Symbolic Dynamics Analysis: a new methodology for foetal heart rate variability analysis

Cardiotocography (CTG) is a widespread foetal diagnostic methods. However, it lacks of objectivity and reproducibility since its dependence on observer's expertise. To overcome these limitations, more objective methods for CTG interpretation have been proposed. In particular, many developed techniques aim to assess the foetal heart rate variability (FHRV). Among them, some methodologies from nonlinear systems theory have been applied to the study of FHRV. All the techniques have proved to be helpful in specific cases. Nevertheless, none of them is more reliable than the others. Therefore, an in-depth study is necessary. The aim of this work is to deepen the FHRV analysis through the Symbolic Dynamics Analysis (SDA), a nonlinear technique already successfully employed for HRV analysis. Thanks to its simplicity of interpretation, it could be a useful tool for clinicians. We performed a literature study involving about 200 references on HRV and FHRV analysis; approximately 100 works were focused on non-linear techniques. Then, in order to compare linear and non-linear methods, we carried out a multiparametric study. 580 antepartum recordings of healthy fetuses were examined. Signals were processed using an updated software for CTG analysis and a new developed software for generating simulated CTG traces. Finally, statistical tests and regression analyses were carried out for estimating relationships among extracted indexes and other clinical information. Results confirm that none of the employed techniques is more reliable than the others. Moreover, in agreement with the literature, each analysis should take into account two relevant parameters, the foetal status and the week of gestation. Regarding the SDA, results show its promising capabilities in FHRV analysis. It allows recognizing foetal status, gestation week and global variability of FHR signals, even better than other methods. Nevertheless, further studies, which should involve even pathological cases, are necessary to establish its reliability.

Analysis of heat-related phenomena and their interactions at different spatio-temporal scales

This thesis analyzes the impact of heat extremes in urban and rural environments, considering processes related to severely high temperatures and unusual dryness. The first part deals with the influence of large-scale heatwave events on the local-scale urban heat island (UHI) effect. The temperatures recorded over a 20-year summer period by meteorological stations in 37 European cities are examined to evaluate the variations of UHI during heatwaves with respect to non-heatwave days. A statistical analysis reveals a negligible impact of large-scale extreme temperatures on the local daytime urban climate, while a notable exacerbation of UHI effect at night. A comparison with the UrbClim model outputs confirms the UHI strengthening during heatwave episodes, with an intensity independent of the climate zone. The investigation of the relationship between large-scale temperature anomalies and UHI highlights a smooth and continuous dependence, but with a strong variability. The lack of a threshold behavior in this relationship suggests that large-scale temperature variability can affect the local-scale UHI even in different conditions than during extreme events. The second part examines the transition from meteorological to agricultural drought, being the first stage of the drought propagation process. A multi-year reanalysis dataset involving numerous drought events over the Iberian Peninsula is considered. The behavior of different non-parametric standardized drought indices in drought detection is evaluated. A statistical approach based on run theory is employed, analyzing the main characteristics of drought propagation. The propagation from meteorological to agricultural drought events is found to develop in about 1-2 months. The duration of agricultural drought appears shorter than that of meteorological drought, but the onset is delayed. The propagation probability increases with the severity of the originating meteorological drought. A new combined agricultural drought index is developed to be a useful tool for balancing the characteristics of other adopted indices.

Pratiche di formative assessment per promuovere abilita di comprensione dei testi. Una sperimentazione in una scuola secondaria di primo grado

I dati delle indagini sugli apprendimenti degli studenti in Italia rivelano l’esistenza di fragilità nell’acquisizione di competenze essenziali e di differenze tra i risultati conseguiti. Per innovare la didattica al fine di adeguarla ai bisogni degli studenti, gli esperti di Docimologia caldeggiano l’uso di pratiche di valutazione formativa, o formative assessment (FA). In ambito internazionale diversi studi hanno mostrato l'efficacia di tali prassi, mentre in Italia non esistono ricerche sperimentali finalizzate a studiarne l’impatto sugli apprendimenti. Il progetto è entrato all’interno di quest’ambito di studi per controllare l’efficacia di un insieme di pratiche di FA sull'incremento delle abilità di comprensione dei testi degli studenti. Lo scopo è stato perseguito realizzando una sperimentazione in una scuola secondaria di primo grado che ha coinvolto gli studenti di due classi prime, i quali sono stati suddivisi a metà attraverso tecniche di randomizzazione per formare i due gruppi, sperimentale e di controllo. Dopo aver effettuato una rilevazione iniziale delle abilità di comprensione dei testi degli studenti (pre-test), è stato realizzato con quelli del gruppo sperimentale un intervento composto da 15 incontri di FA della durata di due ore ciascuno. Alla fine, sono state effettuate due rilevazioni finali (post-test) utilizzando sia la stessa prova utilizzata come pre-test sia una prova parallela. È stata calcolata la differenza post-test-pre-test per ogni gruppo ed è stato verificato quanto avesse influito la partecipazione all’intervento sperimentale su tale differenza tramite test non parametrici. I risultati hanno mostrato un incremento di abilità lievemente maggiore nel gruppo sperimentale, se confrontato con quello del gruppo di controllo, anche se questa differenza tra i due gruppi non è statisticamente significativa. Sebbene le analisi non abbiano consentito di rifiutare l’ipotesi nulla, la rilevanza di tale progetto risiede nel tentativo di aprire il dibattito sull’efficacia di prassi di FA sugli apprendimenti degli studenti in Italia.

Study and characterization of polymorphs of BTBT derivatives and their application in organic electronics

The perquisites of organic semiconductors (OSCs) in the field of organic electronics have attracted much attention due to the advantages like cost-effectiveness, solution processibility, etc. A key property in OSCs is charge carrier mobility, which depends on molecular packing, as even the slightest changes in the packing of OSC can significantly impact the mobility. Organic molecules are constructed by weak interactions, which makes the OSCs prone to adopt multiple packing arrangements, thus giving rise to polymorphism. Therefore, polymorph screening in bulk and thin films is crucial for material development. This thesis aims to present a systematic study of polymorphism of [1]benzothieno[3,2-b]benzothiophene (BTBT) derivatives functionalized with different side chains. The role of peripheral side chains has been studied since they can promote different packing arrangements. The bulk polymorph screening of OSCs was approached with conventional solution mediated recrystallization experiments like evaporation, slurry maturation, anti-solvent precipitation, etc. Each of the polymorphs were inspected for their relative stability and the kinetics of transformation was evaluated. Polymorphism in thin films was also investigated for selected OSCs. Non-equilibrium methods like, thermal gradient and solution shearing were employed to examine the nucleation, crystal growth and morphology in controlled crystallization conditions. After careful analysis of crystal phases in bulk and thin films, OFETs have been fabricated by optimizing the manufacturing conditions and the hole mobility values were extracted. The charge transport property of the OSCs tested for OFETs was supported by the ionization potential and transfer integrals calculation. An attempt to correlate the solid-state structure to electronic properties was carried out. For some of the molecules, mechanical properties have been also investigated, as the response to mechanical stress is highly susceptible to packing arrangements and the intermolecular interaction energy contributions. Additionally, collaborative research was carried out by solving and analysing the crystal structures of six oligorylene molecules.