1,721,027 research outputs found
Giovanni Battista Aleotti da Argenta (1546-1636) : scienza ed architettura delle acque nel Ducato di Ferrara fra 16. e 17. sec.
No full textIdentification and evolution of molecular domains involved in differentiating the cement gland-promoting activity of Otx proteins in Xenopus laevis.
Full text linkOtx genes are a class of vertebrate homeobox genes, homologous to the orthodenticle gene of Drosophila melanogaster, that play a crucial role in anterior embryo patterning and sensory organ formation. In the frog, Xenopus laevis, at least three members of this class have been isolated: otx1, otx2 and otx5 (crx); they are involved in regulating both shared and differential processes during frog development. In particular, while otx2 and otx5 are both capable to promote cement gland (CG) formation, otx1 is not. We performed a molecular dissection of Otx5 and Otx1 proteins to characterize the functional parts of the proteins that make them differently able to promote CG formation. We show that a CG promoting domain (CGPD) is localized at the Otx5 C-terminus, and is bipartite: CGPD1 (aa210-255) is the most effective domain, while CGPD2 (aa177-209) has a lower activity. A histidine stretch disrupts CGPD1 continuity in Otx1 determining its loss of CG promoting activity; this histidine-rich region acts as an actively CG repressing domain. Another Otx1 specific domain, a serine-rich stretch, may also be involved in repressing Otx1 potential to trigger CG formation, though at a much lower level. This is the first evidence that these domains, specific of the Otx1 orthology group, play a role during development in differentiating Otx1 action compared to other Otx family members. We discuss the potential implications of their appearance in light of the evolution of Otx functional activities
Novel evolutionary insights on the interactions of the Holosporales (Alphaproteobacteria) with eukaryotic hosts from comparative genomics
No full textHolosporales are an alphaproteobacterial order engaging in obligate and complex associations with eukaryotes, in particular protists. The functional and evolutionary features of those interactions are still largely undisclosed. Here, we sequenced the genomes of two members of the species Bealeia paramacronuclearis (Holosporales, Holosporaceae) intracellularly associated with the ciliate protist Paramecium, which resulted in high correspondence. Consistent with the short-branched early-divergent phylogenetic position, Bealeia presents a larger functional repertoire than other Holosporaceae, comparable to those of other Holosporales families, particularly for energy metabolism and motility. Our analyses indicate that different Holosporales likely experienced at least partly autonomous genome reduction and adaptation to host interactions, for example regarding dependence on host biotin driven by multiple independent horizontal acquisitions of transporters. Among Alphaproteobacteria, this is reminiscent of the convergently evolved Rickettsiales, which however appear more diverse, possibly due to a probably more ancient origin. We identified in Bealeia and other Holosporales the plasmid-encoded putative genetic determinants of R-bodies, which may be involved in a killer trait towards symbiont-free hosts. While it is not clear whether these genes are ancestral or recently horizontally acquired, an intriguing and peculiar role of R-bodies is suggested in the evolution of the interactions of multiple Holosporales with their hosts
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
Transmission of Members of the “Candidatus Midichloriaceae” Family to Vertebrates and Possible Involvement in Disease Pathogenesis
No full text“Candidatus Midichloriaceae” (order Rickettsiales) is a family that encompasses obligate intracellular bacteria present in a wide range of hosts, from parasitic arthropods (ticks, fleas, bedbugs) to aquatic animals (e.g. sponges and corals) and protists, including pathogenic amoebae (genus Acanthamoeba). In addition, multiple studies have detected evidence of the presence of “Candidatus Midichloriaceae” in vertebrates, suggesting a capacity to cause infections, with possible pathogenic effects. Two members of the family that are described as symbionts of ticks, i.e. “Candidatus Midichloria mitochondrii” and “Candidatus Lariskella arthropodarum” have also been found in the blood of humans and other mammals, using molecular and serological methods. Consequently, it has been hypothesized that these arthropods could transmit the microorganisms during the blood meal, as is known to happen with pathogenic members of the order Rickettsiales; for example, ticks can be vectors of rickettsiosis or ehrlichiosis. Indeed, clinical cases compatible with these pathologies in humans or animals parasitized by ticks, but characterized by the absence of antibody titers for known pathogenic rickettsiae, could be reinvestigated for the presence of “Candidatus Midichloriaceae”. A third member of the family, a “Candidatus Midichloria”-related organism, has repeatedly been found in association with red mark syndrome in the rainbow trout Oncorhynchus mykiss. Although the etiology of this economically relevant disease is currently unknown, multiple independent studies suggest that this member of “Candidatus Midichloriaceae” is the most probable causative agent
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
- …
