The functional morphology of weight bearing: limb joint surface area allometry in anthropoid primates

Biomechanical scaling of long bone joint surface areas was investigated in 13 species of anthropoid primates. It was proposed that joint surface areas should scale with positive allometry with respect to body size in order to maintain relatively constant safety factors for joints in small and large animals and that modifications from the overall pattern of scaling may be expected in the limb joints of species exhibiting specialized locomotor behaviours that radically alter limb loading. Within anthropoids, the brachiating primates, white-handed gibbons ( Hylobates lar ) and black-handed spider monkeys ( Ateles geoffroyi ), were used to test this hypothesis. Total joint surface areas were found to scale with significant positive allometry in 11 of 12 limb joints. The observed pattern of interspecific allometry supports the hypothesis that weight bearing is a major constraint on the design of joints. This positive interspecific allometry is reflected at the intraspecific level as well, with larger joints of larger species showing significant intraspecific scaling. Suspensory species showed no significant deviations from the overall anthropoid pattern, despite their reduced compressive loading of the limb joints, even after controlling for joint mobility. These results suggest that, while evolutionary changes in locomotor behaviour that produce significant increases in loading of a joint may be accompanied by selection for increased joint surface areas, adoption of locomotor repertoires that reduce limb loading may have no selective effect on joint morphology, and joint design in these cases will reflect the biomechanics of the ancestral locomotor condition.     

Intra‐ and interpopulation genetic differentiation and gene flow in a group of isolated populations of Bradybaena fruticum (O. F. Müller, 1774) in South Poland

Intra‐ and interpopulation variation was studied, by means of cellulose acetate allozyme electrophoresis, on 16 populations of helicoid snail Bradybaena fruticum (O. F. Müller, 1774) in South Poland. Four enzyme systems, coded by seven loci, were analysed. Calculated with Fisher's technique and Ohta's D‐statistics, four cases of linkage disequilibrium were detected, reflecting population subdivision. The mean number of alleles per locus equalled 2.16 and the mean expected heterozygosity was 0.287. Exact multipopulation and multilocus tests for Hardy–Weinberg equilibrium indicated a statistically significant homozygote excess in all the loci and all populations but three. Each population, however, was at Hardy–Weinberg equilibrium for most loci, though the values of f (F_IS) were usually high. Homozygote excess was ascribed partly to inbreeding and partly to Wahlund's effect (spatial subdivision of population; at least two cohorts of adult, reproducing snails), disrupting selection in this polymorphic species not excluded. F‐statistics showed relatively low values of θ (F_ST ; mean for all loci = 0.224) and those of Nm usually below 1 (mean 0.866). Pairwise values of either θ or Cavalli‐Sforza and Edwards arc distance were statistically significantly associated with geographic distances. Contrary to this, no geographic pattern of interpopulation differences was detected by correspondence analysis on allele frequencies, non‐linear multidimensional scaling, UPGMA clustering or neighbour‐joining trees constructed on θ and Cavalli‐Sforza and Edwards arc distance. Accordingly, some most distant populations were more similar to one another than the close ones.     

Genetic analysis of oat (Avena sativa L.) by joint scaling test

Comparing the results of genetic analysis of oat varieties with the method of diallel analysis of F1 hybrids and with the joint scaling test the spheres of optimal application of both methods were determined. Quantitative estimation of genetic parameters forming the phenotypic averages in scaling test develops the necessary base for involvement of marker genes for qualitative characters in search of QTLs controlling the traits with continuous variation. The crosses being the most suitable for further investigation with the aim to identify and to allocate the main genes of quantitative traits are indicated.     

Using two palpable measurements improves the subject-specific femoral modeling

Subject-specific musculoskeletal models are essential to biomedical research and clinical applications, such as customized joint replacement, computer-aided surgical planning, gait analysis and automated segmentation. Generating these models from CT or magnetic resonance imaging (MRI) is time and resource intensive, requiring special skills. Therefore, in many studies individual bone models are approximated by scaling a generic template. Thus, the primary goal of this study was to determine a set of clinically available parameters (palpable measures and demographic data) that could improve the prediction of femoral dimensions, as compared to predicting these variables using uniform scaling based on palpable length. Similar to previous non-homogenous anthropometric scaling methods, the non-homogenous scaling method proposed in this study improved the prediction over uniform scaling of five key femoral measures. Homogenous scaling forces all dimensions of an object to be scaled equally, whereas non-homogenous scaling allows the dimensions to be scaled independently. The largest improvement was in femoral depth, where the coefficient of determination (r²) improved from 0.22 (homogenous) to 0.60 (non-homogeneous). In general, the major advantage of this non-homogenous scaling method is its ability to support the accurate and rapid generation of subject-specific femoral models since all parameters can be collected clinically, without imaging or invasive methods.     

