3,155 research outputs found
Stratigraphic analysis on Monte Agnello and Latemar platforms (Southern Alps, Dolomites, Italy)
No full textIntroduction
Cyclostratigraphy is emerging as a central focus in stratigraphy, with its impressive record of global climate changes forced by Earth’s astronomical parameters, and with its capacity to provide high- resolution information about geologic time. Shallow-marine cyclostratigraphy, principally from carbonate-rich peritidal facies, represents the main source of information about astronomical forcing and global climate change prior to the Jurassic. Mineral magnetic parameters (MS, ARM, SIRM, S-ratio, ARM/MS and ARM/SIRM ratio) provide new information about shallow-marine cyclostratigraphy. They reveal a coherent signal indicating magnetic concentration variations in tune with a depth index derived from facies cyclicity (Mayer & Appel, 1999).
The Dolomites area of the Southern Alps (Italy) was characterized, at the end of the Anisian (Middle Triassic), by an episode of exceptionally high subsidence, that caused dramatic aggradation of isolated carbonate platforms. Some carbonate buildups grew up to 700 m (e.g., Brack et al., 2007) until subsidence rates dropped and a progradational phase began (Bosellini, 1984). Thanks to the exceptional preservation and exposure, the sedimentary cyclicity of the Latemar and Monte Agnello platform interiors, represented by high order peritidal cycles, is evident.
The combined study of facies and magnetic parameters is a powerful tool in investigating cyclicities and opens new issues about its origin.
Growth history of the Agnello Platform
Strong dolomitization characterizes the whole platform, making thus impossible every kind of study regarding magnetic parameters. Nonetheless collected field data allowed to reconstruct the growth history of the buildup, a carbonate platform never studied by anyone.
A detailed geological mapping of Monte Agnello platform was undertaken and geological data were draped on a high resolution Digital Terrain Model in order to evaluate the geometrical parameters of the platform. Stratigraphic sections were logged within the upper slope-margin-lagoon progradational system, and the microfacies of the platform interior were compared with those of the nearby aggradational Latemar platform. A biostratigraphic study of dasycladacean algae and scattered ammonoids findings was also carried out, but yielded few results. However, ammonoids of the avisianum and crassus subzones were recovered in the lower-middle part of the aggradational platform interior. It was possible to reconstruct the growth history of this platform. The Agnello massif preserves a portion of a carbonate platform that was prograding towards North, although it is impossible to determine whether the platform was isolated or attached to a putative southern structural high. It grew nearly 600 m until subsidence rates suddenly dropped, and then prograded at least 3.5 km; the buildup reached a total thickness of about 700 m. Clinoforms are steep, 30° on average. The platform sediments are sealed by a subaerial pyroclastic succession that lies on a slightly karstified surface. Extended microbial crusts (including common Tubiphytes), and corals characterized margin and upper slope during the progradational phase. The inner platform is constituted by submetric peritidal sedimentary cycles with prevailing subtidal facies. Microfacies are more micritic, and grains more deeply micritized than those of the aggrading Latemar platform, reflecting longer residence time of lagoonal sediments before burial. Well developed tepee belts as those of the Latemar platform are absent. Thin sections analysis reveals that sedimentary environments changed significantly in the lagoon at the switch from aggradation to progradation. The thickness of the platform is comparable or higher than that of other coeval platforms in the Southern Alps, including those that underwent drowning in the Late Anisian. This suggests that strong subsidence was not the primary cause of drowning, although it may have enhanced the effects of paleoceanographic or climatic factors as suggested by Preto et al. (2005) and Brack et al., (2007).
The petrological and magnetic mineral composition of the Latemar cycles
The Latemar massif appears to be more suitable than Monte Agnello for magnetic analysis because several portions of the platform are not affected by dolomitization. 102 m of inner platform series were sampled at Cimon del Latemar in order to investigate MS, ARM, SIRM, S-ratio, ARM/MS and ARM/SIRM ratio. SEM observation and Lowrie Test were carried out on a subset of samples to determine the mineralogy of the magnetic grains. All the measurements were made in collaboration with prof. Ken Kodama (Lehigh University, Bethlehem, USA) while the spectral analysis was performed with the collaboration of prof. Linda Hinnov (Johns Hopkins University, Baltimore, USA).
