Photocatalytic water splitting using solar energy could contribute to the solution of environmental and energy issues related to the hydrogen production. Key research area in this field is the development of photo-catalyst able to provide high energy conversion efficiency. TiO2 has been mostly preferred material as the photo-electrode due to many advantages, mainly related to the cost factor and stability. We have studied on hydrogen production by water splitting in photo-electrochemical cells prepared by using photoanodes made by two different kinds of TiO2: one deposited by RF sputtering and the other one by sol-gel method. Depositions were performed on electrical conducting ITO whose electrical properties plays vital role to reduce the photon energy loss. The photoanodes have been characterised by several techniques to infer on their optical and compositional properties. The observed differences in hydrogen production have been attributed to the peculiarities in absorption properties of the two TiO2 films that in the case of sputter-deposited films are more prone to absorb radiation also because of the produced defects during the deposition process. Metals like Cr and Fe were doped in TiO2 by RF magnetron sputtering and sol-gel methods to increase the efficiency of hydrogen production by water splitting by sensitizing the doped-TiO2 in visible light spectrum. The doping method, dopant concentration, charge transfer from metal dopants to TiO2, and type of dopants used for modification of TiO2 were investigated for their ability to enhance photocatalytic activity. UV-Visible spectra show that the sputter-metaldoped- TiO2 films are much more efficient than the chemically-prepared samples to induce red shift of the absorption edge for absorbing visible light. In addition, we proved that dopant atoms must be located, at low concentration, near the ITO-TiO2 interface to avoid the formation of recombination centers for photo-generated electron-hole pairs. H2 production rate is higher with Fe-doped TiO2 (15.5 μmole/h) than with Cr-doped TiO2 (5.3 μmole/h) because Fe ions trap both electrons and holes thus avoiding recombination. On the other hand, Cr can only trap one type of charge carrier. To increase the light conversion efficiency and reduce the recombination processes of Cr-doped TiO2, a multilayer structure of ITO/Cr-doped-TiO2 (9 at.%) was developed. When the multilayer films were exposed to visible light, we observed that the photocurrent increases as function of the number of bilayers by reaching the maximum with 6-bilayers of ITO/Crdoped-TiO2. The enhanced photocurrent is attributed to: 1) higher absorption of visible light by Cr-doped-TiO2, 2) number of space-charge layers in form of ITO/TiO2 interfaces in multilayer films, and 3) generation of photoelectrons just in/or near to the spacecharge layer by decreasing the Cr-doped-TiO2 layer thickness. The superior photocatalytic efficiency of the 6-bilayers film implies higher hydrogen production rate through water splitting: we obtained indeed 24.4 μmole/h of H2 production rate, a value about two times higher than that of pure TiO2 (12.5 μmole/h). Similar experiment we performed by doing TiO2 with vanadium metal. With 6-ilayers vanadium doped TiO2 film Shows higher hydrogen production rate of about 31.2 μmole/h. This rate is higher than that of CR doped and pure TiO2. A constant H2 generation rate is obtained for long periods of time by all the investigated TiO2 films because of the separate evolution of H2 and O2 gas, thus eliminating the back-reaction effect. Even Ar+ or N+ ion implantation of energy 30 keV was adopted to vary the energy band gap of TiO2 film in order to absorb visible light.The original anatase phase was not changed by implantation. Increase in full visible absorption range was observed for both kinds of ion implanted-TiO2 films which further increases with the ion fluencies, while N+ ion implantation also causes the shift of the absorption edge from UV to visible light range. N+ implanted TiO2 showed narrowing of band gap from 3.2 eV for untreated anatase TiO2 to 2.78 eV for maximum implantation dose. The Ar+ and N+ implantation creates oxygen vacancies related defect energy level in the band gap. In case of N+ implantation, nitrogen also substitutionally replaces the oxygen atoms thus forming an energy level just above the valence band which further interacts