1,721,100 research outputs found
Provenance characteristic and modifications by transport processes of Palygorskite in wet and dry aerosols in Western Mediterranean
No full textCharacterization of Palygorskite in dust of desertic provenance in aerosols, Sardinia, Western Mediterranean
No full textPalygorskite aggregated grains occur in aerosol dust samples in western Mediterranean Sea. Morphology and texture of palygorskite grains was characterized analytical using SEM with attached X-ray energy dispersive system. Palygorskite occurs as rounded aggregate grains (wind-shaped), as interwoven fibrous mats forming fine laminae, and as porefilling and pore-bridging cements that commonly coat detrital grains and occur among them. The results show distinct and characteristic textures of palygorskite in dry (aerosol in air) and wet (precipitation) deposition. The main sources of this clay mineral are the dry rivers, lake beds, salt lakes, and argillaceous bed-rocks in northwestern Africa. Air mass trajectories calculation independently indicate two different source area
Sviluppo di algoritmi algebrici per la classificazione automatica della granulometria di sedimenti in ambiente GIS
No full textLo studio delle proprietà dei sedimenti è essenziale per comprendere numerosi processi che avvengono sulla superficie del nostro pianeta, come le dinamiche di corsi d’acqua e di mari, la morfologia costiera, il trasporto sedimentario eolico, fluviale o glaciale, i fenomeni di inquinamento, la distribuzione di piante ed animali, ecc.
La granulometria dei sedimenti è un parametro fisico fondamentale per lo studio della superficie terrestre ed è uno strumento essenziale per la classificazione degli ambienti sedimentari (Folk and Ward, 1957; Reed et al., 1975; Taira and Scholle, 1979; McLaren and Bowles, 1985; Singer et al., 1988; Vandenberghe et al., 1997). La granulometria fornisce importanti informazioni sull’energia e la dinamica degli ambienti deposizionali aiutando a comprendere la provenienza, il trasporto e la storia dei sedimenti (Folk and Ward, 1957; Friedman, 1979; McCave and Syvitski, 1991; Pye and Blott, 2004). Negli ultimi 25 anni è considerevolmente aumentato l’interesse per i dati granulometrici negli studi ambientali, soprattutto riguardo a fenomeni di contaminazione da micro-inquinanti (Albertazzi et al., 1987; Moore et al., 1989; Hieke Merlin et al., 1992; Hathaway et al., 1994) o di erosione dei litorali.
Krumbein (1933) ha introdotto l’uso dei diagrammi triangolari per classificare i sedimenti in base alla relativa granulometria. I tre membri limite di questi diagrammi mostrano le proporzioni relative dei vari componenti (per esempio la percentuale di sabbia, silt e argilla o di ghiaia, sabbia e fango). Al giorno d’oggi in letteratura sono disponibili numerosi differenti classificazioni con i relativi diagrammi triangolari.
I sistemi informativi territoriali (GIS) sono frequentemente usati per generare mappe della distribuzione spaziale di varie variabili ambientali. Il recente sviluppo dell’analisi spaziale nel GIS può servire a gestire, elaborare e visualizzare dati sedimentologici come la granulometria. Questi dati sono spesso costituiti da campioni puntuali, che quindi necessitano di modelli di distribuzione spaziale per essere descritti in uno spazio continuo, che è spesso l’obiettivo di questo tipo di ricerca.
L’utilizzo di algoritmi capaci di eseguire l’analisi spaziale può semplificare notevolmente l’interpretazione di dati puntuali passando da dati discreti alla rappresentazione continua nello spazio delle variabili. A questo proposito sono stati sviluppati vari tipi di interpolazione spaziale, da semplici modelli deterministici come l’Inverse Distance Weighting (IDW) a modelli geostatistici più sofisticati come il kriging. Recentemente i GIS sono stati implementati dalla map algebra, un linguaggio informatico usato nell’analisi spaziale (Tomlin, 1990). La map algebra è un insieme di espressioni matematiche applicate a dati spaziali che utilizzano operatori aritmetici, relazionali, booleani e logici con lo scopo di risolvere problemi spaziali complessi.