Scaling threshold characters

A simple method of scaling ordered categorical responses having a joint distribution with an underlying normal variable is presented. Scores are developed that maximize heritability of the observed variate and that in the class of scores based on polychotomies: (1) maximize the correlation between score and the underlying genetic value to be predicted, and (2) minimize mean-square prediction error. Several examples suggest little is lost, in terms of heritability, by using equally spaced scores. The proposed scaling method discriminates among candidates for selection that would be tied if equally spaced scores are used and sometimes yields different rankings of candidates.     

Managing performance and power consumption tradeoff for multiple heterogeneous servers in cloud computing

There are typically multiple heterogeneous servers providing various services in cloud computing. High power consumption of these servers increases the cost of running a data center. Thus, there is a problem of reducing the power cost with tolerable performance degradation. In this paper, we optimize the performance and power consumption tradeoff for multiple heterogeneous servers. We consider the following problems: (1) optimal job scheduling with fixed service rates; (2) joint optimal service speed scaling and job scheduling. For problem (1), we present the Karush-Kuhn-Tucker (KKT) conditions and provide a closed-form solution. For problem (2), both continuous speed scaling and discrete speed scaling are considered. In discrete speed scaling, the feasible service rates are discrete and bounded. We formulate the problem as an MINLP problem and propose a distributed algorithm by online value iteration, which has lower complexity than a centralized algorithm. Our approach provides an analytical way to manage the tradeoff between performance and power consumption. The simulation results show the gain of using speed scaling, and also prove the effectiveness and efficiency of the proposed algorithms.     

Modelling tendon excursions and moment arms of the finger flexors: anatomic fidelity versus function

A detailed musculoskeletal model of the human hand is needed to investigate the pathomechanics of tendon disorders and carpal tunnel syndrome. The purpose of this study was to develop a biomechanical model with realistic flexor tendon excursions and moment arms. An existing upper extremity model served as a starting point, which included programmed movement of the index finger. Movement capabilities were added for the other fingers. Metacarpophalangeal articulations were modelled as universal joints to simulate flexion/extension and abduction/adduction while interphalangeal articulations used hinges to represent flexion. Flexor tendon paths were modelled using two approaches. The first method constrained tendons with control points, representing annular pulleys. The second technique used wrap objects at the joints as tendon constraints. Both control point and joint wrap models were iteratively adjusted to coincide with tendon excursions and moment arms from a anthropometric regression model using inputs for a 50th percentile male. Tendon excursions from the joint wrap method best matched the regression model even though anatomic features of the tendon paths were not preserved (absolute differences: mean<0.33 mm, peak<0.74 mm). The joint wrap model also produced similar moment arms to the regression (absolute differences: mean<0.63 mm, peak<1.58 mm). When a scaling algorithm was used to test anthropometrics, the scaled joint wrap models better matched the regression than the scaled control point models. Detailed patient-specific anatomical data will improve model outcomes for clinical use; however, population studies may benefit from simplified geometry, especially with anthropometric scaling.     

Inverse remodelling algorithm identifies habitual manual activities of primates based on metacarpal bone architecture

Previously, a micro-finite element (micro-FE)-based inverse remodelling method was presented in the literature that reconstructs the loading history of a bone based on its architecture alone. Despite promising preliminary results, it remains unclear whether this method is sensitive enough to detect differences of bone loading related to pathologies or habitual activities. The goal of this study was to test the sensitivity of the inverse remodelling method by predicting joint loading histories of metacarpal bones of species with similar anatomy but clearly distinct habitual hand use. Three groups of habitual hand use were defined using the most representative primate species: manipulation (human), suspensory locomotion (orangutan), and knuckle-walking locomotion (bonobo, chimpanzee, gorilla). Nine to ten micro-computed tomography scans of each species (\(n=48\) in total) were used to create micro-FE models of the metacarpal head region. The most probable joint loading history was predicted by optimally scaling six load cases representing joint postures ranging from \(-\,75^{\circ }\) (extension) to \(+\,75^{\circ }\) (flexion). Predicted mean joint load directions were significantly different between knuckle-walking and non-knuckle-walking groups (\(p<0.05\)) and in line with expected primary hand postures. Mean joint load magnitudes tended to be larger in species using their hands for locomotion compared to species using them for manipulation. In conclusion, this study shows that the micro-FE-based inverse remodelling method is sensitive enough to detect differences of joint loading related to habitual manual activities of primates and might, therefore, be useful for palaeoanthropologists to reconstruct the behaviour of extinct species and for biomedical applications such as detecting pathological joint loading.

