1,720,963 research outputs found
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
Investigating alternative sperm preservation methods for assisted reproductive technologies
Get PDFDissertation (MSc)--University of Pretoria, 2013.Introduction: Cryopreservation of human sperm is considered a routine practice in assisted reproduction laboratories. Semen samples are mainly cryopreserved as a back-up for procedures, donor sperm, and validation of samples from human immunodeficiency virus-positive patients. Human immunodeficiency virus semen samples generally result in a low yield of purified spermatozoa after decontamination. These samples need to be cryopreserved for later use. Unlike conventional cryopreservation, vitrification does not use harmful cryoprotectants, thereby potentially reducing sperm damage. Vitrification is not yet common practice for sperm cryopreservation in assisted reproduction. The aim of this study was to establish the feasibility of utilising vitrification as an alternative to current conventional cryopreservation of spermatozoa.
Methods: Semen samples were collected from human immunodeficiency virus-negative patients seeking diagnostic assistance from the unit. All samples were processed according to the unit’s standard protocol. For Study 1A (n=10) washed samples were divided and cryopreserved using three different cryopreservation media, and two different freezing protocols. In Study 1B (n=15), washed samples were divided and preserved using cryoprotectant-free vitrification in 100 μl, 300 μl and 500 μl volumes. For Study 2 (n=35) washed samples were split and cryopreserved using cryoprotectant-free vitrification (utilizing the volume that resulted in the highest quality spermatozoa in Study 1B) and conventional slow freezing (using the medium and protocol that resulted in superior quality spermatozoa in Study 1A). Post thawing, motility and kinetic parameters (Studies 1 and 2), viability (Study 1), mitochondrial membrane potential (Study 2), and DNA fragmentation (Study 2) of the two groups were compared.
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Results: Study 1A indicated that cryopreserving spermatozoa using Freezing Medium resulted in the highest quality spermatozoa with regards to motility and viability (p0.05). The RBL freezing method is shorter, simpler and requires less equipment, and was therefore deemed the preferred method. Study 1B showed that the larger vitrification volumes (300 μl and 500 μl) yielded better spermatozoa in terms of motility and viability (p<0.05). No significant difference was observed with respect to the 300 μl and 500 μl vitrification volume groups. For practical reasons, 300 μl volumes will provide sufficient sperm for any procedure and, the intermediate volume ensures that more than one straw can be preserved. Study 2 found that cryoprotectant-free vitrification resulted in spermatozoa with significantly higher mitochondrial membrane potential and significantly lower apoptosis post thawing (p<0.05).
Discussion: Conventional cryopreservation methods may compromise various sperm parameters and final yield. In this study, cryopreservation and cryoprotectant-free vitrification had equivalent outcomes with respect to sperm motility. However, the latter method yielded superior results in terms of ΔΨ and DNA sperm fragmentation. In conclusion, vitrification is an easy, rapid and more affordable technique that requires no special equipment. Using vitrification for purified sperm samples of patients could potentially result in a better post thaw quality for ART procedures.gm2014Obstetrics and Gynaecologyunrestricte
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Are HAARTs beneficial for spermatozoa of HIV patients?
Get PDFIntroduction: Globally, HIV/AIDS has been ranked as the 5th largest cause of death in Southern Sub-Saharan Africa and the major cause of death in the world. The review aims to focus on the effects of highly active antiretroviral therapy (HAART) on the male gametes of HIV positive persons in order to give an insight into the fate of men infected with HIV with respect to their chances of having offsprings following the commencement of HAART.Methods: This review considered all original and review articles published on Pubmed from year 2000 to 2015. A few selected, exceptionally relevant publications outside this period were also reviewed.Results: HAART has been shown to improve the health, quality of life and reduction in the morbidity and mortality attributable to HIV-induced immune deficiency. It is anticipated that the survival of patients influence their fertility parameters while on treatment, with focus on young males, within the reproductive age.Conclusion: A better understanding of the influence of HAART on spermatozoa in patients with HIV/AIDS undergoing therapeutic management is therefore vital for knowledge and a proactive measure in order not to add to their burden if there is expression of the desire to conceive a child.Keywords: HIV/AIDS, HAART, sperm, Assisted reproductive technology, Afric
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