1,720,976 research outputs found
Micropore characteristics of organic matter in cemented and non-cemented spodic horizons
No full textSoils store three times as much organic carbon (OC) as is found in living plants, and most forest soils are active CO 2 sinks at present. With climate change however, the capacity of soils to preserve OC against degradation will highly depend on the presence of stabilized organic matter (OM) pools. Podzols are among the most characteristic soils in forest ecosystems and their formation is linked to OM movements through the profile and the following stabilization by metal-organic interactions (Fe-and Al-OM) in deeper soil horizons. Recently, we found that the type of metal-organic association changes with increasing intensity of podzolisation and that the variations can be followed by evaluating specific surface area (SSA) by N 2 adsorption. We hypothesised that at later stages of podzolisation stable OM is more tightly bound to metals, hence more rigid and poorer in N 2-accessible pores. In well-developed Podzols, cemented metal-rich horizons (ortsteins i.e. Bsm or Bhsm) may form in addition to non-cemented Bs or Bhs ones. In orsteins the rigidity/condensation of stabilized OM should be further enhanced both because of component ageing and of high amounts of metals. Consequently, OM in cemented podzolic horizons should have a higher amount of N 2 non-accessible pores. In this work we evaluated the specific surface area and porosity of bulk and stabilized OM in cemented and non-cemented podzolic B horizons using gas-adsorption. Thanks to the different accessibility of the probe molecules, the pores between ~<2 and 50 nm and down to less than 0.5 nm can be characterized by, respectively, N 2 (77K) and CO 2 (273K). Four Podzols were selected in Northwestern Italy and both Bs or/and Bhs and cemented horizons were sampled. The samples were treated with 6% NaClO at pH 8, to eliminate the most labile OM, and surface properties were measured before and after oxidation (UT and T samples, respectively) with both N 2 and CO 2. The Bs/Bhs horizons had around 23% of oxidation-resistant OC while orsteins generally showed a slightly higher proportion (29%). The N 2 detectable specific surface area (SSA) seemed to be strongly affected by the porosity of mineral phase, but the variation of SSA upon oxidation was linked to the horizon type. Only the OC richest horizons (Bs/Bhs and Bhsm) showed the typical increase in SSA after removal of labile OM, while in the cemented horizons the SSA decreased. This probably reflects the exposure of highly stabilized OM, richer in small micropores, in the ortsteins. Plotting the SSA measured by CO 2 vs. the amount of OC revealed that the microporosity occurrence mainly depended on the presence of OM in both UT and T samples (r 2 =0.973 and 0.918, respectively), with the exception of Bhsm horizons that, in both cases, showed a lower SSA with respect to OC content than the other samples. The anomalous behavior of Bhsm could be related to the high presence of roots, hence to the presence of chemical recalcitrance as an additional mechanism in OM stabilization. The relationships between SSA and OM in UT and T samples had equivalent intercept values (4.35 and 4.36 m 2 g-1 , respectively), pointing out that oxidation had no effect on the contribution of the mineral phase on micropore surface. The slopes instead were different, and indicated that stabilized OM increased SSA twice as much as the UT sample. Our results show that stabilized OM structure in Podzols sharply differ from that of more labile OM pools thanks to a larger presence of small micropores. The high amount of <0.5 nm pores may contribute in preserving organic matter towards degradation, thus decreasing its turnover even in a climatic change perspectiv
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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