     

Temporal scaling of molecular evolution in primates and other mammals

Molecular clocks are routinely tested for linearity using a relative rate test and routinely calibrated against the geological time scale using a single or average paleontologically determined time of divergence between living taxa. The relative rate test is a test of parallel rate equality, not a test of rate constancy. Temporal scaling provides a test of rates, where scaling coefficients of 1.0 (isochrony) represent stochastic rate constancy. The fossil record of primates and other mammals is now known in sufficient detail to provide several independent divergence times for major taxonomic groups. Molecular difference should scale negatively or isochronically (scaling coefficients less than 1.0) with divergence time: where two or more divergence times are available, molecular difference appears to scale positively (scaling coefficient greater than 1.0). A minimum of four divergence times are required for adequate statistical power in testing the linear model: scaling is significantly nonlinear and positive in six of 11 published investigations meeting this criterion. All groups studied show some slowdown in rates of molecular change over Cenozoic time. The break from constant or increasing rates during the Mesozoic to decreasing rates during the Cenozoic appears to coincide with extraordinary diversification of placental mammals at the beginning of this era. High rates of selectively neutral molecular change may be concentrated in such discrete events of evolutionary diversification.      

Evaluation of different analytical methods for subject-specific scaling of musculotendon parameters

Musculoskeletal models are often used to estimate internal muscle forces and the effects of those forces on the development of human movement. The Hill-type muscle model is an important component of many of these models, yet it requires specific knowledge of several muscle and tendon properties. These include the optimal muscle fibre length, the length at which the muscle can generate maximum force, and the tendon slack length, the length at which the tendon starts to generate a resistive force to stretch. Both of these parameters greatly influence the force-generating behaviour of a musculotendon unit and vary with the size of the person. However, these are difficult to measure directly and are often estimated using the results of cadaver studies, which do not account for differences in subject size. This paper examined several different techniques that can be used to scale the optimal muscle fibre length and tendon slack length of a musculotendon unit according to subject size. The techniques were divided into three categories corresponding to linear scaling, scaling by maintaining a constant tendon slack length throughout the range of joint motion, and scaling by maintaining muscle operating range throughout the range of joint motion. We suggest that a good rationale for scaling muscle properties should be to maintain the same force-generating characteristics of a musculotendon unit for all subjects, which is best achieved by scaling that preserves the muscle operating range when the muscle is maximally activated.     

Scaling of postcranial joint size in hominoid primates

The scaling of sixteen articular dimensions in the locomotor skeleton of hominoid primates is examined with special reference to a recently proposed model of geometric similarity. Seven species are included in the analysis (gorillas, common chimpanzees, bonobos, orang-utans, siamang, lar gibbons, and modern humans of European descent); all specimens are adult individuals of known body mass (N=87). No significant sexual dimorphism in the scaling of joint size was observed. Overal results are compatible with the biomechanical model predictions of isometry, and lend additional support to the suggestion that joint stresses are of the same order of magnitude in animals differing vastly in body size and locomotor adaptations. The hindlimb and lumbosacral joints of humans, however, are consistently much larger than expected for their body mass. Full-time bipedality obviously precludes the sharing of weight support and propulsion with the forelimbs, and this fundamental difference is accurately reflected in the relative joint size of humans.     

A three-dimensional musculoskeletal model for gait analysis. Anatomical variability estimates

Three-dimensional coordinates defining the origin and insertion of 40 muscle units, and bony landmarks for osteometric scaling were identified on dry bone specimens. Interspecimen coordinate differences along the anterior-posterior axis of the pelvis and the long bone axes of the pelvis, femur and leg were reduced by scaling but landmark differences along the other axes were not. The coordinates were mapped to living subjects using close-range photogrammetry to locate superficial reference markers. The error of predicting the positions of internal coordinates was assessed by comparing joint centre locations calculated from local axes defining the orientation of segments superior and inferior to a joint. A difference was attributed to: anatomical variability not accounted for by scaling; errors in identifying and placing reference landmarks; the accuracy of locating markers using photogrammetry and error introduced by marker oscillation during movement. Anatomical differences between specimens are one source of error in defining a musculoskeletal model but larger errors are introduced when such models are mapped to living subjects.     

