1,720,971 research outputs found
In vivo recruitment of two {"}waves{"} of host{'}s stem/progenitor cells by exogenous mesenchymal stem cells seeded onto porous ceramic scaffolds and role of endothelial progenitors in the new bone formation
No full textX-ray synchrotron radiation pseudo-holotomography as a new imaging technique to investigate angio-and microvasculogenesis with no usage of contrast agents
No full textStandard X-ray micro-computed tomography is a technique that allows a good visualization of the structure of mineralized tissues and biomaterials, but it fails to finely discern soft tissues. Here, we used X-ray synchrotron radiation pseudo-holotomography to visualize, at three-dimensional (3D) level, microvascular networks for the first time with no need for contrast agents, and to extract quantitative structural data in a bone-engineered construct implanted for 24 weeks in a mouse. When compared to standard histology, pseudo-holotomography allowed a previously unavailable 3D resolution of the vessels, which in turn appeared more clearly visible. Thus, pseudo- holotomography is an innovative technique that offers a promising powerful tool to investigate angio-and microvasculogenesis in advanced biomedical research areas such as regenerative medicine and antiangiogenic cancer therapies. © 2009 Mary Ann Liebert, Inc
Ag-, Zn-doped calcium phosphate bone cements for tissue engineering
No full textCalcium phosphate cements (CPC) are biocompatible materials, nowadays widely used for non-load bearing small bone fractures, maxillo- and craniofacial defects. Being compositionally affinitive to the mineral part of the bone tissue, these biomaterials are non-cytotoxic and able to promote a suitable host bone/material interface. When proposing a new synthetic calcium phosphate material, it should be considered that natural bone tissue is composed of the substituted hydroxyapatite, containing a number of cations and anions, each one of them playing a particular role in the new tissue formation and growth chemistry. Therefore, trying to improve the properties of CPC, one might introduce into their composition ionic additives naturally occurring in the human body with the scope to improve or to induce a certain property. Ag+ and Zn2+ are known to possess antibacterial properties, moreover, the latter has also osteogenetic and angiogenetic ones, enhancing the proliferation of osteoblastic cells and activating the large group of enzymes, such as MatrixMetalloProteinases, involved in the process of construction of new blood vessels.
The aim of this work was to perform an X-Ray diffraction insight into the hardening process of three cement compositions: TCP (tricalcium phosphate), Ag- and Zn-containing TCP (both in 0.6 wt% and 1 wt%). The Energy Dispersive X-Ray Diffraction (EDXRD) technique was proved to be a suitable tool for in situ real-time monitoring of the hardening process of CP bone cements. By means of this technique it is possible to obtain information about phase transformations (new phases and intermediate products) and amorphous-into-crystalline conversion (primary and secondary crystallization processes). Moreover, characteristic setting and hardening times and grain size evolution can be followed. Different reagents-to-products rate of conversion, hardening times and crystallinity were registered for doped and non-doped cement samples, and a number of intermediate phases, evidencing the complex hardening mechanism were observed for the Zn-TCP cement. The role of doping elements is discussed
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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