9,230 Works

Studies in strongly coupled quantum field theories and renormalization group flows

Bernardo Zan
This thesis presents studies in strongly coupled Renormalization Group (RG) flows. In the first part, we analyze the subject of non-local Conformal Field Theories (CFTs), arising as continuous phase transitions of statistical models with long-range interactions. Specifically, we study the critical long-range Ising model in a general number of dimension: first we show that it is conformally invariant, and then we study in depth the different regimes of the theory. We find an example of...

Dielectric-sphere-based microsystem for optical super-resolution imaging

Gergely Huszka
Well-established imaging techniques proved that features below the diffraction limit can be observed optically using so-called super-resolution microscopies, which overcome Abbe's resolution limit. In traditional far-field microscopy, the introduction of fluorescent samples and engineered light paths was key for this breakthrough. In parallel, near-field techniques with similar performance were developed, but they suffered from a limited field-of-view. The merge of the two approaches was already demonstrated ~15 years ago, when micrometer-sized dielectric objects positioned on...

Penalization and Bayesian numerical methods for multiscale inverse problems

Andrea Di Blasio
In this thesis we consider inverse problems involving multiscale elliptic partial differential equations. The name multiscale indicates that these models are characterized by the presence of parameters which vary on different spatial scales (macroscopic, microscopic, mesoscopic, etc.). The variations at the smallest scales make these equations very difficult to approximate also when considering forward problems, since classical numerical methods require a mesh resolution at the finest scales, hence a computational cost that is often prohibitive....

MATHICSE Technical Report: Controlling oscillations in high-order Discontinuous Galerkin schemes using artificial\ viscosity tuned by neural networks

Niccolo' Discacciati, Jan S. Hesthaven & Deep Ray
High-order numerical solvers for conservation laws suer from Gibbs phenomenon close to discontinuities, leading to spurious oscillations and a detrimental effect on the solution accuracy. A possible strategy to reduce it comprises adding a suitable amount of artificial dissipation. Although several viscosity models have been proposed in the literature, their dependence on problem-dependent parameters often limits their performances. Motivated by the objective to construct a universal artificial viscosity method, we propose a new technique based...

Snail-inspired crawling locomotion using urethane gel and shape memory alloy

Toshiyuki Araki, Yoishi Masuda & Masato Ishikawa

MATHICSE Technical Report : A minimal stabilization procedure for isogeometric methods on trimmed geometries

Annalisa Buffa, Riccardo Puppi & Rafael Vazquez Hernandez
Trimming is a common operation in CAD, and, in its simplest formulation, consists in removing superfluous parts from a geometric entity described via splines (a spline patch). After trimming the geometric description of the patch remains unchanged, but the underlying mesh is unfitted with the physical object. We discuss the main problems arising when solving elliptic PDEs on a trimmed domain. First we prove that, even when Dirichlet boundary conditions are weakly enforced using Nitsche’s...

Characterization methods of low frequency RTS noise in cooled infrared detectors

Maxence Guénin, Sophie Derelle, Marcel Caes, Laurent Rubaldo & Isabelle Ribet-Mohamed

A multi-technique approach to study the microstructural properties of tin-based transparent conductive oxides

Federica Landucci
Transparent conductive oxides (TCOs) are semiconductor-like materials that exhibit high electrical conductivity and high optical transparency combined. They are adopted in various applications ranging from gas sensors, to electrochromic windows, to photovoltaic cells. Indium-based TCOs represent the industry standard. Nevertheless, indium is among the less abundant elements in the earth crust and forecasts based on its current consumption envisage an urgent need to replace it. Tin-based TCOs are a promising alternative, since their opto- electronic...

Fluorinated surfactants in droplet-based microfluidics: Influence of their composition on the properties of emulsion drops

Gianluca Nicolas Etienne
Miniaturization has been a driving force in many areas of science and technology, most notably in the electronics industry. Droplet-based microfluidics, a methode to produce emulsion drops in a controlled way and at high-throughputs, enables the miniaturization and automation of biological and chemical experiments. Each emulsion drop is used as a closed reaction vessel, enabling the performance of thousands of experiments per second, at throughputs traditional technologies cannot meet. Droplet-based microfluidics is a driving technology...

