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Prebiotic Synthesis of Redox-Active Iron-Sulfur Clusters
Get PDFIron-sulfur clusters are indispensable to extant metabolism and are thought to have had an ancient role in mediating the chemical reactions that led to life. However, there has been no clear proposal for how these inorganic clusters came to occupy such an important position in biology. In this thesis I describe my efforts in delineating a plausible path from short, prebiotically plausible peptides to longer sequences with similar features to modern day iron-sulfur proteins.
Small organic thiolates and short cysteine-containing peptides can give rise to [2Fe-2S] and [4Fe-4S] clusters in aqueous solution when irradiated with UV light in the presence of iron ions. Additionally, duplications of tripeptides coordinated iron-sulfur clusters give sequences which are better able to stabilize iron-sulfur clusters, resembling motifs with cysteinyl ligand spacing highly similar to contemporary ferredoxins. Moreover, the studied iron-sulfur clusters are redox active and are able to mimic extant metabolic pathways, such as the first step of the electron transport chain, within protocells favouring the formation of a proton gradient which could be exploited for central biosynthetic processes
Managing complexity in high-concentration flow modelling aimed at hazard assessment: numerical and practical aspects
Get PDFHigh-concentration flows are complex phenomena typical of Alpine mountain areas. Essentially, they are free-surface flows with intense sediment transport, often caused by intense rainfall events and involving large volumes of solid material. Because of the amount of sediments moved, the intense erosion and deposition processes typically observed and the quite unexpected character, these phenomena represent a serious hazard in populated mountain areas, where reliable and effective hazard-management and -protection strategies are required.
In mountain-hazard management, high-concentration flows modelling represents a key factor, since it allows to evaluate impacts of possible hazard scenarios and the effectiveness of possible protection and mitigation measures. However, the intrinsic phenomenon complexity makes high-concentration flow modelling and hazard assessment quite challenging. In this thesis, some of the effects of high-concentration flow complexity on modelling are experienced directly and suitable solutions are proposed, to make the phenomenon description more reliable and straightforward. Among very different modelling approaches present in the literature, this work embraced the quasi-two phase, mobile-bed approach proposed in Armanini et al. (2009b) and in Rosatti and Begnudelli (2013a), which is implemented in the TRENT2D model. TRENT2D is a quite sophisticated model that solves a system of Partial Differential Equations over a Cartesian mesh by means of a finite-volume method with Godunov-type fluxes. By means of TRENT2D, the back-analysis of a couple of real debris-flow events occurred in Italy was first performed. These applications revealed clearly some troublesome "complexity issues", i.e. modelling issues generated by phenomenon complexity that may affect hazard assessment. Because of the public importance of the subject, four of the "complexity issues" identified were then faced directly. According to the purpose of this thesis, possible solutions to the issues were proposed, to ensure a proper description of the flow behaviour and possibly limit intricacy in the model use. The first complexity issue is "operational" and regards the use of the TRENT2D model and, more in general, the amount of work necessary to perform a complete hazard-assessment job about high-concentration flows. Because of the phenomenon complexity and the sophisticated character of the model, the operational chain necessary to assess hazard by means of TRENT2D appears quite demanding. The large efforts required in terms of handwork, computational charge and resources may divert the user attention from the physical meaning of the hazard-assessment process, possibly leading to inaccurate results. To overcome this issue, a possible solution is proposed, based on the use of a loosely-coupled Service Oriented Architecture approach. The aim is to develop a unique, user-friendly working environment able to support high-quality, cost-effective hazard assessment and, in perspective, the possible development of a Decision Support System for mountain hazard.
