1,721,121 research outputs found
Collagen orientation in compact bone: II. Distribution of lamellae in the whole of the human femoral shaft with reference to its mechanical properties
No full textStarting from a previous personal investigation (Portigliatti Barbos et al., 1983) indicating that the distribution of osteons and interstitial bone in the middle of the femoral shaft is related to their structure, a new procedure has been devised to allow information of the same kind to be gathered from the whole of the femoral diaphysis. Twenty-three exactly plane parallel corss-sections, 100 μm thick, each located 1 cm from the next, were prepared using an annular blade microtome. The distribution of longitudinal lamellae (whose fiber bundles and crystallites have longitudinal course and withstand loading by tension) and transverse lamellae (whose fiber bundles and crystallites have a transverse course and withstand loading by compression) was determined for both osteonic, and insterstitial bone, using circularly polarized light as the illuminating source and a Quantimet 720 image analyzing computer. The results show that along the femoral shaft the transverse and longitudinal lamellae from osteonic and interstitial bone have a characteristic rotational distribution consistent with the distribution of the bending forces normally operative in bone
Collagen orientation in compact bone: I. A new method for the determination of the proportion of collagen parallel to the plane of compact bone sections
No full text[No abstract available
A new method of image formation using cathodoluminescence in the SEM : CL absorption by superficial stains
No full textThe distribution of superficial histological stains on tooth samples can be demonstrated in the scanning electron microscope (SEM) due to the absorption by the stain of the auto-cathodoluminescence (light) arising from the underlying substrate. Practical procedures by which this has been achieved are described
Osteoconduction in large macroporous hydroxyapatite ceramic implants: Evidence for a complementary integration and disintegration mechanism
No full textLarge, cylindrical implants of a porous calcium phosphate ceramic ("hydroxyapatite" starting material, HAC) were used to replace far greater than critical-sized sections of the midshaft of sheep tibiae and retrieved at 2 and 9 months; external fixation was used in the first 5 months, Excellent clinical function of these implants was reported in a previous study. The material retrieved was embedded in PMMA, and blocks were sectioned and surfaces were polished and carbon coated prior to study using digital backscattered electron (BSE) imaging. Detailed scanning electron microscopy study of the pattern of osseointegration of the implanted material at early (2 months) and late (9 months) timepoints revealed a previously unrecognized pattern of integration/disintegration of this implant material in tandem with bone growth. We conclude that bone adaptation to the HAC leads to its fracture and that the newly generated surfaces are equally osteoconductive, This leads to a self-propagating, self-annealing system in which defects in the HAC are mended by intercalation of bone. (Bone 24:579-589; 1999) (C) 1999 by Elsevier Science Inc. All rights reserved
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
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
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