Establishment of the biochemical and molecular nature of cardiac development is essential for us to understand the relationship between genetic and morphological aspects of heart formation. The molecular mechanisms that underly heart development are still not clearly defined. To address this issue we have used two approaches to identify genes involved in early chick cardiac development. Differential display previously conducted in our laboratory led to the identification of two gene fragments differentially expressed in the heart that are further described in this thesis. The full-length cDNA sequence of both eukaryotic translation initiation factor-2b (eIF-2b) and NADH cytochrome b5 reductase (b5R) were isolated using library screening. The upreglation of these genes during heart development is expected given the heart is the first functional organ to form in vertebrates and protein synthesis and cell metabolism at this stage of development is maximal. Limitations in the differential display approach led to the development and optimisation of a subtractive hybridisation approach for use with small amounts of cells or tissue. To focus on cardiac gene expression during the initial phases of heart development, subtractive hybridization was performed between the cardiogenic lateral plate mesoderm of Hamburger and Hamilton stage 4 embryos and the heart primordia of stage 9 embryos. Of the 87 independent clones identified by this procedure, 59 matched known sequences with high homology, 25 matched unknown expressed sequence tag (EST) sequences with high homology, and 3 did not match any known sequence on the database. Known genes isolated included those involved in transcription, translation, cell signalling, RNA processing, and energy production. Two of these genes, high mobility group phosphoprotein A2 (HMGA2) and C1-20C, an unknown gene, were chosen for further characterisation. The role of each gene in early chick heart development and indeed development in general, was addressed using techniques such as in situ hybridisation, transfection analysis, in ovo electroporation and RNAi. HMGA2 is a nuclear phosphoprotein commonly referred to as an architectural transcription factor due to its ability to modulate DNA conformation. In keeping with this function, HMGA2/GFP fusion protein was shown to localise to the nucleus and in particular, the nucleolus. In situ hybridisation analysis suggested a role for HMGA2 in heart and somite development. HMGA2 expression was first detected at HH stage 5 in the lateral plate mesoderm, a region synonymous with cells specified to the cardiac fate. HMGA2 was also strongly expressed in the presomitic segmental plate mesoderm and as somites developed from the segmental plate mesoderm, the expression of HMGA2 showed an increasingly more restricted domain corresponding to the level of maturation of the somite. Restriction of HMGA2 expression was first detected in the dorsal region of the epithelial somite, then the dorsomedial lip of the dermomyotome, and finally the migrating epaxial myotome cells. The novel intronless gene, C1-20C, predicts a protein of 148 amino acids containing a putative zinc finger binding domain and prenyl binding motif. Zinc binding assays showed that the zinc finger domain of C1-20C/MBP fusion protein bound over six times the quantity of zinc compared to MBP alone, although not in a 1:1 stoichiometric molar ratio. C1-20C/GFP fusion protein was shown to localise to as yet unidentified intracellular cytoplasmic vesicular compartments. These compartments did not colocalise with the endosome/lysosome pathway, aparently ruling out a role for C1-20C in protein trafficking, recycling or degradation. Expression of C1-20C in the chick embryo suggests a possible role in heart and notochord development and preliminary results using siRNA suggest that C1-20C is involved in normal heart looping.

