A moment symbolic representation of Lévy processes with applications

By using a symbolic method, known in the literature as the classical umbral calculus, a symbolic representation of Lévy processes is given and a new family of time-space harmonic polynomials with respect to such processes, which includes and generalizes the exponential complete Bell polynomials, is introduced. The usefulness of time-space harmonic polynomials with respect to Lévy processes is that it is a martingale the stochastic process obtained by replacing the indeterminate x of the polynomials with a Lévy process, whereas the Lévy process does not necessarily have this property. Therefore to find such polynomials could be particularly meaningful for applications. This new family includes Hermite polynomials, time-space harmonic with respect to Brownian motion, Poisson-Charlier polynomials with respect to Poisson processes, Laguerre and actuarial polynomials with respect to Gamma processes , Meixner polynomials of the first kind with respect to Pascal processes, Euler, Bernoulli, Krawtchuk, and pseudo-Narumi polynomials with respect to suitable random walks. The role played by cumulants is stressed and brought to the light, either in the symbolic representation of Lévy processes and their infinite divisibility property, either in the generalization, via umbral Kailath-Segall formula, of the well-known formulae giving elementary symmetric polynomials in terms of power sum symmetric polynomials. The expression of the family of time-space harmonic polynomials here introduced has some connections with the so-called moment representation of various families of multivariate polynomials. Such moment representation has been studied here for the first time in connection with the time-space harmonic property with respect to suitable symbolic multivariate Lévy processes. In particular, multivariate Hermite polynomials and their properties have been studied in connection with a symbolic version of the multivariate Brownian motion, while multivariate Bernoulli and Euler polynomials are represented as powers of multivariate polynomials which are time-space harmonic with respect to suitable multivariate Lévy processes.

Mutually catalytic branching at infinite rate

The purpose of this doctoral thesis is to prove existence for a mutually catalytic random walk with infinite branching rate on countably many sites. The process is defined as a weak limit of an approximating family of processes. An approximating process is constructed by adding jumps to a deterministic migration on an equidistant time grid. As law of jumps we need to choose the invariant probability measure of the mutually catalytic random walk with a finite branching rate in the recurrent regime. This model was introduced by Dawson and Perkins (1998) and this thesis relies heavily on their work. Due to the properties of this invariant distribution, which is in fact the exit distribution of planar Brownian motion from the first quadrant, it is possible to establish a martingale problem for the weak limit of any convergent sequence of approximating processes. We can prove a duality relation for the solution to the mentioned martingale problem, which goes back to Mytnik (1996) in the case of finite rate branching, and this duality gives rise to weak uniqueness for the solution to the martingale problem. Using standard arguments we can show that this solution is in fact a Feller process and it has the strong Markov property. For the case of only one site we prove that the model we have constructed is the limit of finite rate mutually catalytic branching processes as the branching rate approaches infinity. Therefore, it seems naturalto refer to the above model as an infinite rate branching process. However, a result for convergence on infinitely many sites remains open.

