Calibration of the dynamic behaviour of incomplete structures in archeological sites: The case of Villa Diomede portico in Pompeii

This paper reports the research activities carried out on Villa Diomede in Pompeii, built during the "Pre-Roman period" (i.e. the 3rd century BC) and discovered between 1771 and 1774 during the archaeological excavations. It is one of the greatest private buildings of Pompeii and it is located on the western corner of the modern archeological site. Three levels compose the building: the ground floor, the lower quadriportico with a square plan and a series of colonnades on the four sides around the inner garden and the cryptoportico. Villa Diomede was damaged by the strong earthquake occurred in AD 63 that caused the collapse of the western pillars of the quadriportico and later damaged after the big eruption of Vesuvius in AD 79. In June 2015 a series of nondestructive tests (NDT) were carried out by the authors in order to obtain information on the state of conservation of the building and to assess its structural behavior. Direct and tomographic sonic pulse velocity tests, ground penetrating radar, endoscopies and operational modal analysis were performed on the remaining structural elements on the two levels of the Villa. The present paper reports the main outcomes and findings of ambient vibration tests implemented to extract the modal parameters in terms of eigenfrequencies, mode shapes and damping ratios. Operational modal analysis and output-only identification techniques were applied to single stone pillars of the quadriportico structure and then to the entire square colonnade of Villa Diomede. Results are then used to study the soil-structure interaction at a local level and extend the gained information for the numerical calibration of the whole structure. Thanks to this methodology a detailed model updating procedure of the quadriportico was performed to develop reliable numerical models for the implementation of advance structural and seismic analysis of this "incomplete" archaeological structure

Operational modal analysis for the characterization of ancient water towers in Pompeii

In the framework of an investigation campaign carried out in June 2015 by the authors on four ancient water towers (10\u201320 BC) in the archaeological site of Pompeii, modal analysis and output-only identification techniques were employed to extract the dynamic properties in order to assess structural vulnerabilities and support numerical model updating. The four investigated towers (selected among the fourteen present within the archaeological site) are free-standing structures at least 6 m tall, belonging to the Castellum Aquae, i.e. the ancient aqueducts system of the city. During the Roman Age, until the destruction of Pompeii due to the volcanic eruption in 79 AD, water towers provided fresh water to houses, palaces and villas. This particular type of structures are classified as no. 1, 2, 3 and 4 by archaeological literature: no. 1 and 4 are made of soft stone masonry (tuff, limestone), while no. 2 and 3 are composed by brickwork masonry. The paper reports the outcomes of ambient vibration tests performed on four towers in terms of extracted modal parameters using various operational modal analysis techniques. Obtained data are then used to study numerically the soil-structure interaction problem and implement model updating procedures

Can Embeddings Analysis Explain Large Language Model Ranking?

Understanding the behavior of deep neural networks for Information Retrieval (IR) is crucial to improve trust in these effective models. Current popular approaches to diagnose the predictions made by deep neural networks are mainly based on: i) the adherence of the retrieval model to some axiomatic property of the IR system, ii) the generation of free-text explanations, or iii) feature importance attributions. In this work, we propose a novel approach that analyzes the changes of document and query embeddings in the latent space and that might explain the inner workings of IR large pre-trained language models. In particular, we focus on predicting query/document relevance, and we characterize the predictions by analyzing the topological arrangement of the embeddings in their latent space and their evolution while passing through the layers of the network. We show that there exists a link between the embedding adjustment and the predicted score, based on how tokens cluster in the embedding space. This novel approach, grounded in the query and document tokens interplay over the latent space, provides a new perspective on neural ranker explanation and a promising strategy for improving the efficiency of the models and Query Performance Prediction (QPP)

Impact of sheep grazing on juvenile sea bass, Dicentrarchus labrax L., in tidal salt marshes

The diet of young of the year sea bass, Dicentrarchus labrax L., from sheep grazed and ungrazed tidal salt marshes were com-pared qualitatively and quantitatively in Mont Saint-Michel Bay. In areas without grazing pressure, the vegetation gradient changes from a pioneer Puccinellia maritima dominated community at the tidal ¯at boundaries through a Atriplex portulacoides dominated community in the middle of the marsh to a mature Elymus pungens dominated community at the landward edge. The A. portula-coides community is highly productive and provides important quantities of litter which provides a habitat and good supply to substain high densities of the detrivorous amphipod Orchestia gammarellus. In the grazed areas, the vegetation is replaced by P. maritima communities, a low productive grass plant, and food availability and habitat suitability are reduced for O. gammarellus. Juvenile sea bass colonise the salt marsh at ¯ood during 43% of the spring tides which inundate the salt marsh creeks. They forage inside the marsh and feed mainly on O. gammarellus in the ungrazed marshes. In grazed areas, this amphipod is replaced by other species and juvenile sea bass consume less food from the marsh. This illustrates a direct effect of a terrestrial herbivore on a coastal food web, and suggests that management of salt marsh is complex and promotion of one component of their biota could involve reductions in other species

Studio di trattabilità di un sito contaminato da arsenico mediante Pteris vittata

