In this thesis work nanoscrystalline optical properties of diamond and two recent new NCD functionalisation techniques involving UV light (one step method and photochemical oxidation) have been investigated. Firstly the oxidation of diamond surface caused by the irradiation of the surface with UV-light in oxygen atmosphere was considered. Two different experiments in situ were realized in order to understand the physic-chemistry of this method. The chemical bonds between oxygen and surface carbon atoms were investigated by firstly performing an annealing treatment in ultra hight vacuum of a oxidized UV surface and then comparing the obtained result with annealing treatments of two different oxygenated diamond surfaces using other two techniques: plasma oxidation and piranha solution oxidation. An other interesting aspect on which clarity has to be made deal with amination process of diamond surface. As a first fundamental step, the efficiency on hydrogenated diamond surface was investigate. Successively the role of oxygen in the chemistry of amination process was studied performing in situ experiments using different terminated diamond surface (hydrogenated, chemically oxidized, UV oxidized) and different gaese (pure NH3 or NH3 + O2).

No description available.

In this thesis I present two different research topics investigated during the course of my PhD, regarding the analysis of spatial structures in a Bose Einstein condensate. Ultracold atomic gases offer a privileged platform for such kind of experiments, thanks to the fine control that can be achieved on the system’s parameters and to the availability of advanced imaging schemes allowing for a great measurement accuracy. The first topic is about the shape of quantized vortices in an elongated condensate, with the goal of providing a quantitative analysis of the density structure of a quantized vortex filament hosted in a bulk 3D superfluid. We analyzed the shape of the vortex and studied its dynamics during a free expansion, or time of flight (TOF), of the hosting BEC, with the goal of making a quantitative comparison between theory and experiment for the structure of the core of a quantized vortex in three-dimensional (3D) condensates. Simultaneously imaging the sample along orthogonal directions after a long TOF allowed to map the complete 3D shape of the vortex at the end of the free flight, while the full expansion dynamics has been simulated with numerical solutions of the Gross-Pitaevskii equation. The same data analysis procedure has been applied to both the experimental images and to the density profiles computed with the simulations to ensure a faithful comparison. We were able to detail the evolution of the vortex parameters at all times combining a simple analytic scaling-law model valid at early times, experimental data for the width and the depth of the core at long expansion times, and the numerics that were used to bridge between the two. Additionally, we could check the validity of the predictions on the scaling of vortex parameters with the size of the BEC using the experimental data to interpolate between theoretical limiting models. We concluded that quantized vortex filaments can be optically imaged with standard techniques in 3D atomic BECs, at a level of accuracy which indeed is enough to show good quantitative agreement with the predictions of the GP theory for the width, depth, and overall shape of the vortex core. The second topic is a measurement of the equation of state of a single component BEC. The goal of this project is to verify the non-monotonic behaviour of the chemical potential of a homogeneous Bose gas of weakly interacting particles as a function of temperature, where one expects to find a maximum across the critical point of transition to the superfluid phase. This effect is believed to be a general feature of the normal-to-superfluid phase transition: it has been already experimentally demonstrated in unitary Fermi gases, and although the same is predicted to happen also in a gas of weakly interacting bosons, no experimental evidence has been reported so far. The measurement relies on the local density approximation, which allows to extract information about the thermodynamics of a homogeneous system from accurate measurements of the local properties of a trapped one. My work has focused on developing a series of imaging and data analysis techniques to measure the 3D density profile of a harmonically trapped gas, even in regimes of extreme density such as inside a Bose condensate. With a new high-dynamic-range method we were able to image the 3D density distribution of a trapped sample, leading to a low-noise measurement of the density distribution. We confirmed the existence of the non-monotonic behaviour of the chemicial potential across, and set the basis for further measurements of the thermodynamics of the system across the transition.In this thesis I present two different research topics investigated during the course of my PhD, regarding the analysis of spatial structures in a Bose Einstein condensate. Ultracold atomic gases offer a privileged platform for such kind of experiments, thanks to the fine control that can be achieved on the system’s parameters and to the availability of advanced imaging schemes allowing for a great measurement accuracy. The first topic is about the shape of quantized vortices in an elongated condensate, with the goal of providing a quantitative analysis of the density structure of a quantized vortex filament hosted in a bulk 3D superfluid. We analyzed the shape of the vortex and studied its dynamics during a free expansion, or time of flight (TOF), of the hosting BEC, with the goal of making a quantitative comparison between theory and experiment for the structure of the core of a quantized vortex in three-dimensional (3D) condensates. Simultaneously imaging the sample along orthogonal directions after a long TOF allowed to map the complete 3D shape of the vortex at the end of the free flight, while the full expansion dynamics has been simulated with numerical solutions of the Gross-Pitaevskii equation. The same data analysis procedure has been applied to both the experimental images and to the density profiles computed with the simulations to ensure a faithful comparison. We were able to detail the evolution of the vortex parameters at all times combining a simple analytic scaling-law model valid at early times, experimental data for the width and the depth of the core at long expansion times, and the numerics that were used to bridge between the two. Additionally, we could check the validity of the predictions on the scaling of vortex parameters with the size of the BEC using the experimental data to interpolate between theoretical limiting models. We concluded that quantized vortex filaments can be optically imaged with standard techniques in 3D atomic BECs, at a level of accuracy which indeed is enough to show good quantitative agreement with the predictions of the GP theory for the width, depth, and overall shape of the vortex core. The second topic is a measurement of the equation of state of a single component BEC. The goal of this project is to verify the non-monotonic behaviour of the chemical potential of a homogeneous Bose gas of weakly interacting particles as a function of temperature, where one expects to find a maximum across the critical point of transition to the superfluid phase. This effect is believed to be a general feature of the normal-to-superfluid phase transition: it has been already experimentally demonstrated in unitary Fermi gases, and although the same is predicted to happen also in a gas of weakly interacting bosons, no experimental evidence has been reported so far. The measurement relies on the local density approximation, which allows to extract information about the thermodynamics of a homogeneous system from accurate measurements of the local properties of a trapped one. My work has focused on developing a series of imaging and data analysis techniques to measure the 3D density profile of a harmonically trapped gas, even in regimes of extreme density such as inside a Bose condensate. With a new high-dynamic-range method we were able to image the 3D density distribution of a trapped sample, leading to a low-noise measurement of the density distribution. We confirmed the existence of the non-monotonic behaviour of the chemicial potential across, and set the basis for further measurements of the thermodynamics of the system across the transition.