Thermal fluctuations and boundary conditions in the lattice Boltzmann method

The lattice Boltzmann method is a popular approach for simulating hydrodynamic interactions in soft matter and complex fluids. The solvent is represented on a discrete lattice whose nodes are populated by particle distributions that propagate on the discrete links between the nodes and undergo local collisions. On large length and time scales, the microdynamics leads to a hydrodynamic flow field that satisfies the Navier-Stokes equation. In this thesis, several extensions to the lattice Boltzmann method are developed. In complex fluids, for example suspensions, Brownian motion of the solutes is of paramount importance. However, it can not be simulated with the original lattice Boltzmann method because the dynamics is completely deterministic. It is possible, though, to introduce thermal fluctuations in order to reproduce the equations of fluctuating hydrodynamics. In this work, a generalized lattice gas model is used to systematically derive the fluctuating lattice Boltzmann equation from statistical mechanics principles. The stochastic part of the dynamics is interpreted as a Monte Carlo process, which is then required to satisfy the condition of detailed balance. This leads to an expression for the thermal fluctuations which implies that it is essential to thermalize all degrees of freedom of the system, including the kinetic modes. The new formalism guarantees that the fluctuating lattice Boltzmann equation is simultaneously consistent with both fluctuating hydrodynamics and statistical mechanics. This establishes a foundation for future extensions, such as the treatment of multi-phase and thermal flows. An important range of applications for the lattice Boltzmann method is formed by microfluidics. Fostered by the "lab-on-a-chip" paradigm, there is an increasing need for computer simulations which are able to complement the achievements of theory and experiment. Microfluidic systems are characterized by a large surface-to-volume ratio and, therefore, boundary conditions are of special relevance. On the microscale, the standard no-slip boundary condition used in hydrodynamics has to be replaced by a slip boundary condition. In this work, a boundary condition for lattice Boltzmann is constructed that allows the slip length to be tuned by a single model parameter. Furthermore, a conceptually new approach for constructing boundary conditions is explored, where the reduced symmetry at the boundary is explicitly incorporated into the lattice model. The lattice Boltzmann method is systematically extended to the reduced symmetry model. In the case of a Poiseuille flow in a plane channel, it is shown that a special choice of the collision operator is required to reproduce the correct flow profile. This systematic approach sheds light on the consequences of the reduced symmetry at the boundary and leads to a deeper understanding of boundary conditions in the lattice Boltzmann method. This can help to develop improved boundary conditions that lead to more accurate simulation results.

Statistical problems related to excitation threshold and reset value of membrane potentials

Die vorliegende Arbeit ist motiviert durch biologische Fragestellungen bezüglich des Verhaltens von Membranpotentialen in Neuronen. Ein vielfach betrachtetes Modell für spikende Neuronen ist das Folgende. Zwischen den Spikes verhält sich das Membranpotential wie ein Diffusionsprozess X der durch die SDGL dX_t= beta(X_t) dt+ sigma(X_t) dB_t gegeben ist, wobei (B_t) eine Standard-Brown'sche Bewegung bezeichnet. Spikes erklärt man wie folgt. Sobald das Potential X eine gewisse Exzitationsschwelle S überschreitet entsteht ein Spike. Danach wird das Potential wieder auf einen bestimmten Wert x_0 zurückgesetzt. In Anwendungen ist es manchmal möglich, einen Diffusionsprozess X zwischen den Spikes zu beobachten und die Koeffizienten der SDGL beta() und sigma() zu schätzen. Dennoch ist es nötig, die Schwellen x_0 und S zu bestimmen um das Modell festzulegen. Eine Möglichkeit, dieses Problem anzugehen, ist x_0 und S als Parameter eines statistischen Modells aufzufassen und diese zu schätzen. In der vorliegenden Arbeit werden vier verschiedene Fälle diskutiert, in denen wir jeweils annehmen, dass das Membranpotential X zwischen den Spikes eine Brown'sche Bewegung mit Drift, eine geometrische Brown'sche Bewegung, ein Ornstein-Uhlenbeck Prozess oder ein Cox-Ingersoll-Ross Prozess ist. Darüber hinaus beobachten wir die Zeiten zwischen aufeinander folgenden Spikes, die wir als iid Treffzeiten der Schwelle S von X gestartet in x_0 auffassen. Die ersten beiden Fälle ähneln sich sehr und man kann jeweils den Maximum-Likelihood-Schätzer explizit angeben. Darüber hinaus wird, unter Verwendung der LAN-Theorie, die Optimalität dieser Schätzer gezeigt. In den Fällen OU- und CIR-Prozess wählen wir eine Minimum-Distanz-Methode, die auf dem Vergleich von empirischer und wahrer Laplace-Transformation bezüglich einer Hilbertraumnorm beruht. Wir werden beweisen, dass alle Schätzer stark konsistent und asymptotisch normalverteilt sind. Im letzten Kapitel werden wir die Effizienz der Minimum-Distanz-Schätzer anhand simulierter Daten überprüfen. Ferner, werden Anwendungen auf reale Datensätze und deren Resultate ausführlich diskutiert.

