9,223 Works

Development and application of dynamic functional connectivity methods to elucidate the neural underpinnings of human behaviour with functional magnetic resonance imaging

Thomas William Arthur Bolton
Human behaviour is exquisitely complex, because it is staggeringly multi-facetted and subtly varies across individuals. Characterising its yet incompletely understood underlying biological mechanisms has profound clinical implications. Here, our goal was thus to study inter-individual behavioural variability. To accomplish this feat, we monitored the dynamics of brain activity through functional magnetic resonance imaging. The acquired signals only indirectly reflect neuronal mechanisms, and can be modulated by several confounding factors. A notorious one is head motion...

Targeting mitochondrial bioenergetics and NAD+ metabolism during sarcopenia and regeneration of skeletal muscle

Tanja Sonntag
The progressive decline of muscle mass and function called sarcopenia is a multi-factorial process associated to frailty, disability, and low quality of life in the elderly. The co-factor nicotinamide adenine dinucleotide (NAD+) becomes a limiting factor in the course of aging and other pathological conditions. It has emerged as a major regulator of cellular metabolism, which is modulated by dietary precursors of the vitamin B3 family. So far, no direct link between sarcopenia and alterations...

The onset of cardiovascular disease in mice: an image-based, computational-experimental approach

Lydia Aslanidou
In a number of cardiovascular diseases, the paucity of longitudinal human data hinders our understanding of disease evolution and forestalls the discovery of new therapeutic strategies. We therefore heavily rely on animal models to elucidate the mechanisms that govern disease development. Nonetheless, the reference mouse arterial physiology and hemodynamics of its systemic circulation have yet to be described. But preclinical research is not limited to healthy mice; it helps decode the elusive etiology of potentially...

Functional Inverse Problems on Spheres: Theory, Algorithms and Applications

Matthieu Martin Jean-Andre Simeoni
Many scientific inquiries in natural sciences involve approximating a spherical field -namely a scalar quantity defined over a continuum of directions- from generalised samples of the latter (e.g. directional samples, local averages, etc). Such an approximation task is often carried out by means of a convex optimisation problem, assessing an optimal trade-off between a data-fidelity and regularisation term. To solve this problem numerically, scientists typically discretise the spherical domain by means of quasi-uniform spherical point...

Adaptive algorithms for two fluids flows with anisotropic finite elements and order two time discretizations

Samuel Dubuis
This thesis is devoted to the derivation of a posteriori error estimates for the numerical approximation of fluids flows separated by a free surface. Based on these estimates, error indicators are introduced and adaptive algorithms are proposed to solve the problem with accuracy and low computational costs. We focus on numerical methods that are combinations of anisotropic finite elements and second order methods to advance in time. We split the technical difficulties in the derivation...

The role of mechanical hysteresis source in mechanical and mechanobiological performances of load-bearing biomaterials

Naser Nasrollahzadeh Mamaghani
Tissue engineering is a promising approach for articular cartilage regeneration as no satisfactory treatment is actually available for cartilage, partly due to the very limited self-healing capability of this tissue. To successfully induce a cartilaginous tissue formation, however, a variety of contributing factors either from a biological or engineering standpoint should be optimized. In particular, sufficient biophysical signals should be provided to promote the response of the spatially distributed cells in a biomimetic three dimensional...

Systems genetics approaches to probe gene function

Hao Li
Genes are the functional units of heredity. However, the functions of many genes remain unknown, which impedes the understanding of the underlying mechanism of complex traits and diseases. Systems genetics approaches try to understand the complexity underlining phenotypic traits using high-throughput experimental and computational approaches. In this thesis, I describe a list of novel systems genetics approaches to identify gene functions based on publicly available datasets. In Chapter 2, I focused on the multi-omics datasets...

Functional de novo Protein Design for Targeted Vaccines and Synthetic Biology Applications

Che Yang
Evolution has created, selected and evolved large repertoires of proteins that operate in various biological systems. Nowadays biotechnological needs are coming up orders of magnitude faster than proteins naturally evolve. The emergence of de novo protein design accelerates the process of creating new proteins to explore a virtually infinite number of protein folds and sequences that can potentially be empowered with functionality. However, there remains a significant need for research in this field for installing...