Weather and climate are topical issues widely present in the media, in the public culture, in political and socio-economic agendas and also in school guidelines. Having said that, confusion and a lot of misconceptions still exist with regards to issues such as climate change, greenhouse gases and the greenhouse effect, pollution, anthropogenic emissions, ozone hole, predictability of weather and climate, stationary processes, radiation fluxes and balances in the Earth system etc. These themes are poorly addressed in the actual teaching practice in secondary schools, particularly from a quantitative point of view involving the underlying laws of physics, which are necessary for the understanding and construction of correct conceptual models of phenomena. Teachers often do not feel comfortable or lack the specific background for addressing such themes quantitatively, claiming for training initiatives which happen unfortunately only as a result of sporadic and local initiatives. For historical reasons, typical of the Italian context, these themes are usually addressed in subjects like geography or natural sciences for what concerns education in formal contexts such as primary and secondary schools and universities, but their treatment and significance would greatly benefit from an interdisciplinary approach, involving also the quantitative experimental approach of physics. At the same time, teaching physics from its general principles to their application in the context of weather phenomena and climate system, would improve the engagement and interest of students, fostering cooperation among teachers of different subjects, bridging boundaries and approaches characteristic of single disciplines. This would promote an integrated view of science as the result of a process, based on the application of the scientific method to the investigation and modeling of phenomena, where also technological advancement plays an important role, rather than as a mere collection of results and knowledge. In this perspective the present work develops from the research in atmospheric physics, performed by the candidate during one year at Concordia station, Antarctica, presenting on one hand a series of physics communication initiatives designed and tested with innovative formats such as TEDx conferences, videoconferences with researchers working on the field, social platforms and traditional media, targeted to different audiences. On the other hand it presents the proposal of a teaching learning sequence based on quantitative experimental activities, demonstrations and simulations, targeted to secondary school students and pre-service teachers, integrating general physics with its applications to the atmosphere and to the climate system. The teaching learning sequence has been experimented with graduate students of the course: ''Experimental physics laboratory at high school I'', held at the Department of Physics of the University of Trento and in collaboration with IPRASE, it has been proposed in the form of a training course for physics and chemistry teachers and their technical assistants as a framework for the integration of physics and chemistry. The results of pre and post tests used as an evaluation tool of this preliminary experimentation will be presented, encouraging future developments of the sequence and further diffusion of weather and climate issues in the teaching practice through capillary pre-teachers' and teachers' training initiatives.

