196,014 research outputs found
CARTA DELLA VEGETAZIONE DELLA RISERVA NATURALE DEI MONTI CANFAITO E SAN VICINO
No full textLo studio della vegetazione è stato condotto utilizzando il metodo fitosociologico della scuola Sigmatista di Zurigo-Montpellier (BRAUN-BLANQUET, 1964), integrato in base alle più recenti acquisizioni sulla sinfitosociologia e geosinfitosociologia (GÉHU e RIVAS-MARTINEZ, 1981; THEURILLAT, 1992; BIONDI et al., 2004).
Il lavoro di campagna è stato effettuato nella stagione vegetativa 2012 mediante la realizzazione di rilievi fitosociologici, al fine di inquadrare le varie tipologie vegetazionali.
Le principali comunità vegetali censite durante la campagna fitosociologica sono riportate nella Carta della vegetazione della Riserva Naturale Regionale del Monte S. Vicino e del Monte Canfaito (scala 1: 10.000).
La metodologia utilizzata per la realizzazione della suddetta carta è stata articolata in tre fasi principali:
- fotointerpretazione e fotorestituzione dei fotolimiti relativi ad unità fisionomiche come boschi, arbusteto, pascoli, campi ed aree urbane;
- inquadramento fitosociologico dei tipi vegetazionali presenti sul terreno;
- delimitazione cartografica dei suddetti tipi vegetazionali
PFAS: a new threat to human health Multi-analyte method development and background levels monitoring
No full text“PFAS are defined as fluorinated substances that contain at least one fully fluorinated methyl
or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e., with a few noted
exceptions, any chemical with at least a perfluorinated methyl group (−CF3) or a perfluorinated methylene group (−CF2−) is a PFAS”. The “noted exceptions” refer to a carbon atom
with a H/Cl/Br/I atom attached to it (Organisation for Economic Co-operation and Development
(OECD), 2021; Wang et al., 2021).
The family of compounds denoted by the acronym PFAS encompass:
• perfluoroalkyl substances, which are defined as aliphatic substances for which all of the H
atoms attached to C atoms in the non-fluorinated substance from which they are notionally
derived have been replaced by F atoms, except those H atoms whose substitution would
modify the nature of any functional groups present;
• polyfluoroalkyl substances, defined here as aliphatic substances for which all H atoms attached to at least one (but not all) C atoms have been replaced by F atoms, in such a manner
that they contain the perfluoroalkyl moiety CnF2n+1− (Buck et al., 2011).
The PFAS molecular structure (R−X) consists of a hydrophobic alkyl chain, R, of varying
length (typically C4−C16) and a hydrophilic end group, X (Figure 4) (EFSA, 2020). The hydrophobic part may be fully [R = F(CF2)n−] or partially fluorinated. The hydrophilic end
group can be neutral, positively, or negatively charged. The resulting substances are non-ionic, cationic, or anionic surface-active agents due to their amphiphilic character (Table 1) (EFSA,
2020).The properties of PFAS depend on the characteristics of the fluorine atom and the nature of the
carbon-fluorine bond. Fluorine belongs to the group of halogens which possess seven valence
electrons. This means they only need one electron to complete the octet. They have high electron affinity, ionization energy, and electronegativity. Fluorine is the element of the periodic
table with the highest electronegativity which gives it a great ability to attract bonding electrons.
For this reason, the bond with carbon has a decidedly more polar character than that of the
carbon-hydrogen bond and has an electric dipole inversion. Fluorine forms the strongest single
bond with carbon due to the optimal overlap of their orbitals during bond formation. This results
from the similarity in energy levels between fluorine and carbon orbitals, especially since they
belong to the same period in the periodic table. Each carbon-fluorine bond increases the strength
of other C−F bonds related to the same carbon atom. Furthermore, being very small, fluorine
has an occupational space like that of hydrogen and guarantees a small steric encumbrance. It
has low polarizability, and this is reflected in the fact that fluorocarbons have weak intermolecular attractive forces, providing these compounds with a low surface energy, lower than that of
the respective hydrocarbons.
PFAS are characterized by high thermal stability and low reactivity, they can be both hydrophobic and lipophobic and their chemical- physical properties vary with the length of the carbon
chain and the functional groups. These characteristics make them of great interest for industrial
applications (Buck et al., 2011; Wang et al., 2017).