The results obtained are here summarized:
Facies measurements exhibit a cyclic pattern. The spectra obtained from the facies rank are anyway quite noisy: that happens because facies ranking is obtained from the basis of interpretation. Problems are still present in the definition of a sedimentary cycle and in its recognition on the field.
A clear cyclic signal emerges from the spectra related to the magnetic parameters. Some of the parameters chosen are more suitable than other for a cyclostratigraphic purpose because it depends on what each parameter is measuring. For example, MS, measuring all the magnetic components of the rock (diamagnetic, paramagnetic and ferromagnetic), is not a good tool in the case of carbonate rocks. The carbonate component is prevailing on the ferromagnetic minerals, masking in this way their contribution. ARM and SIRM are the best parameters because they measure only the ferromagnetic component (all the minerals in the matter of SIRM, low coercivity components in the matter of ARM).
A comparison between the spectra from rank series and magnetic parameters reveals a correlation among them. Two meaningful peaks describing a 5:1 ratio emerge in both cases and they are in the same frequency range.
Box-plot and covariance tests were applied but facies ranking and magnetic parameters appear independent. The correlation between the two is close to zero. This means that they are related to different causes, even if they reveal cyclities beating at the same time. Facies ranking is thus easily linked to sea level changes (exhibiting an alternation of subtidal and supratidal facies), while magnetic parameters reveal values falling in the range of aeolian dust (Oldfield et al. 1985, Hounslow and Maher, 1999).
We can observe in the field two kinds of cycles: a first on one the order of 1 m and a second one one the order of 5 m. They are physical expression of the 5:1 ratio clearly visible also in the spectra. They are traditionally related to the Milankovian parameters of eccentricity and precession occurring every 100 and 22 Kyrs. This implies a 10 Myrs time span for the whole Latemar platform. Radiometric ages instead give instead less than 1 Myr time span for the buildup. In this case, the 5:1 bundling should refer to sub-Milankovitch cycles of unknown origin. Magnetic data do not reveal if the cyclic pattern refers to a Milankovitch or a sub-Milankovitch signal, even if calculations made on the basis of the periodograms suggest a sub-Milankovitch forcing for the 1 m cycle, giving thus reason to radiometric data.
Another problem emerged during sampling the Latemar platform: field observations suggested a much higher microbial (sensu Burne and Moore, 1985) component compared to literature data. This was evident especially in the fore-reef/upper slope zone, were microbials clearly extended for thousands of m up to 350/400 m deep. Point counting analysis in thin sections of reef, slope and inner platform confirmed field evidence. All components were grouped in 5 categories: skeletal grains, allomicrite, microbialite, cements and voids. Quantitative analysis was carried out for each portion of the platform: inner platform, reef and slope. Cements and microbialite are the most represented categories. The difficult distinction between early marine and burial cements does not allow a precise estimate of the microbial contribution to cements. In order to maintain a conservative estimate we decided to group all cements in one category. The percentages of the components were thus recalculated omitting cements; the results are shown in the table below. Our results were found to be similar to those reported for the Sella platform by Keim and Schlager (2001). We thus suggest that the Latemar buildup developed following the M-Factory model (Schlager 2000, 2003). Microbial contribution seems to be higher on the slope, although the whole platform is affected by wide microbial communities, especially in the supratidal inner lagoon facies.
