1,721,133 research outputs found
Improved development to blastocyst of ovine nuclear transfer embryos reconstructed during the presumptive S-Phase of enucleated-activated oocytes
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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
Embryo Cloning in Sheep: work in progress
No full textWe summarize here the procedures for nuclear transfer using S-phase cytoplasts and describe a new method for avoiding loss of reconstructed embryos from the oviducts during in vivo culture. We obtained 2 clones of 5 genetically identical animals following the transfer of blastomeres from 16-cell embryos into enucleated preactivated cytoplasts. Metaphase II oocytes and embryos were surgically collected from superovulated Sarda breed ewes 54 and 120 h after sponge removal, respectively. Oocytes were exposed for 15 min to 5 mu g/ml of Hoechst 33342 and were micromanipulated at room temperature. Efficiency in embryo reconstruction was 100% for enucleation and 98% for fusion. Embryos were embedded in agar as separate clones and transferred into the oviducts of temporary recipients. The fimbriae were closed with glass-nylon made filters. Embryo recovery from the temporary recipients was 97.3%, with a cleavage rate of 81.4%; development to morula-blastocyst stage was 70.6%. A total of 29 Grade 1 blastocysts corresponding to 5 clones were transferred into 13 naturally synchronous ewes, and scanning was performed at 30 and 90 d. Ten ewes were pregnant at the first scanning and nine at the second for a final pregnancy rate of 71.4%; the survival rate at term was 48%. Overall, we obtained 4 clones of identical lambs: two sets of 5 (one male set and one female set) and two sets of twins (both sets male). Pregnancy length in recipients carrying clones was longer than the standard period in Sarda breed (153 vs 150 d, respectively). Weight at birth was higher for male lambs obtained from nuclear transfer than for normal males (4.1 vs 3.6 kg), while the weight for females was normal. (C) 1997 by Elsevier Science Inc
Cloning of Equines
No full textThe cloning of equines by somatic cell nuclear trans- fer (SCNT) was first reported in 2003 (Galli et al., 2003; Woods et al., 2003), 6 years after the birth of Dolly the sheep (Wilmut et al., 1997). Amongst the mammalian spe- cies that have been cloned (Campbell et al., 2007), equines are among the last. In general, the application of assisted reproduction technologies in equines has lagged behind that of other livestock species (Galli et al., 2007) in the poor interest expressed by the industry (still today, for example, the thoroughbred does not allow artificial insemi- nation) and also the limited resources devoted to this kind of research and the few laboratories working in this area. In fact the first equine clone, a mule (Woods et al., 2003), was obtained from in vivo matured oocytes that were transferred back to the oviduct of a synchronized recipi- ent mare immediately after nuclear transfer and activation. This approach was successful because it limited to a mini- mum the time exposure to the in vitro environment. This approach of using in vivo matured oocytes was, however, not sustainable from a practical point of view. In contrast, the first cloned horses (Galli et al., 2003; Lagutina et al., 2005) and those that followed later (Hinrichs et al., 2006, 2007) were all derived from abattoir-recovered and in vitro matured oocytes that, following enucleation and embryo reconstruction, were cultured in vitro to the blastocyst stage prior to non-surgical embryo transfer to a recipient mare. This method could be applied only after the develop- ment of the procedures for in vitro maturation of oocytes, fertilization by ICSI, and in vitro culture of embryos capable of establishing normal pregnancies and generat- ing offspring (Galli et al., 2007; Hinrichs, 2010). In addi- tion to the refinement of the in vitro protocols for oocyte maturation and embryo culture, SCNT protocols had to be adapted and optimized for the equine, which, because of its anatomical and physiological features, provides a lim- ited number of oocytes per ovary when compared to cat- tle or pigs. The protocols currently applied for nuclear transfer are based on a zona-free system (Lagutina et al., 2007) to enhance cell fusion or a piezo-electric device (Westhusin et al., 2003) for enucleation and microinjec- tion of the nucleus directly into the oocyte. Reconstructed embryos also require a specific activation protocol (Hinrichs et al., 2006; Lazzari et al., 2002)
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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