The second complexity issue is "geometrical" and "numerical" and concerns morphology representation. Because of the strong interaction between high-concentration flows and bed morphology, these phenomena require bed morphology to be described with the right level of detail, especially where heterogeneity is outstanding. This is typically the case of urbanised mountain areas, with their characteristic terrain shapes, buildings, infrastructures, embankments and mitigation structures. A believable representation of these geometrical constraints may be fulfilled acting on the computational mesh used to solve model equations, preferably avoiding regular Cartesian meshes. In this work, a new version of the TRENT2D model is developed, based on the use of Delaunay, triangular unstructured meshes. To reach second order accuracy, a MUSCL-Hancock approach is considered, with gradient computation performed by means of the multidimensional method proposed in Barth and Jespersen (1989) for Euler equations. The effects of different gradient limiters are also evaluated, aiming at a proper description of the flow dynamics in heterogeneous morphology contexts.
The third complexity issue is both "geometrical" and "mathematical". It concerns the effects of artificial structures, i.e. artificial geometrical constraints, on the flow dynamics. Among different structures aimed expressly at controlling the high-concentration flow behaviour, attention was paid to sluice gates, which can be used in channels and hydropower reservoirs to control sediment routing. In the literature, the effects of sluice gates have been studied especially with reference to clear water flows over fixed beds, while knowledge about the influence on high-concentration flows over mobile beds is still limited. Here, a rough, bread new mathematical description is proposed, in order to take into account the 3D morphodynamics effects caused by sluice gates in high-concentration flow modelling.
The last complexity issue is pretty "numerical" and arises from the challenge of numerical models to comply with the phenomenon complexity. Generally speaking, reliable numerical models are expected to catch the main characteristics of the physical processes at both a general and a local spatial scale, although with a certain level of approximation, depending on the numerical scheme. Sometimes it may be hard to close the gap between the local phenomenon complexity and its numerical representation, leading to non-physical numerical results that could affect hazard assessment. In this work, a particular numerical issue is investigated, which was identified through a thorough analysis of TRENT2D model results. In particular, it was observed that the direction of the numerical mixture-mass flux is occasionally opposite to the direction of numerical solid-mass flux, despite the isokinetic approach which the model is based on. This incoherence was studied with a rigorous method, trying to fix the source of the problem. However, the question turned out to be quite tricky, due to the sophisticated character of the model.
These four, deliberately heterogeneous, "complexity issues" allow to perceive clearly the size of complexity effects on high-concentration modelling. Furthermore, they give the measure of how much diffcult is reaching the right level of detail in describing and modelling high-concentration flows. The research of solutions that are accurate and as much simple as possible was not straightforward and required a quite large effort. Nonetheless, possible solutions were found in the end for three of the four "complexity issues", therefore the goal of the thesis can be considered as achieved
Gas transport properties and free volume structure of polymer nanocomposite membranes
Get PDFThis thesis work presents the results of experimental studies on the gas transport properties of three polymer-based membrane systems: (i) amine-modified epoxy resins, (ii) epoxy resin nanocomposites containing Few Layer Graphene (FLG) nanoplatelets as dispersed fillers and (iii) nanocellulose-based membranes.
The gas transport properties of the present membrane systems were studied by gas phase permeation techniques changing sample temperature and penetrant molecules; results were discussed in the framework of the free volume theory of diffusion, using information on the samples’ free volume structure as experimentally obtained by Positron Annihilation Lifetime Spectroscopy (PALS). Results evidenced that the transport properties of small penetrant molecules are controlled by the membranes’ free volume structure, which determines, in fact, the penetrant diffusion kinetics.
The free volume of epoxy resins was changed by changing their crosslink density but maintaining same chemical environment for penetrant molecules: it was observed that, reducing the free volume structure, the gas diffusivity decreases but no relevant changes in the gas solubility occurred. The experimentally obtained fractional free volume values permitted to reproduce the measured diffusivity values and their variation with temperature, using equations provided by the free volume theory of diffusion.
Increasing the amount of FLG fillers in epoxy-based nanocomposites, we observed a progressive gas permeability decrease, which was accompanied by a progressive reduction of their free volume. This correlation was attributed to the formation of constrained, gas-impermeable polymer regions at the filler-matrix interfaces. The thickness of these regions was evaluated by the reduction of the nanocomposites’ fractional free volume with respect to the free volume of the pure polymer matrix; its value permits to reproduce quantitatively the experimental permeation data of the nanocomposites at all examined temperatures, filler concentrations and test gases.
