Pair-wise vs group-wise registration in statistical shape model construction: representation of physiological and pathological variability of bony surface morphology

Statistical shape models (SSM) of bony surfaces have been widely proposed in orthopedics, especially for anatomical bone modeling, joint kinematic analysis, staging of morphological abnormality, and pre- and intra-operative shape reconstruction. In the SSM computation, reference shape selection, shape registration and point correspondence computation are fundamental aspects determining the quality (generality, specificity and compactness) of the SSM. Such procedures can be made critical by the presence of large morphological dissimilarities within the surfaces, not only because of anthropometrical variability but also mainly due to pathological abnormalities. In this work, we proposed a SW pipeline for SSM construction based on pair-wise (PW) shape registration, which requires the a-priori selection of the reference shape, and on a custom iterative point correspondence algorithm. We addressed large morphological deformations in five different bony surface sets, namely proximal femur, distal femur, patella, proximal fibula and proximal tibia, extracted from a retrospective patient dataset. The technique was compared to a method from the literature, based on group-wise (GW) shape registration. As a main finding, the proposed technique provided generalization and specificity median errors, for all the five bony regions, lower than 2?mm. The comparative analysis provided basically similar results. Particularly, for the distal femur that was the shape affected by the largest pathological deformations, the differences in generalization, specificity and compactness were lower than 0.5?mm, 0.5?mm, and 1%, respectively. We can argue the proposed pipeline, along with the robust correspondence algorithm, is able to compute high-quality SSM of bony shapes, even affected by large morphological variability.     

The relationship between the longitudinal pressure gradient and the blood flow velocity in the canine superior vena cava

In the superior vena cava of anaesthetized open chest dogs the axial pressure gradient (delta P) was measured simultaneously with the blood flow velocity (V) under a variety of preload conditions. Both delta P and V curves showed distinct systolic and diastolic waves. Peak delta P ranged between 26 and 93 P/cm (0.2-0.7 mm Hg/cm) and V varied between 0.095 and 0.19 m/s. Peak systolic delta P, but not peak diastolic delta P was significantly linearly correlated to respectively peak systolic V and peak diastolic V. The shape of delta P and V curves corresponded fairly well but variations of delta P preceded the variations of V. Both the shape correspondence and the phase lag between delta P and V were evaluated by means of the normalized cross-correlation technique. During volume expansion the shape correspondence improved and the phase lag decreased. It is concluded that the transient vena caval blood velocity variations are directly related to the pulsatile axial pressure gradient.     

The measurement of linguistic change

Summary Two methods for measuring the amount of linguistic change are described: 1. It is possible to measure the correspondence between two phoneme inventories of two periods in a language's development in the same way as in information theory between the inventories of the transmitted and received symbols (measure of correspondence B). 2. This first method, however, does not measure the development of a phonologic pattern. Therefore the correlation of similarity is computed (as applicated in the psychology of development).     

林窗几何特征的测定方法

林窗面积、形状及边界木高是决定林窗环境异质性的3个林窗几何特征,影响林窗内植物更新。林窗几何特征的快速测量方法是林窗研究的基础,测量方法可分为2类:基于地面实际测量的地面法和基于林窗林冠照片的相片法。地面法费时费力,受人为因素影响大,可测量林冠林窗和扩展林窗的面积,但不能测量林窗形状和边界木高。相片法具有简单、客观、可重复的优点,但仅适用于林冠林窗。相片法共有5种:"平面相片法"、"航片法"、"半球面影像法"、"双半球面影像法"和"改进的半球面影像法"。前3种测量方法只能测量林冠林窗面积;"改进的半球面影像法"可测量林冠林窗面积和形状,且精度高于前3种相片法,但所需参数最多;"双半球面影像法"可测量林窗面积、形状及边界木高这3个林窗几何特征,且精度较高,但拍摄要求较高。     

Estimation of body size and physique from hominin skeletal remains

Three methods of measuring stature from skeletal remains are reviewed: the reconstructed skeletal length, the correspondence of long bone length to stature and the regression of stature on long bone length. Each involves problems and difficulties. For the anthropologist, there is the additional problem of applying findings from extant taxa to extinct taxa with potentially different morphologies and limb proportions. Of the various studies involving regression of the stature the findings of Trotter and Gleser are judged the most robust and useful notwithstanding problems and limitations. The lumbar vertebrae are potentially important as stature predictors. Estimation of body mass from the skeleton is also beset with problems. Eight methods are reviewed: Hartwig-Scherer's taxon independent solution, four methods involving measurements from the weight-bearing appendicular skeleton, Ruff's method using the length of the reconstructed skeleton and an estimate of body breadth, estimates from the total skeletal mass and estimates from the body mass index when the stature is known approximately. Lumbar vertebrae provide reasonable estimates of both body mass and stature and thus by derivation the body mass index. At present both forensic scientists and anthropologists lack adequate data and methods to estimate body size and shape from hominin skeletons. A further large and well-designed study using magnetic resonance imaging is required.     

