Swift Heavy Ion Irradiation and Thermal Annealing Induced Modification of Structural, Topographical and Magnetic Properties in Monolayer and Bilayer Films Based on FeNiMoB and Zinc Ferrite

Magnetism and magnetic materials have been playing a lead role in the day to day life of human beings. The human kind owes its gratitude to the ‘lodestone’ meaning ‘leading stone’ which lead to the discovery of nations and the onset of modern civilizations. If it was William Gilbert, who first stated that ‘earth was a giant magnet’, then it was the turn of Faraday who correlated electricity and magnetism. Magnetic materials find innumerable applications in the form of inductors, read and write heads, motors, storage devices, magnetic resonance imaging and fusion reactors. Now the industry of magnetic materials has almost surpassed the semiconductor industry and this speaks volumes about its importance. Extensive research is being carried out by scientists and engineers to remove obsolescence and invent new devices. Though magnetism can be categorized based on the response of an applied magnetic field in to diamagnetic, paramagnetic, ferromagnetic, ferrimagnetic and antiferromagnetic; it is ferrimagnetic, ferromagnetic and antiferromagnetic materials which have potential applications. The present thesis focusses on these materials, their composite structures and different ways and means to modify their properties for useful applications. In the past, metals like Fe, Ni and Co were sought after for various applications though iron was in the forefront because of its cost effectiveness and abundance. Later, alloys based on Fe and Ni were increasingly employed. They were used in magnetic heads and in inductors. Ferrites entered the arena and subsequently most of the newer applications were based on ferrites, a ferrimagnetic material, whose composition can be tuned to tailor the magnetic properties. In the late 1950s a new class of magnetic material emerged on the magnetic horizon and they were fondly known as metallic glasses. They are well known for their soft magnetic properties. They were synthesized in the form of melt spun ribbons and are amorphous in nature and they are projected to replace the crystalline counterparts.

Swift Heavy Ion Irradiation and Thermal Annealing Induced Modification of Structural, Topographical and Magnetic Properties in Monolayer and Bilayer Films Based on FeNiMoB and Zinc Ferrite

Magnetism and magnetic materials have been playing a lead role in the day to day life of human beings. The human kind owes its gratitude to the ‘lodestone’ meaning ‘leading stone’ which lead to the discovery of nations and the onset of modern civilizations. If it was William Gilbert, who first stated that ‘earth was a giant magnet’, then it was the turn of Faraday who correlated electricity and magnetism. Magnetic materials find innumerable applications in the form of inductors, read and write heads, motors, storage devices, magnetic resonance imaging and fusion reactors. Now the industry of magnetic materials has almost surpassed the semiconductor industry and this speaks volumes about its importance. Extensive research is being carried out by scientists and engineers to remove obsolescence and invent new devices. Though magnetism can be categorized based on the response of an applied magnetic field in to diamagnetic, paramagnetic, ferromagnetic, ferrimagnetic and antiferromagnetic; it is ferrimagnetic, ferromagnetic and antiferromagnetic materials which have potential applications. The present thesis focusses on these materials, their composite structures and different ways and means to modify their properties for useful applications.

High Frequency Class DE Converter Using a Multilayer Coreless PCB Transformer

In modern power electronics equipment, it is desirable to design a low profile, high power density, and fast dynamic response converter. Increases in switching frequency reduce the size of the passive components such as transformers, inductors, and capacitors which results in compact size and less requirement for the energy storage. In addition, the fast dynamic response can be achieved by operating at high frequency. However, achieving high frequency operation while keeping the efficiency high, requires new advanced devices, higher performance magnetic components, and new circuit topology. These are required to absorb and utilize the parasitic components and also to mitigate the frequency dependent losses including switching loss, gating loss, and magnetic loss. Required performance improvements can be achieved through the use of Radio Frequency (RF) design techniques. To reduce switching losses, resonant converter topologies like resonant RF amplifiers (inverters) combined with a rectifier are the effective solution to maintain high efficiency at high switching frequencies through using the techniques such as device parasitic absorption, Zero Voltage Switching (ZVS), Zero Current Switching (ZCS), and a resonant gating. Gallium Nitride (GaN) device technologies are being broadly used in RF amplifiers due to their lower on- resistance and device capacitances compared with silicon (Si) devices. Therefore, this kind of semiconductor is well suited for high frequency power converters. The major problems involved with high frequency magnetics are skin and proximity effects, increased core and copper losses, unbalanced magnetic flux distribution generating localized hot spots, and reduced coupling coefficient. In order to eliminate the magnetic core losses which play a crucial role at higher operating frequencies, a coreless PCB transformer can be used. Compared to the conventional wire-wound transformer, a planar PCB transformer in which the windings are laid on the Printed Board Circuit (PCB) has a low profile structure, excellent thermal characteristics, and ease of manufacturing. Therefore, the work in this thesis demonstrates the design and analysis of an isolated low profile class DE resonant converter operating at 10 MHz switching frequency with a nominal output of 150 W. The power stage consists of a class DE inverter using GaN devices along with a sinusoidal gate drive circuit on the primary side and a class DE rectifier on the secondary side. For obtaining the stringent height converter, isolation is provided by a 10-layered coreless PCB transformer of 1:20 turn’s ratio. It is designed and optimized using 3D Finite Element Method (FEM) tools and radio frequency (RF) circuit design software. Simulation and experimental results are presented for a 10-layered coreless PCB transformer operating in 10 MHz.