Modellazione Tridimensionale del Processo di Combustione di un Razzo a Propellente Solido

La regolazione dei sistemi di propulsione a razzo a propellente solido (Solid Rocket Motors) ha da sempre rappresentato una delle principali problematiche legate a questa tipologia di motori. L’assenza di un qualsiasi genere di controllo diretto del processo di combustione del grano solido, fa si che la previsione della balistica interna rappresenti da sempre il principale strumento utilizzato sia per definire in fase di progetto la configurazione ottimale del motore, sia per analizzare le eventuali anomalie riscontrate in ambito sperimentale. Variazioni locali nella struttura del propellente, difettosità interne o eterogeneità nelle condizioni di camera posso dare origine ad alterazioni del rateo locale di combustione del propellente e conseguentemente a profili di pressione e di spinta sperimentali differenti da quelli previsti per via teorica. Molti dei codici attualmente in uso offrono un approccio piuttosto semplificato al problema, facendo per lo più ricorso a fattori correttivi (fattori HUMP) semi-empirici, senza tuttavia andare a ricostruire in maniera più realistica le eterogeneità di prestazione del propellente. Questo lavoro di tesi vuole dunque proporre un nuovo approccio alla previsione numerica delle prestazioni dei sistemi a propellente solido, attraverso la realizzazione di un nuovo codice di simulazione, denominato ROBOOST (ROcket BOOst Simulation Tool). Richiamando concetti e techiche proprie della Computer Grafica, questo nuovo codice è in grado di ricostruire in processo di regressione superficiale del grano in maniera puntuale, attraverso l’utilizzo di una mesh triangolare mobile. Variazioni locali del rateo di combustione posso quindi essere facilmente riprodotte ed il calcolo della balistica interna avviene mediante l’accoppiamento di un modello 0D non-stazionario e di uno 1D quasi-stazionario. L’attività è stata svolta in collaborazione con l’azienda Avio Space Division e il nuovo codice è stato implementato con successo sul motore Zefiro 9.

Synthesis of Hand Exoskeletons for the Rehabilitation of Post-Stroke Patients

This dissertation presents the synthesis of a hand exoskeleton (HE) for the rehabilitation of post-stroke patients. Through the analysis of state-of-the-art, a topological classification was proposed. Based on the proposed classification principles, the rehabilitation HEs were systematically analyzed and classified. This classification is helpful to both understand the reason of proposing certain solutions for specific applications and provide some useful guidelines for the design of a new HE, that was actually the primary motivation of this study. Further to this classification, a novel rehabilitation HE was designed to support patients in cylindrical shape grasping tasks with the aim of recovering the basic functions of manipulation. The proposed device comprises five planar mechanisms, one per finger, globally actuated by two electric motors. Indeed, the thumb flexion/extension movement is controlled by one actuator whereas a second actuator is devoted to the control of the flexion/extension of the other four fingers. By focusing on the single finger mechanism, intended as the basic model of the targeted HE, the feasibility study of three different 1 DOF mechanisms are analyzed: a 6-link mechanism, that is connected to the human finger only at its tip, an 8-link and a 12-link mechanisms where phalanges and articulations are part of the kinematic chain. The advantages and drawbacks of each mechanism are deeply analyzed with respect to targeted requirements: the 12-link mechanism was selected as the most suitable solution. The dimensional synthesis based on the Burmester theory as well as kinematic and static analyses were separately done for all fingers in order to satisfy the desired specifications. The HE was finally designed and a prototype was built. The experimental results of the first tests are promising and demonstrate the potential for clinical applications of the proposed device in robot-assisted training of the human hand for grasping functions.