Dynamics of L-929 cell spreading after mitosis

Changes in the cell shape of L-929 (NCTC, clone 929) during the cell cycle were analyzed with time-lapse microscopy. It was found that the cells pass through three spreading stages. The maximal cell spreading was observed during the first 1.5 h after mitosis. In this period, the cell area increases in correspondence with the sigmoid dependence and enlarges by approximately 3.0–3.5 times. After a short plateau, the cell area begins to increase, also correspondence with the sigmoid dependence. This period is longer (up to 6 h after the beginning of cell division), with an additional 1.5-fold increase in the cell size. Later, cell area enlargement continues linearly up to the beginning of the next mitosis.     

Does morphology predict behavior? Correspondence between behavioral and morphometric data in a Tyrant‐flycatcher (Tyrannidae) assemblage in the Santa Marta Mountains,Colombia

ABSTRACT Morphology is commonly used as a predictor of ecological relationships among species when studying local assemblages of Neotropical birds. Nevertheless, most evidence supporting ecomorphological correspondence in birds comes from studies of communities and not from local assemblages and, moreover, from temperate latitudes. To increase our understanding of ecomorphological correspondence in Neotropical assemblages, we used three multivariate approaches to evaluate correspondence between morphological and foraging behavior data in a tyrant‐flycatcher assemblage (N= 12 species) in the Santa Marta Mountains in Colombia. Principal components analyses revealed similar species ordinations when using morphological measurements (beak size and shape, tarsus length, wing length, and tail length) or behavioral data (behavioral types of searching for prey and prey capture) separately. Discriminant function analyses tested the ability of morphological traits to predict foraging behavior, showing that more than 90% of all measured individuals (N= 267) were correctly classified in previously defined categories of search and attack behavior. Finally, Canonical correlation analyses revealed a significant correlation between morphological data and two independent datasets of search and attack behavior. Our results demonstrate that morphology can accurately predict ecology in an assemblage of Neotropical tyrannids, and similar results have been reported in previous studies of temperate Tyrant‐flycatchers. Our results also show that bill size and shape, wing length, and tarsus length are the best predictors of foraging behavior in this assemblage. Testing for ecomorphological correspondence in other Neotropical taxa would help identify subsets of phenotypic traits that could be used for a practical, but reliable, determination of ecological relationships within different assemblages.     

Geometric morphometrics of the skull of Tinamidae (Aves, Palaeognathae)

The Tinamidae comprise exclusively Neotropical palaegnathous birds, with homogeneous body morphology and no sexual dimorphism. The goal of this work was to explore the variation in skull morphology between taxa and its possible correspondence with features such as diet or gender using geometric morphometric tools. Eleven landmarks were analyzed in 53 skulls of 4 genera that inhabit grasslands: Nothoprocta, Eudromia, Nothura and Rhynchotus. Intrageneric and intergeneric variability was analyzed. The genera studied here can be distinguished based on the geometric shape of their skull, with prenarial region length and neurocranium shape as the most outstanding features. In the genus Eudromia, males and females could be differentiated, while in the genus Nothoprocta, the species differentiated according to their trophic habits. This study allows establishing that genera and, in some cases, the gender of the Tinamidae can be differentiated based on cranial shape.     

Effect of striate visual cortex topography on the parameters of image filtering

A model of spatial-frequency filtering at the level of 4C layer of the striate visual cortex is proposed and based on the well-known literature data. The evidence on conformable character of representation of the visual field on the primary visual cortex and the suggestions concerning uniformity of horizontal connections of cortical neurones serve as the ground of the model. A correspondence between predictions of the model and results of the experiments with shape perception and size discrimination has been obtained.     