Gyroscopic corrections improve wearable sensor data prior to measuring dynamic sway in the gait of people with Multiple Sclerosis

Accelerometers are incorporated into many consumer devices providing new ways to monitor gait, mobility, and fall risk. However, many health benefits have not been realised because of issues with data quality that results from gravitational ‘cross-talk’ when the wearable device is tilted. Here we present an adaptive filter designed to improve the quality of accelerometer data prior to measuring dynamic pelvic sway patterns during a six minute walk test in people with and without Multiple Sclerosis (MS). Optical motion capture was used as the gold standard. Improved wearable device accuracy (≤4.4% NRMSE) was achieved using gyroscopic corrections and scaling filter thresholds by step frequency. The people with MS presented significantly greater pelvis sway range to compensate for their lower limb weaknesses and joint contractures. The visualisation of asymmetric pelvic sway in people with MS illustrates the potential to better understand their mobility impairments for reducing fall risk.     

Genetic analysis of the short-stem populations of rye (Secale cereale L.) for the plant height trait

The process and results of genetic analysis of the short-stem rye populations (Secale cereale L.) for the trait "plant height" are described. The analysis has been performed with the joint scaling test using data of estimation of the parental and hybrid populations developed in the cyclic reciprocal crosses between four initial populations. Monogenic, digenic, and trigenic differences between parental rye populations for two genes of incomplete dominance and one multiallelic gene with additive allelic interaction were determined.     

Density‐dependent offspring interactions do not explain macroevolutionary scaling of adult size and offspring size

Most life forms exhibit a correlated evolution of adult size (AS) and size at independence (SI), giving rise to AS–SI scaling relationships. Theory suggests that scaling arises because relatively large adults have relatively high reproductive output, resulting in strong density‐dependent competition in early life, where large size at independence provides a competitive advantage to juveniles. The primary goal of our study is to test this density hypothesis, using large datasets that span the vertebrate tree of life (fishes, amphibians, reptiles, birds, and mammals). Our secondary goal is to motivate new hypotheses for AS–SI scaling by exploring how subtle variation in life‐histories among closely related species is associated with variation in scaling. Our phylogenetically informed comparisons do not support the density hypothesis. Instead, exploration of AS–SI scaling among life‐history variants suggests that steeper AS–SI scaling slopes are associated with evolutionary increases in size at independence. We suggest that a positive association between size at independence and juvenile growth rate may represent an important mechanism underlying AS–SI scaling, a mechanism that has been underappreciated by theorists. If faster juvenile growth is a consequence of evolutionary increases in size at independence, this may help offset the cost of delayed maturation, leading to steeper AS–SI scaling slopes.     

Sulfur-Deficient Transfer Ribonucleic Acid in a Cysteine-Requiring, “Relaxed” Mutant of Escherichia coli

A cysteine-requiring mutant of the parent strain Escherichia coli Hfr Cavalli (RC(rel), Met(-), lambda) has been isolated. The mutant was selected by using replica plating after mutagenesis by N-methyl-N'-nitro-N-nitrosoguanidine. The mutation appears to be in the gene for sulfite reductase, since the mutant could utilize sulfide but not sulfite as a sulfur source. The mutant was found to be RC(rel) with respect to both methionine and cysteine. During cysteine starvation, transfer ribonucleic acid (tRNA) deficient in 4-thiouracil was produced, and in vivo studies indicate that this tRNA can accept sulfur groups to a greater extent than normal tRNA. Further, there were differences both in the rate and extent of amino acid acceptance between normal and sulfur-deficient tRNA. This suggests that thionucleotides are involved in at least one of the biological functions of the tRNA molecule.     

Perturbation-dependent selection of postural feedback gain and its scaling

In this study we examined whether the selection of postural feedback gain and its scaling is dependent on perturbation type. We compare forward pushes applied to the back of a standing subject to previous work on responses to support translation. As was done in the previous work, we quantified the subject's response in terms of perturbation-dependent feedback gains. Seven healthy young subjects (25±3 yr) experienced five different magnitudes of forward push applied by a 1.25 m-long pendulum falling from the height of 1.4m toward the center of mass of the subject's torso. The loads on the pendulum ranged from 2 to 10 kg. Impulsive force, ground reaction forces and joint kinematics were measured, and joint torques were calculated from inverse dynamics. A full-state feedback control model was used to quantify the empirical data, and the feedback gains that minimized the fitting error between the data and model simulation were identified. As in previously published feedback gains for support translation trials, gradual gain scaling with push perturbation magnitude was consistently observed, but a different feedback gain set was obtained. The results imply that the nervous system may be aware of body dynamics being subjected to various perturbation types and may select perturbation-dependent postural feedback gains that satisfy postural stability and feasible joint torque constraints.     