Magnetic multilayer fabrication technology with selective activation of SU-8 films

Developing magnetic multilayers are essential for reducing the core eddy current losses in the integrated power magnetic components (inductors/transformers). PVD based processes are typically used to achieve the multilayers with thin dielectric spacers. However, those processes are costly, and can be difficult to integrate. It is evident that cost effective alternative is needed. In recent years, electrochemical processes have been investigated to address these issues. One such method would be to successive metallization of insulating photoresists acting as spacer layer (such as SU-8) with soft magnetic films (such as Ni-Fe-Co alloys). This paper describes an experimental procedure to fabricate magnetic multilayers with a thin variant of SU-8 2 (< 1.5 µm) as inter-layers for integrated micro-inductors/transformers for power conversion applications.

El papel de la reparación de roturas de doble cadena de ADN en Escherichia coli en la sensibilidad a quinolonas: implicaciones terapéuticas

Las quinolonas son uno de los tipos de antibióticos cuyas tasas de resistencia se han visto incrementadas en los últimos años. A nivel molecular, bloquean a las topoisomerasas tipo II generando cortes de doble cadena (double strand breaks, DSBs) en el ADN. Se ha propuesto que estos DSBs podrían tener un doble papel, como mediadores de su efecto bactericida y también como responsables de desencadenar los mecanismos de resistencia y tolerancia a las quinolonas. En el presente trabajo hemos estudiado la implicación de los mecanismos de reparación de DSBs en la sensibilidad a las quinolonas: reanudación de horquillas de replicación paradas dependiente de recombinación (RFR), inducción de la respuesta SOS, reparación por síntesis translesional (TLS) y escisión de nucleótidos (NER). Para ello, en los laboratorios de la Universidad Europea de Madrid, se han analizado las concentraciones mínimas inhibitorias (CMIs) de tres quinolonas diferentes en mutantes procedentes de varias colecciones de cultivos tipo de Escherichia coli. Mutantes en recA, recBC, priA y lexA mostraron una disminución significativa de la CMI a todas las quinolonas. No se observaron cambios significativos en estirpes mutantes en los mecanismos de reparación por TLS y NER. Estos datos indican que, en presencia de quinolonas, los mecanismos de RFR y la inducción de la respuesta SOS estarían implicados en la aparición de mecanismos de sensibilidad a quinolonas.

Modeling and Design of Phase Shifted Full Bridge Isolated DC-DC ZVS Converter with Peak Current Mode Control

Nowadays, there is a boom in the use of electrification. Electric vehicles are gaining interest worldwide due to various factors, including climate and environmental awareness. In this thesis, a step-down isolated power supply for electric tractors is investigated, specifically the phase-shifted full-bridge (PSFB) DC-DC with synchronous rectification and zero-voltage switching (ZVS). This converter was selected for its high-power capacity with high efficiency. A 3500 W PSFB converter with peak current control (PCCM) is designed and modeled in MATLAB. The input voltage range is from 550 V to 820 V and the output voltage range is limited to 9 V to 16 V with a maximum output current of 250 A. All components were commercially designed and selected, including magnetics for the high-frequency transformer and inductors, taking into account loss calculations. Zero voltage switching for the lagging leg is achieved at 13% to 100% load. The proven efficiency of the converter is around 90