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A study of stellar debris dynamics during a tidal disruption event
Aurora Clerici, 2020, doctoral dissertation

Abstract: The number of observed tidal disruption events is increasing rapidly with the advent of new surveys. Thus, it is becoming increasingly important to improve TDE models using different stellar and orbital parameters. We study the dynamical behaviour of tidal disruption events produced by a massive black hole like Sgr A* by changing different initial orbital parameters, taking into account the observed orbits of S stars. Investigating different types of orbits and penetration factors is important since their variations lead to different timescales of the tidal disruption event debris dynamics, making mechanisms such as self-crossing and pancaking act strongly or weakly, thus affecting the circularisation and accretion disk formation. We have performed smoothed particle hydrodynamics simulations. Each simulation consists in modelling the star with $10^5$ particles, and the density profile is described by a polytrope with $\gamma$ = 5/3. The massive black hole is modelled with a generalised post-Newtonian potential, which takes into account relativistic effects of the Schwarzschild space-time. Our analyses find that mass return rate distributions of solar-like stars and S-like stars with same eccentricity have similar durations, but S-like stars have higher mass return rate, as expected due to their larger mass. Regarding debris circularisation, we identify four types of evolution, related to the mechanisms and processes involved during circularisation: in type 1 the debris does not circularise efficiently, hence a disk is not formed or is formed after relatively long time; in type 2 the debris slowly circularises and eventually forms a disk with no debris falling back; in type 3 the debris relatively quickly circularises and forms a disk while there is still debris falling back; finally, in type 4 the debris quickly and efficiently circularises, mainly through self-crossings and shocks, and forms a disk with no debris falling back. Finally, we find that the standard relation of circularisation radius $r_{\rm circ} = 2r_{\rm t}$ holds only for $\beta = 1$ and eccentricities close to parabolic.
Keywords: 07.05.Tp Computer modeling and simulation, 95.30.Lz Hydrodynamics, 98.35.Jk Galactic center, bar, circumnuclear matter, and bulge, 98.62.Js Galactic nuclei (including black holes), circumnuclear matter, and bulges, 98.62.Mw Infall, accretion, and accretion disks
Published: 29.09.2020; Views: 75; Downloads: 9
.pdf Fulltext (37,55 MB)

Seismic Vulnerability of a Historical Masonry Building: A Critical Comparison of Analytical Methodologies
Marco Boscolo Bielo, 2020, doctoral dissertation

Abstract: In these last twenty years a new sensibility for the seismic themes around buildings has emerged from a cultural and technical point of view. As a result of some earthquakes happened in Italy, the promulgation of technical codes has accelerated and, essentially, the standards of Eurocodes were accepted. Consequently, also in the field of historical buildings, a set of specific guidelines have been issued. In the current state of art, designers are faced with many methods of calculation which the technical codes offer for the assessment of the seismic vulnerability of historical buildings. Designers can use simplified or complex approaches which assume different starting hypothesisto obtain different results. This thesis aims to investigate the various aspects that the designer meets during the study of the static behaviour of an historical building and the assessment of its seismic vulnerability. A study case is also proposed which regards a Venetian Villa of the XVIth Century located in “Riviera del Brenta” near Venice, with a critical comparison of the results obtained by the application of the various methods of calculation. The thesis begins with an outline of the historical development of seismic technical codes in Italy and shows how the sensibility has developed in the Italian culture. In particular it is illustrated the difference between the approach of the legislation "a posteriori" (where a “patchy zoning” was generally performed after the occurrence of earthquakes), and the probabilistic approach based on the peaking ground acceleration expected in every Italian site. The Second and the Third Chapters contain the analysis of the current seismic legislations and in particular the guidelines for historical buildings. The Chapter 4 provides a general discussion on the masonry and the definition of the mechanical parameters. There are many critical aspects relating to a characterization of models which can realistically represent the historical masonry. They are due to a heterogeneity of variables such as, for instance, the mechanical parameters, the physiological behaviour, the connections, etc. In the Chapter 5 the basic concepts of seismic behaviour of historical buildings are discussed. In particular the Pagano’s classification of masonry buildings is illustrated with special regard of the following factors: stiffness of horizontal structures; efficiency of “masonry beams”; efficiency of intersection between walls. From the Chapter 6 the analysis of the study case begins. Here we can find the description of the Venetian Villa (historical evolution of the buildings, description of geometrical characteristics, structural behaviour, etc. In the Chapter 7, the first level of analysis is performed for the study-case. The method of calculation is contained in the guidelines for historical buildings. A critical discussion of the results is also illustrated. In the Chapter 8 is performed a linear kinematic analysis based on various possible kinematic mechanisms identified through the study of cracking and the lacks of the structural connections. The Chapter 9 shows a non-linear static analysis (pushover) for the study-case which refers to two limit behaviour models: the first one with infinitely rigid diaphragms and efficient masonry beams; the second one based on infinitely flexible diaphragms and weak masonry beams. The results are compared and critically discussed. In the same way the Chapter 10 and 11 perform a linear static analysis and a linear dynamic analysis for the two models of the Chapter 9, so the results can be compared. In the last Chapter a general discussion about all the results of the performed analysis is conducted. Here the work points out the conceptual limits of each method of calculation and the possibility of use related to the objectives which must be reached. Finally some design indications related to the results of the analysis are illustrated.
Keywords: Seismic, Vulneraility, Analitical, Methodologies
Published: 02.07.2020; Views: 270; Downloads: 5
.pdf Fulltext (128,89 MB)