Few micrometers thick nanocellulose films deposited on polylactic acid substrates act as impermeable barriers for CO2, O2, and N2 and reduce the D2 (deuterium) and He permeation flux by a factor of approx. 10^3. Penetrant transport through this biopolymer is controlled by the solution-diffusion mechanism and barrier properties are due to the extremely low penetrant diffusivity. The free volume in the nanocellulose coatings consists of interconnected elongated cavities with sub-nanometer cross-sectional size where the selective transport of the small size penetrants is due to sieving effects. D2 and He diffusion has thermally activated character and occurs in configurational regime
Effects of artificial light at night on benthic primary producers in freshwaters
No full textIn recent decades, the use of artificial nocturnal illumination has rapidly increased worldwide, imposing an increase of nocturnal light levels and a disruption of natural cycles of light and dark that have been stable over geological and evolutionary time scales. This wide-spread alteration of the natural light regime by artificial light at night (ALAN) is contributing to global environmental change and raises concerns about the potentially adverse effects on organisms and processes in illuminated ecosystems. Simultaneously, a global shift in outdoor lighting technologies from yellow high-pressure sodium (HPS) to white light-emitting diode (LED) light is taking place, changing the spectral composition of nocturnal illumination. Mounting evidence suggests that ALAN affects microorganisms, plants and animals in both aquatic and terrestrial ecosystems. Light is a major source of energy and an important environmental cue for primary producers that influences and to a large extent drives their growth, production and community structure. Freshwaters are increasingly illuminated at night, as they are often located near the human population centers. Despite this, the impacts of artificial nocturnal illumination in freshwater ecosystems are still largely unknown. In particular, effects on aquatic primary producers in urban and sub-urban rivers and streams have hardly been addressed.
This thesis aimed to investigate effects of artificial nocturnal illumination on biomass and community composition of communities of benthic primary producers in freshwaters, the periphyton. The presented work is based on manipulative field studies performed in two contrasting freshwater systems whose periphyton communities are characterized by different species. The first study was performed in a stream-side flume system on a sub-alpine stream and the second in a lowland agricultural ditch. I found that two to 13 weeks of exposure to LED light at night decreased the biomass of periphyton in both aquatic systems. In stream periphy-ton, the decrease in biomass was observed for periphyton in early developmental stages (up to three weeks), but not that in the later developmental stages (four to six weeks). The effects of LED on community composition were found only in stream periphyton, where it increased the proportion of the dominant autotroph group, the diatoms and decreased the proportion of cya-nobacteria in early developmental stages, but indicated a decreased proportion of diatoms and an increased proportion of cyanobacteria in the later developmental stages. I found that LED light at night altered pigment composition and quantitative taxonomic composition in stream periphyton in later developmental stages and that several diatom and chrysophyte taxa, both autotrophic and heterotrophic, responded to ALAN by increasing or decreasing in abundance in a taxon-specific manner. LED did not affect periphyton community composition in lowland agricultural ditch, likely because periphyton was composed of different species. All effects of LED light were different between the seasons presumably due to seasonal differences in community composition and environmental variables. I did not find any evidence that HPS-light affects either biomass or community composition of periphyton. Differential effects of the two light sources are likely a result of differences in their spectral composition, in particu-lar the high proportion of blue light emitted by LED but not by HPS.
This thesis provides, for the first time, evidence that LED light at night can profoundly affect benthic primary producers and periphyton communities in freshwater systems by reduc-ing their biomass and altering community composition. Systems dominated by periphyton in its early developmental stages, such as streams prone to physical disturbances, are likely to be more sensitive to ALAN compared to systems with stable flow conditions based on the results presented. Periphyton plays a fundamental role in productivity, nutrient and carbon cycling and food supply for higher trophic levels in small, clear waters; its position in the base of aquatic ecosystems suggests that the alterations induced by ALAN may have important con-sequences for ecosystem functions. This should be considered when developing lighting strat-egies for areas close to freshwaters in order to mitigate potentially adverse effects of nocturnal artificial illumination on aquatic ecosystems
Economics of Privacy: Users' Attitudes and Economic Impact of Information Privacy Protection
Get PDFThis doctoral thesis consists of three essays within the field of economics of information privacy examined through the lens of behavioral and experimental economics.
