1,720,976 research outputs found
Effects of a waste water treatment plant on organic matter dynamics and ecosystem functioning in a Mediterranean stream
No full textWe studied the effects of a waste water treatment plant on organic matter dynamics in Fosso Bagnatore, a Mediterranean stream near Rome (Italy). Concentrations of dissolved organic carbon and seston, along with the standing crops of coarse benthic organic matter and fine benthic organic matter, were monitored monthly during 2002 in two reaches situated upstream and downstream of a waste water treatment plant effluent. Additionally, we examined two stream functional characteristics: whole stream metabolism, which was measured from diel changes in oxygen concentrations, and nutrient removal, which was Studied by experimental additions of NH4-N, NO3-N and PO4-P. The possible influence of WWTP organic matter alterations on ecosystem functioning was addressed by measuring epilithon characteristics (standing crop, C:N:P ratios and chlorophyll a content). The WWTP effluent caused an increase (several-fold) of DOC and seston concentrations, and FBOM standing crop. moreover it modified their temporal variation. Downstream of the wastewater treatment plant we detected an higher heterotrophic microbial biomass and a correspondent higher community respiration. The uptake of NH4-N, NO3-N and PO4-P was highly variable probably as consequence of the high variability of the compartments involved (e.g. DOC, FBOM, community respiration). We showed that WWTP effluent altered the organic matter dynamics of this Mediterranean-type headwater stream and that these effects were reflected in its ecosystem functioning. Because of the linkage of headwaters to downstream ecosystems and due to their significant role in landscape and catchment processes, the alterations of organic matter dynamics that we detected at a local scale may have important consequences on a broader scale
Life history and species composition of the damselfly assemblage along the urban tract of a river in central Italy
No full textThe species composition of the damselfly assemblage and the life history patterns of two Coenagrionidae (Ischnura elegans and Cercion lindeni) were investigated along the urban tract of a river characterized by increasing organic pollution. The assemblage was dominated by generalist species, usually recorded in lentic habitats, rather than by typical riverine species and the proportion of the latter decrease at the most polluted sites. At the end of Winter, the mean size and instar distribution were different between the sampling sites showing that the life history of both species examined were influenced by a degradation of the environmental quality. A longer reproductive period, absence of diapause, and tolerance of low oxygen concentration appear to be key factors that allow generalist species I. elegans and C. lindeni to predominate at the polluted sites
Application of an image analysis system to the determination of biomass (ash free dry weight) of pond macroinvertebrates
No full textThe absence of a rapid and inexpensive method for estimating macroinvertebrate individual biomass is a limit to the study of freshwater communities, given that traditional methods are time- and money-consuming. We propose an inexpensive method to quickly estimate individual biomass from video-recorded images of pond macroinvertebrates. We used a software that automatically measures several body dimensions (area, perimeter, minor and major axes) on each individual and linear regression to relate these body dimensions to dry weight. Area was found to be the best predictor of dry weight. The method allows individual measures of macroinvertebrates at a reasonable speed and accuracy, and may be useful for biomass size spectra or secondary production studies
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Limnological aspects of an Apennine shallow lake
No full textWe present the results of a four-years monitoring program of Lake Duchessa, a small shallow subalpine lake situated at 1788 m a.s.l. in central Apennines (Italy). From 1997 to 2000, during snow free periods, we regularly measured conductivity, pH, macrophyte cover and water transparency. Contemporarily, 4 water samples were collected to determine nutrient (NH3-N, NO 2-N, NO3-N and PO4-P) and phytoplanktonic chlorophyll a concentrations. Taxonomic compositions of aquatic macrophytes, zooplankton and macroinvertebrates were also determined. Inter- and intra-annual variation of water chemistry and phytoplankton biomass were addressed. Lake Duchessa showed some limnological aspects proper to lowland eutrophic situations due to livestock grazing in the watershed pastures and watering in the lake. In particular, nutrient concentration and phytoplankton biomass reached extremely high values, and lake community was relatively poor. However, despite the high nutrient loading, phytoplankton biomass collapsed in August 1997. In the same occasion, lake water became transparent and remained clear until the end of 1999. The occurrence of this clear water phase and its surprising span may be related to the reduction of tench population (due to a natural fish kill observed during the study) and to the extension of Potamogeton pectinatus L. and Myriophyllum spicatum L. cover. Our results support early observations that water transparency (i.e. environmental quality) of eutrophic shallow lakes can be improved also when nutrient loading is not reduced. Many of the Apennine lakes and ponds situated at high altitudes show conditions similar to those of Lake Duchessa. Therefore this study highlights the ecological processes to be considered in a reliable management of these freshwater systems
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
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