23 research outputs found
Effetti del cambiamento climatico e indicatori di stress per le specie ittiche
La definizione di strategie di adattamento ai cambiamenti climatici si articola su un ampio spettro di scale spaziali e temporali, e richiede un concerto di azioni diverse, integrate e sussidiarie a seconda del contesto considerato.
L’Autorità di bacino del fiume Arno ha sviluppato da tempo una linea di ricerca tesa a valutare le peculiarità del cambiamento globale in atto nel territorio del bacino, attraverso l’attività di uno specifico laboratorio territoriale permanente. I risultati mostrano la validità dell’approccio e l’evidente deriva che caratterizza la non stazionarietà del regime delle portate alle scale d’interesse per la pianificazione territoriale.
Ai fini del presente lavoro si pone particolare attenzione alla deriva del regime di portata che, a partire dagli anni ’70, mostra una sensibile riduzione della disponibilità idrica e una progressiva asimmetria rispetto agli usuali contributi stagionali. Tale effetto al suolo rispecchia gli aspetti del cambiamento climatico in termini di distribuzione spaziale e temporale delle precipitazioni e dell’andamento delle temperature.
Tra gli indicatori di vulnerabilità l’evoluzione dell’Area Disponibile Ponderata (ADP, Bovee et al. 1998), in funzione dei
diversi regimi, si è mostrata un indicatore efficace al quale è possibile affiancare specifici segnali di stress.
Per questo si è effettuato un rilievo di dettaglio del fondo dell’alveo in un tronco posto nella sezione di chiusura del bacino laboratorio e, fissata la specie bersaglio nel barbo in fase riproduttiva, si è calcolata l’ADP utilizzando un modello idrodinamico bidimensionale a elementi finiti. Si è poi effettuata l’analisi della serie storica (quasi secolare) delle portate osservate scegliendo, come riferimento, la permanenza della portata media giornaliera al disotto del 50% e del 70% dell’ADP per due giorni consecutivi ed oltre.
I risultati mostrano una forte dinamica del dato che, sopratutto negli ultimi dieci anni, indica un incremento notevole del numero di eventi e dei giorni di permanenza. Mostrano inoltre la validità dell’approccio seguito che tende a fornire una indispensabile dimensione temporale all’analisi alla scala del meso- e del microhabitat
New eastern limit of the geographic distribution of Orsinigobius punctatissimus (Canestrini, 1864) (Teleostei: Gobiiformes: Gobiidae) in northeastern Italy, with biological notes on the species
A record of the gobiid Orsinigobius punctatissimus (Canestrini, 1864) from the springs of the Gorizia Karst (Italy, Friuli-Venezia Giulia) is reported, extending the eastern limit of the geographic distribution of the species. This goby lives in threatened spring habitats, and has recently become rarer. However, although O. punctatissimus is listed in the Italian Red List of threatened species as “Critically Endangered” (CR), the International Union for Conservation of Nature Red List of threatened species classifies it as “Near Threatened” (NT). Despite its risk of extinction, the species is not included in the annexes of the Habitat Directive (EU Directive 92/43/EEC) or other international wildlife protection conventions. Information is given on the taxonomy, distribution, biology and conservation of the species
Thermal, mechanical and rheological behaviors of nanocomposites based on UHMWPE/paraffin oil/carbon nanofiller obtained by using different dispersion techniques.
Ultra-high molecular weight polyethylene (UHMWPE) is a very attractive polymer employed as a high performance material. For its high viscosity, dispersion of fillers is considered a critical point in UHMWPE nanocomposites preparation process. Currently, paraffin oil (PO) is used extensively to overcome this issue in an assisted melt-mixing process. In this work, we have prepared nanocomposites based on UHMWPE, carbon nanofiller (CNF) and PO mixed by different mixing methods: magnetic stirring, ball milling (BM), ultrasonic and Mini-Lab extruder (EX). The aim of this work was to check the effect of the dispersion method on the mechanical and thermal features of UHMWPE/CNF nano composites in order to obtain a material with improved mechanical and physical properties. The samples were characterized by calorimetric, density, mechanical tensile and rheological analyses. Experimental results highlighted that the nanocomposites produced by EX and BM exhibits the best dispersion, good filler matrix interaction and had significantly improved mechanical properties compared to pure UHMWPE. For instance, for the BM method, the yield strength improved to 18.6 MPa (+96%), the yield strain improved by 60%, while stress at break improved by 13%. In summary, the EX improved the stiffness while the BM produced better ductility, melting temperature and the crystalline degree of the nanocomposites
Processing and characterization of bio-polyester reactive blends: From thermoplastic blends to cross-linked networks
The addition of ethyl ester L-lysine tri-isocyanate (LTI) to mixtures of poly(lactide)/poly(ε-caprolactone) has been reported to improve the compatibility of the resulting blends. In the present work, we have investigated the influence of adding increasing amounts of LTI to the mechanical and thermal properties of the blends. Torque trends, plate-plate rheology, differential scanning calorimetry, scanning electron microscopy, and uniaxial tensile characterization were conducted on samples with amounts of LTI comprised between 0.5 and 5 phr. Results suggests that by increasing the content of LTI over 0.5 phr the mechanical and thermal behaviour of the blends tend to change from that of a thermoplastic to that of a cross-linked, rubber-like material with outstanding mechanical properties. Morphological investigations show a very fine, well-dispersed morphology in all cases. Numerical models have been applied to rheological experiments to identify processes and phases in the studied blends, further supporting the hypothesis of a cross-linked phase formed for blends containing more than 0.5 phr of LTI
