1,720,971 research outputs found
The application of visual census on Mediterranean rocky habitats
No full textIn this study we examined the effeect of: observer presence; observer speed; and the impact
that multiple surveys had on the number of counted fish in a visual census survey in a typical
Mediterranean rocky habitat. SCUBA observer presence had no infuence on the number of
fish per survey. An improvement in the methodology to estimate the number of fish was
demonstrated by using two different speeds: slow speed for benthic species and higher speed
for epibenthic ones. No differences in the number of fish per survey were found among suc-
cessive surveys along the same transects, even with the shortest time interval used: 5 min. We
also examined the ability of observers to estimate fish length during visual census by using
wooden fish models. Significant differences in size estimations were found using two different
estimation methods (i.e. size-classes estimates and continuous measures). Estimating fish
length to a size class was more accurate in estimating size, while transformed size to calculate
biomass from length estimates was more accurate using continuous measures
Littoral fish community in Lampedusa Island: a visual census approach.
No full textFish community structure of the Island Lampedusa, with a special focus on the fish assemblage inhabiting the infralittoral rocky substrate, was studied from July to October 1995. Visual census techniques (strip transects and random censuses) and the application of an anaesthetic (quinaldine), to sample cryptic and benthic species, were used. A total of 77 species and 29 fish families were censused. The most common families were Labridae and Spari-dae. Factor analysis applied to the 84 visual assessments, using the 9 most common species, divided the samples according to their position along the coast, depth, substrate, algae cover and presence of the vascular plant, Posidonia oceanica. In addition, discriminant analyses indicated the ecological preferences of some species. Size frequency distributions indicated the distribution of different life stages. Despite the shallow depths sampled, the present study shows how the fish community of this island has high species richness. © 1998 Tay..
Indagini geofisiche nell’area del Gravaglione (Canale di Pirro, Puglia)
No full textSi presentano i risultati di indagini geofisiche svolte nella zona del Canale di Pirro che si estende per 12 km nell’area carsica delle Basse Murge (Parise, 2006, 2011), e che ospita la grotta più profonda della regione (Parise & Benedetto, 2018). Nello specifico, sono state realizzate indagini geoelettriche in località “Gravaglione” (Lat. 40°49’25”, Long. 17°14’4”), dove, durante i temporali, vengono drenati grandi quantitativi di acqua, con tempi di assorbimento variabili
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
Geophysical researches to detect karst caves in the main polje of Apulia
No full textCanale di Pirro, the main polje in Apulia, extends for 12 km in the Low Murge karst area. It hosts the deepest cave in the region, reaching the depth of -324 m. Geophysical analyses have been performed in correspondence of two sites of interest. The first is located about 0,5km upstream of the cave, and is the main swal-low hole in the polje. During rainstorms, most of the water accumulated in this sec-tor is drained at this site, with time of absorption ranging from a few hours to some days, in function of the saturation condition of the sediments. The survey was ad-dressed to verify the existence of caves, and the possibility to open a passage in the cover deposits. By adopting a multi-array and multi-scale strategy, based on the acquisition and joint inversion of geoelectrical data collected by using different ar-rays and with electrode spacing ranging from 5m to 20m, a high-resolution model of the electrical subsurface structure was obtained. With an investigation depth up to ~150 m below the ground, and high surficial resolution, the model shows features compatible with the presence of large caves, providing useful information on their possible extension and the thickness of the cover deposits. The second site is a small sinkhole (3m depth, 7m diameter) within a vineyard in the eastern sector of the polje. The survey was addressed to detect likely ways of water infiltration at the site, and possible presence of underground voids
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
Social organization and sexual pattern in the mediterranean parrotfish Sparisoma cretense (Teleostei: Scaridae)
No full textWe examined the social organization and
reproductive pattern of a population of Sparisoma
cretense L. at Lampedusa Island (Italy). During the
breeding season (July to September) individuals occur
either in territorial or in non-territorial groups, which
quantitatively dier with respect to use of space, sex-
ratio and sexual activity. Territorial groups consist of
one male plus one to three females, whereas in non-
territorial groups as many as 54 ®sh share a common
area. Among non-territorial groups, variations, in both
sex-ratio and behavior, suggest they could represent
either feeding aggregations or reproductive aggrega-
tions. Spawning, always in pairs, occurs daily in a short
period of time before dusk and has been observed only
in territorial groups. Group spawning has never been
observed, but another alternative mating tactic,
streaking on pair spawning, was recorded. In the non-
breeding season ®sh do not aggregate in organized
social units. Histological examination of gonads
showed that adults are larger than 12 cm total length.
Females have an asynchronous ovary, typical of species
spawning several times during the breeding season.
Males show secondary testes, indicating that their go-
nads develop ovaries as juveniles, which are later re-
dierentiated into functional testes. Histological and
demographic data seem to indicate that, as in other
species of this genus, prematurational sex-change oc-
curs. The sexual pattern appears to be essentially go-
nochoristic, but the potential for sex-change is not
excluded
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
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