A current-voltage model for double Schottky barrier devices

Schottky barriers are often formed at the semiconductor/metal contacts and affect the electrical behaviour of semiconductor devices. In particular, Schottky barriers have been playing a major role in the investigation of the electrical properties of mono and two-dimensional nanostructured materials, although their impact on the current-voltage characteristics has been frequently neglected or misunderstood. In this work, we propose a single equation to describe the current-voltage characteristics of two-terminal semiconductor devices with Schottky contacts. We apply the equation to numerically simulate the electrical behaviour for both ideal and non-ideal Schottky barriers. The proposed model can be used to directly estimate the Schottky barrier height and the ideality factor. We apply it to perfectly reproduce the experimental current-voltage characteristics of ultrathin molybdenum disulphide or tungsten diselenide nanosheets and tungsten disulphide nanotubes. The model constitutes a useful tool for the analysis and the extraction of relevant transport parameters in any two-terminal device with Schottky contacts

Digitalisation, social capital and political participation : an investigation of technological affordance and intensity of social media use

Social Network Sites (SNSs) have attracted the attention of academics and practitioners in the field of Political Marketing, Media Studies, Sociology and Political Science for their capacity to boost social, political and civic engagement. Yet, extant research has yielded contrasting empirical evidence on the impact of different SNSs on Social Capital and Political Participation, possibly due to lack of consideration of the differences among SNSs affordances and their intensity of use. The aim of this study is to enhance the understanding of the relationship between Social Capital and Political Participation, by considering the moderating effects of the technological affordances of different SNSs (Facebook and Twitter), their intensity of use and their combined and not combined use. The broad setting of the research is the growth of “mediatisation” and “digitalisation” of social interactions in the UK. The underlying frameworks of this thesis are the Resource Mobilisation Theory from Political Science, the Social Capital Theory and Social Network Theory from Sociology, in an optic of technological determinism through the lens of technology affordance. To fulfil the aim of this study, a quantitative research strategy with a cross-sectional design were employed. Data were collected through an online, self-completion survey employing measures well established in previous academic research. The sample was randomly selected from a consumer panel owned by a reputed UK-based market research agency, resulting in 1212 valid responses. Partial Least Squares Structural Equation Modeling (PLS-SEM) through the SmartPLS software was used to test the moderation effects of the type of SNSs used, their intensity of use and their combined or not combined use on the relationship between Social Capital and Political Participation. A series of parametric two-way ANOVAs in SPSS and non-parametric two-way ANOVA in R were employed to test for the interaction effects of the type of SNSs used and their intensity of use on Social Capital and Political Participation, respectively. Results show that the type of SNS employed and their intensity of use moderates the relationship between online Social Capital and Political Participation. Moreover, the research findings indicate that an interaction effect between the type of SNSs used and their intensity of use must be considered when analysing the effects of SNSs on Social Capital and Political Participation. Given the relevance and use of Social Capital in different disciplines, this thesis contributes to theoretical knowledge in different academic fields. First, this thesis advances prior work in the domain of Engagement and Mobilisation Theories by expanding the Resource Mobilisation Theory framework through moderation mechanisms working in accordance with the principles of Technology Affordance and Technological determinism. Second, this research advances knowledge in the field of Social Capital and Political Participation by delving into the connections between different SNSs, Online (Bridging/Bonding) Social Capital, Political Participation (online/offline) and their relationships, introducing interaction effects that help to explain the contrasting empirical evidence in extant literature. Third, this thesis introduces a novel perspective to Political Marketing studies, by employing Social Capital as the main element of investigation to advance knowledge in engagement and targeting theories through different SNSs meanwhile maximising social, ethical and democratic engagement. Fourth, this thesis expands on previous SNSs studies in the domain of Media and Communication that have argued that social media affordances facilitate specific political behaviour. Integrating the Affordance thesis with the intensity of use of SNSs clarifies several competing theories related to media usage

Emerging Processing Technologies for the Recovery of Valuable Bioactive Compounds from Potato Peels

Potato peel (PP) is the major underutilised by-product in the potato-processing industry and a potential source of valuable bioactive molecules. Among them, glycoalkaloids and polyphenols are important precursors for steroid hormones and natural antioxidants, respectively. Moreover, the huge quantities of industrial potato-peel waste that are produced are a rich source of primary metabolites, which principally include starch as well as non-starch polysaccharides, proteins, lipids, lignin and cellulose. All carbohydrates are prone to undergo fermentation to produce ethanol, lactic and acetic acid. Finally, the main portion of PP is made up of alcohol-insoluble matter with a dietary fibre content of approximatively 40%. The present review summarises the recent advances and emerging technologies in potato-peel extraction and further valorisation processing in the food industry