Sandra Folarin Oloketuyi, 2020, doctoral dissertation

Abstract: Early detection and monitoring of toxic microalgae remains a challenge that will be necessary to overcome for understanding harmful algal bloom events and their consequent ecological and environmental impacts. Although there are diagnostic techniques based on microscopy, fluorescence in situ hybridization (FISH), DNA microarrays, real-time PCR, sandwich hybridization assays employed for the detection of harmful algal species, such techniques are not suitable for field monitoring and especially for the quantification of Alexandrium minutum due to abundance of cryptic species that cannot be differentiated based on morphology or genomic traits. These approaches are also time-consuming and laborious, hence there is need for alternative simple, rapid and cost-effective methods. In this study, our aim was to develop different nanobody-based capture strategies for the detection of A. minutum. Nanobodies were successfully displayed on the surface of Escherichia coli to facilitate detection of A. minutum. The method is simple and cost effective as no antibody purification step is necessary. As an alternative, A. minutum was quantified by exploiting the peroxidase activity of a G-quadruplex DNAzyme covalently bound to nanobodies and by means of a label free electrochemical immunosensor which exploit nanobodies bound via an irreversible SpyTag-SpyCatcher system as the specific immunocapture element. Such immunosensor was prepared by immobilizing the SpyTagged anti-A. minutum nanobody (SpyTagged C1) by means of a selfassembled monolayer (SAMs) of L- cysteine (L-Cys) displayed onto a gold nanoparticle-modified glassy carbon electrode. Electrochemical Impedance Spectroscopy (EIS) was performed to measure the electrical response of the circuit as the function of A. minutum immunocaptured cells. The results of EIS studies confirmed that the sensing chip detected A. minutum selectively, exhibited a wide dynamic range spanning from 103 to 109 cell L-1 and a limit of detection of 3.1× 103 cell L-1. The immunosensor data can be recorded and then analyzed with a portable potentiostat. Such device can be interfaced with a smart phone, a condition suitable for the rapid A. minutum quantification in situ.
Keywords: Alexandrium minutum, nanobodies, bioreagents, immunosensor, toxic microalgae
Published: 17.06.2020; Views: 385; Downloads: 16
.pdf Fulltext (2,95 MB)

Alice Avian, 2020, doctoral dissertation

Abstract: Human Papillomavirus (HPV) infection is the causative agent for the invasive cervical cancer and its precancerous lesions, furthermore, there are growing evidences of HPV being a relevant factor in other anogenital cancers as well as head and neck cancers. Most sexually active women become infected with HPV at least once in their lifetime, but less than 10% of women becomes persistently infected, and it is precisely the persistent infection that contributes to the development of cervical cancer. The preventive effect of cervical cancer screening largely depends in the high women participation and coverage; indeed, a large number of cervical cancers diagnoses normally arise among under-screened and unscreened women. Increase in the screening coverage is essential to improve the effectiveness of cervical screening programmes. The main purpose of this PhD project was to solve some of the most relevant problems in the cervical cancer screening programmes, as the increase of cost-effectiveness and the amelioration of the screening coverage. My work was focused on the development and validation of the first Ulisse BioMed S.p.A. product, the HPV Selfy™ test, an innovative PCR-based kit for the direct detection and genotyping of 12 high-risk HPV types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58 and 59) and 2 possible/probable high-risk (66 and 68), specifically optimized for the analysis of self-collected vaginal specimens. The core of this innovative test is based on high-resolution melting (HRM) analysis, a recently developed technique for fast, high-throughput post-PCR analysis of variance in nucleic acid sequences, that characterizes the amplicons by studying thermal denaturation of double-stranded DNA. Based on this approach and through the design of different HPV type-specific primer pairs and the development of a specific master mix, unique melting peaks in a single fluorescence channel were obtained, allowing the multiple detection and genotyping of 14 HPV types in a single PCR well. Three different clinical studies have been carried out to validate the assay on the vaginal self-collected samples with truly amazing results regarding the assay’s performance, but also for self-sampling acceptability by women. Moreover, data collected in these studies suggest a future possible use of this test for the hard-to-reach women, as an alternative of the conventional clinician-collected sample, in order to increase the cervical cancer screening coverage.
Keywords: Human Papillomavirus, HPV test, cervical cancer screening, prevention, diagnostic test, High resolution melting, HRM, genotyping, PCR, Self-sampling, clinical validation.
Published: 17.06.2020; Views: 279; Downloads: 4
.pdf Fulltext (37,88 MB)

