adolescents’ depressive symptoms are needed

Interaction of photons with plasmas and liquid metals: photoabsorption and scattering

Formulas to describe the photoabsorption and the photon scattering by a plasma or a liquid metal are derived in a unified manner with each other. It is shown how the nuclear motion, the free-electron motion and the core-electron behaviour in each ion in the system determine the structure of photoabsorption and scattering in an electron-ion mixture. The absorption cross section in the dipole approximation consists of three terms which represent the absorption caused by the nuclear motion, the absorption owing to the free-electron motion producing optical conductivity or inverse Bremsstrahlung, and the absorption ascribed to the core-electron behaviour in each ion with the Doppler correction. Also, the photon scattering formula provides an analysis method for experiments observing the ion-ion dynamical structure factor (DSF), the electron-electron DSF giving plasma oscillations, and the core-electron DSF yielding the X-ray Raman (Compton) scattering with a clear definition of the background scattering for each experiment, in a unified manner. A formula for anomalous X-ray scattering is also derived for a liquid metal. At the same time, Thomson scattering in plasma physics is discussed from this general point of view.Comment: LaTeX file: 18 pages without figur

The effects of the spontaneous presence of a spouse/partner and others on cardiovascular reactions to an acute psychological challenge

The presence of supportive others has been associated with attenuated cardiovascular reactivity in the laboratory. The effects of the presence of a spouse and others in a more naturalistic setting have received little attention. Blood pressure and heart rate reactions to mental stress were recorded at home in 1028 married/partnered individuals. For 112 participants, their spouse/partner was present; for 78, at least one other person was present. Women tested with a spouse/partner present showed lower magnitude systolic blood pressure and heart rate reactivity than those tested without. Individuals tested with at least one nonspousal other present also displayed attenuated reactivity. This extends the results of laboratory studies and indicates that the spontaneous presence of others is associated with a reduction in cardiovascular reactivity in an everyday environment; spouse/partner presence would appear to be especially effective for women.\ud \u

Generalized Interpolation Material Point Approach to High Melting Explosive with Cavities Under Shock

Criterion for contacting is critically important for the Generalized Interpolation Material Point(GIMP) method. We present an improved criterion by adding a switching function. With the method dynamical response of high melting explosive(HMX) with cavities under shock is investigated. The physical model used in the present work is an elastic-to-plastic and thermal-dynamical model with Mie-Gr\"uneissen equation of state. We mainly concern the influence of various parameters, including the impacting velocity $v$, cavity size $R$, etc, to the dynamical and thermodynamical behaviors of the material. For the colliding of two bodies with a cavity in each, a secondary impacting is observed. Correspondingly, the separation distance $D$ of the two bodies has a maximum value $D_{\max}$ in between the initial and second impacts. When the initial impacting velocity $v$ is not large enough, the cavity collapses in a nearly symmetric fashion, the maximum separation distance $D_{\max}$ increases with $v$. When the initial shock wave is strong enough to collapse the cavity asymmetrically along the shock direction, the variation of $D_{\max}$ with $v$ does not show monotonic behavior. Our numerical results show clear indication that the existence of cavities in explosive helps the creation of ``hot spots''.Comment: Figs.2,4,7,11 in JPG format; Accepted for publication in J. Phys. D: Applied Physic