Ontogenetic changes in femoral cross-sectional geometry during childhood locomotor development

Objectives: The femur is a major weight-bearing bone that is variably loaded throughout growth as children transition through locomotory states prior to the attainment of a mature bipedal gait. Here, we document ontogenetic trends in femoral cross-sectional geometry (CSG) and explore how changes in loading regime may impact the structural arrangement of cortical bone along the length of the developing diaphysis. Materials and methods: Micro-CT scans of 110 immature femora were generated from a documented archaeological sample ranging in age from birth to 8.5 years old. CSG properties indicative of relative bone strength and bending rigidity were analyzed from cross-sections extracted at 35%, 50% and 65% of total intermetaphyseal length. Results: Infants experience a marked redistribution of cortical bone between birth and 7 months facilitating a more advantageous mechanical structure for early load bearing behaviors as bone is displaced further from the section centroid. Early walkers are characterized by a mediolaterally reinforced cross-section that becomes more circular as gait continues to develop. Discussion: During ontogeny the femur undergoes distinct morphological phases, which correspond with changes in loading regime. This study illustrates the importance of loading conditions in shaping immature bone morphology. Nonmechanical factors such as changes in hormonal environmental can also impact on this dynamic

The vocal apparatus: An understudied tool to reconstruct the evolutionary history of echolocation in bats?

Laryngeal echolocation in bats could have evolved following two scenarios: a single origin from a common ancestor or an independent acquisition inside the two clades Yinpterochiroptera and Yangochiroptera. Later, some members of Yinpterochiroptera possibly lost their ability to echolocate. In bats, the larynx produces vocalizations for communication and, in most species, for echolocation. Here, we describe how comparative chiropteran laryngeal morphology is a novel area of research that could improve the understanding of echolocation and may help resolve the evolutionary history of bats. This review provides morphological descriptions and comparisons of the bat larynx and bioacoustics interpretations. We discuss the importance of understanding: (1) laryngeal sound production so it may be linked with the evolution of the chiropteran auditory system; and (2) the evolution of laryngeal morphology to understand the ecological and behavioural aspects of bat biology. We find that a strong phylogenetic signal is potentially the main source explaining macroevolutionary variation in laryngeal form among bats. We predict that the three parameters of sound production in echolocation (frequency, intensity, and rate of calls) are independently modulated by different laryngeal components, but this hypothesis remains understudied in terms of species diversity

Mistaken-for-Game Hunting Accidents: A Human Factors Review

Hunting accidents can have devastating consequences. One of the most common causes of hunting fatalities in this country, and others, are target identification failures—mistaking people for game. A golden rule in firearm safety is to identify your target beyond all doubt. Despite this message being constantly repeated, accidents are still occurring. Hunter education and awareness about high visibility clothing have reduced accident rates, but these statistics have since plateaued. Contrary to what most people think, the hunters committing these accidents are often experienced and considered to be safe and competent. Crucially, they often believe they have, 100%, correctly identified their target. Psychology and human factors can provide insight into how these situations might occur. When interpreting information, we rely heavily upon mental rules of thumb called heuristics. Heuristics operate outside of our conscious awareness and are utilised even more in stressful or emotionally charged situations. However, they can also make us susceptible to cognitive biases which may lead us astray—we underestimate the impact heuristics will have on our decisions. Attempts to manage heuristics and cognitive biases are often futile because we normally cannot detect them when they occur. Hunters are constantly told that they need to treat every sound or movement as human in an attempt to change their mind-set. However, given the difficulty in detecting cognitive biases, it is unlikely a hunter’s conscious management of heuristics would be consistently possible in the long term. Cognitive biases undoubtedly occur in hunting as in most activities we do. Analyses of accidents and anecdotal reports point to their involvement, as does research showing their involvement in other critical environments, including firearms operations in the military and the police. Given the impracticality of preventing heuristics and cognitive biases from affecting a hunter’s target identification, an additional approach is required. One method to prevent mistaken-for-game hunting accidents may involve the use of objective warning systems, such as those used to prevent friendly fire in the military. This white paper discusses four key cognitive biases which we believe play a role in mistaken-for-game hunting accidents: the availability heuristic, expectancy, confirmation bias, and optimism bias. We also present the assertion that experience may not safeguard a hunter, and may in fact do the opposite. Other contributing factors—buck fever, poor choice of clothing, and snap shooting—are discussed in relation to cognitive biases. However, there is currently a notable lack of research on the role of cognitive biases in hunting accidents per se. As a result, more work needs to be conducted to verify the conclusions of this white paper, for which a human factors approach must be taken

Telomere length is highly heritable and independent of growth rate manipulated by temperature in field crickets

Many organisms are capable of growing faster than they do. Restrained growth rate has functionally been explained by negative effects on lifespan of accelerated growth. However, the underlying mechanisms remain elusive. Telomere attrition has been proposed as a causal agent and has been mostly studied in endothermic vertebrates. We established that telomeres exist as chromosomal-ends in a model insect, the field cricket Gryllus campestris, using terminal restriction fragment and Bal 31 methods. Telomeres comprised TTAGGn repeats of 38 kb on average, more than four times longer than the telomeres of human infants. Bal 31 assays confirmed that telomeric repeats were located at the chromosome-ends. We tested whether rapid growth between day 1, day 65, day 85, and day 125 is achieved at the expense of telomere length by comparing nymphs reared at 23°C with their siblings reared at 28°C, which grew three times faster in the initial 65 days. Surprisingly, neither temperature treatment nor age affected average telomere length. Concomitantly, the broad sense heritability of telomere length was remarkably high at ~100%. Despite high heritability, the evolvability (a mean-standardized measure of genetic variance) was low relative to that of body mass. We discuss our findings in the context of telomere evolution. Some important features of vertebrate telomere biology are evident in an insect species dating back to the Triassic. The apparent lack of an effect of growth rate on telomere length is puzzling, suggesting strong telomere length maintenance during the growth phase. Whether such maintenance of telomere length is adaptive remains elusive and requires further study investigating the links with fitness in the wild.</p

