The hepatitis delta virus (HDV), composed of ~1,700nt, is the smallest circular RNA pathogen known to infect humans. Understanding the mode of replication of HDV implies on investigating the host proteins that bind to its genome. The polypyrimidine tract-binding protein-associated splicing factor (PSF), an HDV interacting protein, was found to interact with the carboxy terminal domain (CTD) of RNA polymerase II (RNAPII), and to facilitate the interaction of RNA transcripts with the CTD of RNAPII. Both PSF and RNAPII were found to interact with both polarities of the terminal stem loop domains of HDV RNA, which possess RNA promoter activity in vitro. Furthermore, PSF and RNAPII were found to simultaneously interact with HDV RNA in vitro. Together, the above experiments suggest that PSF acts as a transcription factor during HDV RNA replication by interacting with both the CTD of RNAPII and HDV RNA simultaneously. PSF knockdown experiments were performed to indicate that PSF is required for HDV RNA accumulation. Mutagenesis experiments of PSF revealed that HDV RNA accumulation might require the N terminal domain, and the RNA recognition motifs RRM1 and RRM2. I propose that the RRM1 and RRM2 domains might interact with HDV RNA, while the N-terminal domain might interact with the CTD of RNAPII for HDV RNA accumulation. Together, the above experiments provide a better understanding of how an RNA promoter might be recognized by RNAPII.

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The use of the stable isotopes, 18O and 2H, has proven to be a valuable tool in determining the importance of various hydrological controls on the modern water balances of Slave River Delta lakes, NWT, Canada. Samples collected during the 2002 and 2003 field season have shown that delta lakes exhibit highly systematic isotopic variability over the entire delta. The major influences observed to be affecting Slave River Delta lakes include spring snowmelt runoff, flood events from the Slave River, seiche events from Great Slave Lake and thaw season precipitation events. An important component of Slave River Delta lake modern water balances is evaporation, the main controlling factor of water loss in the study lakes, as well as isotopic variability experienced throughout the entire delta during the ice-off season. Flood events from Great Slave Lake and the Slave River play a key role in controlling modern water balances and isotopic compositions of lakes in the delta. Levee height throughout the delta seems to strongly affect local hydrology, with areas having the greatest levee heights also having the most enriched lake water compositions, and areas having the lowest levee heights having the most depleted isotopic signatures. Outer delta and mid-delta lakes experience the greatest amount of flooding during the spring. Lakes that are affected by spring flood events have a more depleted isotopic signature than those lakes in the upper delta. Discrepancies between δ18O- and δ2H-derived E/I ratios have been effectively reconciled by incorporating site-specific information into the mass balance equations, and allowing mixing between Great Slave Lake (GSL) vapour δE, a large body of water adjacent to the delta and advected atmospheric vapour δA. The use of locally derived parameters also ensures a more accurate depiction of local conditions. Good correlation can be observed during July 2003, between mixing of GSL vapour and atmospheric moisture, when the lakes water balances were solely affected by evaporation. The mixing ratios obtained from two of the study lakes suggest that 5 – 16% of ambient atmospheric moisture was derived from Great Slave Lake.

Eudora Welty’s sense of place is often discussed by scholars, but they have limited their discussions of place in Welty’s texts to place as region or, more specifically, the South. In so doing, Welty is often pigeonholed as a regionalist writer. Looking at the home when considering place makes Welty’s texts more universal and appealing to readers of all regions and countries. Every individual either has a home or longs for one; all understand the pull toward a home of some kind. Using the theoretical lens of social and psychological theories of space, place, and the home, this study presents a close reading of the homes in Eudora Welty’s Delta Wedding and The Optimist’s Daughter. In addition, archival research from the Eudora Welty collection at the Mississippi Department of Archives and History aids in understanding how drafting the stories and the ways in which the stories evolved add to a reading of home in the texts. In her famous essay “Place in Fiction,” Welty asks, “What place has place in fiction?” (781). In analyzing the role of the home in Welty’s fiction, the reader must ask: What place has the home in fiction? Analyzing the homes in Delta Wedding and The Optimist’s Daughter reveals the characters’ identities – both individual and collective identities, and in so doing, it allows the reader to better understand the motives behind the characters’ actions and reactions.

