8,389 Works

Study and Characterization of Magnetic Materials for Beam Intensity Monitors at CERN

Silvia Aguilera Murciano
The number of particles in the beams used at CERN is measured by a family of devices called the Beam Current Transformers (BCTs). One of such devices is the DC Current Transformer (DCCT) measuring the total number of particles in an accelerator. The DCCT is built around a magnetic core made of a soft magnetic material. Currently, the DCCT cores are purchased from one of a few industrial partners. This situation might result in some...

Practical Applications of Tunnel Field Effect Transistors

Nilay Daǧtekın
Traditional metal-oxide-semiconductor field effect transistor scaling has advanced successfully over 50 years providing significant increases in transistor count per chip and operating frequency, thus enabled the built of ever more performant and complex systems. Approaching to atomic scales, the energy efficiency of the transistors is severely compromised due to short channel effects and the explosion in the leakage current. Although the introduction of new materials and structures postpone the confrontation with theoretical limitations, 2D scaling...

De l'usage des protons hyperpolarisés pour augmenter la sensibilité de la RMN

Aurélien Bornet
Nuclear Magnetic Resonance (NMR) has become an inescapable technique for spectroscopic identification. Its main advantage comes from the sensitivity of NMR active nuclei embedded in a molecule to their chemical environment. NMR is also used daily in medical imaging. Magnetic Resonance Imaging (MRI) is not only remarkably versatile, but has the precious advantage of being non-invasive; moreover, the range of radiofrequency used implies that MRI deposit a limited amount of energy in tissues under investigation....

Stretchable and Highly Bendable Thin Film Transistors Based on Atomically Thin Chemical Vapor Deposited Molybdenum Disulfide

Yen-Cheng Kung
Two-dimensional (2D) materials have received tremendous research attention recently, as they possess peculiar physical properties in their monolayer and few-layer forms, which further lead to novel applications. A wide range of 2D materials covers insulators, metals, superconductors and semiconductors with various bandgap, giving a fresh platform to reinvent conventional electronic and optoelectronic devices with new advantages. Molybdenum disulfide (MoS2), belonging to the group of transition metal dichalcogenides (TMDCs), has been widely studied for its particular...

Ferroelectric Nanowires:an Investigation in Synthesis, Characterization, Functionality, and Modeling of Finite Size Effects

Jin Wang
Ferroelectric perovskites exhibit superior dielectric, piezoelectric and ferroelectric properties. Architecting ferroelectrics in the small scale holds interest in both application and fundamental research. Compared to their 2D counterparts – thin films, ferroelectric nanowires –1D structuresndash; are far less studied. A number of important features of ferroelectric nanowires, such as their piezoelectric activity, domain structure, switching behavior and phase transitions, have not been yet fairly studied, nor understood. In this thesis, we treat central issues in...

Zum Querkraftwiderstand von Stahl- und Spannbetonträgern mit dünnen Stegen

Eckart Hars
The design of reinforced and prestressed concrete girders is usually performed so as to avoid any non ductile failure mode. Amongst these failure modes, one of the most undesirable occurs by crushing of concrete in the web. To avoid this brittle type of failure, it is of paramount importance to know precisely the effective compressive strength of concrete in the web. It is reduced by cracking (transverse strains), which is due to the shear deformations....

A Well-Defined Ni Pincer Catalyst for Cross Coupling of Non-Activated Alkyl Halides and Direct C-H Alkylation

Oleg Vechorkin
Carbon-carbon bond forming reactions are among the most important and useful methods for organic synthesis. During the last years, significant progress has been made in this field. Whereas many catalysts were developed for the coupling of aryl, alkenyl, and alkynyl halides, non-activated alkyl halides remain challenging substrates, mainly due to unproductive β-hydride elimination and difficulty in oxidative addition of alkyl halides. This dissertation is devoted to the development of a well-defined nickel catalyst for cross...

On the Physics of Exciton-Polariton Condensates

Konstantinos Lagoudakis
After the first demonstration of Bose Einstein condensation in the solid state in 2006 and the establishment of exciton polariton condensates in the wider scientific community, an intense interest has been attracted by this phenomenon at both theoretical and experimental level. It is the object of this thesis to follow on from the demonstration of polariton condensation and to study more in detail different aspects of fundamental importance related to the polariton condensation. This thesis...

On the Relationship Between Protein-DNA Interactions and Circadian Gene Expression in Mouse Liver

Guillaume Rey
Virtually every cell in our body tracks daily time using an endogenous mechanism called the circadian clock, which has a period of about 24 hours. This timing system offers a selective advantage by enabling organisms to anticipate periodic changes in environmental conditions, such as light-dark cycles. As a consequence, most behavioral and physiological processes including sleep/wake patterns, body temperature and blood pressure are influenced and thus occur at the appropriate time of the day. Such...

Sediment transport and flow conditions in steep rivers with large immobile boulders

Anton Schleiss & Tamara Ghilardi
In steep mountain rivers, morphological features such as large mostly immobile boulders, strongly influence flow behavior and bedload transport. Without taking into account these large immobile boulders, which are acting as macro-roughness elements, classical bedload transport formula largely overestimate the sediment volume transported. The effect of randomly distributed boulders creating a cascade morphology on the sediment transport capacity and bedload fluctuations in steep mountain channels was studied for the first time by Dr. Tamara Ghilardi...

