High-energy terahertz surface optical rectification

The interest in surface terahertz emitters lies in their extremely thin active region, typically hundreds of atomic layers, and the agile surface scalability. The ultimate limit in the achievable emission is determined by the saturation of the several different mechanisms concurring to the THz frequency conversion. Although there is a very prolific debate about the contribution of each process, surface optical rectification has been highlighted as the dominant process at high excitation, but the effective limits in the conversion are largely unknown. The current state of the art suggests that in field-induced optical rectification a maximum limit of the emission may exist and it is ruled by the photocarrier induced neutralisation of the medium's surface field. This would represent the most important impediment to the application of surface optical rectification in high-energy THz emitters. We experimentally unveil novel physical insights in the THz conversion at high excitation energies mediated by the ultrafast surface optical rectification process. The main finding is that the expected total saturation of the Terahertz emission vs pump energy does not actually occur. At high energy, the surface field region contracts towards the surface. We argue that this mechanism weakens the main saturation process, re-establishing a clearly observable quadratic dependence between the emitted THz energy and the excitation. This is relevant in enabling access to intense generation at high fluences

Stefano Bardini's photographic archive: a visual historical document

Stefano Bardini (1836-1922) was a polymath figure; art dealer, collector, amateur architect and photographer. As an art dealer he dominated the scene of art collecting for fifty years, from 1875 until 1922, the date of his death. Stefano Bardini is considered as the art-dealer who reinvented the idea of mediaeval and Renaissance art in Italy. His work influenced the most important museums and private collections of his time and, in 1883 with the establishment of his showroom in his newly built Palazzo Mozzi Bardini, he created an ultra modern space that combined two important elements: the commercial and the museological. Bardini challenged his clients and their nowledge of art with his enigmatic and fascinating displays. He immortalised these displays in his photographs, using a sophisticated process that combined composition, lighting, perspective, symmetry and frames in a unique manner. This study is based on photographs from the Stefano Bardini photographic archive and is an investigation of the images and their composition as a distinctive language. The thesis will explore the visual language of the photographs as historical documents and investigate the influences of Stefano Bardini’s historical and cultural context in order to understand the creative process of his displays and illuminate how the photographic frame reveals his conscious and unconscious intentions. This study’s aim is to investigate how Bardini’s photographs reflect the original history of his time and how much he created a new historical point of view. Until now these photographs have been used to re-trace the destination of works of art sold by Bardini; this thesis has a different focus as its intention is to unfold the symbolic layers of the images and interpret their meanings with reference to the socio-cultural milieu of Bardini’s time. Letters from the Bardini archive and notebooks provide a more specific context for his innovative displays and show the personality of his clients, their art collecting interests and how photography as a relatively new medium for selling, proved to be a useful tool for the practice of art dealing

Ultrafast terahertz characterisation of surface free carrier dynamics

The invention of ultrafast pulsed laser sources, operating with pulse durations shorter than 10-¹²s, has enabled researchers to fully exploit and observe dynamic systems operating on these timescales. Furthermore, the successful amplification of such short pulses then provided the next leap towards observing such fast processes when under much more extreme nonlinear regimes. The amplification of ultrafast sources was considered such a significant impact that Strickland and Mourou were awarded the Nobel prize in Physics for 2018. One such consequence of the ultrafast laser is the birth of time-resolved pump-probe experimental methodologies, where a weak probe pulse is exploited to observe a sample under investigation, while a strong pump pulse modifies the sample via its nonlinear-optical response at ultrafast timescales. It is then trivial to vary the delay between the pump and probe pulses in order to directly measure the dynamical properties of the sample as it relaxes back to equilibrium. This thesis contains the results obtained in the Emergent Photonics research lab, where I have been developing several embodiments of these pump-probe schemes. Understanding of a system's response to extreme excitation is pivotal to my investigation into the generation and manipulation of Terahertz waves, another field born thanks to the invention of the ultrafast laser. One promising approach to the development of Terahertz technologies is through the nonlinear interaction of ultrashort pulses with matter. Therefore, by developing pump-probe approaches which are able to observe specifically the region where such a nonlinear interaction occurs, I am able to reveal and study the complex processes underpinning the Terahertz generation. This thesis is structured as follows. First, in the introduction I will provide an outline of the physical processes relevant to my work and publications, including a full and critical literature review of the fields impacted by my work. Each chapter will then focus on one of my publications, summarising and describing how it relates to my previous work, and explaining how it was received after publication. I will then finish by outlining how my work could be continued in the future and making any concluding remarks

