No description available.

Intracellular sterol redistribution is an important step in the lipid homeostasis of organisms, a process directly linked to the organizational arrangement in the plasma membrane (PM) of cells. Previous studies in the budding yeast Saccharomyces cerevisiae have demonstrated that the ARV1 (ACAT-related enzyme-2 required for viability 1) protein is a major regulator of sterol transport from the endoplasmic reticulum to the plasma membrane, contributing to the structural organization of the PM, rendering it resistant to anti-fungal compounds as well as maintaining ER integrity. This study assessed the significance of ARV1 in the plant pathogenic fungus Cryphonectria parasitica (Cparv1) and investigated its role in the pathogenesis and virulence of the fungus. C. parasitica is the causative agent of Chestnut blight, which has wreaked havoc on the American chestnut species. Genomic analysis revealed that the Cparv1 gene is very closely linked to another gene that putatively encodes a cyanamide hydratase (Cpcah). An initial gene deletion event resulted in the elimination of both genes and a highly deformed phenotype in C. parasitica that was fully recoverable by complementation. PCR-based expression analysis determined that the lack of Cparv1 was responsible for the debilitated phenotype of the double mutant, with no transcript detectable from Cpcah. Subsequent complementation of the Cparv1 gene was also observed to restore the wildtype phenotype. Mass spectrometry-based (MS) results indicated a decrease in sterol content of the DCparv1 mutant strain compared to wildtype EP155 thus confirming a role for Cparv1 in sterol homeostasis. It has been shown that infection of C. parasitica with virulence-attenuating hypoviruses altered intracellular lipid content and protein secretion. Ultrastructure studies conducted on the Cparv1 strain showed disrupted organelle integrity and the presence of cytoplasmic double membrane stretches. Decreased sterol content in C. parasitica infected with CHV1-EP713 was observed similar to DCparv1 suggesting a connection between the hypovirus-infected phenotype and Cparv1. Furthermore, a non-targeted metabolomic study on all three strains identified 324 metabolites. Through the subsequent pathway analysis, we have investigated the pleiotropic effects in the C. parasitica strains and established a mechanistic linkage between this the activity of the ARV-1 protein and the hypovirus-infected phenotype.

Hochaufgelöste räumlich-selektive Einzelionenimplantation ist eine Schlüsseltechnologie um Festkörper-Qubits herzustellen. Der in dieser Arbeit verwendete Nanoimplanter benutzt zur Kollimation eines niederenergetischen Ionenstrahls auf Nanometerebene eine Rasterkraftmikroskop-(AFM-)Spitze, welche mit einer Nanoapertur ausgestattet ist. Diese Technik wurde bereits für verschiedene Quantenanwendungen genutzt. In dieser Arbeit wird sie auf die Erzeugung strukturierter Stickstoff-Fehlstellen-(NV-)Zentren weiterentwickelt und optimiert. Dies umfasst unter anderem die Installation eines neuen AFM-Systems, welches den Aufbau mit zwei nützlichen Funktionen aufrüstet: die In-situ-Aperturvermessung und die Untersuchung von Ionen-sensitiven Fotolacken. Weiter werden die zwei wichtigsten limitierenden Faktoren der räumlichen Auflösung durch Simulationen und Experimente detailliert untersucht. Die Ergebnisse geben Aufschluss über optimale Nanoaperturen und Implantationsbedingungen. Streueffekte an der AFM-Spitze und Gitterführungen in Diamant können dadurch maßgeblich reduziert werden. Weiter werden NV-limitierende Effekte durch mehrere Ausheizschritte sowie Ionen- und Elektronenbestrahlungen untersucht. Zuletzt werden erstmals diamantbasierte Ionendetektoren hergestellt, welche mit Kapazität- und Strom-Spannungs-Messungen, durch Röntgenbestrahlung und Ionenstrahl-induzierter Ladung (IBIC) charakterisiert werden. Die Ergebnisse zeigen, dass die angefertigten Detektoren die Bedingungen für eine deterministische Implantation erfüllen, so dass dieses Prinzip zukünftig in den Nanoimplanter integriert werden kann. / High-resolution spatial-selective single ion implantation is a key technology to produce solid state qubits. The nanoimplanter used in this work collimates a low-energy ion beam at the nanometer level using an atomic force microscope (AFM) tip, which is provided with a nanoaperture. This technique has already been used for various quantum applications. In this thesis it is further developed and optimized for the generation of structured nitrogen vacancy (NV) centers. This includes the installation of a new AFM system, which upgrades the setup with two useful functions: in-situ aperture measurement and the investigation of ion sensitive photoresists. Furthermore, the two most significant limiting factors of spatial resolution are studied in detail by simulations and experiments. The results indicate optimized nanoapertures and implantation conditions. Scattering effects at the AFM tip and ion channeling in diamond can be significantly reduced. Moreover, NV-limiting effects are investigated by several heating steps as well as ion and electron irradiations. Finally, novel diamond based ion detectors are manufactured, that are characterized by capacitance and current-voltage measurements, by X-ray irradiation and ion beam induced charge (IBIC). The results show these detectors fulfill the conditions for a deterministic implantation, so that this concept can be integrated into the nanoimplanter in the future.