Relativistic MHD with Adaptive Mesh Refinement

This paper presents a new computer code to solve the general relativistic magnetohydrodynamics (GRMHD) equations using distributed parallel adaptive mesh refinement (AMR). The fluid equations are solved using a finite difference Convex ENO method (CENO) in 3+1 dimensions, and the AMR is Berger-Oliger. Hyperbolic divergence cleaning is used to control the $\nabla\cdot {\bf B}=0$ constraint. We present results from three flat space tests, and examine the accretion of a fluid onto a Schwarzschild black hole, reproducing the Michel solution. The AMR simulations substantially improve performance while reproducing the resolution equivalent unigrid simulation results. Finally, we discuss strong scaling results for parallel unigrid and AMR runs.Comment: 24 pages, 14 figures, 3 table

Sex differences in allometry for phenotypic traits in mice indicate that females are not scaled males

Sex differences in the lifetime risk and expression of disease are well-known. Preclinical research targeted at improving treatment, increasing health span, and reducing the financial burden of health care, has mostly been conducted on male animals and cells. The extent to which sex differences in phenotypic traits are explained by sex differences in body weight remains unclear. We quantify sex differences in the allometric relationship between trait value and body weight for 363 phenotypic traits in male and female mice, recorded in >2 million measurements from the International Mouse Phenotyping Consortium. We find sex differences in allometric parameters (slope, intercept, residual SD) are common (73% traits). Body weight differences do not explain all sex differences in trait values but scaling by weight may be useful for some traits. Our results show sex differences in phenotypic traits are trait-specific, promoting case-specific approaches to drug dosage scaled by body weight in mice

Detection of subclinical keratoconus using biometric parameters

The validation of innovative methodologies for diagnosing keratoconus in its earliest stages is of major interest in ophthalmology. So far, subclinical keratoconus diagnosis has been made by combining several clinical criteria that allowed the definition of indices and decision trees, which proved to be valuable diagnostic tools. However, further improvements need to be made in order to reduce the risk of ectasia in patients who undergo corneal refractive surgery. The purpose of this work is to report a new subclinical keratoconus detection method based in the analysis of certain biometric parameters extracted from a custom 3D corneal model. This retrospective study includes two groups: the first composed of 67 patients with healthy eyes and normal vision, and the second composed of 24 patients with subclinical keratoconus and normal vision as well. The proposed detection method generates a 3D custom corneal model using computer-aided graphic design (CAGD) tools and corneal surfaces’ data provided by a corneal tomographer. Defined bio-geometric parameters are then derived from the model, and statistically analysed to detect any minimal corneal deformation. The metric which showed the highest area under the receiver-operator curve (ROC) was the posterior apex deviation. This new method detected differences between healthy and sub-clinical keratoconus corneas by using abnormal corneal topography and normal spectacle corrected vision, enabling an integrated tool that facilitates an easier diagnosis and follow-up of keratoconus.This publication has been carried out in the framework of the Thematic Network for Co-Operative Research in Health (RETICS) reference number RD16/0008/0012 financed by the Carlos III Health Institute-General Subdirection of Networks and Cooperative Investigation Centers (R&D&I National Plan 2013–2016) and the European Regional Development Fund (FEDER)

A simple rule governs the evolution and development of hominin tooth size

The variation in molar tooth size in humans and our closest relatives (hominins) has strongly influenced our view of human evolution. The reduction in overall size and disproportionate decrease in third molar size have been noted for over a century, and have been attributed to reduced selection for large dentitions owing to changes in diet or the acquisition of cooking1, 2. The systematic pattern of size variation along the tooth row has been described as a ‘morphogenetic gradient’ in mammal, and more specifically hominin, teeth since Butler3 and Dahlberg4. However, the underlying controls of tooth size have not been well understood, with hypotheses ranging from morphogenetic fields3 to the clone theory5. In this study we address the following question: are there rules that govern how hominin tooth size evolves? Here we propose that the inhibitory cascade, an activator–inhibitor mechanism that affects relative tooth size in mammals6, produces the default pattern of tooth sizes for all lower primary postcanine teeth (deciduous premolars and permanent molars) in hominins. This configuration is also equivalent to a morphogenetic gradient, finally pointing to a mechanism that can generate this gradient. The pattern of tooth size remains constant with absolute size in australopiths (including Ardipithecus, Australopithecus and Paranthropus). However, in species of Homo, including modern humans, there is a tight link between tooth proportions and absolute size such that a single developmental parameter can explain both the relative and absolute sizes of primary postcanine teeth. On the basis of the relationship of inhibitory cascade patterning with size, we can use the size at one tooth position to predict the sizes of the remaining four primary postcanine teeth in the row for hominins. Our study provides a development-based expectation to examine the evolution of the unique proportions of human teeth