On Abstract Interpretation of Object Calculi

This thesis presents some original results in the framework of program verification, referred in particular to object-oriented languages. Object-oriented concepts and programs are expressed using object calculi, since they allow to formalize the basic ideas behind the object-oriented approach, without considering the details which are peculiar of each particular language. We will initially present a very simple object calculus, which models the classical object-oriented features, and which has the computational power of Church's untyped lambda-calculus. This calculus has a functional behavior, and in the following of the thesis it will be extended to include types, to formalize the natural imperative behavior of object-oriented languages, and to extend the model to concurrent languages. The verification of the properties of object-oriented programs will be based on abstract interpretation, since in many cases it can be more precise than other widely used techniques of analysis, like for example model checking or type inference. We will present in detail the theory behind this verification method that will be used as a unified approach in the rest of thesis. The approach will be used in three examples of analysis of object calculi, applied to the fields of safety, optimization and security. The first analysis, related to safety, is intended to verify that threads belonging to a unique concurrent program do not access shared resources simultaneously. We will extend the simple calculi presented at the beginning of the thesis with primitives for locking and unlocking objects, and using a very simple abstraction, we will be able to be more precise in our results than other approaches based on type systems. The second analysis, related to optimization, is in some way complementary to the first one. In fact, in this second case, our aim is to avoid the use of unnecessary locks in concurrent programs, since they often cause an overhead in computation. We will further extend our language with constructs for tracing the objects and the threads which acquire locks on them. The analysis will then check the dependencies between the various locks, to see if some of them may be safely deleted from programs without incurring in an erroneous behavior due to simultaneous accesses to shared resources. The third analysis will be intended to check a property of secure information flow in concurrent programs. The language will be further extended to include information levels and the analysis will check if, for each point of the computation, the values contained in variables are, in some ways, dependent of other variables with higher information levels

Picoplankton Community Composition by CARD-FISH and Flow Cytometric Techniques: A Preliminary Study in Central Adriatic Sea Water

Data concerning picoplanktonic community composition and abundance in the Central Adriatic Sea are presented in an effort to improve the knowledge of bacterioplankton and autotrophic picoplankton and their seasonal changes. Flow cytometry analyses revealed the presence of two distinct bacteria populations: HNA and LNA cells. HNA cells showed an explicit correlation with viable and actively respiring cells. The study of viability and activity may increase our knowledge of the part that contributes really to the remineralization and bacterial biomass production. Authotrophic picoplankton abundance, especially picocyanobacteria, was strongly influenced by seasonality, indicating that light availability and water temperature are very important regulating factors. In terms of total carbon biomass, the main contribution came from heterotrophic bacteria with a lower contribution from autotrophic picoplankton. CARD-FISH evidenced, within the Eubacteria domain, the dominance of members of the phyla Alphaproteobacteria, with a strong contribution from SAR11clade, followed by Cytophaga-Flavobacterium and Gammaproteobacteria. The bacterial groups detected contributed differently depending when the sample was taken, suggesting possible seasonal patterns. This study documents for the first time picoplankton community composition in the Central Adriatic Sea using two different approaches, FCM and CARD-FISH, and could provide preliminary data for future studies

Observations on development and anomalies in the appendicular skeleton of sea bass, Dicentrarchus labrax L. 1758, larvae and juveniles

The development of the fin skeleton has been studied in both the wild and hatchery sea bass, Dicentrarchus labrax L., larvae, in order to identify and define morphofunctional criteria for larval quality assessments. The cartilaginous and bony skeletal elements of the larvae were studied and standard length and notochord flexure recorded. Fin anomalies were present in reared larvae, whereas they were rare or absent in specimens from the wild. These anomalies were recognizable from the very beginning of skeletal development, indicating that environmental, genetic and broodstock management factors influence even the very early stages of larval development

Predicting Fishing Footprint of Trawlers From Environmental and Fleet Data: An Application of Artificial Neural Networks

The increasing use of tracking devices, such as the Vessel Monitoring System (VMS) and the Automatic Identification System (AIS), have allowed, in the last decade, detailed spatial and temporal analyses of fishing footprints and of their effects on environments and resources. Nevertheless, tracking devices usually allow monitoring of the largest length classes composing different fleets, whereas fishing vessels below a regulatory threshold (i.e., 15 m in length-over-all) are not mandatorily equipped with these tools. This issue is critical, since 36% of the vessels in the European Union (EU) fleets belong to these “hidden” length classes. In this study, a model [namely, a cascaded multilayer perceptron network (CMPN)] is devised to predict the annual fishing footprints of vessels without tracking devices. This model uses information about fleet structures, environmental characteristics, human activities, and fishing effort patterns of vessels equipped with tracking devices. Furthermore, the model is able to take into account the interactions between different components of the fleets (e.g., fleet segments), which are characterized by different operating ranges and compete for the same marine space. The model shows good predictive performance and allows the extension of spatial analyses of fishing footprints to the relevant, although still unexplored, fleet segments

