1,720,967 research outputs found
Characterization of different subsets of spermatogonial stem cells: influence of niche derived factors
Full text linkThe effect of ICSI-related procedural timings and operators on the outcome
No full textStudy question: Do the ICSI-related procedural timings and operators affect the outcomes of an ART cycle? Summary answer: The ICSI-related timings and operators do not associate with the mean blastulation rate per cohort of inseminated oocytes and the cumulative delivery rate per concluded cycle, except for a mild association between the times from induction of ovulation to oocyte denudation and the former outcome. What is known already: In ART, specific timings, protocols and conditions must be complied with to preserve gamete developmental and reproductive competence during the required manipulations. ICSI represents a groundbreaking advancement that has been widely implemented. Nevertheless, the studies that examined the putative impact of ICSI-related procedural timings were mainly conducted in old-fashioned settings or in good prognosis patients. No report addressed issues like operators' skills and experience and uncertainties exist dealing with the effect of cumulus cells in the pre-incubation period in vitro before ICSI. However, all this information is crucial to efficiently plan the daily routine of an IVF lab, fill the existing gaps of knowledge and define proper key performance indicators. Study design, size, duration: Observational study conducted at a private IVF clinic (January 2016 to January 2018). We included all consecutive ICSI procedures (n = 1084 infertile couples undergoing 1444 cycles with or without preimplantation genetic testing (PGT); mean ± SD maternal age: 38.1 ± 4.0 years) with fresh autologous oocytes (n = 7999 oocytes, 5.5 ± 3.2 per treatment) inseminated with fresh non-donor ejaculated sperm. All operators and critical procedural timings (induction of ovulation to oocyte denudation, denudation and ICSI) were automatically recorded through an electronic witnessing system. The primary outcome measure was the cumulative delivery rate among both non-PGT and PGT-concluded cycles (i.e. delivery achieved or no supernumerary cryopreserved blastocyst available). The secondary outcome measure was the mean blastulation rate per cohort of inseminated oocytes. All confounders were registered and included in generalized linear models and multivariate logistic regression analyses. Participants/materials, setting, methods: Fourteen and 12 operators were involved in denudation and ICSI procedures, respectively. Denudation was performed after 4.1 ± 1.2 h (2-7) of pre-incubation in vitro after oocyte retrieval, and ICSI was started immediately after. Beyond procedural timings and operators, all the putative confounders (patients' and cycles' characteristics) on the primary and/or secondary outcomes were systematically registered and included in the statistical analyses. Main results and the role of chance: The mean time from induction of ovulation to oocyte denudation was 39.3 ± 1.3 h. The mean procedural timings for denudation and ICSI were 8.1 ± 3.8 and 12.6 ± 6.4 min; both these variables were significantly dependent on the number of inseminated oocytes and the operators' skills and experience. The overall mean blastulation rate per cohort of inseminated oocytes was 34.0 ± 27.9%. This outcome was significantly associated with the time from induction of ovulation to oocyte denudation (mean blastulation rate stable in the time interval 38-42 h, but significantly higher for timings <38 h), maternal age (the mean blastulation rate drops especially beyond the age of 40 years) and categorized sperm concentration (highest mean blastulation rate for sperm concentrations ≥15 mil/ml and lowest for cryptozoospermic patients) through a generalized linear model that showed an adjusted r2 = 0.053 (P < 0.01). No association was found for denudation and ICSI timings and operators. Lastly, when adjusted for maternal age and number of inseminated oocytes, both ICSI-related procedural timings and operators did not associate with the cumulative delivery rate among both non-PGT- or PGT-concluded cycles. Limitations, reasons for caution: This is a single private IVF center study. Its reproducibility should be assessed in different laboratory conditions, with different protocols and in the hands of different operators. Moreover, specific studies are warranted to address the beneficial/detrimental effect of the other putative confounders under investigation (e.g. kind of ovulation trigger, culture media, incubator, etc.). Wider implications of the findings: Proactive communication between the embryologists and the clinicians might contribute to a reasoned and more efficient organization of the daily workload and increase the mean blastulation rate, especially when poor prognosis couples (advanced maternal age, reduced sperm count and/or ovarian reserve) are treated. Study funding/competing interest(s): No funding. The authors declare no conflict of interest related to the present study
Perspectives in Gamete and Embryo Cryopreservation
No full text: Cryopreserved gametes and embryos are a major feature of human-assisted reproduction and patient care services, accounting for an increasing number of births worldwide. Since the first success obtained using frozen human spermatozoa, cryopreservation technology has been successfully extended to include oocytes and embryos, in a variety of both medical and nonmedical indications. Over the years, the available procedures have become widely implemented and the increasing evidence of its efficacy has contributed to acceptance of the technology. Nevertheless, a gold standard protocol that would be universally shared by clinics has yet to be definitively established and, therefore, research into cryopreservation of gametes and embryos cannot be considered concluded. Moreover, much effort should be committed to the definition and resolution of safety issues, the establishment of automation, and investigations about the potentiality of immature germ cells or stem cells
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
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
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