Bayesian Integration in a Spiking Neural System for Sensorimotor Control

The brain continuously estimates the state of body and environment, with specific regions that are thought to act as Bayesian estimator, optimally integrating noisy and delayed sensory feedback with sensory predictions generated by the cerebellum. In control theory, Bayesian estimators are usually implemented using high-level representations. In this work, we designed a new spike-based computational model of a Bayesian estimator. The state estimator receives spiking activity from two neural populations encoding the sensory feedback and the cerebellar prediction, and it continuously computes the spike variability within each population as a reliability index of the signal these populations encode. The state estimator output encodes the current state estimate. We simulated a reaching task at different stages of cerebellar learning. The activity of the sensory feedback neurons encoded a noisy version of the trajectory after actual movement, with an almost constant intrapopulation spiking variability. Conversely, the activity of the cerebellar output neurons depended on the phase of the learning process. Before learning, they fired at their baseline not encoding any relevant information, and the variability was set to be higher than that of the sensory feedback (more reliable, albeit delayed). When learning was complete, their activity encoded the trajectory before the actual execution, providing an accurate sensory prediction; in this case, the variability was set to be lower than that of the sensory feedback. The state estimator model optimally integrated the neural activities of the afferent populations, so that the output state estimate was primarily driven by sensory feedback in prelearning and by the cerebellar prediction in postlearning. It was able to deal even with more complex scenarios, for example, by shifting the dominant source during the movement execution if information availability suddenly changed. The proposed tool will be a critical block within integrated spiking, brain-inspired control systems for simulations of sensorimotor tasks

Field emission from two-dimensional GeAs

GeAs is a layered material of the IV-V groups that is attracting growing attention for possible applications in electronic and optoelectronic devices. In this study, exfoliated multilayer GeAs nanoflakes are structurally characterized and used as the channel of back-gate field-effect transistors. It is shown that their gate-modulated p-type conduction is decreased by exposure to light or electron beam. Moreover, the observation of a field emission current demonstrates the suitability of GeAs nanoflakes as cold cathodes for electron emission and opens up new perspective applications of two-dimensional GeAs in vacuum electronics. Field emission occurs with a turn-on field of ~80 V/{\mu}m and attains a current density higher than 10 A/cm^2, following the general Fowler-Nordheim model with high reproducibility.Comment: 10 pages, 3 figure

Not only a small liver - The pathologist's perspective in the pediatric liver transplant setting

open8Pediatric liver transplantation represents a safe and long-lasting treatment option for various disease types, requiring the pathologist's input. Indeed, an accurate and timely diagnosis is crucial in reporting and grading native liver diseases, evaluating donor liver eligibility and identifying signs of organ injury in the post-transplant follow-up. However, as the procedure is more frequently and widely performed, deceptive and unexplored histopathologic features have emerged with relevant consequences on patient management, particularly when dealing with long-term treatment and weaning of immunosuppression. : In this complex and challenging scenario, this review aims to depict the most relevant histopathologic conditions which could be encountered in pediatric liver transplantation. We will tackle the conditions representing the main indications for transplantation in childhood as well as the complications burdening the post-transplant phases, either immunologically (i.e., rejection) or non-immunologically mediated. Lastly, we hope to provide concise, yet significant, suggestions related to innovative pathology techniques in pediatric liver transplantation.openGambella, Alessandro; Mastracci, Luca; Caporalini, Chiara; Francalanci, Paola; Mescoli, Claudia; Ferro, Jacopo; Alaggio, Rita; Grillo, FedericaGambella, Alessandro; Mastracci, Luca; Caporalini, Chiara; Francalanci, Paola; Mescoli, Claudia; Ferro, Jacopo; Alaggio, Rita; Grillo, Federic

Characterization of the electric transport properties of black phosphorous back-gated field-effect transistors

We use thin layers of exfoliated black phosphorus to realize back-gated field-effect transistors in which the Si/SiO2 substrate is exploited as gate electrode. To prevent the detrimental effect of the air exposure the devices are protected by Poly(methyl methacrylate). We report the observation of an improved contact resistance at the interface between the layered material and the metal contact by electrical conditioning. We also demonstrate the existence of a hysteresis in the transfer characteristics that improves by increasing the gate voltage sweep range. Finally, we prove the suitability of such transistors as memory devices