Lattice Energy as Emerging General Parameter Describing Ionic Organic Semiconducting Materials Properties

Donatas Gesevicius
Cyanine dyes represent a class of ionic functional materials used by a broad heterogeneous science community contain-ing biologists, chemists, physicists and materials scientists. Their diverse application opportunities are ranging from fluorescence markers, nonlinear optics, CD-R data storage, photography and organic electronics. Therefore the development of cyanine dyes and their applications in chemistry, engineering, medicine and pharmacology is growing continuously. A typical leitmotif of a cyanine dye contains two nitrogen heterocyclic rings joined by a conjugated...

Two nanomachines drive evolution in diverse Vibrio species

Noémie Matthey
Horizontal gene transfer (HGT) has a major impact on bacterial evolution, leading to acquisition or deletion of genes and gene clusters, including those encoding antibiotic resistances and virulence factors. HGT therefore contributes to pathogen emergence, which can have a major impact on human health. As a mode of HGT, natural competence for transformation allows bacteria to directly acquire DNA from the environment and to integrate parts of this genetic material within their genomes. The human...

The mechanics of crack-tip dislocation emission and twinning

Predrag Andric
Dislocation emission from a crack tip is a necessary mechanism for crack tip blunting and toughening. A material is intrinsically ductile under Mode I loading when the critical stress intensity $K_{Ie}$ for dislocation emission is lower than the critical stress intensity $K_{Ic}$ for cleavage. In intrinsically ductile fcc metals, a first partial dislocation is emitted, followed either by a trailing partial dislocation (''ductile'' behavior) or a twinning partial dislocation (''quasi-brittle''). $K_{Ie}^{first}$ for the first partial...

Composite sandwich panels for building floors: recent developments and main challenges

João R. Correia & Mário Garrido

IT Investment and its impacts:does IT matter during crisis, during financing and in Innovation?

Shameem Hasan
This thesis empirically explored the impacts of IT investment on three different scenarios under the common denominator / threads of IT investments. It comprises three different essays on the impacts of IT investments. IT investments and its impact on many aspects of the firms are well known - like performance / productivity, output, market value etc. But I looked into areas that were not explored before and examined events that didnât take place after the...

MATHICSE Technical Report : A posteriori error estimation for the steady Navier-Stokes equations in random domains

Diane Sylvie Guignard, Fabio Nobile & Marco Picasso
We consider finite element error approximations of the steady incompressible Navier-Stokes equations defined on a randomly perturbed domain, the perturbation being small. Introducing a random mapping, these equations are transformed into PDEs on a fixed reference domain with random coefficients. Under suitable assumptions on the random mapping and the input data, in particular the so-called small data assumption, we prove the well-posedness of the problem. We assume then that the mapping depends affinely on $L$...

Dynamic protein-chromatin interactions in heterochromatin and during the DNA damage response on the single molecule level

Andreas Linus Bachmann
Dynamic regulation of chromatin, a structure consisting of DNA and histone proteins, is mediated through histone post-translational modifications (PTMs) and effector proteins. HP1a and PRC2 are recruited to repressive PTMs (H3K9me3, H3K27me3) and enable heterochromatin formation, which leads to gene silencing. During the DNA damage response, tight spatial and temporal control of the chromatin compaction state is required and novel PTMs are installed to guide proteins through dynamic signalling pathways. In the RNF168-mediated signalling cascade,...

Full-field surface and interior deformation measurement of sandwich core material using digital speckle photography

Lingtao Mao, Rui Guo, Yanqi Song & Fu-Pen Chiang

Die multiplen Rechenschaftspflichten von öffentlichen Unternehmen gegenüber dem Staat - Eine empirische Typologie der Entstehung und des Managements inkohärenter Erwartungen

Fabian Liechti
State-owned enterprises (SOEs) provide important services such as power supply, postal services and public transportation. In doing this, SOEs operate at the intersection of political/regulatory and economic expectations. Therefore, SOEs are commonly considered in the academic literature as hybrid organisations. Hybrid organisations in the public sector seem a way to combine the best of two worlds: high-quality, broadly accessible public services and affordable prices thanks to commercial efficiency and flexibility. However, this hybridity has an...