Assessment of coastal fish assemblages before the establishment of a new marine protected area in central Mediterranean: its role in formulating zoning proposal

The fish assemblages of the coastal area of the promontory of Cape Milazzo (Italy, Central Mediterranean), which has been recently designated by the Italian Law to become a national marine protected area (MPA), were characterized by visual censuses carried out over different habitats (rocky algal reef, Posidonia oceanica meadow and soft bottom) and depth ranges (0-3, 4-7, 12-16 and 24-30 m) to identify areas of major concern for the MPA zoning. The study area was divided into 6 sectors to assess spatial-related differences in the assemblage parameters, such as species composition and richness, and the size structure of species of recreational (e.g. SCUBA diving) interest. Fifty-eight taxa (56 species and 2 genera) and 20 families of fishes were totally recorded. Species composition was significantly affected by habitat and depth, whereas no significant changes were detected among sectors. Conversely, species richness and total density of fish showed no significant differences among sectors, habitat types and depth ranges. The majority of species of recreational value was recorded only off the northwestern part of the promontory. The implementation of fishing ban in such an area, characterized by the presence of a rocky bank, would contribute to the recovery of populations of some emblematic species (e.g. groupers and other large predator) and to the enhancement of environmentally sustainable activities such as scuba diving. Throughout the investigated area and, especially, in the eastern and southwestern coasts of the promontory, several species were almost exclusively represented by small and medium sized individuals, a likely consequence of an intense fishing pressure

An updated overview of the geographic and bathymetric distribution of Savalia savaglia

The distribution of gold coral Savalia savaglia is modified on the basis of bibliographic information and recent occurrence data, collected using a ROV (Remotely Operated Vehicle) and SCUBA divers. The species is long-lived, rare and has been exploited in the past by divers for collection purposes. S. savaglia is listed in Annex II of the SPA/BD Protocol of the Barcelona Convention and has a wider distribution than previously thought, including both the Mediterranean Sea and the Atlantic Ocean. Our results highlighted that specimens mainly live at a depth range of 15-90 m, but may reach as deep as 900 m in the Mediterranean Sea. This species can form monospecific facies of hundreds of colonies, as observed in Montenegro (Adriatic Sea), between 10 and 20 m, and in the Canary Islands, at a depth range of 27-70 m. Recent data highlighted numerous cases of specimens that were endangered by lost fishing gear, which exposed this species to further threats. Considering its longevity and structural role, it is urgent to develop an effective protection measure for S. savaglia, thereby increasing research efforts and implementing protection areas for this species

Solitary fibrous tumor

Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm which may be found everywhere in the body. It is now distinguished into two forms, pleural and extrapleural, which morphologically resemble each other. Abdominal localizations are quite rare, with 10 cases only reported in bladder; rarely they can be source of paraneoplastic syndromes (i.e., hypoglycemia secondary to insulin-like growth factor). In April 2006 a 74-year-old white male presented with chills, diaphoresis and acute abdominal pain with hematuria. At admission in emergency he underwent an abdominal Xray (no pathological findings) and an ultrasound examination of the kidneys and urinary tract, which revealed a pelvic hyperechogenic neoformation measuring approximately 10×8×7 cm, compressing the bladder. Blood chemistry at admission revealed only a mild neutrophilic leucocytosis (WBC 16600, N 80%, L 11%), elevated fibrinogen and ESR, and hypoglycemia (38 mg/dL). Macro scopic hematuria was evident, while urinocolture was negative. Contrast enhanced CT scan of the abdomen and pelvic region revealed a large round neoformation dislocating the bladder, with an evident contrast-enhanced periphery and a central necrotic area. Continuous infusion of glucose 5% solution was necessary in order to maintain blood glucose levels above 50 mg/dL. The patient underwent complete surgical resection of an ovoidal mass coated by adipose tissue, with well delimited margins; histological findings were consistent with solitary fibrous tumor (SFT). Hypoglycemia resolved completely with removal of the growth. In this case report we describe a SFT growing in the bladder, a quite rare localization, which presented a unique hypoglycemia. In contrast to the majority of cases reported in the literature, the behavior of this SFT was not aggressive, and, since the patient is still alive, surgical resection was considered conclusive