Furthermore, three new facies were observed in the platform interior. They are located 150-200 m from the margin and represent, with the only exception of few millimetric dolomitic caps, a subtidal environments. This facies association is different from the classical facies description of the inner platform (Preto et al. 2001, 2003): no shallowing upward cycles can be identified. These new facies described, combined with the recent new “horseshoe” shape of the platform proposed by Preto et al. (2011) suggest a new depositional model for the Latemar. From the slope to the central portion of the inner platform depth progressively decreases. The paleorelief of the Latemar was thus mounded in terms of geometries, with the highest area (cyclically subaerially exposed) placed exactly in the middle of the platform interior, where widespread teepee belt developed. This new model strongly differs from the one proposed by Egenhoff et al. (1999), wehere teepee belt, expression of supratidal environments are considered a belt isolating a submerged inner lagoon from a margin, submerged too.Introduzione
Lo studio della Ciclostratigrafia, grazie all’incredibile numero di informazioni e all’alta risoluzione dei dati che fornisce riguardo ai cambiamenti climatici legati a parametri astronomici, rappresenta ormai un punto cardine della stratigrafia. In particolare, studi ciclostratigrafici su sedimenti di acque basse, specialmente carbonati ricchi in facies intertidali, rappresenta una delle principali fonti di informazione riguardo alle variazioni climatiche e al forcing astronomico da tempi recenti sino al Giurassico. Nuove informazioni sulla ciclostratigrafia di ambienti marini di acque basse può essere fornita dallo studio di alcuni parametri (MS, ARM, SIRM, S-ratio, ARM/MS e ARM/SIR) ricavabili da minerali magnetici di origine detritica. L’analisi delle curve legate alle variazioni di concentrazione di questi minerali rivela marcate similitudini con le variazioni di profondità ricavabili dall’analisi di facies(Mayer & Appel, 1999). L’area delle Dolomiti, nelle Alpi
Meridionali (Italia) è stata interessata da un episodio di forte subsidenza durante l’Anisico sommitale (Triassico Medio) che ha portato ad una forte aggradazione di piattaforme carbonatiche isolate. Alcune di esse hanno raggiunto spessori pari a 700 m (es., Brack et al., 2007) prima che la subsidenza cessasse improvvisamente per lasciare spazio ad una fase progradante (Bosellini, 1984). Le piattaforme carbonatiche del Monte Agnello e del Latemar, grazie alla loro ottima preservazione ed esposizione degli affioramenti, mostrano molto bene la ciclicità della piattaforma interna, rappresentata da cicli peritidali di sesto ordine.
Lo studio combinato di facies e parametri magnetici rappresenta dunque un potente mezzo per studiare la ciclicità ed apre nuovi orizzonti circa le sue origini.
Extended abstract (italiano)
La piattaforma del Monte Agnello progradante, con clinoformi rivolte a nord, sebbene sia impossibile determinare se la piattaforma fosse o meno attaccata a qualche alto strutturale presente nell’area. La fase aggradante ha portato alla deposizione di circa 600 m di piattaforma, prima dell’improvvisa diminuzione del tasso di subsidenza. Una progradazione di almeno 3.5 Km è seguita, portando ad uno spesso- re totale della piattaforma di 700 m. Le clinoformi sono ripide, 30° in media. I sedimenti di piattaforma sono coperti da flussi piroclastici subaerei che si sono deposti su una superficie debolmente carsificata. Estese croste microbialitiche e coralli caratterizzano il margine e la porzione sommitale della scarpata surante la fase progradante. La piataforma interna è costituita da da cicli peritidali submetrici con una prevalenza di facies subtidali. Le microfacies sono più micritiche ed i grani molto più micritizzati rispetto a quelli presenti nella porzione aggradante della piattaforma interna del Latemar. Ciò è espressione di un maggior tempo di residenza dei sedimenti prima del seppellimento. Sono assenti le ben sviluppate fasce a teepee che invece si ritrovano nel Latemar. L’analisi in sezione sottile delle rocce di piattaforma mostra un significativo cambiamento nell’ambiente di sedimentazione al passaggio tra aggradazione e progradazione. Lo spessore della piattaforma è comparabile o addirittura maggiore rispetto alle altre piattaforme coeve.