Non-Linear Analysis and Design of Synchronous Bearingless Multiphase Permanent Magnet Machines and Drives

A two-dimensional model to analyze the distribution of magnetic fields in the airgap of a PM electrical machines is studied. A numerical algorithm for non-linear magnetic analysis of multiphase surface-mounted PM machines with semi-closed slots is developed, based on the equivalent magnetic circuit method. By using a modular structure geometry, whose the basic element can be duplicated, it allows to design whatever typology of windings distribution. In comparison to a FEA, permits a reduction in computing time and to directly changing the values of the parameters in a user interface, without re-designing the model. Output torque and radial forces acting on the moving part of the machine can be calculated. In addition, an analytical model for radial forces calculation in multiphase bearingless Surface-Mounted Permanent Magnet Synchronous Motors (SPMSM) is presented. It allows to predict amplitude and direction of the force, depending on the values of torque current, of levitation current and of rotor position. It is based on the space vectors method, letting the analysis of the machine also during transients. The calculations are conducted by developing the analytical functions in Fourier series, taking all the possible interactions between stator and rotor mmf harmonic components into account and allowing to analyze the effects of electrical and geometrical quantities of the machine, being parametrized. The model is implemented in the design of a control system for bearingless machines, as an accurate electromagnetic model integrated in a three-dimensional mechanical model, where one end of the motor shaft is constrained to simulate the presence of a mechanical bearing, while the other is free, only supported by the radial forces developed in the interactions between magnetic fields, to realize a bearingless system with three degrees of freedom. The complete model represents the design of the experimental system to be realized in the laboratory.

Complex chemical dynamics through engineering-like methods

Most of the problems in modern structural design can be described with a set of equation; solutions of these mathematical models can lead the engineer and designer to get info during the design stage. The same holds true for physical-chemistry; this branch of chemistry uses mathematics and physics in order to explain real chemical phenomena. In this work two extremely different chemical processes will be studied; the dynamic of an artificial molecular motor and the generation and propagation of the nervous signals between excitable cells and tissues like neurons and axons. These two processes, in spite of their chemical and physical differences, can be both described successfully by partial differential equations, that are, respectively the Fokker-Planck equation and the Hodgkin and Huxley model. With the aid of an advanced engineering software these two processes have been modeled and simulated in order to extract a lot of physical informations about them and to predict a lot of properties that can be, in future, extremely useful during the design stage of both molecular motors and devices which rely their actions on the nervous communications between active fibres.

Experimental Analysis and Numerical Simulation of Quench in Superconducting HTS Tapes and Coils

The quench characteristics of second generation (2 G) YBCO Coated Conductor (CC) tapes are of fundamental importance for the design and safe operation of superconducting cables and magnets based on this material. Their ability to transport high current densities at high temperature, up to 77 K, and at very high fields, over 20 T, together with the increasing knowledge in their manufacturing, which is reducing their cost, are pushing the use of this innovative material in numerous system applications, from high field magnets for research to motors and generators as well as for cables. The aim of this Ph. D. thesis is the experimental analysis and numerical simulations of quench in superconducting HTS tapes and coils. A measurements facility for the characterization of superconducting tapes and coils was designed, assembled and tested. The facility consist of a cryostat, a cryocooler, a vacuum system, resistive and superconducting current leads and signal feedthrough. Moreover, the data acquisition system and the software for critical current and quench measurements were developed. A 2D model was developed using the finite element code COMSOL Multiphysics R . The problem of modeling the high aspect ratio of the tape is tackled by multiplying the tape thickness by a constant factor, compensating the heat and electrical balance equations by introducing a material anisotropy. The model was then validated both with the results of a 1D quench model based on a non-linear electric circuit coupled to a thermal model of the tape, to literature measurements and to critical current and quench measurements made in the cryogenic facility. Finally the model was extended to the study of coils and windings with the definition of the tape and stack homogenized properties. The procedure allows the definition of a multi-scale hierarchical model, able to simulate the windings with different degrees of detail.

