1,720,959 research outputs found
Role of ionotropic glutamate receptors in the regulation of hippocampal norepinephrine output in vivo
No full textIn vitro evidence indicates that norepinephrine release in the mammalian hippocampus is modulated by glutamate receptors. With the use of microdialysis, we have now evaluated the role of ionotropic glutamate receptors in the regulation of hippocampal norepinephrine output in vivo. Stimulation of N-methyl-D-aspartate (NMDA)-sensitive glutamate receptors by local administration of NMDA (1-100 μM) resulted in a concentration-dependent decrease in the extracellular concentration of norepinephrine in the hippocampus of freely moving rats, whereas the blockade of these receptors with MK801 (1-100 μM) induced a concentration-dependent increase in norepinephrine output. Activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-sensitive glutamate receptors with AMPA (1-100 μM) resulted in a biphasic effect on the extracellular norepinephrine concentration, with a decrease in this parameter apparent at 10 μM and an increase at 100 μM. The AMPA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione had no effect on norepinephrine output. The GABA A receptor antagonist bicuculline (10 μM) prevented the decrease in hippocampal norepinephrine output induced by either NMDA or 10 μM AMPA. Our results thus implicate ionotropic glutamate receptors as key regulators of norepinephrine release in the hippocampus and may therefore provide a basis for the development of new drugs for stress-related disorders
Application of three different methods to evaluate the nitrate pollution of groundwater in the Arborea plain (Sardinia - Italy)
No full textThis paper describes three different methods used to evaluate the nitrate contamination from agricultural practices in a study area located in the Nitrate Vulnerable Zone (NVZ) of the Arborea plain (Sardinia - Italy). Potential risk of contamination and concentration of nitrate pollution in groundwater has been estimated by using Parametric, Numerical and Artificial Neural Networks methods. Parametric methods consider the combination of intrinsic aquifer vulnerability to contamination index (SINTACS) and agricultural nitrates hazard index (IPNOA). The transport numerical model is based on flow model, obtained with modular three dimensional finite difference groundwater flow model (MODFLOW), and it is made applying 3-D Multi-Species Transport Model (MT3D). Artificial Neural Networks (ANNs) are used for the estimation of the nitrate concentration in monitoring well
The Arborea plain (Sardinia - Italy) nitrate pollution evaluation
No full textIn this paper three different methods have been described and applied to evaluate the nitrate contamination from agricultural practices in a study area located in the Nitrate Vulnerable Zone (NVZ) of the Arborea plain (Sardinia - Italy). Potential risk of contamination and concentration of nitrate pollution in groundwater has been estimated by using respectively Parametric and both Numerical and Artificial Neural Networks methods. Parametric methods consider the combination of intrinsic aquifer vulnerability to contamination index (SINTACS) and agricultural nitrates hazard index (IPNOA). The transport numerical model is based on flow model, obtained with Three Dimensional Finite Difference Groundwater Flow Model (MODFLOW), and it is made applying 3D Multi Species Transport Model (MT3D).
Artificial Neural Networks (ANNs) are used for the estimation of the nitrate concentration in monitoring well
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
Prediction of nitrate concentration in groundwater using an Artificial Neural Network (ANN) approach
No full textThis paper evaluates the effectiveness of Artificial Neural Networks (ANNs) for the estimation of the nitrate concentration in a study area located in the Nitrate Vulnerable Zone (NVZ) of the Arborea plain (Sardinia - Italy). Agricultural derived nitrate contamination of groundwater has been estimated by using easily and economical quantifiable parameters such as pH, electrical conductivity, temperature, groundwater level. Data used for training and validating the ANNs derive from a set of 225 measurements coming from 12 piezometers distributed in the study area. In order to define the best topology of the ANN and the best dimension of respectively the training and the validation sets a growing procedure has been applied
- …