Nessuno studio circa le proprietà magnetiche è stato possibile per quanto riguarda la piattaforma del Monte Agnello a causa della forte dolomitizzazione che contraddistingue l’intero edificio. Ciononostante, durante il rilevamento dell’area sono stati raccolti numerosi dati che hanno permesso di ricostruire la storia della piattaforma, di cui non sono presenti dati in bibliografia.
Un rilevamento geologico dettagliato della piattaforma ha prodotto una carta successivamente unita ad un Modello Digitale del Terreno (DTM): in questo modo è stato possibile visualizzare le geometrie della piattaforma. Due sezioni stratigrafiche sono state misurate nella porzione progradante della piattaforma comprendenti il passaggio scarpata-margine-laguna interna. Le microfacies della piattaforma interna sono state confrontate con quelle provenienti dalla porzione aggradante della coeva piattaforma del Latemar. Lo studio biostratigrafico su alghe dasycaldacee e ammonoidi non ha permesso precise datazioni, soprattutto a causa dell’assenza di campioni di ammonoidi ritrovati in situ. I campioni di ammonoidi ritrovati appartengono alle subzone ad avisianum e crassus. Il massiccio del Monte Agnello preserva una porzione della fase
delle Alpi Meridionali, comprese quelle annegate durante l’Anisico sommitale. Sulla base di queste osservazioni, la subsidenza potrebbe non essere la causa primaria dell’annegamento delle piattaforme: potrebbe bensì aver enfatizzato gli effetti legati a fattori paleoceanografici o paleclimatici come suggerito da Preto et al. (2005) e Brack et al. (2007)
La composizione petrografica e magnetica dei cicli del Latemar.
Il massiccio del Latemar è più adatto per analisi di tipo magnetico rispetto alla piattaforma del Monte Agnello in quanto diverse sue porzioni non risultano affette da dolomitizzazione. 102 m di piattaforma interna sono stati campionati sul Cimon del Latemar per studiare l’andamento di MS, ARM, SIRM, S-ratio, ARM/MS e ARM/SIRM. Per determinare la mineralogia dei granuli magnetici una serie di campioni è stata sottoposta ad indagini attraverso microscopio elettronico a scansione (SEM) e il Test di Lowrie. Le prove di laboratorio sono state condotte in collaborazione con il prof. Ken Kodama (Università di Lehigh, Bethlehem, USA), mentre l’analisi spettrale è stata condotta in collaborazione con la prof. Linda Hinnov (Università Johns Hopkins, Baltimora, USA). I risultati ottenuti sono i seguenti:
L’analisi spettarele delle facies mostra un pattern ciclico. Gli spettri ottenuti sono comunque piuttosto rumorosi, un problema imputabile al fatto che la determinazione delle facies è basata sull’interpretazione del dato di terreno. Inoltre, ancora vi sono incertezze circa la definizione e l’identificazione di un ciclo sedimentario.
Un chiaro segnale ciclico emerge dall’analisi spettrale dei parametri magnetici. Alcuni dei parametri scelti appaiono migliori di altri. Per esempio la suscettibilità magnetica (MS), misurando tutte le componenti magnetiche di una roccia (dia, para e ferromagnetica), non risulta essere un buon parametro nei carbonati. La componente carbonatica infatti prevale nettamente sui minerali ferromagnetici mascherandone il contributo. ARM e SIRM sono i parametri migliori in quanto misurano solo la componente ferromagnetica (rispettivamente delle fasi a bassa coercitività nel caso di ARM, di tutte le fasi mineralogiche nel caso di SIRM).
Il confronto tra gli spettri delle facies e quelli dei parametri magnetici mostra importanti similitudini. Due picchi significativi sono presenti in entrambi i casi nello stesso range di frequenza, e mostrano un rapporto tra essi di 5:1
Test statistici (box-plot e analisi di covarianza) sono stati applicati per testare la dipendenza tra facies e parametri magnetici. La correlzione tra loro è tuttavia vicina allo zero, quindi essi sembrano indipendenti. La ciclcità che entrambi mostrano presenta tuttavia nella stessa frequenza: ciò significa che facies e parametri magnetici variano per cause differenti. Le variazioni nelle facies sono facilmente interpretabili come risposta a variazioni eustatiche (alternanza tra facies subtidali e supratidali), mentre i valori legati ai parametri magnetici suggeriscono un legame con l’apporto di eolico di polveri (Oldfield et al., 1985; Hounslow e Maher, 1999).