Managing karst in Coastal British Columbia, Canada
Paul Andre Griffiths, 2020, doctoral dissertation

Abstract: This thesis provides a detailed description and analysis of the system used for managing karst in the forests of coastal British Columbia (BC), where the major land- use activity is industrial forestry. In 2004, BC shifted from a more prescriptive forest management model (the Forest Practices Code) to a less regulated, results-based approach based primarily on the Forest and Range Practices Act (FRPA). The dissertation examines how this results-based management approach for forest resources has worked – or not worked – with respect to karst. The research focused on the five key realms of an environmental management system as defined by the International Standards Organization (ISO 14001 standard): 1) Legislation and Policy, 2) Planning, 3) Implementation, 4) Checking/Corrective Action, and 5) Management Review. The research also examined the roles of professional reliance (another major foundational element of the FRPA model), karst research, and organizational capacity as external factors which influence on the functioning of the karst management system. A combination of interviews, surveys, document reviews and field observations were used to collect qualitative information relevant to all aspects of the karst management system. This research reveals inadequacies in all five realms of BC’s current karst management framework, including gaps in legislation, a lack of implementation of existing standards and guidelines, and non-existent effectiveness and compliance monitoring. The results suggest that BC’s shift to ‘self-regulation’ has yielded unsatisfactory results so far for karst resources and has hindered progress toward implementing a fully integrated science-based ecosystem approach to karst management in the study area. Professional reliance failures are identified as one of the key factors contributing to a breakdown of the management system for karst. This is the first comprehensive study that examines the systems and processes used for managing karst in coastal BC, and consolidates knowledge for government, industry, and others that wish to study or better understand BC’s approach and methods for managing karst. The findings will be useful for private and public forest sector organizations endeavoring to implement fully-functional and effective systems for managing karst in a forestry context. This information may also have more specific applications for managing karst.
Keywords: karst ecosystems, protection and management, legislation, policies, standards and guidelines, environmental degradation, forestry impacts, professional reliance, British Columbia, Canada
Published: 02.03.2020; Views: 501; Downloads: 17
.pdf Fulltext (136,27 MB)

Importance of pedestrianization for urban regeneration. Assessing new bridge solutions for the Golden Horn
Pinar Özge Gezer, 2020, master's thesis

Abstract: The Golden Horn (in Turkish Halic means Gulf or Altın Boynuz "Golden Horn") is a historic inlet of the Bosphorus dividing the city of İstanbul and forming the natural harbor that has sheltered Ottoman and other ships for thousands of years. It is a scimitar-shaped estuary that joins the Bosphorus just at the point where that strait enters the Sea of Marmara, thus forming a peninsula the tip of which is "Old İstanbul". This thesis work focuses on design proposal for the pedestrian bridge for Golden Horn Dis-trict, which links the royal and later historical peninsula to the rest of the city. The main challenge of the thesis is creation of continuous pedestrian network to guarantee uninter-rupted pedestrian connectivity as well as systematic activation of social and environmental urban regeneration.
Keywords: bridge, pedestrianization, walkability, Golden Horn, historical penninsula, connection, transportation, cultural park, green areas, attraction points, İstanbul, Leonardo Da Vinci
Published: 28.02.2020; Views: 375; Downloads: 6
.pdf Fulltext (20,12 MB)

Dissecting the role of REEP1 in preventing Tau-mediated neurodegeneration in a D.melanogaster Alzheimer's disease model
Alessio Guglielmi, 2019, doctoral dissertation