with O 2p states resulting in the narrowing of band gap. The black solar absorber material develop over the copper target to absorb concentrated solar radiation and supply heat to the surrounding water. A black copper oxide layer was synthesized over copper substrate by using chemical oxidation treatment. We varied several treatment parameters and optimized the best condition to obtain a black textured layer which has the properties to absorb total solar radiation. The untreated polished copper showed 50 to 60 % reflectance (R) (incidence angle of 15o) and this value decreases to almost zero for whole wavelength range after formation of black copper oxide. The percentage absorption decreases by negligible amount as the angle of incidence increases. The SEM images of the copper oxide layer at high magnification showed a nano-petal like structure which causes the surface texture effect for higher absorption where surface irregularities such as grooves and pores with dimensions similar to the wavelength of the incident radiation simply increase the solar absorptance by multiple reflections. Long time thermal stability and corrosion resistance in hot water was also studied for the copper oxide film. The results revealed that the copper oxide was very stable and showed no changes in optical properties after the test. For the same water heating system a quartz window is used through which the solar radiation is transmitted on the copper target. Thus to acquire high power conversion efficiency it is necessary for quartz window to transmit the entire solar radiation incident on it without much lost due to the reflection on the surface. In general quartz window is able to transmit 90-91 % of the solar radiation while 1-2 % is absorbed and 7-8 % is reflected from the surface. Thus to have nearly complete transmittance it is necessary to cover the surface of quartz window with anti-reflecting (AR) coating: this was the part of my work. We developed single-layer and multi-layer AR coating for single specific wavelength and broad-band wavelength range respectively. Low reflective index material like MgF2 is deposited by e-beam technique to obtain single-layer AR coating. While Al2O3 and ZrO2 layers deposited, by RF-magnetron sputtering, on top of MgF2 forms multi-layer AR coating. The combination of MgF2/ZrO2/Al2O3/MgF2 deposited on both side of quartz showed excellent results with reflectance value of around 0.8% in broad spectral range. The heat exchanger efficiency obtained after using these developed black copper oxide absorber material and AR coating is around 83 % which seems to be significantly higher than the other commercially available water heating system. Concentrating solar power (CSP) systems are utilized to convert sunlight to thermal electric power by using solar absorber. However, the solar absorber are operated at elevated temperature (700-800 oC) and should be spectrally selective to act as perfect absorbers over the solar spectrum (high solar absorptance (α)) and perfect reflectors in the thermal infrared (IR) (low thermal emittance (ε)). Cermet composite solar absorber shows such selective properties at high temperatures. In the present work, we developed Al-AlN based multilayer cermet films by RF magnetron sputtering. We choose combination of Ni/AlxN(1-x)/AlN layers as a solar absorber due to its stability at elevated temperature and high corrosion resistance. In this combination, Ni layer, deposited near to substrate, act as the IR light reflector to provide high thermal emittance. While AlxN(1-x) layer act as an absorber layer for UV-Vis spectrum of solar radiation and transparent AlN layer on top functions as AR coating. To improve absorptance, 3 or 4 layers of AlxN(1-x) film with grading of metal content was synthesized by varying N2 flow during deposition. The optical measurement for these multilayer selective absorber films showed high solar absorptance of 0.92-0.96 and low thermal emittance of around 0.1-0.07. To test the stability of our multilayer coating at high temperature, we annealed these samples at 700 oC with holding time of 2 hrs in air, low vacuum and high vacuum. We observed a slight decrease in solar absorptance value (0.90) for the annealed samples but the results showed that overall performance was not hindered by heat treatment thus proving the thermal stability of our multilayer cermet coating.