Sul terreno si possono riconoscere due tipo di cicli: uno dell’ordine di un metro, il secondo dell’ordine di 5 m. Essi sono espressione fisica del rapporto 5:1 visibile dagli spettri. Tradizionalmente essi vengono messi in relazione con i parametri Milankoviani di eccentricità e precessione, che si ripetono rispettivamente ogni 100.000 e 22.000 anni. Ciò implicherebbe una durata di sviluppo della piattaforma di 10 milioni d’anni. Dati radiometrici indicano invece che il Latemar si è sviluppato in meno di un milione d’anni: il rapporto di 5:1 evidenziato da facies e parametri magnetici dovrebbe dunque riferirsi a ciclicità submilankoviane di origine al momento sconosciuta. L’analisi dei dati magnetici non permette di capire se il segnale registrato dalle rocce abbia carattere Milankoviano o sub-Milankoviano, sebbene l’analis dei periodogrammi suggerisca una relazione tra il ciclo metrico e un forcing sub-Milankoviano, assecondando i dati radiometrici.
Un nuovo ed interessante problema è poi emerso durante il campionamento della piattaforma del Latemar: sul terreno la componente di origine microbiale (sensu Burne and Moore, 1985) sembra essere molto maggiore rispetto a quanto sinora presente in letteratura. Questo dato è particalrmente evidente nella regione compresa tra il margine esterno e la porzione superiore della scarpata, sulla quale bound-stone microbiali si estendono sino a 350-400 m di profondità. Questa evidenza è stata confermata dai conteggi svolte sulle sezioni sottili di campioni di margine, scarpata e piattaforma interna. Le varie componenti sono state suddivise in 5 categorie: granuli scheletrici, allomicrite, microbialite, cementi e vuoti. Un’analisi quantitative delle componenti è stata svolta su tutte le porzioni di piattaforma. Cementi e microbialite sono le categorie maggiormente rappresentate. La difficile distinzione tra cementi marini precoci e cementi legati a seppellimento non ha permesso una precisa stima del contributo organico sulla precipitazione del cemento, quindi per ottenere una stima maggiormente conservativa si è scelto di raggruppare tutti i cementi in un’unica categoria. I risultati ottenuti sono simili ai dati di Keim e Schlager (2001) per la piattaforma del Sella. Un dato che suggerisce come la piattaforma del Latemar possa essersi sviluppata seguendo il modello della M-factory (Schlager, 2000,
2003). Il contenuto di microbialite sembra essere maggiore nella scarpata, sebbene l’intera piattaforma sia caratterizzata dalla presenza di microbiliti, specialmente nelle facies supratidali della piattaforma interna.
