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The last Antilopini bovids from the Early Pleistocene of Italy
No full textRecent fieldwork in the Coste San Giacomo site (Early Pleistocene - Gelasian; central Italy) led us to discover new fossils of the Antilopini bovids Gazella borbonica and Gazellospira torticornis that are presented and discussed in this paper. These taxa have important palaeoenvironmental and biochronological significance during the Early Pleistocene. They were the last Antilopinae that inhabited the Italian peninsula, characterizing the middle Villafranchian large mammal assemblages living in arid and open environments. Gazella is one of the most diverse and widespread genus among Antilopinae subfamily, living today in Africa and in Asia. G. borbonica was the last species that inhabited Europe. In the Italian peninsula, it has been found in three sites: Montopoli, Dianella and Coste San Giacomo. The spiral horn-cored G. torticornis, larger in size than G. borbonica, has been found in the Italian sites of Montecarlo and Coste San Giacomo. Here, we present the study of the Italian record, based in particular on the horn cores. Finally, this material is compared with the remains coming from the coeval European localities
Thermometers at the Nanoscale: a Molecular Approach to Design and Develop Functional Lanthanoid-based Luminescent Materials
Full text linkThe present work is devoted to the development of lanthanoid-based luminescent thermometers and to the study of the correlations between the thermometric properties and the different building blocks composing the systems. In particular, using rare earth cations, b-diketones (H(b-dike)= dibenzoylmethane, Hdbm; benzoyltrifluoroacetone, Hbta; hexafluoroacetylacetone, Hhfac; thenoyltrifluoroacetone, Htta), and divergent ligands (4,4’-bipyridine, bipy; 4,4’-bipyridine-N-oxide, bipyMO; pyrazine-N-oxide, pyrzMO; 2,5-dihydroxy-1,4-dicarboxylate, H2DHT2-) we prepared molecular systems with different dimensionality: i) dinuclear complexes (0D), ii) Coordination Polymers (CPs, 1D), and Metal-Organic Frameworks (MOFs, 3D).
We started with europium β-dike dinuclear compounds with molecular formula [Eu2(β-dyke)6(L-MO)x] (x=3 for hfac, x=2 for dbm, bta, and tta). Substituting the hfac -CF3 groups with phenyl rings (one in bta, two in dbm) or with a thienyl ring (tta) the β-dike electronic and steric properties were modulated. Conversely, the different steric hindrance of bipyMO and pyrzMO influenced the spatial disposition of the β-dike ligands and the inter- and intra-molecular interactions. In the -50 ÷ 100 °C temperature range, the complexes showed relative thermal sensitivity (Sr) values higher than 1 (generally assumed as a quality criterion for these thermometers) that depended on the nature of both the β-dike and L-MO ligands. The β-diketonates influenced Sr values, thermal operative range, and photostability of the system, while pyrzMO-containing compounds showed improved performances (Sr maximum from 4.6 to 8.1 % °C-1 depending on the β-dike ligand) compared to that based on bipyMO (Sr maximum from 3.4 to 5.1 % °C-1).
In the second part, a series of ratiometric Eu3+/ Tb3+ luminescent thermometers were obtained by mixing different quantities of the two homometallic [Ln(hfac)3(bipy)]n 1D-CPs (Ln3+= Eu3+ and Tb3+) in spectroscopically inert KBr. Here, we studied the effect of the relative metal amounts and of the excitation wavelength on the Sr. For all the samples, Sr values almost independent from the Tb/Eu molar ratio and the excitation wavelength were found between -190 and 110 °C. Each sample showed a peculiar temperature-dependent emission colour, from green to red, that was exploited to develop colour-coded thermometers able to distinguish temperature intervals in the order of 10/ 20 °C.
Then we developed a mild-condition synthetic procedure to obtain single crystal to single crystal post-synthesis modifications of the 3D-MOF [Eu2(H2DHT)3(DMF)4]∙2DMF (DMF= N,N-dimethylformamide) to substitute DMF in the channels with different organic molecules (i.e. CHCl3, imidazole, pyridine, and tetrahydrofuran) and to study the Sr modulation. Depending on the guest molecule, the temperature at which Sr reaches the maximum and its value varied from 2.5 at -90 °C to 4.2 % °C-1 at -10 °C.