In this work we develop Quantum Monte Carlo techniques suitable for exploring both ground state and dynamical properties of interacting many-body systems. We then apply these techniques to the study of excitations in superfluid He4 and to explore the structure of nuclear systems using chiral effective field theory interactions.

Fossil fuels have been critical to the development of modern society, but concerns over pollution, environmental degradation and climate change demand humans transition to renewable sources of energy. Solar energy is, among renewables, by far the largest exploitable resource, providing more energy in 1 hour to the earth than all of the energy consumed by humans in an entire year. The principal problem related to solar energy use is its intermittency. Collecting and storing solar energy in chemical bonds (solar fuel), as nature accomplishes through photosynthesis, is possible through photo-electrochemical water splitting, a clean and sustainable way for hydrogen production. The materials used as photo-electrodes in a photo-electrochemical cell must fulfil a variety of thermodynamic and kinetic requirements to ensure good efficiency and durability. Since there is no material in nature satisfying all these requirements, tailoring the optical, electrical, and morphological properties of the existing materials to construct photo-electrodes with the desired performance is a big task for materials scientists. In this thesis, we study TiO2 based photo-catalysts and Fe2O3 based water oxidation catalysts. TiO2 thin films were deposited by radio frequency magnetron sputtering technique and their optical, electrical and morphological properties were changed to enhance the visible light absorption and/or limit the recombination rate of charge carriers. More specifically, the effect of compensated (V and N) and non compensated (Cu and N) n-p codoping of TiO2 was studied. The role of coupling TiO2 thin films with indium tin oxide films in single and multilayer structures, compact and porous morphologies was underlined. The effect of hydrogen doping in passivating dangling bonds in TiO2 was demonstrated. Fe2O3 nanoparticles assembled coatings were synthesized by pulsed laser deposition and studied for the functionalization of electrodes and absorbers surfaces as water oxidation catalysts. The response of the optical and electrochemical properties of the coating to the tuning of film morphology was studied, ranging from a low-transmittance compact layer to a porous nanoparticle-assembled coating, which resulted to be highly transparent. Materials properties were characterized by various techniques such as Raman spectroscopy, x-ray diffraction, UV-vis spectroscopy, x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, and scanning electron microscopy. Electrochemical and photo-electrochemical properties of the samples were studied by testing them as electrodes in a photoelectrochemical cell. Both materials were chosen because they are widespread, non-hazardous, biocompatible and scalable. This enables the large-scale application of photo-electrochemical water splitting and the full exploitation of the green potential of this technology.

This research deals with the study of current pastoral seasonal settlement patterns in the uplands of Val di Fiemme (Trentino province), in order to create a quantitative locational model for predicting archaeological pastoral site locations. In fact, few archaeological sites related to pastoral economy are known in the Alps, and this lack of data affects the interpretation of the ancient pastoral strategies. A predictive model could be useful to identify new sites and to optimize archaeological surveys in mountain environments. However, inductive predictive modelling is considered a field with many unresolved theoretical problems. Ethnoarchaeology of pastoralism seems to be a good method to provide a behavioural framework for predictive modelling, and the interaction with quantitative approaches may be worthwhile to improve the ethnoarchaeological methods and theory as well. The ethnoarcheological research is divided into two parts: a “desk ethnoarchaeology†, the spatial analysis of the relationship between current pastoral/dairying sites (malghe) and mountain environment of Val di Fiemme, in order to create an inductive predictive model; and a “field ethnoarchaeology†, the study of the relationship between modern shepherds/dairymen and environment, in order to understand their locational strategies. The interaction between the first and the second part has enabled the interpretation of the settlement pattern of modern malghe in Val di Fiemme. It has hence been assumed that the model can predict the location of modern and ancient dairying sites, as the malghe are mainly related to milking, milk-processing and cheese storing activities. The final step has been the archaeological evaluation. The predictive model doesn’t predict the location of Mesolithic hunting sites in the uplands of Val di Fiemme. It predicts instead the location of some dry-stone enclosures in the upland valleys of Ortisé (Mezzana, Val di Sole, TN), while it doesn’t predict the location of rock-shelters in the same area. It has therefore been assumed that enclosures were linked to dairying economy and rock-shelters to simple (“dry†) pastoralism. Further qualitative tests of the model have been carried out in different areas of the Alpine arc. These results allow two different application of the model: a “predictive†application, aimed at finding new pastoral sites in the uplands, and an “interpretative†application, aimed at discriminating hunting sites and simple pastoral sites from dairying sites. Furthermore, this model has suggested that the interaction between predictive modelling and ethnoarchaeology is useful to tackle the theoretical and methodological problems of these fields of research.

