1,720,962 research outputs found
Trabecular Analysis of the Distal Radial Metaphysis during the Acquisition of Crawling and Bipedal Walking in Childhood: A Preliminary Study
No full textIn modern day populations, children following a normal pattern of development acquire independent bipedal locomotion between the ages of 9 and 18 months. Variability in the timing of this psychomotor developmental milestone depends on various factors, including cultural influences. It is well known that trabecular bone adapts to changes in biomechanical loading and that this can be influenced by alternative locomotor modes, such as crawling, which may be adopted before the acquisition of bipedal locomotion. With the onset of crawling, increased loading of the distal metaphysis of the radius, a component of the wrist, may lead to changes in trabecular bone architecture. To test this hypothesis, eight distal metaphyses of the radius of nonpathological children aged 0 to 3 years from the Bologna collection of identified skeletons were μCT-scanned at a resolution of 10.7 μm. The microarchitectural parameters of the trabecular bone (trabecular bone volume fraction, trabecular thickness, trabecular spacing, and trabecular ellipsoid factor) were quantified for the entire metaphysis and 3D morphometric maps of the distribution of the bone volume fraction were generated. Analysis of these microarchitectural parameters and the 3D morphometric maps show changes in the trabecular bone structure between 6 and 15 months, the period during which both crawling and bipedalism are acquired. This preliminary study analyzed the trabecular structure of the growing radius in three dimensions for the first time, and suggests that ontogenetic changes in the trabecular structure of the radial metaphysis may be related to changes in the biomechanical loading of the wrist during early locomotor transitions, i.e. the onset of crawling. Moreover, microarchitectural analysis could supply important information on the developmental timing of locomotor transitions, which would facilitate interpretations of locomotor development in past populations
Unravelling morphological changes of the human talus during growth
Full text linkThe human talus, being located between the lower limb and foot, plays an essential role in distributing the weight of the body during locomotion. One of its most important functions during this process is in allowing for foot movements while efficiently dividing weight between its anterior and posterior portions, where it articulates with the navicular and calcaneus, respectively [1]. As such, the talus plays a pivotal role in the different stages of human locomotion, from crawling, to initial bipedal acquisition, to full striding bipedalism at age 8 [1]. Unfortunately, little is known about the morphological changes of the talus during the first years of life, when infants acquire upright posture and gait maturation.
Using a (semi)landmark based approach we analyse an ontogenetic sample of modern human tali with the aim of exploring the morphological variation of the talus during growth. From this we assess if the variation may then be related to the acquisition and transition to full bipedal locomotion, which might ultimately provide insight into the evolution of hominin bipedalism.
The sample consists of 21 juvenile tali aged between 1.5 years and 11 years: 12 individuals from the Collection of Bologna, Italy (sex and age at death known) [2]; five from the archaeological sample of Roccapelago (Italy) [3]; four from the archaeological sample of Norris Farms #36 (Illinois, USA). All specimens were microCT scanned with a resolution of 20-40 μm. Avizo 9.3® (Visualization Sciences Group, SAS) was used to evaluate the quality of and pre-process the reconstructed scan data (e.g. crop or resample). Segmentation of the image data was performed using the MIA-clustering method [4] and then processed in Medtool 4.2 (Dr. Pahr Ingenieurs.e.U) to obtain 3D meshes of each talus. A template of 11 landmarks, 61 curve semilandmarks and 144 surface semilandmarks was created in Viewbox (dHAL Software) and applied to the 21 tali. The (semi)landmark configuration was superimposed by Generalized Procrustes Analysis, and semilandmarks were allowed to slide against recursive updates of the Procrustes consensus [5]. Finally, a form space Principal Component Analysis was carried out to explore talar shape variation during growth. Data were processed in R 3.4.3 (The R Foundation for Statistical Computing, 2017).
