Organic field-effect transistors for sensing applications

Het proefschrift van Francesco Maddalena beschrijft een studie naar organische veld-effecttransistors (OFET’s) en hun nut voor (bio)sensing-toepassingen. Het onderzoek is gericht op fundamenteel begrip van het gebruik van OFET’s als sensor of biosensor, en niet op de realisatie van de sensoren zelf. In het proefschrift wordt onder andere onderzoek naar een biosensor (Bio-FET) voor het opsporen van sulfaat-ionen besproken. Artsen zouden dergelijke sensoren kunnen gebruiken voor snelle medische analyse. De Bio-FET maakt gebruik van een dual-gate-structuur, waar de top-gate-elektrode wordt vervangen door een eiwitlaag die aan de sulfaationen bindt. The thesis focuses on the study of organic field effect transistors and their usefulness for (bio)sensing applications. The research is more focused toward fundamental understanding of the use of the OFET as a sensor or biosensor rather than realization of the sensors itself. Chapters 1 and 2 give a general introduction in the field of organic electronic devices and describe the materials and experimental methods used throughout the thesis. Chapter 3 gives the characterization of the device operation of dual-gate organic field-effect transistors (DG-OFET), fabricated by solution processing. It is shown that the threshold voltage of the bottom gate of the devices depends on the top gate bias with two linear relationships for two different regimes. Chapter 4 describes the fabrication and testing of the ‘Bio-FET’, an organic field-effect transistor-based biosensor for the detection of sulphate ions. The Bio-FET uses a dual-gate structure where the top-gate electrode is replaced by a protein layer which captures the sulphate ions. The binding of sulphate ions in dry conditions was detected by a shift in the threshold voltage. Chapter 5 investigates the kinetics of acid doping of regio-regular poly-3-hexylthiophene in field-effect transistors. The dopant density was extracted from field-effect transistors, as a function of temperature and exposure time. The change in dopand density in time was phenomenologically described by stretched exponential time dependence. Chapter 6 investigates the charge carrier mobility dependence on the charge carrier density in semiconducting polymers in diodes and transistors.

Very long distance connection of gigawatt size offshore wind farms: extra high-voltage ac versus high-voltage dc cost comparison

This study presents a cost comparison between commercially available high-voltage DC (HVDC) and extra high-voltage AC shore connection (±320 kV voltage source converter and 420 kV-50 Hz single-core and three-core cables), for a 1 GW offshore wind farm cluster, considering transmission distances up to 400 km. The HVDC system is a point-to-point connection whereas multiple AC intermediate compensating stations are envisaged for AC when needed. Capital costs are evaluated from recently awarded contracts, operating costs include energy losses and missed revenues due to transmission system unavailability, both estimated using North Sea wind production curves. Optimal AC intermediate compensation, if any, and reactive profiles are also taken into account. Resultsshow that HVDC has lower transmission losses at distances in excess of 130 km; however, due to the combined effect of lower AC capital cost and unavailability, using three-core aluminium cables can be more convenient up to 360 km distance

Web Services System Development: A Grounded Theory Study

This study in progress presents a grounded theory analysis of a case study in the banking industry with a view to showing the role of \u201cWeb services\u201d technology in information systems development practices. The case study relates to the implementation in the Central Europe Bank (a pseudonym) of a new software application based on Web services technology. In particular, the focus is on the following research question: what are the peculiarities of the Web services software development process? A tentative answer to the question is advanced here in the form of a preliminary formulation of a descriptive theory of the Web services ISD process. In particular, an effort is made to understand whether the Web services ISD process can be considered as a short-cycle development process (Baskerville and Pries-Heje, 2004). The process under observation might be categorised in a preliminary way as a \u201chybrid\u201d one lying between methodical and amethodical development processes. Indeed, the data collected and analysed so far confirm the complexity and richness of the situation taken into consideration, offering useful insights to complete and further extend both theoretical and empirical analysis

Numerical Methods for the Nonlocal Wave Equation of the Peridynamics

In this paper we will consider the peridynamic equation of motion which is described by a second order in time partial integro-differential equation. This equation has recently received great attention in several fields of Engineering because seems to provide an effective approach to modeling mechanical systems avoiding spatial discontinuous derivatives and body singularities. In particular, we will consider the linear model of peridynamics in a one-dimensional spatial domain. Here we will review some numerical techniques to solve this equation and propose some new computational methods of higher order in space; moreover we will see how to apply the methods studied for the linear model to the nonlinear one. Also a spectral method for the spatial discretization of the linear problem will be discussed. Several numerical tests will be given in order to validate our results