1,720,962 research outputs found
An explicit construction of ruled surfaces
Get PDFAbstractThe main goal of this paper is to give a general algorithm to compute, via computer-algebra systems, an explicit set of generators of the ideals of the projective embeddings of ruled surfaces, i.e. projectivizations of rank two vector bundles over curves, such that the fibers are embedded as smooth rational curves.There are two different applications of our algorithm. Firstly, given a very ample linear system on an abstract ruled surface, our algorithm allows computing the ideal of the embedded surface, all the syzygies, and all the algebraic invariants which are computable from its ideal as, for instance, the k-regularity. Secondly, it is possible to prove the existence of new embeddings of ruled surfaces.The method can be implemented over any computer-algebra system able to deal with commutative algebra and Gröbner-basis computations. An implementation of our algorithms for the computer-algebra system Macaulay2 (cf. [Daniel R. Grayson, Michael E. Stillman, Macaulay 2, a software system for research in algebraic geometry, 1993. Available at http://www.math.uiuc.edu/Macaulay2/]) and explicit examples are enclosed
Stem cells derived from human exfoliated deciduous teeth: a narrative synthesis of literature.
No full textAbstract. – BACKGROUND: Stem Cells from Human Exfoliated Deciduous Teeth (SHEDs) rep- resent an immature stem cell population, easily accessible without ethical concerns, able to in- duce pluripotent stem cells and to differentiate in osteoblasts, hepatocytes, adipocytes, neural cells, chondrocytes, myocytes, skin cells and odontoblasts.
AIM: The purpose of this review is to present a comprehensive synthesis of current knowl- edge of SHEDs, through the description of their tissue sources, properties, differentiation poten- tial, and comparative assessment of their advan- tages for tissue engineering.
MATERIALS AND METHODS: Studies were identified by searching electronic databases (MED- LINE via PubMed, Medscape and Web of Science) from 2003 to 30 September 2013 and scanning ref- erences lists of the included publications and of the reviews. No publication date or publication sta- tus restrictions were imposed. Only evidence avail- able in English language was reviewed.
RESULTS: A total of 72 studies were identified for inclusion in the review. Clinical heterogeneity didn’t allow for meta-analysis but only for a nar- rative synthesis. The outcomes of the present narrative synthesis are presented separately for methods of isolation and culture, characteriza- tion of SHEDs, differentiation in vitro and in vivo, use in animal model, and stem cell banking.
CONCLUSIONS: SHEDs display multifactorial potential such as strong and high proliferative capacity, easy accessibility, high viability and multilineage differentiation capacity. Their re- trieval is relatively simple and non-invasive, no risks for developing immune reactions or rejec- tion following transplantation exist and no im- munosuppressive therapy is needed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Leiomyoma of oral cavity: case report and literature review
Get PDFLeiomyoma is a benign smooth muscle tumour, that occurs most frequently in the uterine myometrium, gastrointestinal tract, skin and lower extremities of middle-aged women. Leiomyomas are uncommon in the oral cavity, but in this location are usually localized on the tongue, lips and palate. Most lesions are asymptomatic, although occasional tumours can be painful. The diagnosis is mainly determined by histological studies due to its unspecific clinical appearance.
The purpose of this article is to present a case report of 49-year-old male patient with a lesion of the lower lip.
After surgical resection hematoxylin-eosin staining confirmed the diagnosis of leiomyoma
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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