The performance and power scaling of metal-oxide-semiconductor field-effect-transistors (MOSFETs) has been historically achieved through shrinking the gate length of transistors for over three decades. As Si complementary metal-oxide-semiconductor (CMOS) scaling is approaching the physical and optical limits, the emerging technology involves new materials for the gate dielectrics and the channels as well as innovative structures. III-V materials have much higher electron mobility compared to Si, which can potentially provide better device performance. Hence, there have been tremendous research activities to explore the prospects of III-V materials for CMOS applications. Nevertheless, the key challenges for III-V MOSFETs with high-[kappa] oxides such as the lack of high quality, thermodynamically stable insulators that passivate the gate oxide/III-V interface still hinder the development of III-V MOS devices. The main focus of this dissertation is to develop the proper processes and structures for III-V MOS devices that result in good interface quality and high device performance. Firstly, fabrication processes and device structures of surface channel MOSFETs were investigated. The interface quality of In[subscript 0.53]Ga[subscript 0.47]As MOS devices was improved by developing the gate-last process with more than five times lower interface trap density (D[subscript it]) compared to the ones with the gate-first process. Furthermore, the optimum substrate structure was identified for inversion-type In[subscript 0.53]Ga[subscript 0.47]As MOSFETs by investigating the effects of channel doping concentration and thickness on device performance. With the proper process and channel structures, the first inversion-type enhancement-mode In[subscript 0.53]Ga[subscript 0.47]As MOSFETs with equivalent oxide thickness (EOT) of ~10 Å using atomic layer deposited (ALD) HfO₂ gate dielectric were demonstrated. The second part of the study focuses on buried channel InGaAs MOSFETs. Buried channel InGaAs MOSFETs were fabricated to improve the channel mobility using various barriers schemes such as single InP barrier with different thicknesses and InP/InAlAs double-barrier. The impacts of different high-[kappa] dielectrics were also evaluated. It has been found that the key factors enabling mobility improvement at both peak and high-field mobility in In[subscript 0.7]Ga[subscript 0.3]As quantum-well MOSFETs with InP/InAlAs barrier-layers are 1) the epitaxial InP/InAlAs double-barrier confining carriers in the quantum-well channel and 2) good InP/Al₂O₃/HfO₂ interface with small EOT. Record high channel mobility was achieved and subthreshold swing (SS) was greatly improved. Finally, InGaAs tunneling field-effect-transistors (TFETs), which are considered as the next-generation green transistors with ultra-low power consumption, were demonstrated with more than two times higher on-current while maintaining much smaller SS compared to the reported results. The improvements are believed to be due to using the In[subscript 0.7]Ga[subscript 0.3]As tunneling junction with a smaller bandgap and ALD HfO₂ gate dielectric with a smaller EOT. / text

Chez les eucaryotes pluricellulaires, la différenciation des cellules repose en partie sur l'activation oula répression des gènes. Les profils d'expression génique mis en place vont perdurer d'une générationcellulaire à l'autre. Ce phénomène met en jeu des mécanismes épigénétiques qui remodèlentlocalement la structure de la chromatine. Chez Drosophila melanogaster, les protéines des groupesPolycomb (PcG) et Trithorax (TrxG) participent au maintien du profil d'expression des gènes au coursdu développement. Les protéines PcG maintiennent les gènes réprimés tandis que les protéines TrxGmaintiennent les gènes activés. Une troisième classe de protéines nommée Enhancers of Trithoraxand Polycomb (ETP) module l'activité des PcG et TrxG. Dorsal Switch Protein 1 (DSP1) est uneprotéine HMGB (High Mobility Group B) classée comme une ETP. Par tamisage moléculaire, nousavions montré que la protéine DSP1 était présente au sein de complexes de poids moléculaire de 100kDa à 1 MDa. Le travail de thèse présenté ici a pour but d'identifier les partenaires de la protéineDSP1 dans l'embryon et de mieux connaître les propriétés biochimiques de DSP1. Premièrement, j'aimis en place puis effectué l'immunopurification des complexes contenant DSP1 dans des extraitsprotéiques embryonnaires. Cette approche nous a permis d'identifier 23 partenaires putatifs de laprotéine DSP1. Parmi ces protéines, nous avons identifié la protéine Rm62 qui est une ARN hélicaseà boîte DEAD. Les relations biologiques entre DSP1 et Rm62 ont été précisées. Deuxièmement, j'aidéterminé, par une approche biochimique, de nouvelles caractéristiques physico-chimiques de laprotéine DSP1.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (p. 68-76).

