1,721,774 research outputs found
Exploring plant species richness along the Tiber River within the city of Rome
No full textThe Tiber River stretch crossing the metropolitan area of Rome (Italy) is regarded as one of the main biological corridors of the city, as it diversifies the urban landscape while contributing to the plant diversity. This paper aims to document the current plant richness occurring along the Tiber within the city by providing a comprehensive inventory of the spontaneous vascular flora and an overview of its composition, and structural, chorological and ecological features. This flora lists 493 species and it is characterized by: i) high species richness (more than 30% of Rome’s flora), ii) presence of species with naturalistic value, as rare or included in Red List IUCN categories, iii) high number of ruderal and multizonal species (including several aliens) that have well adapted to human disturbance, and have partially replaced the typical riverine plants, iv) wide spread of eutrophic aquatic species, and rarefaction of those species that are more sensitive to eutrophication and water pollution. The dataset and the overview reported in this study can be useful for future research, with a special focus on a better naturalistic management of the urban river ecosystem, and the conservation of the floristic heritage within the city of Rome
The flora of Vesole, Soprano, Sottano and Chianello mountains (Campania Apennines, Salerno) | La flora del complesso dei monti Vesole, Soprano, Sottano e Chianello (Appennino campano, Salerno)
No full textIn-plane and out-of-plane tensile behaviour of single-layer graphene sheets: a new interatomic potential
No full textThis paper compares simple interatomic potentials for carbon nanostructures with hexagonal lattice, by investigating the in-plane and the out-of-plane tensile behaviour of single-layer graphene sheets. Attention is given both to potentials already considered in the literature and to a new one, which we call the damped DREIDING potential, in which damping functions are added to the DREIDING potential. For each potential, a calibration of its parameters and a focus on its performance are carried out in the in-plane context, by comparison with ab initio results of the rigidities and of the tensile limit properties, under periodic conditions. In addition, the damped DREIDING potential is used to perform in-plane tensile tests on both pristine and perforated single-layer graphene sheets of finite size. In the out-of-plane context, the calibration from ab initio results is only possible with reference to the rigidity. For the damped DREIDING potential, a sensitivity analysis, applied to a nanoindentation problem, on a pristine single-layer graphene sheet of finite size is provided. In doing so, a narrow range of value of the force needed to remove an atom from a sheet is given
Ho’s theorem in global–local mode interaction of pin-jointed bar structures
No full textThis paper is focused on the interaction phenomena among a global critical mode and some local Eulerian critical modes in pin-jointed
structures. These phenomena are framed within Koiter’s theory of elastic instability, by an asymptotic reduction into cubic systems. The aim
is to present an algorithm for the appraisal of the lowest critical load characterizing the structure under the effect of small imperfections. First
of all, the Ho’s theorem, concerning the definition of the most dangerous imperfection, is presented and discussed. Then, a FEM code aimed
at the determination of the most dangerous shape for the imperfection, and at performing the related sensitivity analysis, is implemented, by
superimposing a proper FE beam model (able to model Eulerian instability) to a non-linear FE model for spatial pin-jointed structures. Some
numerical results having a practical interest are presented and discussed
Buckling and post-buckling analysis of single wall carbon nanotubes using molecular mechanics
No full textThis paper deals with a numerical model for the buckling and post-buckling analysis of single-wall carbon nanotubes. Reasons of efficiency lead to the choice of a simple molecular statics model, wherein binary, ternary and quaternary atomic interactions are accounted for and described using Morse and cosine potential functions. The equations of the model are discussed in depth and the parameters of the potential functions are justified in the light of a comparison with ab-initio results. Several case studies regarding zigzag and armchair tubes of different aspect ratios, under compression, bending and torsion, are addressed with the aim of investigating the efficacy of the model and the role of the quaternary interactions, in contexts of both global and local behaviours
La vegetazione del basso corso del Fiume Tevere e dei suoi affluenti (Lazio, Italia). Fitosociologia
No full textThe vegetation of the terminal course of the Tiber River and of its affluents (Latium, Italy). The aquatic and riverbank vegetation of the Tiber River’s
terminal course and of its main affluents (Treia, Farfa, Aniene) are described. The phytosociological approach is applied and, utilizing ecological and
water chemical-physical analysis, it has been possible to define more accurately the synecology of macrophytes communities. This study allowed to
identify thirty-one vegetational types, among which aquatic communities mainly belonged to classes Lemnetea minoris and Potametea pectinati,
bank macrophyte types to Phragmito-Magnocaricetea and, in conditions of higher human disturbance, to Bidentetea tripartitae. The woody riparian
vegetation has been included in Salicetea purpureae and Querco-Fagete
La flora del complesso dei monti Vesole, Soprano, Sottano e Chianello (appennino campano, SA)
No full textGli Autori hanno indagato la flora del comprensorio dei monti Vesole, Soprano, Sottano e Chianello per la quale non esistevano in letteratura dati preesistenti.; tale lavoro va dunque ad integrare le conoscenze realtive alla parte settentrionale del Parco Nazionale del Cilento e Vallo di Diano. Nel corso del lavoro sono state individuate e classificate 861 entità; di queste 21 non risultavano segnalate in precedenza per il territorio del Cilento. Per alcune specie di rilevante interesse fitogeografico (Geranium macrorrhizum L., Ophioglossum vulgatum L., Cleistogenes serotina (L.) Keng, Genista sagittalis L., Lathyrus niger (L.) Bernh. subsp. jordanii (Ten.) Arcangeli) si tratta del primo ritrovamento per la Campania o di conferma della loro presenza nella regione. Nel complesso le 861 entità ritrovate definiscono uno spiccato carattere di mediterraneità del popolamento floristico; ben rappresentato è inoltre il contingente di specie eurasiatiche dovuto allo sviluppo degli orizzonti montano e submontano. Le endemiche ammontano al 4% del totale e fra queste vanno citate le oro-ipsofile Viola pseudogracilis Strobl. subsp. pseudogracilis e Potentilla rigoana T. Wolf. Dall’analisi dello spettro biologico si evince una predominanza di terofite, a conferma del carattere mediterraneo della flora e anche della presenza di aree sottoposte a coltura. Elevato è nel contempo il contingente di fanerofite, dovuto all’ampio sviluppo delle aree boschive e alla diversificazione delle cenosi forestali
Nesting behaviour in Onitis Alexis septentrionalis Balth. (Coleoptera: Scarabaeidae: Onitini)
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