Ausbreitung einer Infektion durch ein System Brownscher Bewegungen

In dieser Arbeit werden wir ein Modell untersuchen, welches die Ausbreitung einer Infektion beschreibt. Bei diesem Modell werden zunächst Partikel gemäß eines Poissonschen Punktprozesses auf der reellen Achse verteilt. Bis zu einem gewissen Punkt auf der reellen Achse sind alle Partikel von einer Infektion befallen. Während sich nicht infizierte Partikel nicht bewegen, folgen die infizierten Partikel den Pfaden von voneinander unabhängigen Brownschen Bewegungen und verbreitet die Infektion dabei an den Orten, welche sie betreten. Wenn sie dabei auf ein nicht infiziertes Partikel treffen, ist dieses von diesem Moment an auch infiziert und beginnt ebenfalls, dem Pfad einer Brownschen Bewegung zu folgen und die Infektion auszubreiten. Auf diese Art verschiebt sich nun der am weitesten rechts liegende Ort R_t, an dem die Infektion bereits verbreitet wurde. Wir werden mit Hilfe des subadditiven Ergodensatzes zeigen, dass sich dieser Ort mit linearer Geschwindigkeit fortbewegt. Ferner werden wir eine obere und eine untere Schranke für die Ausbreitungsgeschwindkeit angeben. Danach werden wir zeigen, dass der Prozess Regenerationszeiten hat, nämlich solche zufällige Zeiten, zu denen er eine Art Neustart unter speziellen Startbedingungen durchführt. Wir werden diese für eine weitere Charakterisierung der Ausbreitungsgeschwingkeit nutzen. Ferner erhalten wir durch die Regenerationszeiten auch einen Zentralen Grenzwertsatz für R_t und können zeigen, dass die Verteilung der infizierten Partikel aus Sicht des am weitesten rechts liegenden infizierten Ortes gegen eine invariante Verteilung konvergiert.

Comportamento tribologico di materiali per componenti di interesse industriale: Failure analysis e prove tribologiche in laboratorio

L’attività di ricerca della presente tesi di dottorato ha riguardato sistemi tribologici complessi di interesse industriale per i quali sono stati individuati, mediante failure analysis, i meccanismi di usura dominanti. Per ciascuno di essi sono state studiate soluzioni migliorative sulla base di prove tribologiche di laboratorio. Nella realizzazione di maglie per macchine movimentazione terra sono ampiamente utilizzati i tradizionali acciai da bonifica. La possibilità di utilizzare i nuovi microlegati a medio tenore di carbonio, consentirebbe una notevole semplificazione del ciclo produttivo e benefici in termini di costi. Una parte della tesi ha riguardato lo studio del comportamento tribologico di tali acciai. E’ stato anche affrontato lo studio tribologico di motori idraulici, con l’obiettivo di riuscire a migliorarne la resistenza ad usura e quindi la vita utile. Sono state eseguite prove a banco, per valutare i principali meccanismi di usura, e prove di laboratorio atte a riprodurre le reali condizioni di utilizzo, valutando tecniche di modificazione superficiale che fossero in grado di ridurre l’usura dei componenti. Sono state analizzate diverse tipologie di rivestimenti Thermal Spray in termini di modalità di deposizione (AFS-APS) e di leghe metalliche depositate (Ni,Mo,Cu/Al). Si sono infine caratterizzati contatti tribologici nel settore del packaging, dove l’utilizzo di acciai inox austenitici è in alcuni casi obbligatorio. L’acciaio inossidabile AISI 316L è ampiamente utilizzato in applicazioni in cui siano richieste elevate resistenze alla corrosione, tuttavia la bassa resistenza all’usura, ne limitano l’impiego in campo tribologico. In tale ambito, è stata analizzata una problematica tribologica relativa a macchine automatiche per il dosaggio di polveri farmaceutiche. Sono state studiate soluzioni alternative che hanno previsto sia la completa sostituzione dei materiali della coppia tribologica, sia l’individuazione di tecniche di modificazione superficiale innovative quali la cementazione a bassa temperatura anche seguita dalla deposizione di un rivestimento di carbonio amorfo idrogenato a-C:H