Rapid development and expansion of Internet, mobile and network technologies in the last decades has provided multitudinous opportunities and benefits to both business and society proposing the customized services and personalized offers at a relatively low price and high speed. However, such innovations and progress have also created complex and hazardous issues. One of the main
problems is related to the management of extensive flows of information, containing terabytes of personal data. Collection, storage, analysis, and sharing of this information imply risks and trigger usersâ concerns that range from nearly harmless to significantly pernicious, including tracking of online behavior and location, intrusive or unsolicited marketing, price discrimination, surveillance, hacking attacks, fraud, and identity theft. Some users ignore these issues or at least do not take an action to protect their online privacy. Others try to
limit their activity in Internet, which in turn may inhibit the online shopping acceptance. Yet another group of users gathers personal information protection, for example, by deploying the privacy-enhancing technologies, e.g., ad-blockers, e-mail encryption, etc. The ad-blockers sometimes reduce the revenue of online publishers, which provide the content to their users for free and do not receive the income from advertisers in case the user has blocked ads. The economics of privacy studies the trade-offs related to the positive and negative economic consequences of personal information use by data subjects and its protection by data holders and aims at balancing the interests of both parties optimising the expected utilities of various stakeholders. As technology is penetrating every aspect of human life raising numerous privacy issues and affecting a large number of interested parties, including business, policy-makers, and legislative regulators, the outcome of this research is expected to have a great impact on individual economic markets, consumers, and society as a whole.
The first essay provides an extensive literature review and combines the theoretical and empirical evidence on the impact of advertising in both traditional and digital media in order to gain the insights about the effects of ad-blocking privacy-enhancing technologies on consumersâ welfare. It first studies the views of the main schools of advertising, informative and persuasive. The informative school of advertising emphasizes the positive effects of advertising on sales, competition, product quality, and consumersâ utility and satisfaction by matching buyers to sellers, informing the potential customers about available goods and enhancing their informed purchasing decisions. In contrast, the advocates of persuasive school view advertising as a generator of irrational brand loyalty that distorts consumersâ preferences, inflates product prices, and creates entry barriers. I pay special attention to the targeted advertising, which is typically assumed to have a positive impact on consumersâ welfare if it does not
cause the decrease of product quality and does not involve the extraction of consumersâ surplus through the exploitation of reservation price for discriminating activities. Moreover, the utility of personalized advertising appears to be a function of its accuracy: the more relevant is a targeted offer, the more valuable it is for the customer. I then review the effects of online advertising on the main stakeholders and users and show that the low cost of online advertising leads to excessive advertising volumes causing information overload,
psychological discomfort and reactance, privacy concerns, decreased exploration activities and opinion diversity, and market inefficiency. Finally, as ad-blocking technologies filter advertising content and limit advertising exposure, I analyze the consequences of ad-blocking deployment through the lens of the models on advertising restrictions. The control of advertising volume and its partial restriction would benefit both consumers and businesses more than a complete ban of advertising. For example, advertising exposure caps, which limit the number of times that the same ad is to be shown to a particular user, general reduction of the advertising slots, control of the advertising quality standards, and limitation of tracking would result in a better market equilibrium than can offer an arms race of ad-blockers and anti-ad-blockers. Finally, I review the
solutions alternative to the blocking of advertising content, which include self regulation, non-intrusive ads programs, paywall, intention economy approach that promotes business models, in which user initiates the trade and not the marketer, and active social movements aimed at increasing social awareness and consumer education.
