1,720,969 research outputs found
La modellazione a meso-scala per la valutazione e quantificazione dell'habitat in torrenti e fiumi alpini
No full textHabitat modeling in high gradient streams: the meso-scale approach and application
No full textThe study aims to set out a new methodology for habitat modeling in high gradient streams. The methodology is based on the meso-scale approach of the MesoHABSIM simulation system and can support the definition and assessment of environmental flow and habitat restoration measures. Data coming from 40 study sites located within the mountainous areas of the Valle d'Aosta, Piemonte and Liguria regions (NW Italy) are used in the analysis. To adapt MesoHABSIM to high gradient streams, we first modified the data collection strategy to address the challenging conditions of surveys by using GIS and mobile mapping techniques. Secondly, we built the habitat suitability models at a regional scale to enable their transferability among different streams with different morphologies. Thirdly, due to the absence of stream gauges in headwaters, we proposed a possible way to simulate flow time series and, therefore, generate habitat time series. The resulting method is evaluated in terms of time expenditure for field data collection and habitat modeling potentials, and it represents a specific improvement of the MesoHABSIM system for habitat modelling in high gradient streams, where other commonly used methodologies can be unsuitable. Through its application in several study sites, the proposed methodology adapts well to high gradient streams and allows: (1) definition of fish habitat requirements for many streams simultaneously, (2) modeling of habitat variation over a range of discharges, and (3) determination of environmental standards for mountainous watercourses
Meso-scale habitat models for the mitigation of hydro-power impacts in high gradient streams
No full text
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
Modelling habitat requirements of bullhead (Cottus gobio) in Alpine streams
No full textIn the context of water resources planning and management, the prediction of fish distribution related to habitat characteristics is fundamental for the definition of environmental flows and habitat restoration measures. In particular, threatened and endemic fish species should be the targets of biodiversity safeguard and wildlife conservation actions. The recently developed meso-scale habitat model (MesoHABSIM) can provide solutions in this sense by using multivariate statistical techniques to predict fish species distribution and to define habitat suitability criteria. In this research, Random Forests (RF) and Logistic Regressions (LR) models were used to predict the distribution of bullhead (Cottus gobio) as a function of habitat conditions. In ten reference streams of the Alps (NW Italy), 95 mesohabitats were sampled for hydro-morphologic and biological parameters, and RF and LR were used to distinguish between absence/presence and presence/abundance of fish. The obtained models were compared on the basis of their performances (model accuracy, sensitivity, specificity, Cohen's kappa and area under ROC curve). Results indicate that RF outperformed LR, for both absence/presence (RF: 84 % accuracy, k = 0.58 and AUC = 0.88; LR: 78 % accuracy, k = 0.54 and AUC = 0.85) and presence/abundance models (RF: 79 % accuracy, k = 0.57 and AUC = 0.87; LR: 69 % accuracy, k = 0.43 and AUC = 0.81). The most important variables, selected in each model, are discussed and compared to the available literature. Lastly, results from models' application in regulated sites are presented to show the possible use of RF in predicting habitat availability for fish in Alpine stream
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
M. Habitat time series analysis to develop flow management criteria in rivers affected by hydropeaking.
No full textHydropeaking induced by storage hydropower plants can modify the natural flow regime at different time scales, with severe impacts on the biodiversity of the downstream river ecosystems. In this research, a case study on the Noce River (NE Italy) is presented, where habitat simulation models and habitat time series were used to compare restoration scenarios and develop flow management criteria. Habitat time series analyses are based on the assumption that habitat events occurring rarely in nature create stress to aquatic fauna and shape the community. The identification of habitat stressor thresholds (HST) provided a means of quantitatively comparing different flow magnitude scenarios as well as duration and frequency of events. Results indicate that (i) the proposed flow management plan should nullify the rare habitat stress events to support the recovery of existing fish populations and (ii) HST can be used to identify flow release strategies in rivers affected by hydropeaking
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