Tre nuove facies infine sono state descritte nella piattaforma interna. Esse si rinvengono a circa 150- 200 metri dal margine e rappresentano ambienti subtidali, eccezzion fatta per pochi millimetrici livelli dolomitizzati. Questa associazione di facies è diversa da quella classica descritta per la piattaforma interna (Preto et al. 2001, 2003): non vi sono evidenze di cicli sedimentari. La descrizione di queste nuove facies, unita alla recente forma a ferro di cavallo proposta da Preto et al. (2011) per la piattaforma, permette di ipotizzare un nuovo modello deposizionale per il Latemar. Partendo dallo slope e muovendosi verso la porzione centrale della piattaforma interna si evidenzia una progressiva diminuzione della paleoprofondità. Il paleorilievo del Latemar risulterebbe dunqe arrotondato, presentando la parte più rilevata (e ciclicamente esposta ad emersione) esattamente al centro della piattaforma, proprio dove si vedono oggi le fasce a teepee. Questo nuovo modello differisce di molto rispetto a quello proposto da Egenhoff et al. (1999), dove le fasce a teepee, rappresentanti ambienti supratidali, vengono identificate come la porzione esterna della piattaforma capace di isolare una laguna interna sommersa
A imagem de Alessandro Baricco no Brasil
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Estudos da Tradução, Florianópolis, 2013.Com a intenção de delinear o modo pelo qual o escritor italiano Alessandro Baricco se inseriu no sistema literário brasileiro e os caminhos percorridos pelos seus livros traduzidos, esta dissertação dá voz às experiências tradutórias de seus tradutores. A inserção de Bariccono Brasil tem seu início em 1997, através de uma proposição da Profa. Dra. Roberta Barni à editora Iluminuras da tradução de Oceano Mare. A partir daí, outras sete obras foram publicadas no Brasil, sendo três delas traduzidas por Roberta Barni e as outras quatro por quatro tradutores diferentes. De um lado, considera-se o tradutor como figura principal namediação entre culturas, e, de outro, se analisa a realidade desta figuradentro do sistema literário, sua invisibilidade, seus limites e o exercíciode sua profissão. A pesquisa conta, ainda, com críticas e resenhas referentes ao autor italiano publicadas em jornais consagrados no Brasil, considerando estas como parte constituinte da imagem de Baricco refletida em território nacional. Abstract : Intending to delineate the way the Italian writer Alessandro Baricco has been inserted in the Brazilian literary system and the paths his translated books have followed, this thesis gives voice to the translating experiences of his translators. Baricco's insertion in Brazil began in 1997, through a personal project of Dr. Roberta Barni, with her translation of Oceano Mare. Since then, seven other of his works have been published in Brazil, three of which were translated by Roberta Barni and the other four by four different translators. On the one hand,the translator is considered as the main figure in mediation betweencultures and, on the other, this figure's reality is analyzed within theliterary system: its invisibility, its limits and its professional practice. Criticisms and reviews of this Italian author published in well established Brazilian newspapers are also considered, with the understanding that they are part of Baricco's image reflected here
Linear and non-linear structural analysis of notched components with local energy approaches
No full textIn engineering practice, mechanical components are weakened by a wide range of sharp or blunt notches and their presence has to be accurately taken into account in the design. In fact near notches a strong stress gradient is always induced when a far field loading is applied.
Aiming to investigate the integrity of notched components subjected to different loading histories, for many years to nowadays a lot of stress and strain based damage criteria have been proposed. However, in the last years, some energy based criteria have been introduced and successfully applied on notched members proving to be powerful damage prediction tools.
In particular the averaged strain energy density criterion (Lazzarin and Zambardi 2001) has been developed and used in order to assess the strength of notched components with various notch geometries subjected to different types of loading.
The aim of this work is to extend the validity of the averaged SED criterion to the three-dimensional effects arising in the vicinity of a notch and to the problems induced by the application of multiaxial static and cyclic loadings.
Taking advantage of some results obtained from multiaxial cyclic analyses, the effect of the phase displacement between the applied loads has been addressed presenting a new proposal based on the maximum tangential stress averaged over an entire loading cycle.