Cette thèse est porté sur l'étude du transport électronique dans différents matériaux organiques semi-conducteurs, considérés comme candidats potentiels pour des applications en Electronique de Spin Organique. Pour rendre possible la diffusion d'un courant polarisée en spin à l'intérieur d'un semi-conducteur (injection-transport-détection), le mécanisme de transport et la mobilité des porteurs de charge, ainsi que la nature et la valeur de la résistance de contact de l'interface séparant matériau organique et électrodes métalliques ferromagnétiques, doivent répondre à des critères très stricts. Tous les dispositifs sont en géométrie latérale. Nous étudions trois matériaux organiques différents: des fibres supramoléculaires auto-assemblées, une encre de nana-flocons de graphene exfolié en phase liquide et un polymère semi-conducteur fortement dopé en forme de couche mince. Nos résultats montrent que les conditions sont partiellement respectées, mais que des défis demeurent. / In this thesis, we study the electronic charge transport properties in different high mobility organic semiconductors considered as possible candidates for applications in Organic Spintronics. Stringent conditions are needed to make possible the diffusive transport of a spin-polarized current through an organic spacer (injection-transport-detection): the mechanism of charge transport and the carriers mobility, as well as the interface between the organic semiconductor and the ferromagnetic metallic electrodes, should meet special criteria. Our devices are in lateral geometry. We investigate three organic materials, all compatible with wet processing of organic electronics: supramolecular fibers self-assembled by light irradiation, an ink of liquid-phase exfoliated graphene nano-sheets and a conjugated polymer semiconductor thin film exposed to strong electrochemical doping. We observe that the criteria are partially matched, but some challenges are still present.

The diploma work is focused on a complex design of a high mobility multipurpose vehicle. We live in a world full of dramatic changes and it brings many situations, which for a special equipment is needed. That should be right this vehicle. Thanks to its unique character, especially total variability and driving abilities, it is possible to solve various quests in all kinds of weather, terrain or environmental conditions. It is specially aimed on an projects economy and on an future development upgrade possibility.

GaN-based High Electron Mobility Transistors (HEMT) are appealing because of their large breakdown field, high saturation velocity, and superior thermal conductivity. They work at high temperature without much degradation. HEMTs have a few drawbacks despite many positives. The cost of developing GaN HEMTs on a native substrate is high. It would be cost effective to fabricate HEMTs on an alternative substrate without affecting their performance. The goal of this project is to characterise GaN HEMTs on various substrates like Si, SiC and Sapphire. This thesis focuses mainly on DC measurements for threshold voltage, leakage current, and breakdown voltage of these transistors. It is observed that HEMT devices grown on Si substrate provides maximum saturation current, however, the breakdown voltage is about 650 V. The breakdown voltage for HEMTs grown on SiC is superior showing about 1410 V with saturation drain current of 0.49 A/mm making it a good fit for power electronic applications. The threshold voltage for the devices on SiC substrate is -8.5 V. Additionally, different device architectures with different gate lengths, gate widths, and gate to drain distances are also evaluated and compared. It is noticed that the gate length of 1.5 μm and gate-drain length of 20 μm showed the best results for devices on all the substrates. / Hög elektronmobilitetstransistorer (HEMT) baserade på galliumnitrid (GaN) är mycket aktuella på grund av materialets höga genombrottsfält, hög mättnadshastighet för elektroner och bra termisk ledningsförmåga. Dessutom kan komponenter också användas vid höga temperaturer, men det finns även nackdelar. En nackdel är att kostnaden för GaN-substrat är mycket stor och man letar därför efter mer kostnadseffektiva substratmaterial. I detta projekt jämförs därför prestanda för HEMT-komponenter tillverkade på tre olika alternativa substrat som bedöms vara mer kostnadseffektiva än GaN, kisel (Si), kiselkarbid (SiC) och safir (Al2O3). Projektet fokuseras på DC mätningar av tröskelspänning, läckströmmar och genombrottsspänning för att utröna om komponenternas elektriska prestanda påverkas av dessa substratmaterial. Resultaten visar att HEMT-komponenter på Si-substrat uppvisar något högre mättnadsström, men genombrottsspänningar på bara ca 650 V. Genombrottsspänningar på HEMT-komponenter tillverkade på SiC-substrat ligger däremot på över 1400 V och har mättnadströmmar på omkring 0.50A/mm, vilket gör dom klart bättre än komponenter på Si och safir. Tröskelspänningen för HEMT-komponenter på SiC uppmäts till -8.5 V. Ytterligare mätningar gjordes också av komponenter med olika gemoetrier, som grindbredd och längd, samt olika avstånd mellan grind och utlopp (drain), och det kan konstateras att en grindlängd på 1.5 μm och ett avstånd mellan grind och utlopp på 20 μm uppvisar de bästa resultaten oberoende av substratmaterial.

