Influence of Hole Localization on Local and Global Dynamic Response of Thin-Walled Laminated Cantilever Beam

In this study, we discuss the effects of the diameter and position of a hole on the dynamic response of a thin-walled cantilever beam made of carbon-epoxy laminate. Eigen-frequencies and corresponding global and local eigen-modes were considered, where deformations of the beam wall were dominant, without significant deformation of the beam axis. The study was focused on the circumferentially uniform stiffness (CUS) beam configuration. The laminate layers were arranged as [90/15(3)/90/15(3)/90]T. The finite element method was employed for numerical tests, using the Abaqus software package. Moreover, a few numerical results of the structure’s behaviour, with and without a hole, were verified experimentally. The experimental eigen-frequencies and the corresponding modes were obtained using an experimental modal analysis, comprising the LMS system with modal hammer. We found that the size and location of the hole affected the eigen-frequencies and corresponding modes. Furthermore, even a small hole in a beam could significantly change the shape of its local modes. The numerical and experimental results were observed to have high qualitative compliance

Do males hatch first and dominate sex ratios in White Stork chicks?

International audienceSex allocation has been a fertile topic in the development of evolutionary theory. The dominant models for vertebrates have provided predictions of sex ratios based on asymmetry in breeding success between sexes and the relative effect of local competition. In birds, empirical work has provided some support for these models, but has also generated apparently contradictory observations. Recent models have provided some predictions for both individual and population sex ratios, showing that the availability of high quality habitat patches and dispersal rates can critically affect both population- and individual-level expectations. We explore patterns in offspring sex ratio among chicks of the White Stork , a large migratory bird species with bi-parental care, which does not show strong sexual dimorphism in size and survival patterns. We checked the hatching order and body weight of 342 nestlings from 124 broods, and their sexes were recorded over 4 years (2005-2008) in a dense healthy stork population in western Poland. Sex ratio in the study population was skewed to males (57.5%) which was consistent between years. We have assumed that chick age was directly related to their size. The heavier (and assumed older) chicks were significantly dominated by males

Sex and other sources of variation in the haematological parameters of White Stork Ciconia ciconia chicks

Biochemical and blood cell parameters have commonly been employed as useful minimally invasive indicators of the health or nutritional status of many species. Here, we present data on a suite of commonly measured blood parameters from 342 White Stork Ciconia ciconia chicks of molecularly known sex. Samples were collected in western Poland during four breeding seasons (2005-2008). We examine whether sex, and also season (year), nesting locality, hatch date and brood size, contributed to variation in these blood parameters. There were significant seasonal differences in levels of the heterophil/lymphocyte ratio, red blood cell count, haematocrit, haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin concentration, and particularly in white blood cell count. Significant nesting locality effects were detected in haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration. Hatch date, virtually synonymous with chick age, significantly negatively influenced (i.e. later hatch dates (younger chicks when sampled) had lower values of red blood cell count, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration. Male chicks had significantly lower levels of red blood cell count, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration. There was a significant sex/hatch date interaction for red blood cell count, haematocrit and haemoglobin. Brood size did not significantly affect any of the analysed parameters. Our work shows that blood parameters are influenced by many factors, including sex and age of individuals, and such factors may need to be taken into consideration when using blood parameters as indicators of health. Such considerations are especially critical in the establishment of reference ranges of blood parameters which may be of use in captive rearing of this endangered species.</p

Relatedness of wildlife and livestock avian isolates of the nosocomial pathogen Acinetobacter baumannii to lineages spread in hospitals worldwide

The natural habitats and potential reservoirs of the nosocomial pathogen Acinetobacter baumannii are poorly defined. Here, we put forth and tested the hypothesis of avian reservoirs of A. baumannii. We screened tracheal and rectal swab samples from livestock (chicken, geese) and wild birds (white stork nestlings) and isolated A. baumannii from 3% of sampled chicken (n = 220), 8% of geese (n = 40) and 25% of white stork nestlings (n = 661). Virulence of selected avian A. baumannii isolates was comparable to that of clinical isolates in the Galleria mellonella infection model. Whole genome sequencing revealed the close relationship of an antibiotic-susceptible chicken isolate from Germany with a multidrug-resistant human clinical isolate from China and additional linkages between livestock isolates and human clinical isolates related to international clonal lineages. Moreover, we identified stork isolates related to human clinical isolates from the United States. Multilocus sequence typing disclosed further kinship between avian and human isolates. Avian isolates do not form a distinct clade within the phylogeny of A. baumannii, instead they diverge into different lineages. Further, we provide evidence that A. baumannii is constantly present in the habitats occupied by storks. Collectively, our study suggests A. baumannii could be a zoonotic organism that may disseminate into livestock