Finally, a dedicated software based on the cyclic plasticity theory has been developed in order to obtain the stress/strain distributions at the tip of a rounded notch subjected to uniaxial and multiaxial low cycle fatigue. A particular link between the plastic hysteresis energy at the notch tip and the averaged SED has been found representing the first potential step for a future extension of the averaged SED criterion to cyclic plasticity
La maturità di Alessandro Fei del Barbiere, in bilico tra Maniera e Riforma
No full textThis article studies the mature career of the Florentine painter Alessandro Fei del Barbiere (1537-1592), beginning with the rediscovery of the 'Ascension' altarpiece formerly in the Albizi Chapel in the destroyed church of San Pier Maggiore, Florence. Studying this painting and others recorded in 1584 by the biographer Raffaello Borghini, such as the two altarpieces for Santa Maria delle Grazie and the Madonna dell'Umiltà in Pistoia, the author reconstructs a body of works showing how in the 1580s Fei gradually went beyond the archaic style of his apprenticeship - he had been trained by Ridolfo del Ghirlandaio and Pierfrancesco Foschi, but was also marked by the Maniera of Vasari - evolving towards naturalism in both mimesis and pictorial handling. In Florence, his development partly parallels that of Santi di Tito and his circle, but Fei was also influenced by a probable sojourn during the early part of that decade in Rome, where he could have been inspired by Girolamo Muziano and the painters working for Pope Gregory XIII. Among other proposals, the author suggests that the artist was responsible for decorating the chancel of Fiesole Cathedral (c. 1584-1589), which consisted of an altarpiece, only rarely discussed by scholars, and a cycle of frescoes hitherto attributed to Nicodemo Ferrucci
From Natural Woods to High Density Materials: An Ecofriendly Approach
No full textRecently, different methods have been proposed to develop wood materials, termed “densified woods”, with density increment and improvement in mechanical proprieties. Almost all the proposed methods involve the use of reducing agents and strong bases. In this work, a new method has been developed involving the use of less polluting agents. The formation of densified woods is divided into two steps: delignification involves the removal of lignin, hemicelluloses, and shorter chains of cellulose, whereas densification involves the plastering of the delignified woods. The obtained materials showed a density increase of two to four times. The obtained densified woods were characterized by spectroscopic, microscopic, and thermogravimetric techniques and mechanical tests. The characterizations aimed at determining the variations of chemical and structural compositions of the samples after delignification and densification processes, showing, respectively, a decrease in lignin and a significant increase in the density and force necessary to bring the materials to yield. The final density of wood was two to three times higher and the force necessary to reach the yield point reached more than three times the initial one for some of the studied samples. These characterizations showed how different woods, with different properties, reach comparable densities and final mechanical properties after delignification and densification process. The increased mechanical properties of the materials allow their application in place of other composite woody materials
Tra socialdemocrazie e Perestrojka. Le relazioni internazionali del Pci attraverso le carte di Alessandro Natta
No full textThis essay reconstructs the foreign policy of the Italian Communist Party during the four
years of Alessandro Natta’s secretariat (1984-1988) through largely original archival documentation,
from the Alessandro Natta Fonds of the Historical Archive of the Chamber of
Deputies. Natta’s papers are also cross-referenced with those kept in the PCI Archive at the
Gramsci Foundation. The author analyses the relationship that the PCI establishes with
Gorbachev’s Perestroika, Deng’s China, and European social democracies during the last
years of the Cold War
The Latemar: A flat-topped, steep fronted platform dominated by microbialites and synsedimentary cements
No full textFacies analyses on the Latemar isolated carbonate platform suggest a higher proportion of microbial carbonates
compared to literature. This is evident especially in the margin-upper slope zone, where microbial boundstone
associated with Tubiphytes, calcareous sponges, botryoidal aragonite and radiaxial fibrous cements extended
down to 250mwater depth. The Latemar flat-topped high-relief platformhas been subdivided into five different
facies belts: inner and outermost platform,margin, upper and lower slope. Each facies belt represents subtidal environments
except for the inner platform, which is characterized by a peritidal facies association. Point counting
analysis was carried out on ca. 90 thin sections to quantify the different platform components. Microbialite and
cements are most abundant: they represent, respectively, ca. 40% and ca. 34% of the whole platform volume.
These results suggest that carbonate production at Latemar occurred in a M-Factory. Microbial carbonates, as
well as early marine cements are most abundant on the upper slope, margin and outermost platform, although
microbialites are found in all facies belts.