This thesis proposes to provide a unified and systematic strategy to overcome the second timescale in protein folding, by exploiting qualities and drawbacks of the Bias Functional Method and proposing new theoretical approaches to overcome its limitations. The first half of the thesis is dedicated to the development of theoretical solutions to the dependence of the Bias Functional Method on an a-priori defined collective coordinate and microscopic non-reversibility of the dynamics. The second part of the manuscript is devoted to applications of the BF method on two different proteins: Canine milk lysozyme and alpha1-antitrypsin (A1AT).

The aim of this thesis is the study of electronic transport and mechanical properties of materials using computer simulations. In particular, we dealt with the charge transport in semiconduc- tor and metallic samples and with the peeling of a graphene layer from bulk graphite. The computational methods used to investigate the samples are (i) the Monte Carlo (MC) statis- tical method to simulate the transport of electrons in solids and (ii) the molecular dynamic (MD) approach to study the mechanical characteristics. A relevant part of this thesis is focused on carbon-based material, such as diamond and graphite, and the stable two-dimensional al- lotrope, graphene. The response of diamond and graphite to external electromagnetic pertur- bations, due to e.g. an impinging electron beam, was investigated by calculating reflection electron energy loss (REEL) spectra with MC simulations. By comparing the calculated spec- tra, obtained using different dielectric models, and in-house recorded experimental results, the most effective dielectric model better describing the plasma losses was identified. Moreover, an extension to these models to describe the anisotropic response of graphite to an external electromagnetic perturbation was developed and included in the MC approach. Owing to the central role of carbon for future electronic and technological applications, also its mechanical properties were investigated by means of MD simulations. In particular, the peeling process of a layer of graphene from a bulk of graphite was investigated. This process is exploitable for graphene production and for adhesive applications of this material. Moreover, the MC approach, employed for calculating REEL spectra, was tested and compared to other com- putational techniques based on the solution of the Ambartsumian-Chandrasekhar equations. This consistency test was realized by considering three metals (copper, silver and gold) as tar- get materials. Further studies were carried out on these materials by calculating secondary electron emission yields as a function of the electron beam energy. A remarkable good agreement with experimental data was obtained. The MC approach was also used to investigate the growth of particles in a W(CO)6 layer deposited on a SiO2 substrate upon irradiations by an electron beam in the context of the focused electron beam induced deposition technique. In particular, by applying the MC method, the radial distribution of emitted secondary electrons was calculated and then utilized as input data for further MD simulations. Moreover, the study of electron transport in an organic polymer (P3HT) was performed in order to understand how the molecular ordering affects the secondary electron emission. This aspect is of paramount importance to construct efficient organic electronic devices.

This thesis deals with the theoretical and computational modelling of materials by using a variety of ab-initio approaches to accurately predict the properties of realistic structures. A number of known and novel carbon-based materials are studied, exploiting the unique versatility of carbon to bind into several bonding configurations, with the aim of tailoring their electronic and mechanical characteristics. In this regard, the methods used to carry out electronic structure simulations depend on the system size: from the Dirac-Hartree-Fock approach to model molecular properties, to Density Functional Theory used for periodic solids, such as diamond and graphene-related materials composed by a few to some hundred of atoms, to Density Functional Tight Binding or plane Tight Binding to study nanowires or Beltrami pseudospheres, which are composed by some hundreds to a few millions atoms. The details of these methods are introduced in the chapters where they are used. The criterion used to present these concepts is to organize the chapters, with the exception of the last one, according to the increasing dimension of the systems. More in details, the first chapter uses the Dirac-Hartree-Fock approach to simulate atoms and molecules, such bromotrifluoromethane; the second chapter deals with periodic systems characterized by unit cells with a relatively small number of atoms, such as diamond and graphite; the third one discusses graphene and graphene-related materials with lower density; the fourth one present a new computational and experimental model of silicon carbide nanowires coated with silicon dioxide shell; the fifth chapter is focused on the study of sp2-hybridized carbon atoms, arranged on a Beltrami surface. The latter topic spans different research fields such as geometrical topology, physics and mechanical engineering. Finally, the last chapter is dedicated to an on going work which deals with the Non-Adiabatic Molecular Dynamics simulation of amorphous silica samples where we couple the nuclear dynamic of the system to the electronic structure.