Photovoltaic technologies use light from the sun to create electricity, using a wide range of materials and mechanisms. The generation of clean, renewable energy using this technology must become price competitive with conventional power generation if it is to succeed on a large scale. The field of photovoltaics can be split into many sub-groups, however the overall aim of each is to reduce the cost per watt of the produced electricity. One such solar cell which has potential to reduce the cost significantly is the dye sensitised solar cell (DSC), which utilises cheap materials and processing methods. The reduction in cost of the generated electricity is largely dependent on two parameters. Firstly, the efficiency that the solar cell can convert light into electricity and secondly, the cost to deposit the solar cell. This thesis aims to address both factors, specifically looking at altering the transparent conducting oxide (TCO) and substrate in the solar cell. One method to improve the overall conversion efficiency of the device is to implement the DSC as the top cell in a tandem structure, with a bottom infra-red absorbing solar cell. The top solar cell in such a structure must not needlessly absorb photons which the bottom solar cell can utilise, which can be the case in solar cells utilising standard transparent contacts such as fluorine-doped tin oxide. In this work, transparent conducting oxides with high mobility such as titanium-doped indium oxide (ITiO) have been used to successfully increase the amount of photons through a DSC, available for a bottom infra-red sensitive solar cell such as Cu(In,Ga)Se2 (CIGS). Although electrically and optically of very high quality, the production of DSCs on this material is difficult due to the heat and chemical instability of the film, as well as the poor adhesion of TiO2 on the ITiO surface. Deposition of a interfacial SnO2 layer and a post-deposition annealing treatment in vacuum aided the deposition process, and transparent DSCs of 7.4% have been fabricated. The deposition of a high quality TCO utilising cheap materials is another method to improve the cost/watt ratio. Aluminium-doped zinc oxide (AZO) is a TCO which offers very high optical and electronic quality, whilst avoiding the high cost of indium based TCOs. The chemical and thermal instability of AZO films though present a problem due to the processing steps used in DSC fabrication. Such films etch very easily in slightly acidic environments, and are susceptible to a loss of conductivity upon annealing in air, so some steps have to be taken to fabricate intact devices. In this work, thick layers of SnO2 have been used to reduce the amount of etching on the surface of the film, whilst careful control of the deposition parameters can produce AZO films of high stability. High efficiency devices close to 9% have been fabricated using these stacked layers. Finally, transferring solar cells from rigid to flexible substrates offers cost advantages, since the price of the glass substrate is a significant part of the final cost of the cell. Also, the savings associated with roll to roll deposition of solar cells is large since the production doesn't rely on a batch process, using heavy glass substrates, but a fast, continuous process. This work has explored using the high temperature stable polymer, polyimide, commonly used in CIGS and CdTe solar cells. AZO thin films have been deposited on 7.5um thick polyimide foils, and DSCs of efficiency over 4% have been fabricated on the substrates, using standard processing methods.