Population status, distribution and trophic implications of Pinna nobilis along the South-eastern Italian coast

The dramatic Mass Mortality Event, MME, of Pinna nobilis populations initially detected in the western Mediterranean basin, has also spread rapidly to the central and eastern basin. Unfortunately, there is still a significant lack of information on the status and health of P. nobilis, since only a fragmentary picture of the mortality rate affecting these populations is available. Regarding the Italian coast, several surveys have given only localized or point-like views on the distribution of species and the effect of the MME. Therefore, for the first time, this study investigated P. nobilis density of individuals, distribution and mortality throughout 161 surveys along 800 km of coastline in the Apulia region (South-east of Italy). The geographical scale of this investigation made it the largest ever conducted in Italy, and this was achieved through a rapid and standardized protocol. During this monitoring campaign, 90 km of linear underwater transects were surveyed, along which no live individuals were observed. This result allowed to estimate that the P. nobilis populations had totally collapsed, with a mortality rate of 100% in Apulia. The distributional pattern of the species showed a strong overlap with seagrass meadows on meso- and macro-geographical scale, however this was not the case on a micro-scale. This result evidenced that relationships between P. nobilis and seagrass meadows are not limited to the habitat patch, but cross the boundaries of seagrass leading us to suggest that the distribution of P. nobilis hold a trophic link through the cross-boundary subsidy occurring from seagrass meadows to the nearby habitat, by means of the refractory detrital pathway

smartR: An r package for spatial modelling of fisheries and scenario simulation of management strategies

Abstract Overfishing or exploitation patterns with high juvenile mortalities often negatively impact demersal fish stocks. Meanwhile, the increased availability and diffusion of georeferenced information is propelling a revolution of marine spatial planning. A spatial‐explicit approach to the management of fishing effort should protect the Essential Fish Habitats and minimize the impact of trawlers on areas where juveniles of commercial species concentrate. The smartR package is a data‐driven model that implements the Spatially explicit bio‐economic Model for Assessing and managing demeRsal Trawl fisheries to edit and format the raw data; construct and maintain coherent datasets; to numerically and visually inspect the generated metadata; to simulate management scenarios and forecast the possible effects in terms of resources status and economic performances of the fleets. Explicit inclusion of the spatial dimension is essential to improve the understanding of the fishery system, and to enhance the ability of management plans to improve stocks statuses

Psychological aspects of students with learning disabilities in e-environments: a mini review and future research directions

What are the main learning difficulties or advantages encountered by students with learning disabilities within e-environments? As a result of the Covid-19 emergency, e-learning is being increasingly used to support students’ learning processes. A number of countries closed their schools altogether, so face-to-face lessons were and have been replaced by distance lessons. A search of current literature via Scopus, Eric and Google Scholar electronic databases was conducted according to Prisma Guidelines. Other sources of literature were also considered, starting from the references in the full text of the articles consulted. We used the following search keywords: “learning disabilities” combined with the “AND/OR” Boolean operator and “e-learning platforms”, “well-being”, “psychological factors”, “emotional distress”, “self-regulation”. One body of literature highlights the lack of inclusive accessibility standards and a lack of attention to specific tools for addressing neuropsychological syndromes, which causes students to develop high levels of stress/anxiety and emotional distress, in addition to low levels of well-being, self-esteem and self-efficacy. Another area of literature looks at how students can develop high levels of self-regulation and emotional awareness, as well as high levels of inclusion. Results are discussed in terms of the promotion of e-learning that focuses on the psychological well-being of students and teachers use of technological tool

All is fish that comes to the net: metabarcoding for rapid fisheries catch assessment

Monitoring marine resource exploitation is a key activity in fisheries science and biodiversity conservation. Since research surveys are time‐consuming and costly, fishery‐dependent data (i.e. derived directly from fishing vessels) are increasingly credited with a key role in expanding the reach of ocean monitoring. Fishing vessels may be seen as widely ranging data‐collecting platforms, which could act as a fleet of sentinels for monitoring marine life, in particular exploited stocks. Here, we investigate the possibility of assessing catch composition of single hauls carried out by trawlers by applying DNA metabarcoding to the dense water draining from fishing nets just after the end of hauling operations (hereafter ‘slush’). We assess the performance of this approach in portraying β‐diversity and examining the quantitative relationship between species abundances in the catch and DNA amount in the slush (read counts generated by amplicon sequencing). We demonstrate that the assemblages identified using DNA in the slush satisfactorily mirror those returned by visual inspection of net content (about 71% of species and 86% of families of fish) and detect a strong relationship between read counts and species abundances in the catch. We therefore argue that this approach could be upscaled to serve as a powerful source of information on the structure of demersal assemblages and the impact of fisheries