The first three PCs explain 92.9% of the total variation. Most of the morphometric variation is explained by PC1 (89.8%), i.e. ontogenetic allometry, where negative scores account for small, sub-parallelepiped talar morphology (the youngest individuals), while positive scores account for an elongation of the entire body of the talus, due to the development of the neck, and a clear growth of the lateral malleolar facet, while the posterior side of the trochlear facet is not well defined yet. The anterior calcaneal facet is well developed since the youngest phases (negative scores), while the posterior calcaneal facet becomes larger, less triangular, and more concave towards PC1 positive. PC2 (1.7%) and PC3 (1.4%) describe only subtle morphological differences. Negative values of PC2 account for a longer lateral ridge, that shortens along positive values, due to the growth of the talar head, development of the neck, trochlea, and lateral malleolar facet, with a more concave aspect of the lateral side. It is also possible to discern a narrowing of the sulcus tali and a clear medial rotation of the talar head. PC3 negative scores show a more compact shape, that becomes higher along positive values with the development of the posterior calcaneal facet and head.
This study is part of an ongoing project focusing on ontogenetic changes. Here we present preliminary results showing how external talar morphology varies during the early stages of human bipedalism. Future analyses will combine external morphological analyses with an assessment of trabecular bone architecture, thus providing a more holistic vision of these changes during development.
Acknowledgements
This project is funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 724046 - SUCCESS); website: http://www.erc-success.eu/. We are grateful to Dr Mirko Traversari for his willingness on the use of the Roccapelago sample.
References:
[1] Hellier, C.A., & Jeffery, N. 2006. Morphological plasticity in the juvenile talus. Foot and Ankle surgery, 12(3), 139-147.
[2] Belcastro, M.G., Bonfiglioli, B., Pedrosi, M.E., Zuppello, M., Tanganelli, V., & Mariotti, V. 2017. The history and composition of the identified human skeletal collection of the Certosa Cemetery (Bologna, Italy, 19th‐20th century). International Journal of Osteoarchaeology. DOI: 10.1002/oa.2605
[3] Figus, C., Traversari M., Scalise L. M., Oxilia G., Vazzana A., Buti L., Sorrentino R., Gruppioni G., Benazzi, S. 2017. The study of commingled non-adult human remains: Insights from the 16th-18th centuries community of Roccapelago (Italy). Journal of Archaeological Science: Reports, 14:382-391
[4] Dunmore C.J., Wollny G., Skinner M.M. (2018) MIA-Clustering: a novel method for segmentation of paleontological material. PeerJ 6:e4374
[5] Rohlf, F.J., Slice, D. 1990. Extensions of the Procrustes method for the optimal superimposition of landmarks. Syst. Biol. 39, 40-59
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Exploring age-related variations during calcaneal growth
Full text linkMethods for age estimation in juvenile osteological samples are highly accurate compared to those of adults, but little is known about the variation of the foot bones during growth. This study explores the age-related morphological changes
of the calcaneus, which is often well preserved even in the case of multiple or damaged burials, using Geometric Morphometric Methods. A sample of 33 modern human juvenile calcanei (known age/sex= 22; unknown sex/age= 11) was 3D scanned using an Artec3D Space Scanner. 5 age categories (0-15 years) were defined; unknown sex/age specimens were classified as ND. A template of 15 landmarks and 209 semi-landmarks was applied to the digital models. The (semi)landmark configurations were superimposed by Generalized Procrustes Analysis. A form space Principal Component Analysis (PCA) was computed using the known sample to explore variation during growth, while ND specimens were projected within it. The analysis shows that PC1 (ca. 93%) is highly correlated with size and accounts for ontogenetic allometry. Negative scores (youngest individuals) are characterized by a compact morphology
while positive scores (oldest individuals) show both a greater definition of the sustentaculum talii and sinus tarsii and more pronounced edges for the talar and cuboid articular facets. The projected sample follows the trajectory of the
known sample, which means that our ND specimens can be aged in the 5 categories after being projected. Our results suggest that age-related morphological changes of the calcaneus during growth may be used to estimate the general age of juvenile skeletal remains
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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