Abstract: Tau is natively an unfolded protein that promotes the assembly and the stability of the axonal microtubules in the central nervous system. Increased formation of Tau protein aggregates has been causatively implicated in several neurodegenerative diseases called tauopathies. In the present study, we used the Drosophila melanogaster system to express the longest isoform of human Tau (2N4R) in the nervous system of adult flies, recreating the main features of the human pathology. Herein, this Tau-mediated neurodegeneration model was used as a platform to perform genetic screenings to identify putative modifiers of Tau toxicity. Our strategy exploited the modulation of genes considered as risk factors of Alzheimer’s disease (AD), Frontotemporal Dementias and other neurodegenerative diseases by RNA interference in vivo. This approach allowed us to identify a new gene which participates in the neuronal response against Tau induced neurotoxicity in Drosophila: D-Reep1, homologue of human REEP1 gene (h-Reep1). D-Reep1 knockout flies showed no apparent phenotypes in physiological growing and developmental conditions, however, they showed peculiar sensitivity to stress conditions. In addition, D-Reep1 knockout enhanced the neurodegeneration mediated by Tau expression in Drosophila eyes. On the contrary, the overexpression of UAS-D-Reep1 and UAS-h-Reep1 abolished the typical rough eye phenotype induced by the presence of Tau. The Co-expression of D-Reep1 in Tau backgrounds did not alter the phosphorylation pattern of this protein while, the presence of D-Reep1 seemed to prevent the formation of Tau aggregates in vivo. Thus, the data support the idea that D-Reep1 exerts a protective role on Tau induced toxicity which is independent of its phosphorylation status. In this work, I analysed the mechanisms behind the neuroprotective role of D-Reep1 and, in particular, I found that REEP1 is involved in the regulation of the unfolded protein response (UPR) through the PERK-ATF4 cascade within the ER. By the activation of this pathway, the neurotoxic aggregates of Tau are removed from Drosophila neuronal tissues rescuing the normal characteristics of the affected tissues. Evidences also suggest that the activation of autophagy was behind the removal of Tau aggregates, providing new molecular information about the physiological role of D Reep1 in the nervous system.
Keywords: AD Alzheimer Disease APP Amyloid precursor protein CNS Central Nervous System DM Drosophila melanogaster HSP Hereditary Spastic Paraplegia LN Lewy’s neurite MT Microtubule MAP Microtubule associated protein MT Microtubule/s MTBD Microtubule binding domain NFT Neurofibrillary tangle NP Neuritic plaques PHF Paired helical filament PS1 Presenilin 1 PS2 Presenilin 2 SPG Spastic Paraplegia ThS Thioflavin S
Published: 06.12.2019; Views: 620; Downloads: 25
.pdf Fulltext (2,59 MB)

Photoactive nanocomposite thin films on glass and thermosensitive substrates
Nives Vodišek, 2019, doctoral dissertation