The effect of fragment area on site‐level biodiversity

Habitat fragmentation accompanies habitat loss, and drives additional biodiversity change; but few global biodiversity models explicitly analyse the effects of both fragmentation and loss. Here we propose and test the hypothesis that, as fragment area increases, species density (the number of species in a standardised plot) will scale with an exponent given by the difference between the exponents of the species–area relationships for islands (z ~ 0.25) and in contiguous habitat (z ~ 0.15), and test whether scaling varies between land uses. We also investigate the scaling of overall abundance and rarefaction‐based richness, as some mechanisms make different predictions about how fragment area should affect them. The relevant data from the taxonomically and geographically broad PREDICTS database were used to model the three diversity measures, testing their scaling with fragment area and whether the scaling exponent varied among land uses (primary forest, secondary forest, plantation forest, cropland and pasture). In addition, the consistency of the response of species density to fragment area was tested across three well represented taxa (Magnoliopsida, Hymenoptera and ‘herptiles’). Species density and total abundance showed area‐scaling exponents of 0.07 and 0.16, respectively, and these exponents did not vary significantly among land uses; rarefaction‐based richness by contrast did not increase consistently with area. These results suggest that the area‐scaling of species density is driven by the area‐scaling of total abundance, with additive edge effects (species moving into the small fragments from the surroundings) opposing – but not fully overcoming – the effect of fragment area on overall density of individuals. The interaction between fragment area and higher taxon (plants, vertebrates and invertebrates), which remained in the rarefied richness model, indicates that mechanisms may vary among groups.     

Multivariate Data Analysis as a Semi-quantitative Tool for Interpretive Evaluation of Comparability or Equivalence of Aerodynamic Particle Size Distribution Profiles

The purpose of this article is to investigate the performance of multivariate data analysis, especially orthogonal partial least square (OPLS) analysis, as a semi-quantitative tool to evaluate the comparability or equivalence of aerodynamic particle size distribution (APSD) profiles of orally inhaled and nasal drug products (OINDP). Monte Carlo simulation was employed to reconstitute APSD profiles based on 55 realistic scenarios proposed by the Product Quality Research Institute (PQRI) working group. OPLS analyses with different data pretreatment methods were performed on each of the reconstituted profiles. Compared to unit-variance scaling, equivalence determined based on OPLS analysis with Pareto scaling was shown to be more consistent with the working group assessment. Chi-square statistics was employed to compare the performance of OPLS analysis (Pareto scaling) with that of the combination test (i.e., chi-square ratio statistics and population bioequivalence test for impactor-sized mass) in terms of achieving greater consistency with the working group evaluation. A p value of 0.036 suggested that OPLS analysis with Pareto scaling may be more predictive than the combination test with respect to consistency. Furthermore, OPLS analysis may also be employed to analyze part of the APSD profiles that contribute to the calculation of the mass median aerodynamic diameter. Our results show that OPLS analysis performed on partial deposition sites do not interfere with the performance on all deposition sites.     

Can Power-Law Scaling and Neuronal Avalanches Arise from Stochastic Dynamics?

The presence of self-organized criticality in biology is often evidenced by a power-law scaling of event size distributions, which can be measured by linear regression on logarithmic axes. We show here that such a procedure does not necessarily mean that the system exhibits self-organized criticality. We first provide an analysis of multisite local field potential (LFP) recordings of brain activity and show that event size distributions defined as negative LFP peaks can be close to power-law distributions. However, this result is not robust to change in detection threshold, or when tested using more rigorous statistical analyses such as the Kolmogorov–Smirnov test. Similar power-law scaling is observed for surrogate signals, suggesting that power-law scaling may be a generic property of thresholded stochastic processes. We next investigate this problem analytically, and show that, indeed, stochastic processes can produce spurious power-law scaling without the presence of underlying self-organized criticality. However, this power-law is only apparent in logarithmic representations, and does not survive more rigorous analysis such as the Kolmogorov–Smirnov test. The same analysis was also performed on an artificial network known to display self-organized criticality. In this case, both the graphical representations and the rigorous statistical analysis reveal with no ambiguity that the avalanche size is distributed as a power-law. We conclude that logarithmic representations can lead to spurious power-law scaling induced by the stochastic nature of the phenomenon. This apparent power-law scaling does not constitute a proof of self-organized criticality, which should be demonstrated by more stringent statistical tests.