Il presente studio riporta i risultati di una sperimentazione in campo riguardante la fattibilità dell’impiego della specie vegetale Pteris vittata L. per il fitorimedio di un suolo contaminato da arsenico, la Rotonda di San Giuliano a Mestre (VE), caratterizzata da particolari condizioni microambientali e pedologiche. La felce P. vittata è, infatti, una nota iperaccumulatrice di arsenico ed è particolarmente indicata per la fitoestrazione, essendo molto efficiente nella traslocazione di As verso le parti aeree; è una pianta perenne, versatile, resistente, con un’elevata velocità di crescita ed un esteso network di radici e peli radicali. Il sito in esame presenta un suolo di natura limo-argillosa e carenza di sostanza organica umificata. Di conseguenza si ha formazione di crepe e croste superficiali nei periodi secchi, mentre in quelli piovosi si ha rigonfiamento del suolo, perdita di porosità, ristagno d’acqua e l’instaurarsi di condizioni asfittiche locali. Le analisi chimiche condotte sul suolo hanno evidenziato un inquinamento superficiale da arsenico diffuso in tutta l’area, con valore di circa 45 mg∙kg-1, e hanno messo in luce che tutto il contenuto di arsenico è associato agli ossidi/idrossidi di Fe e Mn e quindi potenzialmente biodisponibile in condizioni riducenti. La sperimentazione in campo si è svolta tra l’estate e l’autunno 2007. Nonostante le difficoltà di crescita e sopravvivenza delle piante, dovute alle caratteristiche avverse del suolo e accentuate dalle particolari condizioni microambientali, P. vittata ha mostrato un’elevata capacità di accumulare arsenico. Infatti, a fronte di concentrazioni iniziali pari a circa 4 mg∙kg-1, dopo 105 giorni le concentrazioni misurate nelle fronde erano comprese tra 200 e 900 mg∙kg-1 p.s. con fattori di bioaccumulo compresi tra 4.8 e 20 e fattori di traslocazione circa uguali a 10. I risultati hanno evidenziato la necessità di stabilizzare la struttura del suolo nei riguardi degli sbalzi idrici e migliorare la resistenza di P. vittata mediante l’ottimizzazione delle pratiche agronomiche, anche attraverso l’eventuale utilizzo di piante micorrizate

Phytoremediation potential of the arsenic hyperaccumulator Pteris vittata: preliminary results from a field study

Phytoextraction is a promising technique for the remediation of soils contaminated by metals and metalloids and is proposed as a green alternative to conventional remediation methods. This paper reports the preliminary results of a field study carried out to evaluate the potential of the fern Pteris vittata for the phytoremediation of arsenic polluted sites. P. vittata is a known arsenic hyperaccumulator and its properties have been assessed in a number of studies, mainly at laboratory or glasshouse scale, while few field investigations are reported in the literature. The experimental activity was planned to compare and evaluate the effect of different conditions on plant growth and on as uptake by P. vittata. The study area is located in northeastern Italy. During the experimental period, pedoclimatic conditions were shown to affect strongly plant growth as well as As bioaccumulation. The results of two consecutive field trials confirm the phytoextraction ability of P. vittata under field conditions, but indicate also that the optimization of agronomic practices is crucial for the success of a phytoextraction application at fullscale. The inoculation of ferns with arbuscular mycorrhizal (AM) fungi seems to have a positive influence on plant growth, while its role on phytoextraction efficiency still remains unclear

Composition of fish communities in macrotidal salt marshes of the Mont Saint-Michel bay (France)

At least 100 fish species are known to be present in the intertidal areas (estuaries, mudflats and salt marshes) of Mont Saint-Michel Bay. These and other comparable shallow marine coastal waters, such as estuaries and lagoons, play a nursery role for many fish species. However, in Europe little attention has been paid to the value of tidal salt marshes for fishes. Between March 1996 and April 1999, 120 tides were sampled in a tidal creek. A total of 31 species were caught. This community was largely dominated by mullets (Liza ramada represent 87% of the total biomass) and sand gobies(Pomatoschistus minutus and P. lozanoi represent 82% of the total numbers). These species and also Gasterosteus aculeatus, Syngnathus rostellatus, Dicentrarchus labrax, Mugil spp., Liza aurata and Sprattus sprattus were the most frequent species (>50% of monthly frequency of occurrence). In Europe, salt marshes and their creeks are flooded only during high spring tides. So, fishes only invade this environment during short immersion periods, and no species can be considered as marsh resident. But, the salt marsh was colonized by fish every time the tide reached the creek, and during the short time of flood, dominant fishes fed actively and exploited the high productivity. Nevertheless, this study shows that there is little interannual variation in the fish community and there are three ‘ seasons ’ in the fish fauna of the marsh. Marine straggler and marine estuarine dependent species colonize marshes between spring (recruitment period in the bay) and autumn before returning into deeper adjacent waters. Estuarine fishes are present all year round with maximum abundances in the end of summer. The presence of fishes confirms that this kind of wetland plays an important trophic and nursery role for these species. Differences in densities and stages distribution of these species into Mont Saint-Michel systems (tidal mudflats, estuaries and tidal salt marshes) can reduce the trophic competition