Tribological Approach to the Watch Movements

Valentine Agnès Madeleine Magnin
Mechanical watches are complex and sensitive systems that have to maintain a faultless precision over their lifetime. However, this precision can be altered by disturbances occurring during the functioning time, such as friction, lubricant drying, or wear, leading to surface modification. Due to the significant number of contacts, and diversity of materials, geometries, motions, and lubricants, these disturbances and their consequences over time are difficult to control. To deeply understand these phenomena and limit their...

Analysis of High Temperature Degradation of Alloys in Solid Oxide Fuel Cell

Manuel Bianco
Solid oxide fuel cells (SOFCs) are approaching commercialization to improve power production efficiency. Currently, cost and lifetime reliability limit their spread in the market. The SOFC is ceramic-based, but refractory metal alloys are in fact the majority materials present in SOFC systems. The lifetime behaviour of SOFC stacks, and of the metallic components in particular, remain in need of further investigation. The degradation processes behind the possible failure of selected metal interconnect (MIC) and balance...

Fluorogenic probes for live-cell imaging

Aleksandar Salim
The development of novel fluorogenic probes and their use in live-cell imaging lead to a plethora of discoveries in biological research. Herein I report on novel red fluorogenic probes for live-cell super-resolution microscopy of various cellular organelles. First, I describe a new silicon rhodamine fluorophore termed SiR595. As most other SiR derivatives, SiR595 exists in an equilibrium between two chemical forms, a fluorescent zwitterion and a non-fluorescent spirolactone. Compared to regular SiR, the equilibrium of...

Multi-physical characterization of cellular ceramics for high-temperature applications

Ehsan Rezaei
The use of cellular ceramics in enhancing the performance of a high-temperature latent heat thermal energy storage unit was investigated. A detailed design methodology is presented, which consists of a combined analytical-numerical analysis followed by a multi-objective optimization. This optimization indicated that within the selected design space, effectiveness values as large as 0.95 and energy densities as large as 810 MJ/m3 could be achieved. Motivated by the results of this study, new porous structures were...

Statistical methods for accounting and understanding ozone trends derived from observations

Eirini Boleti
Emissions of ozone precursors have been regulated in Europe since around 1990 with air quality control measures, which resulted in reductions of nitrogen oxides and volatile organic compounds concentrations. In order to understand how these measures have affected tropospheric ozone, it is important to investigate its long-term temporal evolution in different types of environments and various geographic regions. Uncertainties in ozone long-term trends are associated to variations originating from meteorological influence on ozone. Also, ozone...

Orientation, rotation and solvation of ions in helium nanodroplets

Verónica Oliver Álvarez De Lara
Helium nanodroplets are liquid, finite size, nanoscale helium clusters that have been employed since the 1990s as a matrix for high-resolution spectroscopy of molecules. Spectroscopic studies of ionic species inside helium droplets were not however realised until 2010, even though the potential information about their structure is of special interest since they are fundamental reaction intermediates in biochemistry. Additionally, the interaction of these species with the helium environment can be determined from these experiments, which...

Charge-carrier Dynamics in Metal Oxides and Hybrid Lead Perovskites investigated by Time-Resolved UV and X-ray Spectroscopy

Thomas Charles Henry Rossi
In modern ultrafast optoelectronic technologies based on wide band gap insulators, the non-equilibrium dynamics of photogenerated charges plays a major role. Unravelling the mechanisms of interaction between these charge carriers and their environment is crucial to support the design of more efficient devices. Especially, the absorption of photons with more energy than the optical band gap generates electrons-hole pairs (EHP) whose transport and dissociation as excitons or free charge carriers is of pivotal importance for...

Language Independent Query by Example Spoken Term Detection

Dhananjay Ram
Language independent query-by-example spoken term detection (QbE-STD) is the problem of retrieving audio documents from an archive, which contain a spoken query provided by a user. This is usually casted as a hypothesis testing and pattern matching problem, also referred to as a ``zero-resource task'' since no specific training or lexical information is required to represent the spoken query. Thus it enables multilingual search on unconstrained speech without requiring a full speech recognition system. State-of-the-art...

Measurement of the branching fractions for B+ -> D*+ D- K+, B+ -> D*- D+ K+, and B0 -> D*- D0 K+ decays

Pavol Stefko
Charmed hadron spectroscopy is a quickly progressing field that has enjoyed a growing interest in recent years from both theorist and experimentalists. Open-charmed hadrons consist of a heavy $c$ quark bound to a light quark ($u$, $d$, $s$ quarks). These particles are in particular spin-parity states making for a very interesting quantum mechanical system allowing the study of the QCD potential holding them together. Decays of type $B\rightarrow D^{*}DK$ offer a rich environment to study...

