1,720,958 research outputs found
Measurement errors of water retention curve using pressure plates: consequences on parameterization
No full textPressure plates are very common experimental devices to measure the soil water retention curve. However, recent
studies have demonstrated the lack of reliability of pressure plates when measuring the soil water retention curve
in the dry range, due to low plate and soil conductance, lack of soil-plate contact and soil dispersion. In a recent
investigation on a silt loam soil, water retention data were determined using pressure plates only and a combination
of pressure plates and a dew point meter, showing errors in the measurement of the soil water retention curve
at potentials less than 20 m-H2O. This error led to unreliable evaluation of soil hydraulic properties and their
parameterization. We extended the investigation on the effects of water retention measurement error to eighteen
soils having different textural properties, by comparing measurements of soil water retention curves obtained with
a combination of Stackman’s beds and pressure plates and soil water retention curves obtained with the chilledmirror
dew point technique. The aim of this research was to investigate the differences between the soil water
retention curves as function of different soil textural properties and their effect of soil hydraulic properties and
water drainage. Comparison between retention curves and fitting van Genuchten parameters, showed an error
in measurements made by the combination Stackman’s beds and Richards’ pressure plates, for potential values
below 1 m-H2O to 57 m-H2O. By characterizing textural properties by using geometric mean diameters, a clear
relationship between texture and errors in water retention was established. In particular coarser soil displayed
errors at lower potential (in absolute value) with respect to finer textures. The occurrence of these errors in the
water retention measurement performed with pressure plates showed that it is advisable to use a combination of
methodologies to correctly measure an entire soil retention curve and current parameters database should be used
with caution
Errori nella misura della ritenzione idrica dei suoli: conseguenze sulla stima del drenaggio profondo
No full textErrors in water retention curves determined with pressure plates: Effects on the soil water balance
No full textPressure plates apparatus are very common experimental devices utilized to measure the soil water retention curve. Many studies have demonstrated the lack of reliability of pressure plates apparatus when they are used to measure the soil water retention curve in the dry range, due to low plate and soil
conductance, lack of hydrostatic equilibrium, lack of soil–plate contact and soil dispersion.
In this research, we investigated measurements of soil water retention curves obtained with a combination of
Stackman’s tables, pressure plates apparatus and the chilled-mirror dew point technique. Specifically,
the aim of this research was: (a) to investigate the differences in the measured soil water retention curves
by the different experimental methods, (b) evaluate relationships between the experimental differences
and soil texture, (c) analyze the effect of experimental differences on hydraulic properties parameterization
and (d) investigate the effects of the different parameters set on water transport computation.
The results showed differences in measurements made by the combination of Stackman’s tables and Richards’ pressure plates apparatus as compared to the dew point method, for fine textured soils, while no significant differences were detected for coarse textured soils. Computed cumulative drainage and evaporation
displayed lower values if soil water retention curves were obtained from data obtained with the Stackman’s
tables and Richards’ pressure plates apparatus instead of the dew point method. In soils, where the soil water retention curve was measured with traditional methods (Stackman’s tables and Richards’ pressure plates apparatus) average cumulative drainage was 173 mm, with respect to a combination of
methods including the dew point methods, where the average cumulative drainage was 184 mm. Average cumulative evaporation was 77 mm for the traditional methods, while it was 91 mm, for the combination of methods. Overall, when simulation models are used for studies related to solute transport, polluted soil remediation, irrigation management and others, erroneous measurement of the SWRC for fine textured soils, may lead to erroneous computation of the soil water balance
The geochemistry of leucite-bearing lavas from early stages of the Somma-Vesuvius volcanic complex. Feeder systems and mantle enrichment processes in the Neapolitan district of the Roman Magmatic Province
Full text linkThe lavas of the Monte Somma activity (early stage of the Somma-Vesuvius volcanic
complex) are mildly differentiated plagioclase-clinopyroxene-olivine- ± leucite-bearing
lavas (leucite tephrites, leucite-bearing shoshonites, latites), low in MgO, Cr and Ni,
with a Sr-Nd-isotope range (87Sr/86Sr = 0.706865-0.707861; 143Nd/144Nd =
0.51244-0.51258) overlapping that of the Vesuvian lavas late after 1638 CE (late stage
of the Somma-Vesuvius volcanic complex). The differentiation is dominated by
fractional crystallization of clinopyroxene, calcic plagioclase, olivine and leucite, with
limited interaction with crustal rocks. Oxygen isotopes on clinopyroxene and olivine
phenocrysts (δ18O = 6.5-7.9 ‰) are higher than typical uncontaminated mantle
magmas. However, these values are also not fully consistent with the sole opensystem assimilation+fractional crystallization of a mantle-derived ultrapotassic magma.
A contribution from a recycled crustal component in the mantle source is required,
likely dominated by sediment-derived fluids and melts. The Somma lavas are
characterized by distinctly different geochemical features compared to the mafic
products of the neighboring volcanic areas (i.e., Phlegrean Fields, Procida and Ischia
volcanoes), where the recycled crustal component is less pronounced
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
Stoccare il metano influenza la qualità ambientale?
Full text linkStudio di impatto ambientale di una stazione di stoccaggio ed erogazione di metano in Abruzzo, tramite biomonitoraggio lichenico e misure dirette di concentrazione di sostanze chimiche. La qualità ambientale è stata valutata attraverso due diverse tipologie di monitoraggio: un metodo diretto che ha previsto la misura della concentrazione di ozono, azoto e isoprene in atmosfera e uno indiretto dato da un biomonitoraggio lichenic
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
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