1,720,989 research outputs found
Nature and reactivity of charcoal produced and added to soil during wildfire are particle-size dependent
No full textCharcoal added to soil by wildfires is usually considered to be part of the most stable pool of soil organic matter (SOM). It consists of a continuum of slightly burned plant residues to completely charred material. We sampled the macroscopic charcoal pool produced by a moderate-intensity wildfire in a pine coastal forest in Tuscany (Central Italy) with the aim of assessing the relationship between its particle size and chemical composition as well as its reactivity. Our conceptual approach included particle size separation by dry sieving and analysis of four size fractions (> 2 mm, 2-1 mm, 1-0.5 mm and < 0.5 mm) for elemental composition. The composition of the charcoal fractions was studied using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy, diffuse reflectance fourier transform infrared (DRIFT) spectroscopy, analytical pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and CuO oxidation. The reactivity of the fractions was assessed using acid dichromate oxidation, while the morphology was observed using scanning electron microscopy (SEM). There were clear differences in chemistry and reactivity between the fractions. The different fractions are probably the result of both type of original plant material and the fire conditions. In fact, wood-derived charcoal largely prevailed in the largest fraction, while pine needles and herbs were most probably precursors of charcoal in the smallest fractions. The degree of charring was greatest for the coarse fraction, which represented 56% of the total charcoal, and decreased gradually to the finest fraction. The composition was completely aromatic for the coarsest fraction, whereas the finest fraction showed a greater contribution from aliphatic C- and N-containing components. The greatest reactivity was found for the smallest fraction, which represented 24% of the total charcoal. It is particularly rich in N and potentially susceptible to microbial decomposition. The study demonstrates that properties of charcoal added to soil during wildfires may be reliably discriminated on the basis of particle size
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
Application of thermal and spectroscopic techniques to assess fire-induced changes to soil organic matter in a Mediterranean forest
No full textOrganic matter is the soil component most sensitive to fire, being the fuel on the ground and below. It is affected by fire in terms of both abundance and composition. Incomplete combustion yields condensed carbon forms characterized by higher recalcitrance to biological and chemical attack compared to the parent material. In this study, thermogravimetry (TG-DTG), differential scanning calorimetry (DSC), attenuated total reflectance/Fourier transform infrared spectroscopy (ATR/FT-IR), and Raman spectroscopy were applied to (1) charcoal particles accumulated on the ground, (2) the top 10 cm of soil, and (3) the SOM extracted using an alkaline solution, to investigate the wildfire effect on the organic pool of the loamy and sub-acid soil of a maritime pine (Pinus pinaster Ait.) forest. The same investigations were performed on the litter layer and the mineral soil of an adjacent unburnt area, similar to the burnt one before fire occurrence. TG-DTG and DSC measurements highlighted an accumulation of soil organic matter (SOM) in the burnt soil, which suggests an incorporation of partly charred necromass into soil and the formation of pyrogenic highly refractory organic matter, i.e. black carbon. The ATR/FT-IR showed changes in the fire affected extractable SOM compatible with the formation of stable N containing compounds in the fire affected extractable SOM, which was well confirmed also by the presence of CN groups vibration in the Raman spectrum. The combined application of thermal and spectroscopic techniques resulted to be highly useful to rapidly estimate many of the effects of fire on soil organic matter
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
PyOM characterisation in fire-prone Mediterranean pine forests
No full textFire is a major disturbance to vegetation and soil and a driving factor of ecosystems in the Mediterranean basin, as up to 90% of all forest fires in the EU occur in Mediterranean countries (De la Rosa et al., 2008). The aboveground vegetation and the soil organic matter (SOM), which is the fuel in soil, are affected in terms of both abundance and composition. Fire impact on soil organic matter is usually confined to the organic horizon and a few top cm of the underlying mineral soil (Certini et al., 2011). A major outcome of wildfires is the production of charcoal – the result of incomplete combustion of plant biomass and litter ‐ and its release to soil (Knicker, 2011). In terms of composition, fire increases the heterogeneity of soil organic matter (SOM) because apparently no original component is totally removed, while new thermally‐condensed aromatic compounds form as a consequence of chemical reactions driven by the high temperatures (González‐Pérez et al., 2004). These fire‐derived compounds collectively form the so‐called pyrogenic organic matter (PyOM). Some PyOM is usually reported to have longer residence times in soil compared to the parent materials, enhancing the potential of soil to store carbon for long time, offsetting the release of human induced CO2 to the atmosphere (Schmidt and Noack, 2000). However, PyOM structure and composition is not yet well‐understood. PyOM is not so inert as formerly believed (Farrell et al., 2013) and can play crucial roles in soil biological processes (Zackrisson et al., 1996) and on SOM dynamics (Wardle et al., 2008). Consequently, there is gathering interest in collecting reliable information on structure and properties of PyOM and understanding its behaviour in soil. Mediterranean soils, in spite of being particularly affected by wildfires, were poorly investigated compared to soils of other environments. The present work deals with some wildfires occurred in Mediterranean pine forests of Tuscany, central Italy, and it is aimed at disentangling the composition and structure of PyOM produced during wildfire. To overcome the complexity of the investigated matter, we used various techniques and we fractionated charcoal according to particles size, starting from the assumption that those fractions have different composition and reactivity, which is plausible on the basis of previous studies (Rumpel et al., 2007; Nocentini et al., 2010; Francioso et al., 2011). By thermal (thermogravimetry, differential scanning calorimetry) and spectroscopic (FT‐IR, Raman, NMR) techniques, we observed that fire caused an accumulation of recalcitrant and refractory compounds at the expense of the SOM fraction most labile to thermal degradation. Charring, on the other hand, was not complete, as part of the burnt material still contained a fraction thermally degradable under 500 °C. As a consequence, the partly charred materials accumulated on the surface and into the first layer of mineral soil are prone to be oxidised by further fire events. The thermally recalcitrant pool was enriched in N poliaromatic molecules whose formation provides evidence that PyOM formed at temperatures not exceeding 400 °C. The size fractions we separated the macroscopic charcoal, actually showed different elemental composition, lignin signature and reactivity, as verified by dichromate chemical oxidation. This induces to hypothesise different precursor plant materials from which these fractions were originated and/or different fire conditions under which they were produced. Spectroscopic analyses (FT‐IR, normal Raman, surface‐enhanced fluorescence and surface‐enhanced Raman scattering, NMR) support such a hypothesis, clearly showing that the charcoal found on the ground immediately after a wildfire has a different chemical structure depending on size of particles, type of burnt biomass and fire conditions under which charcoal was produced. In particular, fine charcoal is generally less aromatic but richer in N‐bearing aromatic structures, aliphatic chains and carbonyl groups; it is also more reactive, suggesting a relatively fast mineralization in soil. On the contrary, the coarse fractions are less reactive, mainly comprising condensed aromatic material apparently more crystallised, being probably composed of larger graphitic clusters
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