Numerical studies of colloidal systems

The interplay of hydrodynamic and electrostatic forces is of great importance for the understanding of colloidal dispersions. Theoretical descriptions are often based on the so called standard electrokinetic model. This Mean Field approach combines the Stokes equation for the hydrodynamic flow field, the Poisson equation for electrostatics and a continuity equation describing the evolution of the ion concentration fields. In the first part of this thesis a new lattice method is presented in order to efficiently solve the set of non-linear equations for a charge-stabilized colloidal dispersion in the presence of an external electric field. Within this framework, the research is mainly focused on the calculation of the electrophoretic mobility. Since this transport coefficient is independent of the electric field only for small driving, the algorithm is based upon a linearization of the governing equations. The zeroth order is the well known Poisson-Boltzmann theory and the first order is a coupled set of linear equations. Furthermore, this set of equations is divided into several subproblems. A specialized solver for each subproblem is developed, and various tests and applications are discussed for every particular method. Finally, all solvers are combined in an iterative procedure and applied to several interesting questions, for example, the effect of the screening mechanism on the electrophoretic mobility or the charge dependence of the field-induced dipole moment and ion clouds surrounding a weakly charged sphere. In the second part a quantitative data analysis method is developed for a new experimental approach, known as "Total Internal Reflection Fluorescence Cross-Correlation Spectroscopy" (TIR-FCCS). The TIR-FCCS setup is an optical method using fluorescent colloidal particles to analyze the flow field close to a solid-fluid interface. The interpretation of the experimental results requires a theoretical model, which is usually the solution of a convection-diffusion equation. Since an analytic solution is not available due to the form of the flow field and the boundary conditions, an alternative numerical approach is presented. It is based on stochastic methods, i. e. a combination of a Brownian Dynamics algorithm and Monte Carlo techniques. Finally, experimental measurements for a hydrophilic surface are analyzed using this new numerical approach.

Total internal reflection fluorescence cross-correlation spectroscopy: theory and application for studying boundary slip phenomenon

I present a new experimental method called Total Internal Reflection Fluorescence Cross-Correlation Spectroscopy (TIR-FCCS). It is a method that can probe hydrodynamic flows near solid surfaces, on length scales of tens of nanometres. Fluorescent tracers flowing with the liquid are excited by evanescent light, produced by epi-illumination through the periphery of a high NA oil-immersion objective. Due to the fast decay of the evanescent wave, fluorescence only occurs for tracers in the ~100 nm proximity of the surface, thus resulting in very high normal resolution. The time-resolved fluorescence intensity signals from two laterally shifted (in flow direction) observation volumes, created by two confocal pinholes are independently measured and recorded. The cross-correlation of these signals provides important information for the tracers’ motion and thus their flow velocity. Due to the high sensitivity of the method, fluorescent species with different size, down to single dye molecules can be used as tracers. The aim of my work was to build an experimental setup for TIR-FCCS and use it to experimentally measure the shear rate and slip length of water flowing on hydrophilic and hydrophobic surfaces. However, in order to extract these parameters from the measured correlation curves a quantitative data analysis is needed. This is not straightforward task due to the complexity of the problem, which makes the derivation of analytical expressions for the correlation functions needed to fit the experimental data, impossible. Therefore in order to process and interpret the experimental results I also describe a new numerical method of data analysis of the acquired auto- and cross-correlation curves – Brownian Dynamics techniques are used to produce simulated auto- and cross-correlation functions and to fit the corresponding experimental data. I show how to combine detailed and fairly realistic theoretical modelling of the phenomena with accurate measurements of the correlation functions, in order to establish a fully quantitative method to retrieve the flow properties from the experiments. An importance-sampling Monte Carlo procedure is employed in order to fit the experiments. This provides the optimum parameter values together with their statistical error bars. The approach is well suited for both modern desktop PC machines and massively parallel computers. The latter allows making the data analysis within short computing times. I applied this method to study flow of aqueous electrolyte solution near smooth hydrophilic and hydrophobic surfaces. Generally on hydrophilic surface slip is not expected, while on hydrophobic surface some slippage may exists. Our results show that on both hydrophilic and moderately hydrophobic (contact angle ~85°) surfaces the slip length is ~10-15nm or lower, and within the limitations of the experiments and the model, indistinguishable from zero.