In this work we discuss some of the most interesting new doors that the diffusion of low-cost, high-tech devices is opening. It is divided in two main sections. In the first part, Chapter I, the general research framework in which we are working is presented. Then, in the second, third and fourth chapters several examples of practical applications regarding the presented topics, all designed and realized by the author (within his research group) are discussed. In particular: a workshop about scientific visualization held at the University of Trento in Chapter II; a teaching/learning sequence based on a low-cost spectrometer in Chapter III; a mediated reality setup for physics education in Chapter IV.

La specificità dell'acquisizione di contenuti attraverso le interfacce digitali condanna l'agente epistemico a un'interazione frammentata, insufficiente da un punto di vista computazionale, mnemonico e temporale, rispetto alla mole informazionale oggi accessibile attraverso una qualunque implementazione della relazione uomo-computer, e invalida l'applicabilità del modello standard di conoscenza, come credenza vera e giustificata, sconfessando il concetto di credenza razionalmente fondata, per formare la quale, sarebbe invece richiesto all'agente di poter disporre appunto di risorse concettuali, computazionali e temporali inaccessibili. La conseguenza è che l'agente, vincolato dalle limitazioni ontologiche tipiche dell'interazione con le interfacce culturali, si vede costretto a ripiegare su processi ambigui, arbitrari e spesso più casuali di quanto creda, di selezione e gestione delle informazioni che danno origine a veri e propri ibridi (alla Latour) epistemologici, fatti di sensazioni e output di programmi, credenze non fondate e bit di testimonianze indirette e di tutta una serie di relazioni umano-digitali che danno adito a rifuggire in una dimensione trascendente che trova nel sacro il suo più immediato ambito di attuazione. Tutto ciò premesso, il presente lavoro si occupa di costruire un nuovo paradigma epistemologico di conoscenza proposizionale ottenibile attraverso un'interfaccia digitale di acquisizione di contenuti, fondato sul nuovo concetto di Tracciatura Digitale, definito come un un processo di acquisizione digitale di un insieme di tracce, ossia meta-informazioni di natura testimoniale. Tale dispositivo, una volta riconosciuto come un processo di comunicazione di contenuti, si baserà sulla ricerca e selezione di meta-informazioni, cioè tracce, che consentiranno l'implementazione di approcci derivati dall'analisi decisionale in condizioni di razionalità limitata, approcci che, oltre ad essere quasi mai utilizzati in tale ambito, sono ontologicamente predisposti per una gestione dell'incertezza quale quella riscontrabile nell'istanziazione dell'ibrido informazionale e che, in determinate condizioni, potranno garantire l'agente sulla bontà epistemica del contenuto acquisito. / The specificity of the acquisition of content through digital interfaces condemns the epistemic agent to a fragmented interaction, with respect to the huge informational bulk today available through any standard implementation of the man-computer relationship, and invalidates the applicability of the standard model of knowledge as justified true belief, by repudiating the concept of rationally founded belief, to form which would instead require the agent to be able to have precisely the conceptual resources and computational time inaccessible. Thereby the agent, bound by the ontological limitations belong to cultural interfaces, is forced to fall back on ambiguous, arbitrary and often more casual than he takes into account, selection and management information process that produce real epistemological hybrids (by Latour) made of feelings, program outputs, unfounded beliefs, bits of indirect testimonies and of a series of human-digital relationships that give rise to escape in a transcendent dimension belonging to anthropological area of the sacred. Starting from this analysis the work deals with constructing a new epistemological paradigm of propositional knowledge obtained through a digital content acquisition, based on the new concept of Digital Tracings, defined as a process of digital capture of a set of tracks , ie meta-information of a testimonial kind. This device, once recognized as a communication process of digital contents, will be based on the research and selection of meta-information, ie tracks, which allow the implementation of approaches derived from analysis of decision-making under bounded rationality, which approaches, as well to be almost never used in this context, are ontologically prepared for dealing with uncertainty such as that came into the informational hybrid and that can provide the agent on the epistemic goodness of acquired content.

Thèse - Toulouse, 1961. / Without thesis statement. Bibliography: p. [289]-296.