1,723,415 research outputs found
Ultrastruttura di tre diatomee appartenenti al genere Cocconeis Ehr. epifite di Posidonia Oceanica (L.) Delile
No full textLe specie del genere Cocconeis Ehr. rappresentano la componente maggioritaria della comunità epifitica a diatomee presente sulle fanerogame marine.
Tale componente, che presenta una variabilità specifica piuttosto bassa, risulta costituita da un film di cellule fittamente appressate e distribuite su buona parte della superfice fogliare (Mazzella et al. 1995). Nell’ambito di uno studio sulla distribuzione e successione della comunità epifita su Posidonia oceanica (L.) Delile presente nelle acque dell’isola di Ischia, abbiamo condotto delle osservazioni sull’ultrastruttura di alcune specie. Le specie studiate, C. britannica Näegeli in Kützing, C. maxima (Grunow) Peragallo et Peragallo, C. pseudomarginata Gregory , pur essendo costantemente presenti non dominano la comunità, presentano dimensioni relativamente grandi, habitus solitario e, frequentemente, sono epibionti sulle altre specie congeneri più piccole che costituiscono la gran parte del film epifita.
L’analisi ultrastrutturale, condotta con l’ausilio del microscopio elettronico a scansione e a trasmissione, ci ha mostrato una morfologia delle valve per molti dettagli contrastante con le descrizioni al microscopio ottico, le uniche finora disponibili per queste specie. Ciò è in parte dovuto alla non risolvibilità a basso ingrandimento di alcuni di questi dettagli ma anche alla sovrapposizione in luce trasmessa di elementi strutturali presenti esclusivamente o nella faccia esterna o in quella interna delle valve.
É stato possibile, inoltre, interpretare in un ottica morfo-funzionale alcuni degli elementi strutturali osservati. In particolare il sistema di aggancio delle due valve presente in due delle tre diatomee osservate, che risulta mediato dal preciso incastro di elementi diversi ma visibilmente complementari presenti sulle due valvocopulae.
L. Mazzella, M.C. Buia and L. Spinoccia 1995: Biodiversity of epiphytic diatom community on leaves of Posidonia oceanica. - In: D. Marino & M. Montresor (Eds.) Proceedings of the 13th International Diatom Symposium. Biopress; Bristol. 241-25
Scipione Mazzella, Descrizione del Regno di Napoli.
No full textDelille Gérard. Scipione Mazzella, Descrizione del Regno di Napoli. . In: Études rurales, n°46, 1972. p. 142
Diversity of epiphytic diatom flora on Mediterranean seagrasses: morphological aspects and ecological role
No full textDIVERSITY OF EPIPHYTIC DIATOM FLORA ON MEDITERRANEAN SEAGRASSES: MORPHOLOGICAL ASPECTS AND ECOLOGICAL ROLE
M. DE STEFANO (1,2), D.Marino (2), L. Mazzella (1)
Stazione Zoologica di Napoli.
(1) Laboratorio di Ecologia del Benthos, 80077 Ischia (NA),
(2) Laboratorio di Botanica Marina, Villa Comunale, 80100 Napoli
The aim of the present work was to characterize the epiphytic diatom flora on seagrass leaves and to assess their role in such important ecosystems.
Of the different mediterranean seagrasses, such as Posidonia oceanica, Cymodocea nodosa and Zostera noltii, highest diatom species richness and diversity was recorded on P. oceanica, due to the greater surface area for colonization and the complexity of microhabitats. The most frequently encountered diatoms were the genera Cocconeis, Gomphonemopsis, Fragilaria,. Mastogloia and Navicula, belonging to different “growth forms”. In Cymodocea and Zostera the diatom flora was meanly characterized by the Cocconeis group.
Diatom abundances reached densities as high as 3000 cells/mm2 in Posidonia and 8000 in Cymodocea; in Zostera diatoms were at times the only recorded flora with concentrations up to 2500 cells/mm2. The biomass of the Cocconeis group, dominant in all seagrasses, was highest in P. oceanica (1,3 mgC/sh-1), due to the large leaf canopy.