Approved for public release, distribution is unlimited / The Marine Corps is fielding the MTVR Truck as a replacement for its aging fleet of five-ton cargo trucks. The MTVR is an Acquisition Category II program that was a multi-service Army-Marine Corps program. The purpose of this thesis is to examine the effectiveness of having an Army Product Office execute a Marine Corps Program. The study analyzes the effectiveness of the timing of the program's transition from the Army to the Marine Corps. A detailed literature search, as well as information gathered from attending various IPRs and conducting interviews with program officials and contractors, provided the basis for the in-depth background study presented. Analysis of the data gathered led to a justification for multi-service managed programs, as well as to recommendations on the timing of the MTVR program transition. / Civilian, United States Army

This thesis presents several experiments, generally aiming at visualising the ballistic and topological transport on the high-mobility graphene/boron nitride heterostructure using the scanning gate microscope. For the first experiment, we use the scanning gate microscopy to map out the trajectories of ballistic carriers in high-mobility graphene encapsulated by hexagonal boron nitride and in a weak perpendicular magnetic field. We employ a magnetic focusing transport configuration to image carriers that emerge ballistically from an injector, follow a cyclotron path due to the Lorentz force from an applied magnetic field, and land on an adjacent collector probe. The local potential generated by the scanning tip in the vicinity of the carriers deflects their trajectories, modifying the proportion of carriers focused into the collector. By measuring the voltage at the collector while scanning the tip, we are able to obtain images with arcs that are consistent with the expected cyclotron motion. We also demonstrate that the tip can be used to redirect misaligned carriers back to the collector. For the second experiment, we investigate the graphene van der Waals structures formed by aligning monolayer graphene with insulating layers of hexagonal boron nitride which exhibit a moiré superlattice that is expected to break sublattice symmetry. However, despite an energy gap of several tens of millielectronvolts opening in the Dirac spectrum, electrical resistivity remains lower than expected at low temperature and varies between devices. While subgap states are likely to play a role in this behaviour, their precise nature is still unclear in the community. We therefore perform a scanning gate microscopy study of graphene moiré superlattice devices with comparable activation energy but with different charge disorder levels. In the device with higher charge impurity ($\sim$ 10$^-$ cm$^{-2}$) and lower resistivity ($\sim$ 10 k$\Omega$) at the Dirac point we observe scanning gate response along the graphene edges. Combined with simulations, our measurements suggest that enhanced edge doping is responsible for this effect. In addition, a device with low charge impurity ($\sim$ 10$^{9}$ cm$^{-2}$) and higher resistivity ($\sim$ 100 k$\Omega$) shows subgap states in the bulk. Our measurements provide alternative model to the prevailing theory in the literature in which the topological bandstructures of the graphene moiré superlattices entail an edge currents shunting the insulating bulk. In the third experiment, we continue our study in the graphene moir$\acute e$ superlattices with the newly reported non-local Hall signals at the main Dirac point. It has been associated with the non-zero valley Berry curvature due to the gap opening and the nonlocal signal has been interpreted as the signature of the topological valley Hall effects. However, the nature of such signal is still disputed in the community, due to the vanishing density of states near the Dirac point and the possible topological edge transport in the system. Various artificial contribution without a topological origin of the measurement scheme has also been suggested. In connection to the second experiment, we use the scanning gate microscope to image the non-local Hall resistance as well as the local resistance in the current path. By analysing the features in the two sets of images, we find evidence for topological Hall current in the bulk despite a large artificial components which cannot be distinguished in global transport measurement. In the last experiment, we show the development of a radio-frequency scanning impedance microscopy compatible with the existing scanning gate microscopy and the dilution refrigerator. We detailed the design and the implementation of the radio-frequency reflectometry and the specialised tip holder for the integration of the tip and the transmission lines. We demonstrate the capability of imaging local impedance of the sample by detecting the mechanical oscillation of the tip, the device topography, and the Landau levels in the quantum Hall regime at liquid helium temperature and milli-Kelvin temperature.