Molecular compounds like complexes, CPs and MOFs are ideal systems to study the correlations between structure, composition (in the meaning of molecular functionalization) and functional properties because they can be easily modified through chemical processes. Nevertheless, to exploit the unique properties of these compounds in commonly used tools and instruments they need to be integrated into a device. Surface functionalization is a recurrent way to achieve this target. However, maintaining the control on the arrangement of the various building blocks and characterize the functionalized surface is not straightforward, so that the development of “ad hoc” synthetic protocols and methods is required. In this context, we developed a general procedure for surface functionalization. We exploited the reactivity of lanthanoid N,N-dialkylcarbamate complexes to create an ordered Eu3+-Tb3+ heterobimetallic sequence grafted on amorphous silica using terephthalic acid as divergent ligand to connect the two Ln3+ ions. Photoluminescence was here used to determine the spatial disposition of the two metal ions on silica. In particular, Tb3+-to-Eu3+ energy transfer was used as molecular ruler to study the Ln3+ ions spatial distribution and intermetal distances that allow us to obtain data supporting the formation of the desired sequence.Questo lavoro è volto allo sviluppo di termometri molecolari a base di ioni lantanoidei ed allo studio delle correlazioni tra proprietà termometriche ed i diversi building blocks che compongono i sistemi. In particolare, usando cationi lantanoidei, β-dichetoni (H(β-dike)= dibenzoilmetano, Hdbm; benzoiltrifluoroacetone, Hbta; esafluoroacetilacetone, Hhfac; tenoiltrifluoroacetone, Htta), e leganti divergenti (4,4’-bipiridina, bipy; 4,4’-bipiridina-N-ossido, bipyMO; pirazina-N-ossido, pyrzMO; 2,5-diidrossi-1,4-dicarbossilato, H2DHT2-) sono stati preparati sistemi molecolari con diversa dimensionalità: i) complessi dinucleari (0D), polimeri di coordinazione (CPs, 1D) e Metal Organic Frameworks (MOFs, 3D).
Nei complessi dinucleari di europio [Eu2(β-dike)6(L-MO)x] (x=3 per hfac, x=2 per dbm, bta, and tta) le proprietà elettroniche e steriche del β-dichetonato sono state modulate sostituendo i gruppi -CF3 di hfac con anelli fenilici (uno nel bta, due nel dbm) o con un anello tienilico (tta). Il diverso ingombro sterico dei leganti bipyMO e pyrzMO influenzarono invece la disposizione spaziale dei leganti β-dichetonato e le loro interazioni inter- ed intra-molecolari. I complessi mostrarono valori di sensibilità termica relativa (Sr) maggiori di 1 (valore generalmente usato come criterio di qualità per questi termometri) dipendenti dalla natura dei leganti β-dike e L-MO nell’intervallo di temperatura -50 ÷ 100 °C. I leganti β-dichetonato influenzarono i valori di Sr, l’intervallo applicativo di temperature e la fotostabilità dei complessi. I composti contenenti pyrzMO mostrarono performances migliori (Sr massimo da 4.6 a 8.1 % °C-1 a seconda del β-dike) rispetto agli analoghi con bipyMO (Sr massimo da 3.4 a 5.1 % °C-1).
Successivamente è stata ottenuta una serie di termometri luminescenti raziometrici a base di Eu3+ e Tb3+ miscelando diverse quantità dei due polimeri di coordinazione 1D [Ln(hfac)3(bipy)]n (Ln3+= Eu3+ e Tb3+) in KBr (inerte dal punto di vista spettroscopico). In questo caso è stato studiato l’effetto su Sr della quantità relativa dei due ioni metallici e della lunghezza d’onda di eccitazione nell’intervallo -190 ÷ 110 °C. Per tutti i campioni i valori di Sr risultarono non influenzati dal rapporto molare Tb/Eu e dalla lunghezza d’onda di eccitazione. Ciascun campione mostrò un peculiare colore emesso (dal verde al rosso) in funzione della temperatura. Ciò è stato sfruttato per sviluppare termometri basati su codici di colori capaci di distinguere intervalli di temperatura di 10/ 20 °C.
È stata inoltre sviluppata una procedura basata su condizioni blande per attuare la modifica post-sintetica da cristallo singolo a cristallo singolo del MOF [Eu2(H2DHT)3(DMF)4]∙2DMF (DMF= N,N-dimetilformamide) sostituendo la DMF nei canali con diverse molecole (CHCl3, imidazolo, piridina e tetraidrofurano) per studiare la modulazione di Sr. A seconda della molecola ospitata, la temperatura alla quale si raggiunge il massimo di Sr e il suo valore variarono da 2.5 a -90 °C a 4.2 % °C-1 a -10 °C.