Due to its diversity and abundance, the epiphytic diatom flora largely contribute to the production of the seegrass systems and to the grazing activity of mesoherbivores living in the meadows
The Importance of the Model Choice for Experimental Semivariogram Modeling and Its Consequence in Evaluation Process
Full text linkGeostatistics was created during the second half of 20th century by Georges Matheron, on the basis of Danie Krige’s and Herbert Sichel’s theories. The purpose of this new science was to achieve an optimal evaluation of mining ore bodies. The interest in geostatistical tools has grown, and nowadays its techniques are applied in many branches of engineering where data analysis, interpolation, and evaluation are necessary. This paper presents an overview of the geostatistics approach in data analysis and describes each operative step from experimental semivariogram calculation to kriging interpolation, focusing and underlining the experimental semivariogram modeling step. To help any data analysts during geostatistical analysis process, an innovative geostatistical software was created. This new software, named “Kriging Assistant” (KA) and developed within the Department of Geoengineering and Environmental Technologies University of Cagliari, is able, with a marginal support of the user, to produce 2D and 3D grids and contour maps of sampled data. A comparison between kriging results obtained by KA and two of the most common data analysis softwares (Golden Software Surfer and ESRI Geostatistical Analyst for ArcMap) is presented in this paper. Reported data showed that KA minimizes interpolation errors and, for this reason, provides better interpolation results
Kriging Assistant: a geostatistical analysis and evaluation tool
No full textThe definition of the investigation area border line, the choice of
the optimal sampling mesh and exploration technique, the proper analysis of the
collected data, represent the most important steps during an environmental
research project. The “Krige Diagram” demonstrates that the evaluation results
depend on the accuracy by with each of these phases has been performed. This
paper introduces an innovative geostatistics-based technique for environmental
data analisys and evaluation, called “Kriging Assistant” (KA). This new
technique, developed within the Department of GeoEngineering and
Environmental Technologies – University of Cagliari (Italy), is able to work both
in 2D and 3D dimensions and, especially, can fit the experimental semivariogram
curve through an innovative procedure that is no longer based on the evaluator
experience but on an automatic modeling routine
A combination of TIN meshing, geometric extrapolation and linear interpolation for deep ore bodies modelling: case of Sulcis Coal Basin (Sardinia, Italy)
No full textThe realization of any kind of environmental and/or mining project is not possible without a
strong knowledge of the main features of the geological body involved in. Usually the
evaluation of these characteristics is based on reality models built on a limited set of data
deriving from different survey campaigns. Consequently, the decision-making and the
planning processes are based on models that are, obviously, affected by errors. The
seriousness of these errors is closely related to the modeling technique, to the data accuracy,
to the approximations that have been taken to build them and, especially, to the real variability
of the ore body inhomogeneity inside the study domain. Therefore from an engineering point
of view the consequences can be very dangerous especially where, because of the presence
of geological noises elements (i.e. tectonic faults and folds), it is not possible to apply directly
a statistical and/or a geostatistical interpolation technique (because of the limitations of these
techniques) without producing high errors of evaluation (like could happen in the target area
of this study). For this reason, in these cases, the only possible solution is proceeding with a
preliminary analysis of the available data and of the environmental/geological features in
order to define the most appropriate modeling technique to hold the evaluation errors down.
In this paper, exploiting GIS analysis tools, an innovative 3D modeling technique based on a
combined use of TIN meshing, geometric extrapolation and linear interpolation will be
presented and its results on the Sulcis Coal Basin (Sardinia, Italy) will be introduced and
discussed
Dan Bechmann, Ville et immigration, prière d'insérer, en collaboration avec Rody Lahsinat., 1995
No full textMazzella Sylvie. Dan Bechmann, Ville et immigration, prière d'insérer, en collaboration avec Rody Lahsinat., 1995. In: Les Annales de la recherche urbaine, N°73, 1996. Ville et santé publique. pp. 143-145
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