Technical note: The effect of midshaft location on the error ranges of femoral and tibial cross‐sectional parameters

In comparing long‐bone cross‐sectional geometric properties between individuals, percentages of bone length are often used to identify equivalent locations along the diaphysis. In fragmentary specimens where bone lengths cannot be measured, however, these locations must be estimated more indirectly. In this study, we examine the effect of inaccurately located femoral and tibial midshafts on estimation of geometric properties. The error ranges were compared on 30 femora and tibiae from the Eneolithic and Bronze Age. Cross‐sections were obtained at each 1% interval from 60 to 40% of length using CT scans. Five percent of deviation from midshaft properties was used as the maximum acceptable error. Reliability was expressed by mean percentage differences, standard deviation of percentage differences, mean percentage absolute differences, limits of agreement, and mean accuracy range (MAR) (range within which mean deviation from true midshaft values was less than 5%). On average, tibial cortical area and femoral second moments of area are the least sensitive to positioning error, with mean accuracy ranges wide enough for practical application in fragmentary specimens (MAR = 40–130 mm). In contrast, tibial second moments of area are the most sensitive to error in midshaft location (MAR = 14–20 mm). Individuals present significant variation in morphology and thus in error ranges for different properties. For highly damaged fossil femora and tibiae we recommend carrying out additional tests to better establish specific errors associated with uncertain length estimates. Am J Phys Anthropol 2010. © 2009 Wiley‐Liss, Inc.     

Technical note: A stereological analysis of the cross‐sectional variability of the femoral osteon population

Unbiased selection of regions of interest (ROIs) and unbiased definition of histological structures are needed to improve the repeatability of microscopic methods for age at death determination and to reduce operator subjectivity. We present results obtained by selecting ROIs according to stereological principles on a sample of 28 femoral cross sections of Caucasoid males aged 20–89 years. A regular grid was overlaid on the cross section, and the ROIs were selected as close as possible to the periosteum in the anterior, lateral, and medial regions. The areas consisting of all intact secondary osteons plus fragments were outlined and osteon population density, percent osteon population, area, and perimeter were calculated using stereological methods and software. Overall, the analyses of intra‐ and inter‐section variability showed no significant difference between the ROIs, i.e., the location within the cross section of the ROIs does not affect the outcome of the analyses. The individual variability was found to be higher in adults aged 30–55 years than in other age ranges. ranges. Am J Phys Anthropol 2010. © 2010 Wiley‐Liss, Inc.     

Periosteal versus true cross‐sectional geometry: A comparison along humeral,femoral, and tibial diaphyses

Cross‐sectional geometric (CSG) properties of human long bone diaphyses are typically calculated from both periosteal and endosteal contours. Though quantification of both is desirable, periosteal contours alone have provided accurate predictions of CSG properties at the midshaft in previous studies. The relationship between CSG properties calculated from external contours and “true” (endosteal and periosteal) CSG properties, however, has yet to be examined along the whole diaphysis. Cross‐sectional computed tomography scans were taken from 21 locations along humeral, femoral, and tibial diaphyses in 20 adults from a late prehistoric central Illinois Valley cemetery. Mechanical properties calculated from images with (a) artificially filled medullary cavities (“solid”) and (b) true unaltered cross‐sections were compared at each section location using least squares regression. Results indicate that, in this sample, polar second moments of area (J), polar section moduli (Z_p), and cross‐sectional shape (I_max/I_min) calculated from periosteal contours correspond strongly with those calculated from cross‐sections that include the medullary cavity. Correlations are high throughout most of the humeral diaphysis and throughout large portions of femoral and tibial diaphyses (R² = 0.855–0.998, all P < 0.001, %SEE ≤ 8.0, %PE ≤ 5.0), the major exception being the proximal quarter of the tibial diaphysis for J and Z_p. The main source of error was identified as variation in %CA. Results reveal that CSG properties quantified from periosteal contours provide comparable results to (and are likely to detect the same differences among individuals as) true CSG properties along large portions of long bone diaphyses. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.     

The influence of body proportions on femoral and tibial midshaft shape in hunter‐gatherers

Variation in femoral and tibial diaphyseal shape is used as an indicator of adaptation to patterns of terrestrial mobility. Recent experimentation has implied that lower limb diaphyseal shape may be primarily influenced by lower limb length, and less so by mobility patterns. If valid, this would, at most, render previous interpretations of mobility patterns based on analyses of diaphyseal shape questionable, and, at least, require additional standardization that considers the influence of limb length. Although the consequences could be profound, this implication has yet to be directly tested. Additionally, the influence of body breadth on tibial shape (and to a lesser extent femoral shape) remains uncertain. Tibial and femoral cross‐sectional midshaft shape measurements, taken from nine Pleistocene and Holocene skeletal populations, were compared against lower limb length, limb segment length, and bi‐iliac breadth. Generally, limb length and limb segment length do not significantly influence femoral or tibial midshaft shape. After controlling for body mass greater bi‐iliac breadth is associated with a relative mediolateral strengthening of the femoral midshaft, while the influence of a wider body shape (BIB/length) is associated with a relative M‐L strengthening of the tibia and femur of males, and the tibia of females. We conclude that; (1) mechanical interpretations of lower limb diaphyseal shape are most parsimonious due to the lack of evidence for a consistent relationship between segment length and shape; however, (2) further work is required to investigate the influence of bi‐iliac breadth on both femoral and tibial midshaft shape. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