Miniature hyperspectral systems

Dragos Constantin
Spectroscopy methods have been used for decades to obtain information about various materials, ranging from galaxies billions of light years from earth, to Petri dishes containing rich bacteria cultures. From spectrometers in chemical labs to spectral cameras on satellites, the high dimensionality of spectral data is proven to be an excellent source of information for detection and classification of materials. In this study, state-of-the-art solutions for aerial hyperspectral surveys are reviewed and improved upon. In...

Electronic Transport in 2D Materials with Strong Spin-orbit Coupling

Artem Pulkin
The thesis describes the computational study of structural, electonic and transport properties of monolayer transition metal dichalcogenides (TMDs) in the stable 2H and the metastable 1T' phases. Several aspects have been covered by the study including the electronic properties of the topological quantum spin Hall (QSH) state in the 1T' monolayer phase as well as the effects of strain, periodic line defects, interfaces and edges of monolayer TMDs. The electronic properties of the bulk monolayer...

Growth mechanisms of III-V semiconductor nanostructures on silicon

Eleonora Russo
The aim of this thesis is to understand the dynamics of the growth of catalyst-free III-V semiconductor nanostructures on silicon substrates, focusing the attention mainly on the early stages of growths. A detailed understanding of this first phase of the process is a key step to obtain a completely successful integration of highly functional materials, like the III-Vs, on the CMOS platform, and to synthesize nanostructures with tailored properties. Indeed, the first mandatory step in...

Advanced fatigue theory and structural response monitoring for safety verification of existing RC slabs subject to railway traffic

Vasileios Grigoriou
Experience has shown that when the models and methods that have been developed for the design of new structures are “blindly” used for the examination of existing ones, the management of civil infrastructure lacks substantially in financial efficiency and social sustainability–one feels that in these cases the above models and methods are unduly conservative. This is not surprising since the design of new structures is performed under conditions of larger uncertainty and lower risk-reduction-cost comparing...

A hybrid cementitious based-G/CFRP sandwich panel: concept, design and initial outcomes

Gonçalo Escusa, Joaquim Barros, José Sena-Cruz, Eduardo Pereira, Isabel Valente, Honeyeh Ramezansefat & Diogo Figueira

Advanced technologies to control stem-cell based organogenesis

Nathalie Brandenberg
Organoids represent the first in vitro cell culture systems that closely resemble native tissues in terms of cellular composition, architecture and key aspects of physiology. Through the discovery of these cultures, researchers could demonstrate that stem cells retain in vitro their innate tendency to self-organize, thus giving rise to complex structures resembling functioning tissues. Until now, most organoid systems have been obtained relying on ill-defined and clinically irrelevant 3D matrices, in which these organoids are...

Computational Aesthetics and Image Enhancements using Deep Neural Networks

Bin Jin
Imaging devices have become ubiquitous in modern life, and many of us capture an increasing number of images every day. When we choose to share or store some of these images, our primary selection criterion is to choose the most visually pleasing ones. Yet, quantifying visual pleasantness is a challenge, as image aesthetics not only correlate with low-level image quality, such as contrast, but also high-level visual processes, like composition and context. For most users,...

Advanced Architectures and Processing for High-Efficiency Silicon Heterojunction Solar Cells

Jonas Geissbühler
Crystalline silicon solar cells currently represent the largest part of the photovoltaic market. In response to the demand for higher efficiency devices, silicon heterojunction technology, which merges a crystalline silicon wafer with thin amorphous silicon (a-Si:H) films enabling the achievement of passivating contacts, may be considered as one of the most promising approaches for the next generation of industrial solar cells. These cells demonstrate record energy conversion efficiency enabled by excellent surface passivation leading to...

Spatial hearing rendering in wireless microphone systems for binaural hearing aids

Gilles André Courtois
In 2015, 360 million people, including 32 million children, were suffering from hearing impairment all over the world. This makes hearing disability a major worldwide issue. In the US, the prevalence of hearing loss increased by 160% over the past generations. However, 72% of the 34 million impaired American persons (11% of the population) still have an untreated hearing loss. Among the various current solutions alleviating hearing disability, hearing aid is the only non-invasive and...

Characterization of Solid-Liquid Interfaces with High-Resolution Atomic Force Microscop

Maria Ricci
Solid-liquid interfaces are ubiquitous. Despite the unquestioned relevance, many scientific research fields rely on simplified or macroscopic descriptions, discarding the molecular nature of the constituents. However, it is the specific molecular interactions and the complex chemistry in the interfacial region that are fundamental in phenomena such as heterogeneous catalysis, electrochemistry, crystal growth, membrane transport and body-antibody recognition. In particular, the models used to describe the so-called electrical double layer of ionic distributions at charged surfaces...

A (Nearly) Free Lunch:Extending NAND Flash Lifetime by Exploiting Neglected Physical Properties

Xavier Jimenez
NAND flash is a key storage technology in modern computing systems. Without it, many devices would probably not exist today or would at least not benefit from as many features. The very large success of this technology motivated massive efforts to scale it down in order to increase its density further. However, NAND flash is currently facing physical limitations that prevent it reaching smaller cell sizes without severely reducing its storage reliability and lifetime. Accordingly,...

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