Nonparametric estimation of directional highest density regions

Highest density regions (HDRs) are defined as level sets containing sample points of relatively high density. Although Euclidean HDR estimation from a random sample, generated from the underlying density, has been widely considered in the statistical literature, this problem has not been contemplated for directional data yet. In this work, directional HDRs are formally defined and plug-in estimators based on kernel smoothing and associated confidence regions are proposed. We also provide a new suitable bootstrap bandwidth selector for plug-in HDRs estimation based on the minimization of an error criteria that involves the Hausdorff distance between the boundaries of the theoretical and estimated HDRs. An extensive simulation study shows the performance of the resulting estimator for the circle and for the sphere. The methodology is applied to analyze two real data sets in animal orientation and seismology.

Animal Orientation Affects Brain Biomechanical Responses to Blast-Wave Exposure

In this study, we investigated how animal orientation within a shock tube influences the biomechanical responses of the brain and cerebral vasculature of a rat when exposed to a blast wave. Using three-dimensional finite-element models, we computed the biomechanical responses when the rat was exposed to the same blast-wave overpressure (100 kPa) in a prone (P), vertical (V), or head-only (HO) orientation. We validated our model by comparing the model-predicted and the experimentally measured brain pressures at the lateral ventricle. For all three orientations, the maximum difference between the predicted and measured pressures was 11%. Animal orientation markedly influenced the predicted peak pressure at the anterior position along the mid-sagittal plane of the brain (P = 187 kPa; V = 119 kPa; and HO = 142 kPa). However, the relative differences in the predicted peak pressure between the orientations decreased at the medial (21%) and posterior (7%) positions. In contrast to the pressure, the peak strain in the prone orientation relative to the other orientations at the anterior, medial, and posterior positions was 40-88% lower. Similarly, at these positions, the cerebral vasculature strain in the prone orientation was lower than the strain in the other orientations. These results show that animal orientation in a shock tube influences the biomechanical responses of the brain and the cerebral vasculature of the rat, strongly suggesting that a direct comparison of changes in brain tissue observed from animals exposed at different orientations can lead to incorrect conclusions.

Challenging identity: development of a measure of veterinary career motivations

BackgroundWhile little is known about the motivations underpinning veterinary work, previous literature has suggested that the main influences on veterinary career choice are early/formative exposure to animals or veterinary role models. The aim of this study was to develop and provisionally validate a veterinary career motivations questionnaire to assess the strength of various types of career motivations in graduating and experienced veterinarians.MethodsA cross-sectional sample of experienced veterinarians (n=305) and a smaller cohort of newly graduated veterinarians (n=53) were surveyed online using a long-form questionnaire. Exploratory factor analysis (EFA) was used to iteratively derive a final, short-form questionnaire for survey of a second cross-sectional sample of experienced veterinarians (n=751).ResultsEFA derived a final questionnaire with 22 items loading onto six factors (social purpose, animal orientation, vocational identity, challenge and learning, career affordances, and people orientation). While motivations based on animal orientation were predictably strong, those based on vocational identity were not universal and were weaker in younger and graduate veterinarians; both of these motivations were rated lower by male veterinarians. Motivations based on challenge and learning emerged as some of the strongest, most universal and most influential; people orientation and social purpose were also important, particularly for older veterinarians.ConclusionThe major motivations for pursuing a veterinary career may best be represented as an intrinsic passion for animal care and for learning through solving varied challenges. These motivations are largely intrinsically oriented and autonomously regulated, thus likely to be supportive of work satisfaction and wellbeing.

Weak radiofrequency fields affect the insect circadian clock

It is known that the circadian clock in Drosophila can be sensitive to static magnetic fields (MFs). Man-made radiofrequency (RF) electromagnetic fields have been shown to have effects on animal orientation responses at remarkably weak intensities in the nanotesla range. Here, we tested if weak broadband RF fields also affect the circadian rhythm of the German cockroach ( Blatella germanica ). We observed that static MFs slow down the cockroach clock rhythm under dim UV light, consistent with results on the Drosophila circadian clock. Remarkably, 300 times weaker RF fields likewise slowed down the cockroach clock in a near-zero static magnetic field. This demonstrates that the internal clock of organisms can be sensitive to weak RF fields, consequently opening the possibility of an influence of man-made RF fields on many clock-dependent events in living systems.