1,720,977 research outputs found
Non ionizing Electromagnetic Fields effects on fertility: a scientometrics study shows that a higher standardization is required
No full textNowadays living beings, especially human beings, are completely surrounded by magnetic (MF) and electromagnetic fields (EMF). In this scientometrics study, we found that, currently, a reliable and universally adopted exposure model doesn't exist, and that a stronger effort is required by the scientific community to share the knowledge and to act as a connected community
A scientometric analysis of reproductive medicine
No full textHere, we carried out a scientometric analysis of the scientific literature published in the field of reproductive medicine (RM), an important and rapidly evolving branch of Medicine. To this aim, we analysed the research papers published in the period 1996–2011 in RM and we assessed the bibliometric parameters (number of citable documents, cites per document and H-index) and the extent of international collaboration among different geographical Regions and Countries. Further, we studied the link of RM with other disciplines in a Journals co-citation study, then the keyword citation bursts were assessed. Ultimately, the social behaviour of Authors involved in RM was analysed in a social network study. As a result, we found that still it exists marked differences in term of quantity and quality of production in RM among the different Regions and Countries, likely due to the different economic effort to sustain research. The most productive ones, Western Europe and Northern America and USA and UK, respectively, display a slow decrease in production, while Asia (and China) are amazingly growing. Unfortunately, Eastern Europe, Latin America and Africa are still very backward. In addition, RM is directly connected with basics disciplines but not with other medical specialities and the most cited keywords suggest the shift from basic to more applied research. Finally, the Authors involved in RM originate a small world community, in which it is possible to identify the brokers of information flow. In conclusion, this analysis could contribute to the knowledge of scientific production related to RM field
Capacitation-Related Lipid Remodeling of Mammalian Spermatozoa Membrane Determines the Final Fate of Male Gametes: A Computational Biology Study
No full textTo become fully fertile, mammalian spermatozoa must undergo a complex process of biochemical maturation within the female genital tract, which determines a marked lipid remodeling (LR) of membranes. Here, we represent this process as a biological network, which is a graph constituted by nodes (the molecules involved in LR) and by edges (their interactions). As a result, we found that LR network has a scale-free and small world topology. This implies that it is robust against random damage and that it allows a fast and specific transmission of information. In addition, the hubs in the network allow identification of the control mechanisms involved in membrane-related signaling, which could concur in determining the fate of ejaculated spermatozoa. Interestingly, different pathways involved in LR (maintenance of functional incompetence, reaching of fertilizing ability, apoptosis) are overlapped and some molecules take part in different signalling cascades; thus their role in sperm biology needs to be interpreted in a more large context. In addition, it was possible to differentiate, either based on their topological and biological characteristics, the molecules acting as global or local controller in LR. These findings may contribute to the understanding of capacitation-related signaling and of sperm physiopathology
Membrane remodelling events occurring during mammalian spermatozoa capacitation: A systems biology study
No full textImmediately after ejaculation, mammalian spermatozoa are unable to fertilize the homologous oocyte. They reach their fertilizing ability only after they reside for hours to days, depending on the species, within the female genital tract. Here a complex process, the capacitation, takes place as a consequence of the functional dialogue of activating (hormones, bicarbonate, calcium ions, etc...) and inhibiting (seminal plasma, endocannabinoids) factors present in female genital tract fluids. This process involves virtually all the component of male gametes: the intracellular pH rises, the ionic composition of cytosol changes, the proteins tyrosine phosphorylation pattern modifies, the actin cytoskeleton reorganizes, and the sperm membranes change their physical/chemical proprieties1. In particular, the cholesterol/phospholipids ratio decreases, the microdomains architecture reorganizes, and the plasma membrane (PM) anisotropy decreases, then PM becomes more instable and fluid2. These lasts events attracted the attention of researchers because of their possible implication in the determinism of “idiopathic infertility” of male origin, which is at the present one of the most important causes of fertilization failure. In addition, recently, has emerged the intriguing question of interconnection of signaling systems involved in capacitation and those expressed in apoptosis3.
To study the structure of signaling systems involved in the lipid remodeling process that occurs during capacitation, we applied a systems biology approach. In particular, we realized a computational model of lipid remodeling, by using a biological networks-based modeling strategy: each molecule involved in that process was represented as a node, each interaction between molecules was represented as a link4.
The database representing the lipid remodeling of spermatozoa and endocannabionid system have been de novo manually compiled. The one concerning apoptosis has been downloaded from Reactome, version v51 (http://www.reactome.org/), a free, open-source, curated and peer reviewed pathways database. All the networks have been realized with Cytoscape 3.1.1 (http://www.cytoscape.org/), an open source software for visualizing and integrating complex networks. All the analysis have been carried out with the plug-in Network Analyzer (http://apps.cytoscape.org/apps/networkanalyzer).
As a result, we obtained a network that contains a single connected component composed by 244 nodes and 418 links. The in- and out-node degree, i.e. the probability distribution of the number of connection per node, followed the exponential law (exponent = -1.522 and -1.792 respectively), while the clustering coefficient, i.e. the measure the network tendency to form clusters, was near 0 (0.061). The node degree was correlated with the centrality of nodes within the network (r=0.802), expressed as beetweenness centrality. i.e. as the number of shortest paths from all vertices to all others that pass through a node. The values of characteristic path length was 6.373, while that of the average number of neighbors was 3.287.
The statistical analysis of the obtained network clearly showed that it has a scale free topology and a small word structure. This specific feature could lead to take some important biological inferences. Firstly, it implies that the most of nodes is scarcely linked, while only a few nodes, the hubs, are highly connected. In other words the network is robust against random failure4. The low value of clustering coefficient, together with the values of averaged number of neighbors and of characteristic path length suggest that the messages will spread within the networks quickly and efficiently. Finally, it is possible to identify the nodes that show a higher level of control within the networks, i.e. the most connected ad central ones, listed in decreasing order: [Ca2+]I, ATP, Protein tyrosine Phosphorilation, PKA, cholesterol efflux, apoptosis, scramblase, acquisition of fertilizing ability, PKC, cAMP, AEA, membrane symmetry, oxysterols, sAC, cholesterol, pHi rise, PLD1, CaV, acrosome reaction, CB1, NADH. In our opinion, these findings could contribute to the knowledge of such an important event, which leads the spermatozoa to gain their fertilizing ability, and allows identifying the molecular mechanisms involved in the final fate of spermatozoa and in the check points involved
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
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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