To gain a deeper insight on the local origin of NTE in zincblende crystals, EXAFS measurements have been performed on CdTe, which has NTE properties intermediate between Ge and CuCl. In this work an accurate evaluation of the bond thermal expansion, parallel and perpendicular MSRDs and distribution asymmetry of the first shell of CdTe has been made, obtaining a good agreement between two different procedures of the data analysis (i) ratio method (ii) FEFF6-FEFFIT method. The values of the relevant parameters of CdTe were found intermediate between the corresponding values previously found for Ge and CuCl. The positive contribution to thermal expansion due to the bond stretching and the negative contribution due to the tension effects are disentangled and quatified in terms of the bond thermal expansion and the perpendicular MSRD, respectively, determined by the EXAFS analysis. A critical comparison of EXAFS and Bragg diffraction results; thermal expansion, thermal factors and correlation of atomic vibration, for the iso-structural crystals Ge, CdTe and CuCl has been performed. The correlation between several quantities measured by EXAFS and NTE properties is confirmed.

Matter at the nanoscale exhibits peculiar properties, often not shown by the bulk counterpart, and strongly coupled to the specific size, shape and structure of the atomic aggregate. Particularly, the enormous surface-to-volume ratio implies boosted reactivity with respect to the environment, while the electronic confinement might cause quantum effects to dominate physical properties. Characterization techniques are of course essential to investigate properties at the atomic scale. Scattering techniques have tremendously evolved in the recent past benefiting from third and fourth generation light sources, producing beams with unprecedented spatial and temporal resolution. In a different realm, atomistic simulations have also greatly evolved deriving advantages from both recent theories and modern computing units. In this framework, a detailed description of the system in a spatial and temporal range compatible with lengths probed by scattering techniques is provided. In a single sentence, the subject of this Thesis is the effort of tying atomistic methods and scattering techniques so to increase the comprehension around size, shape and structure of nanostructured particles.

Nell'aprile del 1773, Parigi fu scossa dal timore che una cometa provocasse un disastroso cataclisma. All'origine del clamore, il "Mémoire sur les comètes" dell'astronomo Lalande (Bourg-en-Bresse 1732-Paris, 1807), che aveva sostenuto la non impossibilità fisica e matematica di uno scontro/incontro tra Terra e comete.

When a second-order phase transition is crossed at finite speed, domains with independent order parameters can appear in the system, with the consequent formation of defects at the domain boundaries. The Kibble-Zurek theory provides a description for this universal phenomenon, which applies to many different systems in nature, and it predicts a power-law dependence of the defect density on the quench rate. This thesis reports on the results of the experimental study of the Kibble-Zurek mechanism in elongated Bose-Einstein condensates of atomic sodium gases, following the observations on the spontaneous formation of defects after temperature quenches across the BEC transition. The power-law scaling of the defect number with the quench speed was observed and characterized for the first time in ultracold gases. The characterization of the density and phase profiles of the defects allowed their identification as solitonic vortices, representing the first direct experimental evidence for this kind of long living excitation, which sets a link between solitons and vortices. The measurements reported in this thesis provide a novel approach to the study of the critical phenomena happening at phase transitions, and introduce to the possibility of exploring the turbulent dynamics of quenched systems through the spontaneous production of solitonic vortices.