Fluctuation spectroscopy of single plasmonic nanostructures

Plasmonic nanoparticles are great candidates for sensing applications with optical read-out. Plasmon sensing is based on the interaction of the nanoparticle with electromagnetic waves where the particle scatters light at its resonance wavelength. This wavelength depends on several intrinsic factors like material, shape and size of the nanoparticle as well as extrinsic factors like the refractive index of the surrounding medium. The latter allows the nanoparticle to be used as a sensor; changes in the proximate environment can be directly monitored by the wavelength of the emitted light. Due to their minuscule size and high sensitivity this allows individual nanoparticles to report on changes in particle coverage.rnrnTo use this single particle plasmon sensor for future sensing applications it has to meet the demand for detection of incidents on the single molecule level, such as single molecule sensing or even the detection of conformational changes of a single molecule. Therefore, time resolution and sensitivity have to be enhanced as today’s measurement methods for signal read-out are too slow and not sensitive enough to resolve these processes. This thesis presents a new experimental setup, the 'Plasmon Fluctuation Setup', that leads to tremendous improvements in time resolution and sensitivity. This is achieved by implementation of a stronger light source and a more sensitive detector. The new setup has a time resolution in the microsecond regime, an advancement of 4-6 orders of magnitude to previous setups. Its resonance wavelength stability of 0.03 nm, measured with an exposure time of 10 ms, is an improvement of a factor of 20 even though the exposure time is 3000 times shorter than in previous reports. Thus, previously unresolvable wavelength changes of the plasmon sensor induced by minor local environmental alteration can be monitored with extremely high temporal resolution.rnrnUsing the 'Plasmon Fluctuation Setup', I can resolve adsorption events of single unlabeled proteins on an individual nanorod. Additionally, I monitored the dynamic evolution of a single protein binding event on a millisecond time scale. This feasibility is of high interest as the role of certain domains in the protein can be probed by a study of modified analytes without the need for labels possibly introducing conformational or characteristic changes to the target. The technique also resolves equilibrium fluctuations in the coverage, opening a window into observing Brownian dynamics of unlabeled macromolecules. rnrnA further topic addressed in this thesis is the usability of the nanoruler, two nanospheres connected with a spacer molecule, as a stiffness sensor for the interparticle linker under strong illumination. Here, I discover a light induced collapse of the nanoruler. Furthermore, I exploit the sensing volume of a fixed nanorod to study unlabeled analytes diffusing around the nanorod at concentrations that are too high for fluorescence correlation spectroscopy but realistic for biological systems. Additionally, local pH sensing with nanoparticles is achieved.

Simulazione dinamica di un veicolo dotato di powertrain ibrido endotermico-elettrico

Nel panorama motoristico ed automobilistico moderno lo sviluppo di motori a combustione interna e veicoli è fortemente influenzato da diverse esigenze che spesso sono in contrasto le une con le altre. Infatti gli obiettivi di economicità e riduzione dei costi riguardanti la produzione e la commercializzazione dei prodotti sono in contrasto con gli sforzi che devono essere operati dalle case produttrici per soddisfare le sempre più stringenti normative riguardanti le emissioni inquinanti ed i consumi di carburante dei veicoli. Fra le numerose soluzioni presenti i veicoli ibridi rappresentano una alternativa che allo stato attuale è già presente sul mercato in varie forme, a seconda della tipologie di energie accoppiate. In letteratura è possibile trovare numerosi studi che trattano l’ottimizzazione dei componenti o delle strategie di controllo di queste tipologie di veicoli: in moltissimi casi l’obiettivo è quello di minimizzare consumi ed emissioni inquinanti. Normalmente non viene posta particolare attenzione agli effetti che l’aggiunta delle macchine elettriche e dei componenti necessari per il funzionamento delle stesse hanno sulla dinamica del veicolo. Il presente lavoro di tesi è incentrato su questi aspetti: si è considerata la tipologia di veicoli ibridi termici-elettrici di tipo parallelo andando ad analizzare come cambiasse il comportamento dinamico del veicolo in funzione del tipo di installazione considerato per la parte elettrica del powertrain. In primo luogo è stato quindi necessario costruire ed implementare un modello dinamico di veicolo che permettesse di applicare coppie alle quattro ruote in maniera indipendente per considerare diverse tipologie di powertrain. In seguito si sono analizzate le differenze di comportamento dinamico fra il veicolo considerato e l’equivalente versione ibrida e i possibili utilizzi delle macchine elettriche per correggere eventuali deterioramenti o cambiamenti indesiderati nelle prestazioni del veicolo.