1,721,142 research outputs found
Vitellogenin gene family in vertebrates: evolution and functions
No full textAbstract
The vitellogenin gene family is constituted of variable gene numbers encoding for polypeptides that are precursors of yolk
proteins and derivatives in oviparous and ovoviviparous vertebrates. The comprehension of which mechanisms have shaped
the evolution of vtg gene family represents an attractive field of research. The primary intent of this review is to summarize the
evolutionary hypotheses that have been proposed over recent decades, highlighting the differences between the proposed
models. Overall in vertebrates the evolutionary history of this gene family is the result of complex modifications deeply
influenced by events such as Whole Genome Duplications (WGDs), lineage-specific gene losses and duplications. Interestingly
the last hypothesis allowed to date the vitellogenin gene cluster origin in the common ancestor of gnathostomes. In addition, in
the last decades, several works evidenced non-nutritional functions such as antibacterial, immunological and antioxidant
activities overcoming its classical view as a simple source of nourishment for the developing embryos
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
Source estimation of surface Laplacian transformed EEG potentials on a Talairach-based source space.
No full textAppropriate 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
Energy storage and multi energy systems in local energy communities with high renewable energy penetration
No full textThis study investigates how a district with a high capacity of non-controllable renewable electricity generation can entirely self-consume its production at a community level either directly or for heating and cooling, thus potentially fulfilling the concept of "Renewable Energy Community". It investigates the potential role of storage systems and polygeneration in renewables self-consumption, by also exploiting the synergies among different energy networks in a real residential district with high PV penetration. Two scenarios were modeled other than the "baseline": the first one evaluating the optimal portfolio of energy conversion and storage technologies, and a second one achieving the same goal only using batteries. Both scenarios proved to be a viable solution to exploit the excess of electricity production from the PV plants in the district only through local self-consumption. The results show that a multi-energy system is the most cost-effective solution in doing so, exploiting polygeneration technologies (CHP) and the storage of energy as thermal, electrical, and chemical through power-to-gas. In particular, the least cost solution entails a 42 kWe CHP micro gas engine fueled by a natural gas-hydrogen blend, a 135 kWh battery system, and a 2830 kWh hydrogen storage
Achieving low carbon local energy communities in hot climates by exploiting networks synergies in multi energy systems
No full textDesign and planning of low carbon cities and districts must consider the synergies between all the energy networks available. Energy systems optimal design thus assumes a critical importance in determining both costs and environmental impact of operating such districts. This is particularly true following the concept of Local Energy Community, with a single entity representing both the demand and the manager of the energy generation assets. This paper proposes an innovative model for the optimal design of an energy community aiming at lowering its carbon footprint. The community is modeled as a network of spatially dislocated energy hubs, each with its own demand of electricity, heating and cooling energy. The model aims at defining the optimal mix of energy systems, thermal and electric energy storages and energy network infrastructures needed to satisfy the district's users energy demands. The model is validated using energy demand data from the Nanyang Technological University campus in Singapore by analyzing three scenarios. In the first one, the optimization goal is purely economic and it aims at minimizing the overall cost of operating the district. The second and third scenarios focus on reducing the carbon footprint of the district by imposing an additional constraint, which limits the overall primary energy consumption. In all the scenarios the algorithm chooses to partially or totally connect the five sites with a district cooling network and take advantage of cold thermal storage, proving their potential in hot climates. In the first scenario, the advantages of the district cooling solution are mainly related to the savings in the capital cost of electric chillers that partially offset the cost of the district cooling network; indeed, district cooling network allows the sites to share cooling power thus achieving a reduction in chillers total installed size of 33%. In the second scenario, in order to meet the target of 10% reduction of the overall primary energy, the optimal solution also requires the installation of a photovoltaic system. In the third scenario, imposing a 20% reduction of the overall primary energy, also a natural gas fed trigeneration plant comes into play
The vitellogenin genes in Cynops orientalis: New insights on the evolution of the vtg gene family in amphibians
Full text linkThe vitellogenins (Vtgs) are glycolipophosphoproteins that play a key role in constituting nutritional reserves for embryo development in nonmammalian vertebrates. However, additional functional roles have been evidenced. These vtg genes are present in multiple copies, different in number and sequences in various vertebrate lineages. The comprehension of the vtg gene family evolutionary history remains a matter of intense interrogation for this field of research. In tetrapods, information about vtg genes are limited to few taxa. Up to date concerning amphibians, detailed studies have been conducted only in Anura. Therefore, in this study, to further increase knowledge about vtg genes in Amphibia class, the urodele Cynops orientalis (Amphibia: Caudata) was analyzed and four complete vtg sequences were obtained. Moreover, genomic data available for the caecilians Microcaecilia unicolor and Rhinatrema bivittatum (Amphibia: Gymnophiona) were also included. In these amphibians, our findings evidenced the presence of a vtgI sequence ortholog to that of tetrapods, absent in Anura. Moreover, microsyntenic, phylogenetic, and gene conversion analyses allowed postulating two hypotheses to explain the complex evolutionary history of this gene family
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
- …