Tra Paley e Bentham l’utilitarismo attraversò, nel giro di pochi anni, la sua linea d’ombra, e pur mantenendo dei tratti riconoscibili di continuità mutò in modo evidente la propria configurazione e organizzazione teorica. Nella prospettiva della storia di questa peculiare dottrina, lo scoccare di uno dei più importanti momenti di passaggio della modernità si può collocare con una certa precisione, tra il 1785 (l’anno della pubblicazione dei Principles of Moral and Political philosophy di Paley) e il 1789 (l’anno della pubblicazione della Introduction to the principles of Morals and Legislation di Bentham, e che evidentemente è significativo anche per altre clamorose manifestazioni di novità nel mondo istituzionale e politico). Anche in quella peculiare elaborazione collettiva che fu in quel periodo il dibattito che portò alle più importanti prese di posizione pubbliche degli utilitaristi inglesi, si può situare in quegli anni il momento in cui il progressivo “disincanto del mondo” si è fatto concezione generale e sistematica della vita associata degli uomini e del mondo cui essi appartengono. Proprio il passaggio, nel volgere di pochi anni, dall’utilitarismo di Paley a quello di Bentham, comportò – partendo da elementi dottrinali molto simili – una concezione completamente nuova della legittimazione dell’autorità, e una parte rilevante di questo spostamento teorico ed ideologico riguardò questioni apparentemente eterogenee, quali il tema dell’origine del mondo, l’opportunità o meno di prestare giuramento nei tribunali, l’analisi della coerenza logica del catechismo impiegato nell’istruzione religiosa inglese e l’indirizzo esatto della casa di un certo Anania, oscuro abitante della Damasco del primo secolo dopo Cristo.

The experimental achievement of Bose-Einstein condensation and Fermi degeneracy with ultracold gases boosted tremendous progresses both in theoretical methods and in the development of new experimental tools. Among them, intriguing possibilities have been opened by the implementation of optical lattices: periodic potentials for neutral atoms created by interfering laser beams. Degenerate gases in optical lattices can be forced in highly anisotropic traps, reducing the effective dimensionality of the system. From a fundamental point of view, the behavior of matter waves in reduced dimensions sheds light on the intimate properties of interparticle interactions. Furthermore, such reduced-dimensional systems can be engineered to quantum-simulate fasci- nating solid state systems, like bidimensional crystals, in a clean and controllable environment. Motivated by the exciting perspectives of this field, we devote this Thesis to the theoretical study of two systems where matter waves propagate in reduced dimensions. The long-range and anisotropic character of the dipole-dipole interaction critically affects the behavior of dipolar quantum gases. The continuous experimental progresses in this flourishing field might lead very soon to the creation of degenerate dipolar gases in optical potentials. In the first part of this Thesis, we investigate the emergence of a single dipolar-induced resonance in the two-body scattering process in quasi-one dimensional geometries. We develop a two-channel approach to describe such a resonance in a highly elongated cigar-shaped harmonic trap, which approximates the single site of a quasi-one-dimensional optical lattice. At this stage, we develop a novel atom-dimer extended Bose-Hubbard model for dipolar bosons in this quasi-one-dimensional optical lattice. Hence we investigate the T = 0 phase diagram of the model by exact diagonalization of a small-sized system, highlighting the effects of the dipolar-induced resonance on the many-body behavior in the lattice. In the second part of the Thesis, we present a general scheme to realize cold-atom quantum simulators of bidimensional atomic crystals, based on the possibility to independently trap two different atomic species. The first one constitutes a two-dimensional matter wave which interacts only with the atoms of the second species, deeply trapped around the nodes of a two-dimensional optical lattice. By introducing a general analytic approach, we investigate the matter-wave transport properties. We propose some illustrative applications to both Bravais (square, triangular) and non-Bravais (graphene, kagomeÌ ) lattices, studying both ideal periodic systems and experimental- sized, eventually disordered, ones. The features of the artificial atomic crystal critically depend on the two-body interspecies interaction strength, which is shown to be widely tunable via 0D-2D mixed-dimensional resonances. Keywords: matter waves, reduced dimensions, dipolar-induced resonances, mixed-dimensional resonances, extended Bose-Hubbard model, atomic artificial crystals.