No description available.

This thesis describes a project in which algorithms are developed for the rapid and accurate solution of Poisson's equation in the presence of a dielectric boundary and multiple point charges. These algorithms are then used to perform Brownian dynamics simulations on realistic models of biological ion channels. An iterative method of solution, in which the dielectric boundary is tiled with variable sized surface charge sectors, provides the flexibility to deal with arbitrarily shaped boundaries, but is too slow to perform Brownian dynamics. An analytical solution is derived, which is faster and more accurate, but only works for a toroidal boundary. Finally, a method is developed of pre-calculating solutions to Poisson's equation and storing them in tables. The solution for a particular configuration of ions in the channel can then be assembled by interpolation from the tables and application of the principle of superposition. This algorithm combines the flexibility of the iterative method with greater speed even than the analytical method, and is fast enough that channel conductance can be predicted. The results of simulations for a model single-ion channel, based on the acetylcholine receptor channel, show that the narrow pore through the low dielectric strength medium of the protein creates an energy barrier which restricts the permeation of ions. They further show that this barrier can be removed by dipoles in the neck of the channel, but that the barrier is not removed by shielding by counter-ions. The results of simulations for a model multi-ion channel, based on a bacterial potassium channel, show that the model channel has conductance characteristics similar to those of real potassium channels. Ions appear to move through the model multi-ion channel via rapid transitions between a series of semi-stable states. This observation suggests a possible physical basis for the reaction rate theory of channel conductance, and opens up an avenue for future research.

A method is described for preset-count irradiations between 1 and 100 ions singling-out individual ions from an ion beam with more than a billion ions arriving per second. The ion tracks are etched in a conductometric system with real-time evaluation of the acquired data. The etch process can be interrupted when reaching a preset channel diameter. Cylindrical channels are obtained by adding surfactants to the etch solution forming a self-assembled barrier between etching medium and polymer. Asymmetric etching of single ion tracks leads to pH sensitive conical pores with diode-like properties. Using etched channels as template, homogeneous and multilayer magnetic single-wires are electrodeposited. The magnetoresistivity of the wires is studied. Single-track applications comprise critical apertures (cylindric, conic, necked), asymmetric pores (pH sensitive, biospecific), Giant Magneto Resistance sensors, and spintronic devices. On the basis of studies with individual ion tracks we tackled tilted multiporous systems such as ion beam lithography with a masked ion beam leading to micro-structures with inclined walls and anisotropic superhydrophobic ion track textures, analogous to biological shingle structures on butterfly wings. We demonstrated qualitatively, that the asymmetry of the texture translates into motion under ultrasonic agitation. This could lead to the development of rotary drives.

This thesis discusses two different magnetic materials: epitaxial yttrium iron garnet (YIG) and heteromorphous CoFeB-SiO2 films. YIG films were grown by pulse laser deposition (PLD) techniques onto gadolinium gallium garnet (GGG) substrates of (111) and (001) crystal orientations. Using stoichiometric and overstoichiometric ablative targets, we developed two types of YIG submicron films. The films grown from overstoichiometric targets have magnetic properties slightly different from standard liquid phase epitaxy (LPE) YIGs. They also demonstrate good substrate matching and approximately 6% nonstoichiometry. In contrary, films grown from stoichiometric targets posses surprisingly high values of uniaxial anisotropy, meanwhile cubic anisotropy is reduced several times. These films also reveal strong lattice distortions and nonstoichiometry around 17%. Employing Weiss molecular field theory and single-ion anisotropy model we determined the preferential occupancy of the octahedral [a] positions in the YIG cubic lattices by Fe3+ vacancies. The vacancies were found to be preferentially oriented along the growth direction perpendicular to the film surface. We called this effect “deformation blockade”. Different magnetostatic surface wave (MSSW) filters were also demonstrated. The filters employ high uniaxial anisotropy in YIG submicron films with magnetic losses ΔH ~ 1 Oe.  Heteromorphous CoFeB-SiO2 films were deposited onto glass substrates employing carrousel magnetron sputtering. This novel technique allows amorphous films fabrication with record high in-plane anisotropy. The induced anisotropy fields here are approximately dozen times greater the values achieved using conventional growth technique when external bias field is applied during deposition process. Interesting observations were made studying CoFeB-SiO2 magnetization dynamics in the wide frequency range from 500 kHz up to 15 GHz.  Two different anomalies of the magnetic susceptibility were found at the field of in-plane anisotropy Hp and critical field Hcr (0 < Hcr < Hp). We explained the anomalies appearance by sequence of the domain walls transformations so that Néel-Bloch-Néel domain wall transition stands for the instability at H = ±Hcr and transition from the uniformly magnetized state to the domain state with Néel domain wall and vice versa is responsible for the instability at H = ±Hp. / QC 20111122