Human-friendly solutions for last-centimeter drone delivery

Przemyslaw Mariusz Kornatowski
The popularity of delivery drones is constantly increasing due to their ability to deliver packages more rapidly and economically than current transportation methods. Consequently, drones have been employed by logistics companies for delivering payloads to hard-to-reach places and for daily door-to-door deliveries. However, logistic companies focus mainly on large platforms for long-range (<150km) and last-mile delivery (<20km), not designed to deliver directly to individual consumers. The drones suffer four major limitations: limited safety, difficulty for...

Scalable Nanowire Networks: Growth and Functionality

Martin George Friedl
With the rise of quantum computing and recent experiments into topological quantum computers come exciting new opportunities for III-V semiconductor quantum nanostructures. In this thesis, we explore the scalable fabrication of patterned arrays and branched networks of horizontally-oriented III-V nanowires with potential applications in the highly-relevant fields of topological quantum computing and infrared photodetection. We approach this challenge through the use of selective-area epitaxy applied to the technique of molecular beam epitaxy. The first part...

Development of novel tools for imaging of metabolic fluxes in vivo

Tamara Maric
Bioluminescent imaging is a powerful technique that enables imaging in living organisms with high sensitivity, low background signal, low cost and without the need for radioactivity. The emitted photons are produced in the oxidation reaction of luciferin catalyzed by luciferase. In the caged luciferin approach, the bioluminescent readout is used for measuring the activity of a specific biochemical process. Luciferin is caged in order to prevent catalysis by luciferase, and only when the cage is...

Brillouin scattering in gas-filled hollow-core fibres

Flavien Gyger
Edward E. Hagenlocker and William G. Rado demonstrated Brillouin interaction in gas for the first time in 1965, right after the very first demonstrations of stimulated Brillouin scattering in solid materials. In their experiment, they used a megawatt pulsed ruby laser that they focused in a gas cell. Such a high optical power was required due to the weak efficiency of the interaction, as a result of the impossibility of confining a high optical intensity...

Hydraulic stimulation of pre-existing discontinuities in tight rocks

Federico Ciardo
Hydraulic stimulation is an engineering technique whose aim is to enhance the permeability of fractured rock masses at depths ranging from one to five kilometers. It consists in the injection of fluid at sufficiently high pressure in order to shear pre-existing fractures and/or to create new fractures. The local reduction of effective stresses can indeed result into localized inelastic deformations along pre-existing discontinuities which upon dilation increase the overall permeability of the rock mass. Although...

The politics of participation in transdisciplinary sustainability research: an analysis of knowledge, values and power at the science-society interface

Livia Bianca Fritz
Problem. In the field of sustainability, scholars and policy-makers herald the transformative power of participation in transdisciplinary (TD) research. The increasing use of TD in science policy is rooted in the expectation that involving practitioners in the research process produces 'socially robust' knowledge and fosters the desired societal change. However, there is a strong discrepancy between these expectations, ideal-typical conceptions of TD, and a limited understanding of the complex interactions that forge participation in knowledge...

Just-in-time performance without warm-up

Denys Shabalin
Scala has been developed as a language that deeply integrates with the Java ecosystem. It offers seamless interoperability with existing Java libraries. Since the Scala compiler targets Java bytecode, Scala programs have access to high-performance runtimes including the HotSpot virtual machine. HotSpot provides impressive performance results achieved via just-in-time compilation. It starts program execution in interpreter mode, collecting profile feedback about called methods. This information allows HotSpot to identify hot spots in the program, which...

Towards integrated control of tokamak plasmas: physics-based control of neoclassical tearing modes in the TCV tokamak

Mengdi Kong
Neoclassical tearing modes (NTMs), magnetic islands located at rational $q$ surfaces, are an important class of resistive magnetohydrodynamics (MHD) instabilities in tokamak plasmas, with $q$ the safety factor. NTMs are one of the main constraints of the achievable plasma pressure by increasing the local radial transport and NTMs can lead to plasma disruptions. It is therefore crucial to understand the physics of NTMs and ensure their reliable control. This thesis explores the physics and control...

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