In 2018, the "Global PFC Group" coordinated by the Organisation for Economic Co-operation
and Development (OECD) and the United Nations Environment Programme (UNEP), released
a comprehensive list of more than 4700 PFAS compounds. These compounds were identified
as containing either a −CnF2n− (n ≥ 3) or −CnF2nOCmF2m− (n and m ≥ 1) moiety and were confirmed or presumed to have been present in the global market (Figure 5) (Organisation for Economic Co-operation and Development (OECD), 2018, 2021)
Changes in species and functional composition in the herb layer of sub-Mediterranean Ostrya carpinifolia abandoned coppices
No full textIn recent decades, the traditional management of woods has ceased in several parts of the Apennine ridge, with the result that some woods have not undergone forestry for 40–70 years. The research aim was to assess the variation of species and functional composition in the herb layer of Ostrya carpinifolia woods (central Italy), after cessation of the usual management (coppice-with-standards). Using a space-for-time substitution, we compared stands at the end of the usual rotation cycle (20–25 years) with stands not subjected to silvicultural treatments for about 40–45 years and collected environmental and structural data. The main drivers of the herb layer modification, assessed using Ellenberg indicator values analysis and redundancy analysis (RDA), were primarily related to time since the last coppicing and wood structure. Results of indicator species analyses (ISAs) and Wilcoxon rank sum tests indicated that in abandoned coppices, the regenerative processes proceed through the spread of late-successional species, while the light filtering through canopy fosters species usually considered of fringe habitats. The functional strategies revealed by ISA and RDA underlined still stressful conditions in stands at the end of the usual coppicing rotation cycle, which might be thought as a legacy of the post-logging condition, and processes of recovery/maturation of the forest systems in abandoned woods leading to a better spatial and temporal niche partitioning. The preferential distribution of species usually growing in the Apennine beech woods supports the hypothesis that the studied O. carpinifolia woods are secondary forest ecosystems originating from the degradation of mixed beech woods
How the interplay between management and interannual climatic variability influences the NDVI variation in a sub-Mediterranean pastoral system: Insight into sustainable grassland use under climate change
No full textThe modification of precipitation regimes and the increase in summer aridity under the predicted climate change scenarios are hypothesized to have repercussions on the semi-extensive pastoral systems of Mediterranean grasslands, leading to change in forage quantity/quality, increased interannual variability in phytomass production, reduction of the carrying capacity of rangelands, and worsening of animal welfare. The research aims were to find what climatic features affect changes in the annual peak of Aboveground Net Primary Production (ANPP), and how topographic variables and management conditions influence these variations in a pastoral system of central Apennines (Italy). We monitored Normalized Difference Vegetation Index (NDVI) variations at the peak of phytomass production using Landsat satellite images, used as a proxy for ANPP changes in the most productive phase of the growing season, when herds are carried to pastures and hay-meadows are mown, on a dataset of 10,000 randomly sampled pixels (30 × 30 m), in the years 2003, 2007, 2009, 2010, and 2013−2015. We investigated the relation between NDVI and climatic variables, topographic parameters, vegetation physiognomy, and management type, using generalized linear mixed-effects modeling, variation partitioning, and correlation analysis. We observed an increase in average yearly temperatures and high variability in the rainfall seasonal distribution pattern, particularly of spring precipitation. Climatic fluctuations influenced the overall amount of forage production more than management and topographic conditions. The spring variation of climatic variables (precipitation in March, drought stress in April and May), the drought and cold stress intensities in the previous year and the cold stress in the preceding winter were the main drivers of NDVI change. The landform factors interacted with climate variability in determining the amplitude of NDVI changes, which were the widest in semi-flat mountain tops and flat valley bottoms and the smallest in south-facing slopes. The effect of the climatic variables on NDVI was different depending on the management condition, suggesting that grassland management partially filters the climatic drivers of changes in forage production. Based on our results, the most productive grassland communities and the areas used for grazing by domestic herbivores could be the most impacted by the predicted climate changes for the Mediterranean basin, potentially reducing the economic sustainability of semi-extensive farming in the Apennine mountains
Effect of climatic and topographic variables on NDVI variations in a sub-Mediterranean mountain pastoral system
No full textWe mapped the NDVI of our study area and randomly extracted 10,000 pixels falling on grasslands. We collected topographic parameters for each pixel (altitude, aspect, slope and land form) and climatic variables (average monthly temperatures and monthly precipitation), and calculated bioclimatic indices.
The considered variables explained about the 40% of the total NDVI variability, most of which was related to climatic parameters, while topographic variables (especially aspect) mostly acted in intensifying the effects of climate variations
Changes in species and functional composition in not managed(by more than 40 years) Ostrya carpinifolia coppicced woods
No full textThe study present the effect of long term absence of management in former coppicced Ostrya carpinifolia-dominated woods from a taxonomic, ecologic and functional point of view. Results highlighted a proces of ecosystem maturation with the increase of specialist forest species and of light-demanding taxa growing at the edge of intense managed woods
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
- …