The second essay describes a model of factors affecting Internet usersâ perceptions of websitesâ trustworthiness with respect to their privacy and the intentions to purchase from such websites. Using focus group method I calibrate
a list of websitesâ attributes that represent those factors. Then I run an online survey with 117 adult participants to validate the research model. I find that privacy (including awareness, information collection and control practices),
security, and reputation (including background and feedback) have strong effect on trust and willingness to buy, while website quality plays a marginal role. Although generally trustworthiness perceptions and purchase intentions
are positively correlated, in some cases participants are likely to purchase from the websites that they have judged as untrustworthy. I discuss how behavioral biases and decision-making heuristics may explain this discrepancy between perceptions and behavioral intentions. Finally, I analyze and suggest what factors, particular websitesâ attributes, and individual characteristics have the strongest effect on hindering or advancing customersâ trust and willingness to buy. In the third essay I investigate the decision of experimental subjects to incur the risk of revealing personal information to other participants. I do so by using a novel method to generate personal information that reliably induces privacy concerns in the laboratory. I show that individual decisions to incur privacy risk are correlated with decisions to incur monetary risk. I find that partially depriving subjects of control over the revelation of their personal information does not lead them to lose interest in protecting it. I also find that making
subjects think of privacy decisions after financial decisions reduces their aversion to privacy risk. Finally, surveyed attitude to privacy and explicit willingness to
pay or to accept payments for personal information correlate with willingness to incur privacy risk. Having shown that privacy loss can be assimilated to a monetary loss, I compare decisions to incur risk in privacy lotteries with risk attitude in monetary lotteries to derive estimates of the implicit monetary value of privacy. The average implicit monetary value of privacy is about equal to the average willingness to pay to protect private information, but the two measures do not correlate at the individual level. I conclude by underlining the need to know individual attitudes to risk to properly evaluate individual attitudes to privacy as such
Some aspects in Cosmology: Quantum fluctuations in non flat FLRW space-time and Gravitational mimetic models
No full textThis work is mainly divided in two parts and deals with some aspects of quantum field theory in curved space-time and some open problems related with the cosmological history of our Universe
Imaging Chloride Homeostasis in Neurons
Get PDFIntracellular chloride and pH are fundamental regulators of neuronal excitability and they are often co-modulated during excitation-inhibition activity. The study of their homeostasis requires simultaneous measurements in vivo in multiple neurons. Combining random mutagenesis screening, protein engineering and two-photon-imaging this thesis work led to the discovery of new chloride-sensitive GFP mutants and to the establishment of ratiometric imaging procedures for the quantitative combined imaging of intraneuronal pH and chloride. These achievements have been demonstrated in vivo in the mouse cortex, in real-time monitoring the dynamic changes of ions concentrations during epileptic-like discharges, and in glioblastoma primary cells, measuring osmotic swelling responses to various drugs treatment
Il giudicato e l'esecuzione penale in prospettiva de iure condendo
No full textLa recente casistica giurisprudenziale, elaborata dalle Corti sovranazionali in un continuo e serrato dialogo con le Supreme Corti nazionali, ha dato nuova linfa al dibattito interdisciplinare circa l’incidenza delle fonti sovranazionali rispetto alla modifica e all’integrazione dei sistemi giuridici interni. La complessa evoluzione giurisprudenziale, ancora in atto, ha progressivamente elaborato un nucleo essenziale di garanzie a tutela dei diritti umani della persona sottoposta a procedimento penale, sia nella fase preliminare sia in sede processuale, che ha notevolmente inciso sulle sorti della struttura del processo penale, comportandone, di fatto, un parziale ripensamento in un’ottica sostanziale, e non più, quindi, secondo una visione strettamente procedurale.