Role of actin filaments in shape formation of mesenteric mesothelial cells of the bullfrog

The role of actin filaments in the development of cellular shape in the mesenteric mesothelium of the bullfrog was studied by using a simple, new technique for making en face preparations of mesothelial sheets. By using these mesothelial cell preparations, the distribution of actin was determined by means of fluorescence microscopy with 7-nitrobenz-2-oxa-1,3-diazole (NBD)-phallacidin and that of myosin by means of immunofluorescence microscopy. Although fluorescence produced by both NBD-phallacidin and antimyosin staining was found exclusively along the margins of the cells, its intensity was altered in correspondence with changes in cell shape. For instance, tadpole-type mesothelial cells with either an irregular or very slender cell shape showed very weak fluorescence. On the other hand, frog-type mesothelial cells with a polygonal shape showed intense fluorescence at their margins and had circumferential bundles of actin filaments at their apices. Furthermore, intercellular junctions between the mesothelial cells developed as the cell shape became polygonal during metamorphosis. The present study showed that development of circumferential bundles of actin filaments and intercellular junctions may serve to establish and maintain the definitive polygonal cellular pattern in the mesenteric mesothelium of the bullfrog.     

Stereoscopic correspondence for ambiguous targets is affected by elevation and fixation distance

Binocular correspondence must be determined if disparity is to be used to provide information about three-dimensional shape. The current study investigated whether knowledge of the statistical distribution of disparities in the natural environment is employed in this process. A simple model, which produces distributions of distances similar to those found in the natural environment, was used to predict the distribution of disparities in natural images. This model predicts that crossed disparities will be more likely as (i) stimulus elevation decreases below fixation and (ii) fixation distance increases. To determine whether these factors influence binocular correspondence for human observers, ambiguous stereograms were presented to observers, as stimulus elevation and fixation distance were manipulated. Clear biases were observed in the depth perceived in these stereograms, which were more likely to be seen as closer than fixation (i) for stimuli presented below fixation and (ii) as fixation distance increased. These results suggest that binocular correspondence is determined in a manner consistent with the distributions of disparities expected in natural scenes.     

QUANTITATIVE GENETICS OF SIZE,SHAPE, LIFE-HISTORY,AND FRUIT CHARACTERISTICS OF THE SEED HETEROMORPHIC COMPOSITE HETEROSPERMA PINNATUM. II. CORRELATION STRUCTURE

We have investigated phenotypic, environmental, within-population broad-sense genetic correlations and among-population genetic correlations for 17 traits in six populations of Heterosperma pinnatum Cav. (Compositae) grown in the greenhouse. The within-population genetic, environmental, and phenotypic correlations were somewhat similar while the among-population genetic correlations showed little correspondence to these. The different correlation matrices were compared to a hypothesis matrix, which predicted higher correlations for groups of functionally and developmentally related traits. The groups were seed and head traits, size and shape traits, and life history traits, with subgroups predicted to have still higher correlations. The phenotypic and environmental matrices corresponded well to the hypothesis matrix, the within-population broad-sense genetic matrix showed weaker, though still significant, correspondence, and the among-population genetic correlations showed no correspondence. Genetic correlations did not differ significantly among populations, though the power of these comparisons was low. Some particular genetic correlations are discussed as possible examples of adaptive correlations (e.g., a negative correlation between dispersal and dormancy) and as examples of developmental or physiological constraints including life-history tradeoffs.     

The settlement of Patagonia: a matrix correlation study.

Matrix correlation represents an innovative methodology to evaluate the explanatory power of several hypotheses by measuring their correspondence with observed morphological variation. In this paper, we view the origins of Patagonians from a matrix correlation approach. Personal and published data on nonmetric cranial traits were used to estimate a biological distance matrix involving five major groups from Patagonia and two from the northwest and northeast regions of Argentina. To evaluate correspondence with other important factors, we used a geographic distance matrix and four design matrices, representing several patterns of settlement and differentiation. Biological distance was found to be strongly associated with spatial separation; the correlation between geography and nonmetric cranial distances was highly significant. When geographic distance is held constant, correlation between a model representing high levels of heterogeneity between the samples and morphological (nonmetric) variation becomes highly significant.     

Attenuation of water velocity and incident light as a function of shape parameters inGracilaria

Characteristic shape parameters, light intensities and relative water velocities were estimated in thalli of free-moving seaweeds, using threeGracilaria-like species:G. cornea, G. conferta andGracilariopsis lemaneiformis. Relative velocities over the branches were determined mostly by rotation of the algae in the water as opposed to linear translation. The tree major shape parameters of the thallus, weight, volumetric specific weight and areal specific weight, explain the differences in relative velocity. Relative velocities near the center of the thallus were about 50% to 80% of the external velocity. Light intensities at the vicinity of the center ofG. cornea ranged between 60% to 90% of the external light intensity. Light attenuation in the center was proportional to the weight of the thallus. The significance of light and velocity attenuation as a function of shape parameters is discussed.Author for correspondence     

Fragmentation and pre-existing species turnover determine land-snail assemblages of tropical rain forest