In recent years, improved control of the motional and internal quantum states of ultracold neutral atoms and ions has opened intriguing possibilities for quantum simulation and quantum computation. Many-body effects have been explored with hundreds of thousands of quantum-degenerate neutral atoms and coherent light-matter interfaces have been built. Systems of single or a few trapped ions have been used to demonstrate universal quantum computing algorithms and to detect variations of fundamental constants in precision atomic clocks. Now in our experiment we investigate how the two systems can be advantageously combined. We immerse a single trapped Yb+ ion in a Bose-Einstein condensate of Rb atoms. Our hybrid setup consists of a linear RF-Paul trap which is overlapped with a magnetic trap and an optical dipole trap for the neutral atoms. A first synergetic effect is the sympathetic cooling of the trapped ions to very low temperatures through collisions with the ultracold neutral gas and thus without applying laser light to the ions. We observe the dynamics of this effect by measuring the mean ion energy after having an initially hot ion immersed into the condensate for various interaction times, while at the same time monitoring the effects of the collisions on the condensate. The observed ion cooling effect calls for further research into the possibility of using such hybrid systems for the continuous cooling of quantum computers. To this end a good understanding of the fundamental interaction processes between the ion and the neutrals is essential. We investigate the energy dependent elastic scattering properties by measuring neutral atom losses and temperature increase from an ultracold thermal cloud of Rb. By comparison with a Monte-Carlo simulation we gain a deeper understanding of how the different parameters affect the collisional effects. Additionally, we observe charge exchange reactions at the single particle level and measure the energy-independent reaction rate constants. The reaction products are identified by in-trap mass spectrometry, revealing the branching ratio between radiative and non-radiative charge exchange processes.

No description available.

La technologie Lithium-air développée par EDF utilise une électrode à air qui fonctionne avec un électrolyte aqueux ce qui empêche l’utilisation de lithium métal non protégé comme électrode négative. Une membrane céramique (LATP:Li1+xAlxTi2-x(PO4)3) conductrice d’ion Li+ est utilisée pour séparer le milieu aqueux de l’électrode négative. Cependant, cette céramique n'est pas stable au contact du lithium, il est donc nécessaire d'intercaler entre le lithium et la céramique un matériau conducteur des ions Li+. Celui-ci devant être stable au contact du lithium et empêcher ou fortement limiter la croissance dendritique. Ainsi, ce projet s'est intéressé à l'étude d'électrolytes copolymères à blocs (BCE).Tout d'abord, l'étude des propriétés physico-chimiques spécifiques de ces BCEs en cellule lithium-lithium symétrique a été réalisée notamment les propriétés de transport (conductivités, nombre de transport), et la résistance à la croissance dendritique du lithium. Puis dans un second temps, l'étude des composites BCE-céramique a été mise en place. Nous nous sommes en particulier focalisés sur l'analyse du transfert ionique polymère-céramique.Plusieurs techniques de caractérisation ont été utilisées telles que la spectroscopie d'impédance électrochimique (transport et interface), le SAXS (morphologies des BCEs), la micro-tomographie par rayons X (morphologies des interfaces et des dendrites).Pour des électrolytes possédant un nombre de transport unitaire (single-ion), nous avons obtenus des résultats remarquables concernant la limitation à la croissance dendritique. La micro-tomographie des rayons X a permis de montrer que le mécanisme de croissance hétérogène dans le cas des single-ion est très différent de celui des BCEs neutres (t+ < 0.2). / The lithium-air (Li-air) technology developed by EDF uses an air electrode which works with an aqueous electrolyte, which prevents the use of unprotected lithium metal electrode as a negative electrode. A Li+ ionic conductor glass ceramic (LATP:Li1+xAlxTi2-x(PO4)3) has been used to separate the aqueous electrolyte compartment from the negative electrode. However, this glass-ceramic is not stable in contact with lithium, it is thus necessary to add between the lithium and the ceramic a buffer layer. In another hand, this protection should ideally resist to lithium dendritic growth. Thus, this project has been focused on the study of block copolymer electrolytes (BCE).In a first part, the study of the physical and chemical properties of these BCEs in lithium symmetric cells has been realized especially transport properties (ionic conductivities, transference number), and resistance to dendritic growth. Then, in a second part, the composites BCE-ceramic have been studied.Several characterization techniques have been employed and especially the electrochemical impedance spectroscopy (for the transport and the interface properties), the small angle X-ray scattering (for the BCE morphologies) and the hard X-ray micro-tomography (for the interfaces and the dendrites morphologies). For single-ion BCE, we have obtained interesting results concerning the mitigation of the dendritic growth. The hard X-ray micro-tomography has permitted to show that the mechanism involved in the heterogeneous lithium growth in the case of the single-ion is very different from the one involved for the neutral BCEs (t+ < 0.2).