Il graduale mutamento del procedimento penale si percepisce maggiormente nella fase dell’esecuzione, in cui la giurisprudenza sovranazionale è intervenuta ripetutamente ad affermare la supremazia dei diritti fondamentali del condannato ed, in particolare, della libertà personale del detenuto, a scapito dei principi procedurali dell’esecuzione della pena, quali, in primis, l’intangibilità del giudicato penale. Si è ritenuto fondamentale quindi procedere, in primo luogo, ad un’indagine sull’effettività dei rapporti tra processo e pena (id est: giudicato e funzione della pena), per suggerire un metodo di studio e di ricerca univoco, nella dimensione del sistema multilivello dei diritti umani, che ad oggi connota profondamente le dinamiche della giustizia penale, per poi procedere, in un secondo tempo, ad una sua applicazione concreta, attraverso una prospettiva privilegiata quale è quella del giudicato e della pena, suggerendo, per tale via, un ripensamento complessivo dell’esecuzione penale e del binomio processo e pena
La repressione all'epoca delle passioni tristi
No full textLa presente tesi di dottorato ha lo scopo di indagare circa il fondamento della potestà punitiva che accomuna le tendenze di politica criminale post-moderne. Queste ultime, infatti, nonostante gli ampi approfondimenti, non hanno trovato ancora un unico paradigma entro il quale ricondursi: in queste pagine, perciò, si proporrà il soggettivismo punitivo, quale chiave di lettura giusfilosofica di tali tendenze. A tal fine, seguendo le diverse fasi del pensiero giuridico occidentale, si tenta innanzitutto di individuare una corrispondenza tra la concezione di diritto e metodo giuridico, da un lato, e l’autorappresentazione filosofica dell’uomo, dall’altro. Si arrivano così a delineare due modelli opposti di diritto penale, che rimandano ciascuno ad uno specifico fondamento della potestà punitiva: da un lato, il modello liberale di carattere oggettivista, che riposa su una concezione dell’uomo quale soggetto autonomo, capace di autodeterminazione; dall’altro, il paradigma soggettivista di stampo autoritario, in cui sembra prevalere un processo di reificazione dell’uomo, che, pur interessando l’intero corpo sociale, ha risvolti particolarmente drammatici per i soggetti coinvolti nel sistema punitivo. Al fine di individuare gli elementi caratterizzanti del soggettivismo punitivo, si passa, dunque, a studiarne alcune manifestazioni storiche: l’animismo, la concezione teocratica del diritto e la teoria dei tipi di autore nazionalsocialista. La struttura che se ne ricava funge da modello per inquadrare le tre correnti post-moderne che si è scelto di prendere ad esame e che presentano le medesime caratteristiche: il diritto penale del nemico, la criminologia mediatica e il diritto penale simbolico.
Oggettivismo e soggettivismo punitivo si presentano, così, come categorie ermeneutiche funzionali a svelare la concezione filosofica sottesa alle tendenze politico-criminali. Il collegamento tra la concezione dell’uomo e la legittimazione della potestà punitiva giunge, dunque, a rivelare che le odierne deviazioni rispetto al modello oggettivista non rappresentano delle mere alterazioni aleatorie, bensì tradiscono una concezione dell’uomo e della società strutturalmente incompatibile con quella alla base del modello garantista: in esse si riflette in tutta la sua portata la crisi di valori di un’epoca dalle passioni tristi
Learning with Shared Information for Image and Video Analysis
Get PDFImage and video recognition is a fundamental and challenging problem in computer vision, which has progressed tremendously fast recently. In the real world, a realistic setting for image or video recognition is that we have some classes containing lots of training data and many classes that contain only a small amount of training data. Therefore, how to use the frequent classes to help learning the rare classes is an open question. Learning with shared information is an emerging topic which can solve this problem. There are different components that can be shared during concept modeling and machine learning procedure, such as sharing generic object parts, sharing attributes, sharing transformations, sharing regularization parameters and sharing training examples, etc. For example, representations based on attributes define a finite vocabulary that is common to all categories, with each category using a subset of the attributes. Therefore, sharing some common attributes for multiple classes will benefit the final recognition system. In this thesis, we investigate some challenging image and video recognition problems under the framework of learning with shared information. My Ph.D research comprised of two parts. The first part focuses on the two domains (source and target) problems where the emphasis is to boost the recognition performance on the target domain by utilizing useful knowledge from source domain. The second part focuses on multi-domains problems where all domains are considered equally important. This means we want to improve performance for all domains by exploring the useful information across domains. In particular, we investigate three topics to achieve this goal in the thesis, which are active domain adaptation, multi-task learning, and dictionary learning, respectively