In questo poster si presentano alcuni algoritmi di map algebra che sono stati sviluppati allo scopo di generare automaticamente le mappe della distribuzione spaziale delle classi granulometriche e di classificare automaticamente la granulometria dei sedimenti sulla base dei diagrammi triangolari più comuni, come il diagramma di Shepard (1954) e di Flemming (2000) per i sedimenti composti da sabbia, silt e argilla, Folk et al. (1970) e Blair and McPherson (1999) per quelli composti da ghiaia, sabbia e fango.
La procedura proposta trova largo impiego in diversi ambiti di studio sedimentario, come (a) la classificazione della granulometria dei sedimenti in un ambiente sedimentario (b) lo sviluppo di mappe della distribuzione granulometrica dei sedimenti; (c) l’individuazione di cambiamenti e modificazioni nella distribuzione dei sedimenti sia nel tempo che nello spazio
First video documented presence of Mediterranean monk seal in Southern Apulia (Italy)
Full text linkSightings of Endangered monk seal (Monachus monachus) specimens have been increasingly reported along the
coasts of its historic Mediterranean distribution over the last two decades, even from countries where the species
was considered extinct for about half a century. These encounters have been documented and verified particularly
along the coasts of the Adriatic-Ionian basin. The activities carried out in Salento (Southern Apulia, Italy) since 2012,
engaging with local protected areas, authorities and different stakeholders (organizations, museums, universities,
fishermen’s cooperatives and tourism sectors enterprises) allowed us to record and verify 10 monk seal sightings (from
2009 to 2014) in the area. However, the last sighting with photographic documentation dates back to 1973. In June
2017, after six years of monitoring and awareness of the territory, immediately after the sighting, we received a video
evidence of such presence. The footage, and the resulting interview with the witnesses, documented the presence of a
Mediterranean monk seal’s specimen, about 2 meters in length, along the coast of Tricase (Lecce, Apulia). This new event
has a remarkable importance to the hypothesis that Salento and the Adriatic-Ionian basin might play an important role
in the overall conservation of the specie
Thirty-year changes (1970 to 2000) in bathymetry and sediment texture recorded in the Lagoon of Venice sub-basins, Italy.
Full text linkA detailed comparison was made of two bathymetric charts of the Lagoon of Venice (LV) from 1970 and 2000, in tandem with a comparison of sediment grain size data. Analysis of the data revealed marked changes in both morphology and sedimentation, with more than 50% of the 400 km2 assessed in this study 15-20 cm shallower in 1970 than in 2000. The four sub-basins into which the LV is subdivided saw different patterns of change.
The Northern basin A was identified as “pristine”, i.e. still in quasi-natural condition, with slight clay enrichment and a small degree of deepening (4-5 cm), essentially due to sea level rise (SLR).
The bathymetry and sedimentology of the northern-central sub-basin B (identified as “urban”) and the southern-central basin C (identified as “open”) were affected by infill activities and excavation of industrial navigation channels in the 1970s, causing the loss of ~ 60 km2 of mudflats, and creating an “open” lagoon.
The southernmost basin D (identified as “exploited-subsiding”) of the LV was found to be relatively unchanged and still in semi-natural condition.
Comparison of sediment types showed depletion of fine-grained fractions (< 22 µm) in all sub-basins except the northernmost one. Consequent enrichment in sand (> 63 µm) was recorded, except in the southern-central sub-basin C where medium and coarse sand fractions declined.
The results suggest that climate-related SLR accounts for a small fraction of bathymetric change, whilst variations in hydrodynamics (currents and wind patterns) and sediment supply are likely causal factors for the different evolution of the four sub-basins.
Definition of the attributes of each sub-basin provided data that was essential not only for the LV but also for predicting the fate of transitional environments facing both anthropic (fishing, navigation, land use changes) as well natural (SLR, eustatism) forcing factors
Uncontrolled trampling on dunal habitats; monitoring and conservation measures in the “Penisola del Sinis - Isola di Mal di Ventre” Marine Protected Area, Sardinia (Italy)
No full textMonitoraggio e misure di protezione della fascia costiera nella penisola del Sinis (Area Marina Protetta “Penisola del Sinis - Isola di Mal di Ventre” - Sardegna occidentale)
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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
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