Abstract: Photocatalysis is a well-known process for the last few decades; it is predominantly used for water and air purification, but also for self-cleaning and antibacterial surfaces. The photocatalytic process is one of the advanced oxidation processes, where semiconductors are mainly used as photocatalysts. The most known and used semiconductor is nanosized titania, which can non-selectively decompose organic matters. One of the side effects of nano TiO2 under UV irradiation is photoinduced hydrophilicity, which furthermore improves the self-cleaning effect. The main drawback of TiO2 is that for its activation UV light is needed, which represents only 5 percent of the solar spectrum. Consequently, actinic irradiance power is low and the response of photocatalyst is limited. Novel approaches are being introduced to improve TiO2 response to visible light such as doping, coupling, modification of surface morphology and others. The thesis consists of five principal chapters. The first chapter is focused on a short literature review and explanation of some basic terms and principles that are related to this thesis. The aim of the research was to prepare transparent photocatalytically active thin films on glass and thermosensitive substrates. Four thermosensitive substrates were used: polyvinyl chloride (PVC) foil, polymethyl methacrylate (PMMA) sheet and polyester (PES) fabric coated with a polyvinyl and acrylic coating, with (D1) or without (D2) an additional polyvinylidene fluoride topcoat. The synthesis of films was modified with the introduction of zirconium aiming at improving the photocatalytic activity of the TiO2 films, and the final films had a SiO2 phase present for increased mechanical robustness. The third chapter is dedicated to the experimental part of the thesis. The detailed process of synthesis is described. The sol-gel process was used to prepare initial Ti-Zr sols, colloidal aqueous solutions with TiO2 and ZrO2 nanoparticles derived from titanium and zirconium alkoxides. The four different Ti-Zr sols were prepared with 0, 5, 10 and 20 molar % of Zr according to Ti. The depositing solution was prepared by mixing Ti-Zr sol, SiO2 sol binder, 1-propanol and 2-propoxyethanol, and then thin films were deposited by dip-coating technique. After the deposition, samples did not require high-temperature calcination since the photocatalytic anatase phase was present already after drying the deposited layers. Coated glass slides were put into a furnace at 150 °C, while samples on thermosensitive substrates were just treated by a heat gun. Samples in powder and thin film form were characterized by UV-Vis, FTIR-ATR and laser beam deflection spectroscopy, X-ray diffraction, scanning electron microscopy and thermal analysis. One of the main aspects of the photocatalyst is its activity. Photocatalytic activity of the thin films was determined, either quantitatively by the formation of fluorescent hydroxyterephthalic acid, one of the first degradation products of terephthalic acid deposit, or qualitatively by a visual-based method where degradation of resazurin ink was observed. Two additional methods were used on glass samples, electron paramagnetic resonance, and degradation of methyl stearate by observing the change in water contact angle under UVA irradiation. Mechanical stability of films on various substrates is an essential factor, describing how successful was immobilization of the photocatalytic materials on the substrate. It was determined by the pencil hardness test, i.e., Wolff-Wilborn method. In the fourth chapter, titled “Results and Discussion,” the most important part of the thesis is placed. Materials characterization and associated discussion of the results are divided into three major parts: i) powder samples characterization; ii) characterization of thin films on a glass substrate, and iii) characterization of films on thermosensitive substrates. In the conclusions, the main findings of the Ph.D. research work are summarized. One of our initial hypotheses was disapproved, thin films were not more active with a higher content of zirconium. However, they were more durable. All the obtained films were transparent and photoactive, despite the low-temperature synthesis procedure. Besides commonly used glass substrate, immobilization on thermosensitive substrates was also successful.
Keywords: glass substrate, immobilization, nanocomposite, nanomaterials, PES, photocatalysis, PMMA, PVC, self-cleaning surfaces, silica, plastic substrates, thin films, titania, zirconia
Published: 14.10.2019; Views: 711; Downloads: 58
.pdf Fulltext (6,23 MB)

Marta Trini, doctoral dissertation

Abstract: The detection of Ultra-High-Energy (UHE) neutrinos around and above 10 18 eV (1 EeV) can be the key to answering the long-standing question of the origin of the UHE cosmic rays. The Pierre Auger Observatory is the largest experiment that can detect the extensive air showers produced when the cosmic rays and neutrinos interact in the earth’s atmosphere. In particular, with the Infilled array of the Surface Detector of the Pierre Auger Observatory we can detect sub-EeV neutrino-induced particle showers. In this thesis we demonstrate that it is possible to discriminate neutrino-induced showers from the background showers produced by the more numerous nucleonic cosmic rays. The sensitivity to neutrinos is enhanced in the inclined directions with respect to the vertical to the ground, where cosmic ray-induced showers starting in the upper layers of the atmosphere are dominated by the muonic component of the shower, while deeply- penetrating neutrino showers in contrast exhibit a large electromagnetic component. Based on this idea in this thesis we have developed a search procedure for UHE neutrinos that consists on selecting inclined events in the Infilled array of the Pierre Auger Observatory in which the signals in the water-Cherenkov stations are spread in time, characteristic of the presence of electromagnetic component in the shower. We have established a complete chain of criteria to first select the inclined events among the sample of all events triggering the Infilled array, and then identifying those that have a large electromagnetic component at ground, and hence can be considered as neutrino candidates. We have identified a single variable, the so-called area-over-peak averaged over all of the stations in each event, as a suitable observable for neutrino identification purposes. The neutrino selection was established using extensive Monte Carlo simulations of the neutrino-induced showers in the Infilled array of Auger as well as a fraction of the data assumed to be totally constituted of background nucleonic cosmic rays. Using these neutrino simulations we have also computed the exposure of the Infilled array to UHE neutrinos in the period 1 January 04 - 31 December 2017. Associated systematic uncertainties on the exposure are also described. Expecting no candidate neutrinos in the period up to 31 December 2017, and adopting a differential neutrino diffuse flux dN ν /dE ν = k E ν −2 in the energy range from 0.05 to 1 EeV, we have obtained a 90% C.L. upper limit on the all neutrino flavor, k 90 < 7.97 × 10 −8 GeV cm −2 s −1 sr −1 .
Keywords: astroparticles, astrophysical neutrinos, cosmic rays showers, Pierre Auger Observatory, Infilled array
Published: 03.10.2019; Views: 1300; Downloads: 33
.pdf Fulltext (6,02 MB)

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