Effect of Ethyl Ester L-Lysine Triisocyanate addition to produce reactive PLA/PCL bio-polyester blends for biomedical applications
We report in this paper the effects of Ethyl Ester L-Lysine Triisocyanate (LTI) on the physical-mechanical properties of Poly(lactide)/Poly(ε-caprolactone) (PLA/PCL) polyesters blends. The PLA/PCL ratios considered were 20/80, 50/50 and 80/20 (wt/wt %) and LTI was added in amounts of 0.0-0.5-1.0 phr. PLA and PCL reacted with LTI during processing in a Brabender twin screw internal mixer to produce block copolymers in-situ. The resulting blends have been characterized by torque measurements, uniaxial tensile tests, Differential Scanning Calorimeter, contact angle measurements with a Phosphate Buffered Saline (PBS) solution, ATR analysis and morphological SEM observations. Experimental results highlighted how LTI enhanced interaction and dispersion of the two components, resulting into a synergic effect in mechanical properties. Mechanical and physical properties can be tailored by changing the blend composition. The most noticeable trend was an increase in ductility of the mixed polymers. Besides, LTI decreased blend’s wet ability in PBS and lowered the starting of crystalline phase formation for both polymers, confirming an interaction among them. These reactive blends could find use as biomedical materials, e.g. absorbable suture threads or scaffolds for cellular growth
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A global assessment of freshwater fish introductions in Mediterranean-climate regions
Mediterranean-climate regions (med-regions) are global hotspots of endemism 40 facing mounting environmental threats associated with human-related activities, including the ecological impacts associated with non-native species introductions. We review freshwater fish introductions across med-regions to evaluate the influences of non-native fishes on the biogeography of taxonomic and functional diversity. Our synthesis revealed that 136 freshwater fish species (26 families, 13 orders) have been introduced into med-regions globally. These introductions, and local extirpations, have increased taxonomic and functional faunal similarity among regions by an average of 7.5% (4.6-11.4%; Jaccard) and 7.2% (1.4-14.0%; Bray-Curtis), respectively. Faunal homogenization was highest in Chile and the western Med Basin, whereas sw Cape and the Aegean Sea drainages showed slight differentiation (decrease in faunal similarity) over time. At present, fish faunas of different med-regions have widespread species in common (e.g. Gambusia holbrooki, Cyprinus carpio, Oncorhynchus mykiss, Carassius auratus, and Micropterus salmoides) which are typically large-bodied, non migratory, have higher physiological tolerance, and display fast population growth rates. Our findings suggest that intentional and accidental introductions of freshwater fish have dissolved dispersal barriers and significantly changed the present-day biogeography of med-regions across the globe. Conservation challenges in med-regions include understanding the ecosystem consequences of non-native species at macro-ecological scales.This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10750.Keywords: Conservation biogeography, Introduced species, Non-native species, Taxonomic homogenization, Functional homogenizatio
Effect of Ethyl Ester L-Lysine Triisocyanate addition to produce reactive PLA/PCL bio-polyester blends for biomedical applications
This paper was accepted for publication in the journal Journal of the Mechanical Behavior of Biomedical Materials and the definitive published version is available at http://dx.doi.org/10.1016/j.jmbbm.2017.02.018We report in this paper the effects of Ethyl Ester L-Lysine Triisocyanate (LTI) on the physical-mechanical properties of Poly(lactide)/Poly(ε-caprolactone) (PLA/PCL) polyesters blends. The PLA/PCL ratios considered were 20/80, 50/50 and 80/20 (wt/wt %) and LTI was added in amounts of 0.0-0.5-1.0 phr. PLA and PCL reacted with LTI during processing in a Brabender twin screw internal mixer to produce block copolymers in-situ. The resulting blends have been characterized by torque measurements, uniaxial tensile tests, Differential Scanning Calorimeter, contact angle measurements with a Phosphate Buffered Saline (PBS) solution, ATR analysis and morphological SEM observations. Experimental results highlighted how LTI enhanced interaction and dispersion of the two components, resulting into a synergic effect in mechanical properties. Mechanical and physical properties can be tailored by changing the blend composition. The most noticeable trend was an increase in ductility of the mixed polymers. Besides, LTI decreased blend’s wet ability in PBS and lowered the starting of crystalline phase formation for both polymers, confirming an interaction among them. These reactive blends could find use as biomedical materials, e.g. absorbable suture threads or scaffolds for cellular growth
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New eastern limit of the geographic distribution of Orsinigobius punctatissimus (Canestrini, 1864) (Teleostei: Gobiiformes: Gobiidae) in northeastern Italy, with biological notes on the species
A record of the gobiid Orsinigobius punctatissimus (Canestrini, 1864) from the springs of the Gorizia Karst (Italy, Friuli-Venezia Giulia) is reported, extending the eastern limit of the geographic distribution of the species. This goby lives in threatened spring habitats, and has recently become rarer. However, although O. punctatissimus is listed in the Italian Red List of threatened species as “Critically Endangered” (CR), the International Union for Conservation of Nature Red List of threatened species classifies it as “Near Threatened” (NT). Despite its risk of extinction, the species is not included in the annexes of the Habitat Directive (EU Directive 92/43/EEC) or other international wildlife protection conventions. Information is given on the taxonomy, distribution, biology and conservation of the species