Aim The main aims of the study were: (1) to investigate the effect of fragment age in relation to other patch‐ and landscape‐scale measures of forest fragmentation, and (2) to assess the relative importance of fragmentation, habitat degradation (i.e. degradation caused by selective logging and past shifting cultivation) and putative pre‐existing species turnover in structuring current land‐snail assemblages. Location South‐western Sri Lanka. Methods The land‐snail fauna was sampled using standardized belt transects. Fifty‐seven transects were sampled in 21 lowland rain forest fragments (c. 1–33,000 ha). The spatial arrangement of fragments in the study area was explicitly considered in an effort to take into account the non‐random nature of fragmentation and degradation and the possibility that current species composition may reflect patterns of species turnover that existed prior to fragmentation. The data set of 57 land‐snail species and 28 environmental and spatial variables was analysed using canonical correspondence analysis and partial canonical correspondence analysis. Results Fragment age, mean shape complexity (i.e. a landscape‐scale measure of shape complexity), altitude, and the spatial variables x (longitude), y (latitude) and y² explained significant variation in land‐snail species composition. None of the three nominal variables quantifying habitat degradation was significantly correlated with variation in species composition. The independent effects of fragment age and mean shape complexity were similar. The combined effect of the spatial variables alone was larger than the independent effects of fragment age, mean shape complexity or altitude, but was of the same order of magnitude. The total variation explained by the spatial variables was comparable to the total non‐spatial variation accounted for by fragment age, mean shape complexity and altitude. Main conclusions Fragment age was found to be one of only two key determinants (the other was shape complexity at the landscape scale) driving fragmentation‐related changes in community composition. The influence of pre‐fragmentation patterns of species turnover on assemblage structure can be stronger than the effects of fragmentation measures, such as age, and may override the effects of forest degradation. Thus, strong patterns of pre‐existing turnover may potentially confound interpretation of the effects of forest fragmentation and degradation.     

Measurement of protein surface shape by solid angles

A method for measuring the gross shape of local regions of protein surface is presented and applied to an examination of three proteins. Any point on the protein surface can be assigned a number that measures the degree of convexity or concavity of the surface in the vicinity of the point. This number is computed by centring a sphere at that point and measuring how much of the sphere lies inside the protein. The sphere radius is a parameter chosen according to the scale of the features that are being analysed. The amount of sphere intersecting the protein is interpreted as a solid angle, denoted omega. Three proteins are analysed by this method: lysozyme, Superoxide dismutase and chymotrypsin. The resulting omega values are used to colour code the protein surfaces displayed on a colour raster graphics terminal. The method can be seen to reliably identify protrusions and depressions. The difficulty of developing a generally useful method for measuring protein surface shape is discussed. Possible applications of the solid-angle method include the analysis of shape complementarity at protein interfaces, the development of computer algorithms for predicting complexes between proteins, or between proteins and ligands, the identification of homologous epitopes on different proteins that might be immunologically crossreactive, and the determination of correlations between surface geometry and chemical properties.     

Plant lock and ant key: pairwise coevolution of an exclusion filter in an ant-plant mutualism

Although observations suggest pairwise coevolution in specific ant-plant symbioses, coevolutionary processes have rarely been demonstrated. We report on, what is to the authors' knowledge, the strongest evidence yet for reciprocal adaptation of morphological characters in a species-specific ant-plant mutualism. The plant character is the prostoma, which is a small unlignified organ at the apex of the domatia in which symbiotic ants excavate an entrance hole. Each myrmecophyte in the genus Leonardoxa has evolved a prostoma with a different shape. By performing precise measurements on the prostomata of three related myrmecophytes, on their specific associated ants and on the entrance holes excavated by symbiotic ants at the prostomata, we showed that correspondence of the plant and ant traits forms a morphological and behavioural filter. We have strong evidence for coevolution between the dimensions and shape of the symbiotic ants and the prostoma in one of the three ant-Leonardoxa associations.     

Computational studies of the extraction of visual spatial information from binocular and motion cues

This paper reviews some of the contributions that work in computational vision has made to the study of biological vision systems. We concentrate on two areas where there has been strong interaction between computational and experimental studies: the use of binocular stereo to recover the distances to surfaces in space, and the recovery of the three-dimensional shape of objects from relative motion in the image. With regard to stereo, we consider models proposed for solving the stereo correspondence problem, focussing on the way in which physical properties of the world constrain possible methods of solution. We also show how critical observations regarding human stereo vision have helped to shape these models. With regard to the recovery of structure from motion, we focus on how the constraint of object rigidity has been used in computational models of this process.