The presence of supratidal sedimentary facies restricted only to the inner platform and of a completely subtidal
outermost platform suggests a new depositional profile for the Latemar. The central portion is occupied by the
flat platform interior, cyclically subaerially exposed. Facies of the subtidal outermost platform surround the
inner platform and display a progressive increase in depth toward the margin. The margin is submerged
and essentially constituted bymicrobial and cement boundstone. The slope is characterized by steep clinoforms
(~35°) dominated by in situ microbialites in the upper-middle portion (0–250 m depth), evidently precipitated
by non light-dependent microbially influenced processes. The lower slope is mostly detrital, poor in platform
top-derived sediments and dominated by margin and upper-slope derived rudstone and grainstone. All these
observations are in agreement with the slope-shedding model observed in the Pennsylvanian microbialmargin
in Asturias (N Spain) and allow the interpretation of the Latemar as a flat-topped, steep fronted platform
dominated by microbialites and cement boundstones
Synthesis and Characterization of Lignin-Derived Porous Materials from Phyllostachys edulis (Bamboo Moso) for the Removal of Aromatic Pollutants
No full textIn recent decades, pollution from dyes has increasingly attracted the attention of researchers. For this reason, the development of new materials capable of sequestering this type of pollutant has been extensively studied, especially as research using plant biomass to produce new materials. Considerable
attention has been directed toward bamboo moso, which has been the focus of extensive studies. The chemical composition of bamboo culms indicates that cellulose and hemicellulose comprise 65−70%, whereas lignin accounts for 18−30%. In this study, lignin has been extracted from bamboo culms using the hydrothermal methodology under basic conditions. Water-soluble lignin was dispersed in a porogenic organic solvent and polymerized via the Friedel-Craft alkylation reaction. 13C CPMAS NMR spectroscopy was used to study the modification of the water-soluble lignin before and after polymerization; the peaks related to the linker reaction were detected and confirmed the successful cross-linking reaction. The biopolymer-composite was also characterized by FTIR spectroscopy to explore the surface functionality and its interaction with the aromatic molecules, using toluene as a model compound. To gain a deeper understanding of the surface properties, N2 physisorption analysis was performed at 77 K. To evaluate the material’s capacity to act as an adsorbent for organic dyes, the adsorption kinetics of organic pollutants were simulated using Crystal Violet as a model molecule, tracking the adsorption trends through UV−vis spectroscopy. In this context, the adsorption capacity of Crystal Violet was determined to exceed 98% within the initial 4 h period
Volta Alessandro
No full textThe New Dictionary of Scientific Biography (extension and updating of the Dictionary of Scientific Biography) is one of the most substantial reference works in the field of the history of science. An up-to-date overview on Alessandro Volta's science with new perspectives offered by the author. Information and critical analysis is also provided on the main secondary literature produced on this main protagonist of enlightenment science after the 1976 entry "Volta Alessandro" in the Dictionary of Scientific Biography
High precipitation rate in a Middle Triassic carbonate platform: Implications on the relationship between seawater saturation state and carbonate production
No full textThree-dimensional geological modeling of the Middle Triassic Latemar carbonate platform is coupled with facies modal analysis to estimate its carbonate precipitation rate (G). The 3D model, strongly constrained by field data, encompasses a specific stratigraphic interval of the platform, bounded by two isochronous surfaces. Modal analysis of thin sections allows estimating the proportion of syndepositional vs postdepositional carbonate in the facies associations of the platform. This, together with the 3D facies distribution in the model that takes into account lateral and vertical facies variability, permits to calculate the volumes of syndepositional carbonate preserved at Latemar between the two considered isochrones. Given the peculiar characteristics of the platform, that does not show evidences of strong dissolution processes or large carbonate mass loss through export in the nearby basins, results can be used to estimate the average precipitation rate of the platform in the considered time interval. This estimate allows discussion in relation to models of ocean water saturation state (Ω) with respect to carbonates in the geological past, and comparison to the calculated precipitation rates of modern tropical coral reef ecosystems at global and reef scale. A high G value is found at Latemar and represents the first empirical confirmation that, in the Triassic, extremes in Ω may have triggered high carbonate precipitation in shallow water settings; moreover, comparison to modern reefs points to a possible common relationship that may link seawater Ω and precipitation rate in carbonate platform ecosystems through geological time. © 2016 Elsevier B.V.
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