Composti molecolari come complessi, CPs e MOFs sono ideali per lo studio delle correlazioni tra struttura, composizione (nel senso di funzionalizzazione molecolare) e proprietà funzionali in quanto facilmente modificabili tramite processi chimici. Tuttavia, è necessario integrare questi sistemi in dispositivi per sfruttare le loro proprietà in strumenti di uso comune. La funzionalizzazione di superfici è una procedura comunemente usata per questo scopo. In questo caso tuttavia, non è semplice mantenere il controllo sulla disposizione dei vari building blocks e caratterizzare la superficie funzionalizzata così che è fondamentale sviluppare un adeguato protocollo sintetico. In questo contesto, è stata messa a punto una procedura sintetica per la funzionalizzazione di superfici. Per questo scopo è stata sfruttata la reattività degli N,N-dialchilcarbammati lantanoidei per creare una sequenza eterobimetallica Eu3+-Tb3+ ordinata aggraffata su silice amorfa, usando l’acido tereftalico come legante divergente per connettere i due centri metallici. La fotoluminescenza è stata qui utilizzata per determinare la distribuzione spaziale dei due ioni metallici sulla silice. In particolare, fenomeni di trasferimento energetico dal Tb3+ all’Eu3+ sono stati usati come righello molecolare per determinare la distribuzione e le distanze intermetalliche ottenendo dati a supporto della formazione della sequenza desiderata
Hippopotamus remains in the middle Villafranchian Faunal assemblages of Anagni basin (Central Italy): evidence for an early dispersal of the genus in Europe
No full textGG from CSG: the Middle Villafranchian antilopine bovids from Coste San Giacomo (Anagni Basin, central Italy)
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New paleontological data from the earliest Pleistocene site of Coste San Giacomo (Anagni basin, central Italy)
No full textThe Gelasian (Late Villanyan-MN17) diversified micromammal assemblage with Mimomys pliocaenicus from Coste San Giacomo (Anagni basin, central Italy), taxonomy and comparison with selected european sites
Full text linkThe Gelasian site of Coste San Giacomo (CSG) (central Italy) provides a unique opportunity to investigate the faunal and environmental changes occurred in Mediterranean Europe during the Early Pleistocene. The finding of both large and small mammal fauna has a great biochronological and palaeoenvironmental value. In this work the description of the small mammal assemblage is presented and discussed in detail for the first time. Twelve taxa, belonging to three orders, have been in fact identified and described (six Rodentia, one Lagomorpha and five Eulipotyphla). In particular, the CSG small mammal assemblage has provided the largest collection in Europe of Mimomys pliocaenicus and, for this reason, it can be considered as a reference. Finally, the occurrence of the Desmaninae subfamily is reported for the first time in Italy. © 2015 Associazione Teriologica Italiana
In silico design, building and gas adsorption of nano-porous graphene scaffolds
Full text linkGraphene-based nano-porous materials (GNM) are potentially useful for all those applications needing a large specific surface area (SSA), typical of the bidimensional graphene, yet realized in the bulk dimensionality. Such applications include for instance gas storage and sorting, catalysis and electrochemical energy storage. While a reasonable control of the structure is achieved in micro-porous materials by using nano-micro particles as templates, the controlled production or even characterization of GNMs with porosity strictly at the nano-scale still raises issues. These are usually produced using dispersion of nano-flakes as precursors resulting in little control on the final structure, which in turn reflects in problems in the structural model building for computer simulations. In this work, we describe a strategy to build models for these materials with predetermined structural properties (SSA, density, porosity), which exploits molecular dynamics simulations, Monte Carlo methods and machine learning algorithms. Our strategy is inspired by the real synthesis process: starting from randomly distributed flakes, we include defects, perforation, structure deformation and edge saturation on the fly, and, after structural refinement, we obtain realistic models, with given structural features. We find relationships between the structural characteristics and size distributions of the starting flake suspension and the final structure, which can give indications for more efficient synthesis routes. We subsequently give a full characterization of the models versus H2 adsorption, from which we extract quantitative relationship between the structural parameters and the gravimetric density. Our results quantitatively clarify the role of surfaces and edges relative amount in determining the H2 adsorption, and suggest strategies to overcome the inherent physical limitations of these materials as adsorbers. We implemented the model building and analysis procedures in software tools, freely available upon request
Large mammal biochronology framework in Europe at Jaramillo. The Epivillafranchian as a formal biochron
No full textEuropean large mammal assemblages in the 1.2-0.9 Ma timespan included Villafranchian taxa together with newcomers, mostly from Asia, persisting in the Middle Pleistocene. A number of biochronological schemes have been suggested to define these "transitional" faunas. The term Epivillafranchian, originally proposed by Bourdier in 1961 and reconsidered as a biochron by Kahlke in the 1990s, is at present widely introduced in the literature. This contribution, after selecting the most representative European large mammal assemblages within this chronological interval, provides a new definition proposal for the Epivillafranchian as a biochron included within the Praemegaceros verticornis FO/Bison menneri FO, and Crocuta crocuta FO
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