An updated overview of the geographic and bathymetric distribution of Savalia savaglia

The distribution of gold coral Savalia savaglia is modified on the basis of bibliographic information and recent occurrence data, collected using a ROV (Remotely Operated Vehicle) and SCUBA divers. The species is long-lived, rare and has been exploited in the past by divers for collection purposes. S. savaglia is listed in Annex II of the SPA/BD Protocol of the Barcelona Convention and has a wider distribution than previously thought, including both the Mediterranean Sea and the Atlantic Ocean. Our results highlighted that specimens mainly live at a depth range of 15-90 m, but may reach as deep as 900 m in the Mediterranean Sea. This species can form monospecific facies of hundreds of colonies, as observed in Montenegro (Adriatic Sea), between 10 and 20 m, and in the Canary Islands, at a depth range of 27-70 m. Recent data highlighted numerous cases of specimens that were endangered by lost fishing gear, which exposed this species to further threats. Considering its longevity and structural role, it is urgent to develop an effective protection measure for S. savaglia, thereby increasing research efforts and implementing protection areas for this species

Optimization of a 3D dynamic culturing system for in vitro modeling of Frontotemporal Neurodegeneration-relevant pathologic features

Frontotemporal lobar degeneration (FTLD) is a severe neurodegenerative disorder that is diagnosed with increasing frequency in clinical setting. Currently, no therapy is available and in addition the molecular basis of the disease are far from being elucidated. Consequently, it is of pivotal importance to develop reliable and cost-effective in vitro models for basic research purposes and drug screening. To this respect, recent results in the field of Alzheimer’s disease have suggested that a tridimensional (3D) environment is an added value to better model key pathologic features of the disease. Here, we have tried to add complexity to the 3D cell culturing concept by using a microfluidic bioreactor, where cells are cultured under a continuous flow of medium, thus mimicking the interstitial fluid movement that actually perfuses the body tissues, including the brain. We have implemented this model using a neuronal-like cell line (SH-SY5Y), a widely exploited cell model for neurodegenerative disorders that shows some basic features relevant for FTLD modeling, such as the release of the FTLD-related protein progranulin (PRGN) in specific vesicles (exosomes). We have efficiently seeded the cells on 3D scaffolds, optimized a disease-relevant oxidative stress experiment (by targeting mitochondrial function that is one of the possible FTLD-involved pathological mechanisms) and evaluated cell metabolic activity in dynamic culture in comparison to static conditions, finding that SH-SY5Y cells cultured in 3D scaffold are susceptible to the oxidative damage triggered by a mitochondrial-targeting toxin (6-OHDA) and that the same cells cultured in dynamic conditions kept their basic capacity to secrete PRGN in exosomes once recovered from the bioreactor and plated in standard 2D conditions. We think that a further improvement of our microfluidic system may help in providing a full device where assessing basic FTLD-related features (including PRGN dynamic secretion) that may be useful for monitoring disease progression over time or evaluating therapeutic interventions

Cancer incidence and congenital anomalies evaluation in the contaminated sites of Sesto San Giovanni – the SENTIERI Project

The Italian Institute for Environmental Protection and Research defines National Priority Contaminated Sites (NPCSs) as land where hazardous substances are likely to pose a risk to human health. SENTIERI was the first national project evaluating the health status of residents in NPCSs. We have extended, for the site of Sesto San Giovanni, the evaluation to cancer incidence and congenital anomalies (CAs). We have found an overall protective effect of living in the NPCS for overall cancer incidence in all ages and no association in paediatric, adolescent and young adults’ population. We have found an excess risk for bladder cancer, leukaemia, lymphoid leukaemia and chronic lymphocytic leukaemia in men and for lung and breast cancer in women. For the paediatric and adolescent population, we have found an excess in embryonic tumours. Total CAs were not different from expected, while we have found excesses regarding congenital ear, face and neck, digestive system and chromosomal defects