The ecological importance of crocodylians: towards evidence‐based justification for their conservation

Large‐bodied predators are well represented among the world's threatened and endangered species. A significant body of literature shows that in terrestrial and marine ecosystems large predators can play important roles in ecosystem structure and functioning. By contrast, the ecological roles and importance of large predators within freshwater ecosystems are poorly understood, constraining the design and implementation of optimal conservation strategies for freshwater ecosystems. Conservationists and environmentalists frequently promulgate ecological roles that crocodylians are assumed to fulfil, but often with limited evidence supporting those claims. Here, we review the available information on the ecological importance of crocodylians, a widely distributed group of predominantly freshwater‐dwelling, large‐bodied predators. We synthesise information regarding the role of crocodylians under five criteria within the context of modern ecological concepts: as indicators of ecological health, as ecosystem engineers, apex predators, keystone species, and as contributors to nutrient and energy translocation across ecosystems. Some crocodylians play a role as indicators of ecosystem health, but this is largely untested across the order Crocodylia. By contrast, the role of crocodylian activities in ecosystem engineering is largely anecdotal, and information supporting their assumed role as apex predators is currently limited to only a few species. Whether crocodylians contribute significantly to nutrient and energy translocation through cross‐ecosystem movements is unknown. We conclude that most claims regarding the importance of crocodylians as apex predators, keystone species, ecosystem engineers, and as contributors to nutrient and energy translocation across ecosystems are mostly unsubstantiated speculation, drawn from anecdotal observations made during research carried out primarily for other purposes. There is a paucity of biological research targeted directly at: understanding population dynamics; trophic interactions within their ecological communities; and quantifying the short‐ and long‐term ecological impacts of crocodylian population declines, extirpations, and recoveries. Conservation practices ideally need evidence‐based planning, decision making and justification. Addressing the knowledge gaps identified here will be important for achieving effective conservation of crocodylians.     

A Facile and Very Effective Method to Enhance the Mechanical Strength and the Cyclability of Si‐Based Electrodes for Li‐Ion Batteries

It is well known that the mechanical properties of lithium‐ion battery electrodes impact their electrochemical performance. This is especially critical for Si‐based negative electrodes, which suffer from large volume changes of the active mass upon cycling. Here, this study presents a postprocessing treatment (called maturation) that improves the mechanical and electrochemical stabilities of silicon‐based anodes made with an acidic aqueous binder. It consists of storing the electrode in a humid atmosphere for a few days before drying and cell assembly. This results in a beneficial in situ reactive modification of the interfaces within the electrode. First, the binder tends to concentrate at the silicon interparticle contacts. As a result, the cohesion of the composite film is strengthened. Second, the corrosion of the copper current collector, inducing the formation of copper carboxylate bonds, improves the adhesion of the composite film. The great improvement of the mechanical stability of the matured electrode is confirmed by in‐operando optical microscopy showing the absence of film delamination. The result is a significant electrochemical performance gain, up to a factor 10, compared to a not‐matured electrode. This maturation procedure can be applied to other types of electrodes for improving their electrochemical performance and also their handling during cell manufacturing.     

CAD‐score: A new contact area difference‐based function for evaluation of protein structural models

Evaluation of protein models against the native structure is essential for the development and benchmarking of protein structure prediction methods. Although a number of evaluation scores have been proposed to date, many aspects of model assessment still lack desired robustness. In this study we present CAD‐score, a new evaluation function quantifying differences between physical contacts in a model and the reference structure. The new score uses the concept of residue–residue contact area difference (CAD) introduced by Abagyan and Totrov (J Mol Biol 1997; 268:678–685). Contact areas, the underlying basis of the score, are derived using the Voronoi tessellation of protein structure. The newly introduced CAD‐score is a continuous function, confined within fixed limits, free of any arbitrary thresholds or parameters. The built‐in logic for treatment of missing residues allows consistent ranking of models of any degree of completeness. We tested CAD‐score on a large set of diverse models and compared it to GDT‐TS, a widely accepted measure of model accuracy. Similarly to GDT‐TS, CAD‐score showed a robust performance on single‐domain proteins, but displayed a stronger preference for physically more realistic models. Unlike GDT‐TS, the new score revealed a balanced assessment of domain rearrangement, removing the necessity for different treatment of single‐domain, multi‐domain, and multi‐subunit structures. Moreover, CAD‐score makes it possible to assess the accuracy of inter‐domain or inter‐subunit interfaces directly. In addition, the approach offers an alternative to the superposition‐based model clustering. The CAD‐score implementation is available both as a web server and a standalone software package at http://www.ibt.lt/bioinformatics/cad‐score/ . Proteins 2013. © 2012 Wiley Periodicals, Inc.