Navigating and Managing the Complexity of Genome Scale Metabolic Networks for Studies in Cellular Physiology and Industrial Biotechnology

Meriç Ataman
Metabolism is a network of biochemical reactions that converts carbon sources to cellu-lar fuels and building blocks. Metabolism of many organisms has been studied for many decades. These studies define metabolism as a very large and complex network. Stoichi-ometric models have been used extensively to study these complex networks. With the introduction of Genome Scale Models (GEMs), the studies on metabolism entered a new era, and gained a more systems approach. GEMs have been used...

Bioengineering human bone marrow models to elucidate the triggers of the stem cell niche

Queralt Vallmajó Martín
The bone marrow (BM) microenvironment, or niche, significantly affects behaviors of its resident stem cell populations. Disruptions in the BM niche contribute to a number of severe clinical pathologies. Discovery of novel therapeutic strategies for BM-related diseases necessitates development of superior preclinical models to study parameters affecting BM homeostasis. To address this, a poly(ethylene glycol) hydrogel featuring a particular crosslinking chemistry based on the enzyme transglutaminase factor XIII, dubbed TG-PEG, was utilized to engineer humanized...

Euclidean classical solutions in quantum field theory and gravity: Higgs vacuum metastability and the hierarchy problem

Andrey Shkerin
The thesis is dedicated to two groups of questions arising in modern particle physics and cosmology. The first group concerns with the problem of stability of the electroweak (EW) vacuum in different environments. Due to its phenomenological significance, the problem attracts high attention in recent research. We contribute to this research in two directions. First, we study decay rate of the EW vacuum at the inflationary stage of the universe. While in a low density,...

MATHICSE Technical Report : A theoretical study of COmpRessed SolvING for advection-diffusion-reaction problems

Simone Brugiapaglia, Fabio Nobile, Stefano Micheletti & Simona Perotto
We present a theoretical analysis of the CORSING (COmpRessed SolvING) method for the numerical approximation of partial differential equations based on compressed sensing. In particular, we show that the best s-term approximation of the weak solution of a PDE with respect to an orthonormal system of N trial functions, can be recovered via a Petrov-Galerkin approach using m << N orthonormal test functions. This recovery is guaranteed if the local a-coherence associated with the bilinear...

A Gauss-Bonnet Theorem for Asymptotically Conical Manifolds and Manifolds with Conical Singularities

Adrien Giuliano Marcone
The purpose of this thesis is to provide an intrinsic proof of a Gauss-Bonnet-Chern formula for complete Riemannian manifolds with finitely many conical singularities and asymptotically conical ends. A geometric invariant is associated to the link of both the conical singularities and the asymptotically conical ends and is used to quantify the Gauss-Bonnet defect of such manifolds. This invariant is constructed by contracting powers of a tensor involving the curvature tensor of the link. Moreover...

Bioengineering the Human Muscle Stem-Cell Niche for Therapeutic Applications

Omid Mashinchian
In spite of decades of research, no feasible method for obtaining sufficient numbers of uncommitted muscle stem cells (MuSCs) for therapy of degenerative muscle diseases exists. One of the most fundamental problems associated with stem cell therapy of muscle is that removal of MuSCs from their tissue microenvironment and expansion in conventional culture induces their terminal commitment to myogenic differentiation. This in-vitro loss of stemness impairs the long-term engraftment potential of MuSCs and renders them...

Turbulent Flows over Rough Permeable Beds in Mountain Rivers: Experimental Insights and Modeling

Gauthier Paul Daniel Marie Rousseau
Steep mountain streams exhibit shallow waters with roughness elements such as stones and pebbles that are comparable in size to flow depth. Owing to the difficulty in measuring fluid velocities at the interface, i.e., from the rough permeable bed to the free surface, experimental results are rare although they are essential to improve models. Using a novel experimental procedure, this thesis attempts to improve predictions of the vertical structure of turbulent flows over rough permeable...

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