1,721,157 research outputs found
Cyathocephalus truncatus (Cestoda: Spathebothridea) in its intermediate host Echinogammarus stammeri (Amphipoda) from the River Brenta, northern Italy
No full textA study was carried out on the occurrence of the tapeworm Cyathocephalus truncatus (Pallas, 1781) (Cestoda: Spathebothridea) in its intermediate host, the amphipod Echinogammarus stammeri, in the River Brenta. A total of 18,860 E. stammeri was examined from July 1990 to June 1994; only 25 of them (prevalence 0.13%) were infected with tapeworm larvae (intensity of infection 1 larva/host). Co-occurrence of C. truncatus larvae with the larva of the acanthocephalan Pomphorhynchus laevis (Müller, 1776) was recorded in 15 amphipods. Tapeworms were localized in the anterior portion of each amphipod's hemocoel, in intimate contact with E. stammeri internal organs such as the alimentary canal, and frequently induced its displacement. No differences in integumental pigmentation were noticed between infected and non-infected amphipods, and some infected E. stammeri females were ovigerous
Khawia japonensis (Cestoda: Caryophyllidea): another invasive parasite of carp, Cyprinus carpio L., imported to Europe
No full textCarp, Cyprinus carpio L., is one of the most
important cultured fish, especially in Central
Europe and Asia. In
Europe, it is infected with a large number of
parasites, many of them introduced from Asia,
mainly from the Far East of Russia and China. Parasitic worms,
i.e. helminths, are represented, among others, by
tapeworms (Cestoda) including the most pathogenic
species, the Asian fish tapeworm Bothriocephalus
acheilognathi Yamaguti, 1934 (syn. B. gowkongensis
Yeh, 1955), recently placed in the order Bothriocephalidea.
Other potentially pathogenic cestodes of carp
belong to the order Caryophyllidea, the species of
which possess a monozoic (only one set of genital
organs) and unsegmented body and use tubificid
oligochaetes as intermediate hosts.
Khawia sinensis Hsu, 1935 (Caryophyllidea:
Lytocestidae), is native in East Asia and was
described from the vicinity of Beijing in China
(Hsu, 1935). It successfully colonized a major part
of Europe and was also imported to North America. However, the veterinary importance of K. sinensis has decreased considerably during the last few decades, possibly as a result of the more
recent introduction of Atractolytocestus huronensis Anthony, 1958 (Lytocestidae), to Europe. In this paper, another caryophyllidean cestode, Khawia japonensis (Yamaguti, 1934), which occurred
originally in East Asia, is reported from Europe for the first time
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
Spermiogenesis and sperm ultrastructure of Cyathocephalus truncatus (Pallas, 1781) Kessler, 1868 (Cestoda: Spathebothriidea)
No full textABSTRACT: Spermiogenesis and sperm ultrastructure of adult Cyathocephalus truncatus, a member of presumably basal group
of ‘‘true’’ cestodes (Eucestoda), have been examined for the first time by using transmission electron microscopy. The process
of sperm formation corresponds in basic pattern to that of the Pseudophyllidea. In addition, the 2 pairs of electron-dense attachment zones are present in median cytoplasmic process of C. truncatus. However, mature spermatozoa of C. truncatus differ
significantly from those of the pseudophyllideans, especially in the morphology of the proximal and distal spermatozoon extremities.
The proximal extremity of the mature spermatozoon lacks a crested body, which is present in more derived cestodes and
some pseudophyllideans. The distal end of the mature spermatozoa exhibits different morphology in the gametes from testes and those from receptaculum seminis. New for the Eucestoda is a finding that a lateral cytoplasmic extension creates the distal end of the spermatozoa from testes, resembling sperm of some Monogenea and Digenea. In contrast, the distal extremity of the spermatozoa from receptaculum seminis contains only a nucleus. Despite the above-mentioned peculiarities, the ultrastructural data on sperm/spermiogenesis suggest close relationships of the Spathebothriidea and Pseudophyllidea.
Tapeworms of the Spathebothriidea are characterized by a
complete absence of segmentation, with possession of a typically
linear series of internal proglottids (Gibson, 1994; Mackiewicz,
2003; Roberts and Janovy, 2005). Spathebothriideans
are considered to belong among the most primitive tapeworms
(Hoberg et al., 1997, 2001; Mariaux, 1998; Mariaux and Olson,
2001; Olson et al., 2001). Because the systematic position and
relationship of the Spathebothriidea to other cestodes remains
to be resolved, additional information is necessary to unravel
phylogenetic relationships of these enigmatic parasites.
Recently, the male and female reproductive ducts and vitellogenesis
Challenges and Solutions for the QB50 Telecommunication Network
Full text linkQB50 space mission will provide the biggest CubeSat network in orbit. A constellation of 50 CubeSats in
a ‘string-of-pearls’ configuration will be launched together in January 2016 by a single rocket, into a
circular orbit at 380 km altitude. Due to the atmospheric drag the orbit will decay and progressively
lower layers of the atmosphere will be explored. Main goals are exploration of the lower thermosphere
with multi-point measurements, re-entry research and in-orbit science and technology demonstration.
In this analysis of communication functions the ground segment is analyzed, with a global overview of
different architectures, the main elements of a ground station, mission and control centres, and the link
between them
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