1,720,985 research outputs found
Relationship between groundwater salinity and biodiversity in the Pine forests near Ravenna, Italy
No full textThe coastal watershed of Marina Romea in the province of Ravenna is surrounded on all sides by salt water and covered for a large part with a Pine forest, planted in the early 1900’s to prevent salt spray on agricultural land. Monthly monitoring of water table elevation and salinity during a year (March 2007, February 2008) in the Pine forest shows that the water table fluctuates strongly with the seasons and ground water salinity is very high. Using precipitation data, data from the pumping station that keeps the city from flooding and estimates of tree water use based on sap flow measurements published by Teobaldelli et al., (2004), we calculated a simplified monthly water balance. In four monitoring periods out of twelve, the tree water use is larger than the precipitation. In nine out of 12 monitoring periods drainage is larger than precipitation or tree water use. In some months, intense drainage corresponds to large precipitation but in other periods drainage does not correspond to strong precipitations: drainage continues during the summer while precipitations are scarce. These observations suggest that both tree water use and drainage contribute to the salinization of the ground water that is observed in piezometers. The measured changes in water level are used to get an independent estimate of tree water use. The values derived vary between 9 and 34. l/day per tree which are of the same magnitude as the values derived from sap flow measurements (between 10 and 30 l/day/tree). The trees ironically now attract salt intrusion from below in the ground water by taking up so much water and this inhibits their own well being. Analytical calculations based on the Ghyben Herzberg Dupuit formulation suggest that even a small annual recharge of15 mm could stabilize a freshwater lens of 2 m deep in the unconfined aquifer. This freshwater lens is currently not present and this is most likely due to the fact that tree water use and drainage take out a lot of fresh water and also because water table fluctuations may enhance dispersion of salt throughout the aquifer. Forest managers, water managers and hydrologists and hydraulic engineers should work together to find a sustainable furnishing of Marina Romea, that takes into account a drainage and managed aquifer recharge system that prevents flooding of the city but that feeds at the same time a stable freshwater lens that can support in a sustainable way the vegetation that perhaps should exist of fewer Pine trees and of more less water consuming species
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
Lenti d'acqua dolce nelle dune della costa Adriatico-Romagnola
No full textStudi condotti negli ultimi sette anni sulle dune costiere relitte della costa Adriatico-Romagnola hanno rilevato l’esistenza di lenti di acqua dolce al loro interno. Queste lenti di acqua dolce sono importanti per l’ecosistema delle zone umide costiere e per contrastare l’intrusione di acqua salina nell’acquifero freatico. Studi geochimici delle acque di falda contenute nelle dune indicano che è in atto una tendenza alla progressiva salinizzazione di questa risorsa idrica che peraltro è soggetta a forti oscillazioni in quantità e qualità durante le diverse stagioni dell’anno. Le ragioni di questa progressiva salinizzazione delle acque contenute nelle dune sono da ricercarsi nel drenaggio della zona costiera, nella presenza di vegetazione non in equilibrio con il locale ecosistema, nella subsidenza, nell’innalzamento del livello marino e nel progressivo smantellamento degli apparati di dune rimasti a causa di fattori antropici e naturali. Studi di modellistica analitica e numerica indicano che le dune costiere romagnole sarebbero ancora in grado di mantenere una lente di acqua dolce spessa alcuni metri se esse non fossero costantemente drenate. Dove la duna costiera è stata ricostituita, come è il caso di Foce Bevano, almeno per un anno dopo l’intervento si è registrata una tendenza alla formazione di una nuova lente di acqua dolce all’interno della duna artificiale. Le dune costiere per le loro caratteristiche di ottimi serbatoi, date la loro alta conduttività idraulica e porosità, sono dei luoghi ideali per interventi di ravvenamento artificiale dell’acqua sotterranea. Un ravvenamento artificiale in una duna oltre ad immagazzinare acqua che può poi essere utilizzata in periodi di siccità dall’ecosistema circostante permette anche la formazione di un battente d’acqua sopra il livello del mare che come previsto dalla legge di Ghyben-Herzberg costituisce una forte barriera contro l’intrusione di acqua salina negli acquiferi dell’entroterra
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
The effects of climate change on the hydrology and groundwater of Terceira island (Azores)
No full textUntil recently the water flowing from rain fed springs was abundant enough on Terceira
(Azores, Portugal) and groundwater exploration was limited to the Lajes basin. This
paper discusses the effects of climate change on the hydrology of Terceira and presents
an estimate of the size of the fresh water lens underneath the whole island of Terceira
using fault orientation as an indication for conductivity anisotropy. Longer periods of
drought are thought to be one of the effects of greenhouse warming for Terceira and
the exploration and exploitation of the freshwater lens may become necessary
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
The influence of surface water evaporation on salt water intrusion in Ravenna, Italy. Implications for climate change.
No full textWe investigate to what extent open surface water evaporation contributes now, and in
a possible future, to the salinization of quarry lakes in the Quinto Basin, Ravenna Italy.
Net evaporation rates are currently up to 894 mm/yr. Numerical models show that
evaporation is one of the driving forces for salinization of the unconfined aquifer.
Evapotranspiration by pine trees and drainage of the polders around the quarries
contribute as well. Evaporation depends on many weather variables and in the future
IPPC climate scenarios A1B and A2 for the area, evaporation may slightly decrease,
because of decreasing wind and increasing air humidity in winter, even though average
temperatures will increase
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