A new low power, wideband wireless transmitter able to convert any RF signal into a constant envelope signal enabling the use of a nonlinear and efficient power amplifier is presented. In the transmitter architecture, two normalized phase signals and the envelope are separated and processed separately. A 1-bit 2nd order SD modulator codes the envelope. Quantization noise is attenuated by a S&H interpolator introducing notches at multiples of the sampling frequency. Phase and Envelope signals are recombined and upconverted directly to radio frequencies using a novel full-digital, wideband quadrature modulator. This mixer takes advantage of the 1-bit SD output. As both LOs and envelope signals are represented by two-level signals, the product of these signals (XOR function) leads to a two-level signal, which can be used as command signal in the multiplexors. Phase signals or theirs complements that are generated by a simple Inversion Block are passed through this multiplexor at the rate of driving signals. This enables to implement a high frequency, wideband mixer instead of a more complex three-input modulator. This IQ mixer is very simple to implementate as it uses only CMOS logic gates. The generation of the quadrature clock signals in the mixer is obtained by carefully design of two paths to avoid mismatch to assure an error less than 1º (only demonstrated in simulation) and the use of SR flipflops to generate correctly the complementary signal prior to the divide-by-two circuit. Two asynchronous 9-bit DACs eliminate the 10-bit high-speed digital adder at the output of the IQ modulator and the 10-bit DAC before the PA, saving power and relaxing adder design constraints. Each DAC is divided into two full binary-weighted DACs of 4 and 5 bits. This topology enables to reduce the size ratios between the most and least significant bits related to a classic 9-bit binary-weighted structure (16 instead of 256). To test the speed and the gain control of the standalone DAC over 45 dB, a prototype DAC is designed in 0.13 ;m BiCMOS technology from STMicroelectronics together with a 1.4 GHz 9-bit CMOS ROM-less direct digital frequency synthesizer (DDFS). Over the output power range, measurements show a SFDR>25 dB with a power dissipation of 25 mW at the maximum differential output power of -3 dBm (RL=50 @). The whole transmitter is designed and implemented and a prototype transmitter is built in 0.13 μm BiCMOS STMicroelectronics process. This low cost single chip digital radio transmitter demonstrates a data rate of 1.8 GHz. The image level is measured to be -12 dBc at this sampling frequency. Dynamic range in the transmitter is 35 dB for sampling frequencies lower than 800 MHz and 25 dB for higher sampling frequencies up to 1.8 GHz. For a two-tone signal, the maximum single-ended output power is -31dBm for each tone and the power dissipation is about 35 mW. This architecture enables flexible and software-defined transmitter. Sampling frequency in the SD coder can be varied to adapt to different communications standards in terms of in-band and outof-band noise requirements and variable LO frequencies can be used. Moreover, the transmitter can adapt dynamically the output power to the power amplifier depending of the required transmitted power at the output of the PA. The transmitter has demonstrated its potential for use as a universal transmitter for applications targeting any frequency band and modulation schema up to 900 MHz (carrier frequency) and occupies a die area of 300x320 ;m2. The generated differential signal can be easily amplified by a switched-mode Power Amplifier (PA) in an efficient way because it presents constant-envelope and the PA can work in the saturation zone, which represents its optimal operation point.

The development of resistance measurement techniques is very important for characterization of future nanoelectronics. Pulsed IV measurement techniques are very useful for accurate resistance measurements on nanoscale samples because of the efficient removal of e.g. EMF errors. In the project we have designed a pulsed IV-setup based on a state-of-the art current source (6221) and nanovoltmeter (2182A) from Keithley, and used the setup for resistance measurements on ferromagnetic samples. Two different samples were investigated using the pulsed IV system – ferromagnetic wires with a central nanoconstriction and amorphous microwires. We have tested the pulse delta system with different pulse widths, duty cycles and voltage levels. The results show a successful integration of the setup. From the measurement results we confirm that the pulse delta system provides accurate measurements with a low noise of about 0.02Ω. The resistance of the samples increases approximately quadratically with bias which is interpreted as a heating effect due to the very high current density of about 107A∙cm-2.

The thesis demonstrates a low-cost, low-bandwidth and low-resolution Analog-to- Digital Converter(ADC) in 0.35 um CMOS Process. A second-order Sigma-Delta modulator is used as the basis of the A/D Converter. A Semi-Uniform quantizer is used with the modulator to take advantage of input distributions that are dominated by smaller-amplitude signals e.g. Audio, Voice and Image-sensor signals. A Single-bit feedback topology is used with a multi-bit quantizer in the modulator. This topology avoids the use of a multi-bit DAC in the feedback loop – hence the system does not need to use digital correction techniques to compensate for a multi-bit DAC nonlinearity. High-Level Simulations of the second-order Sigma-Delta modulator single-bit feedback topology along with a Semi-Uniform quantizer are performed in Cadence. Results indicate that a 5-bit Semi-Uniform quantizer with a Over-Sampling Ratio of 32, can achieve a resolution of 10 bits, in addition, a semi-uniform quantizer exhibits a 5-6 dB gain in SNR over its uniform counterpart for input amplitudes smaller than –10 dB. Finally, this system is designed in 0.35um CMOS process.

Comparator is the main building block in an ADC architecture. Main purpose of the comparator is to compare a signal with a reference signal and produce an output depending on whether the input signal is greater or smaller than reference. Many architectures for comparators exist for various purposes. In this thesis, Latched comparator architecture is used for sigma delta modulator. This particular design has two main characteristics that are very important for sigma delta application. First characteristic is the cancellation of memory effect which increases the speed and reliability of the system and the second is, with this architecture, high sensitivity can be achieved. The design and implementation of lathed comparator for sigma delta modulator is presented in this thesis work. Various non-linearities and performance parameters are discussed in detail. Practical implementation and circuit design issues are highlighted to achieve maximum sensitivity along with reasonable speed and accuracy.

The sigma-delta modulator is a popular signal amplitude quantization error (or noise) shaper used in oversampling analogue-to-digital and digital-to-analogue converter systems. The shaping of the noise frequency spectrum is performed by feeding back the quantization errors through a time delay element filter and feedback loop in the circuit, and by the addition of a possible stochastic dither signal at the quantizer. The aim in audio systems is to limit audible noise and distortions in the reconverted analogue signal. The formulation of the sigma-delta modulator as a discrete dynamical system provides a useful framework for the mathematical analysis of such a complex nonlinear system, as well as a unifying basis from which to consider other systems, from pseudorandom number generators to stochastic resonance processes, that yield equivalent formulations. The study of chaos and other complementary aspects of internal dynamical behaviour in previous research has left important issues unresolved. Advancement of this study is naturally facilitated by the dynamical systems approach. In this thesis, the general order feedback/feedforward sigma-delta modulator with multi-bit quantizer (no overload) and general input, is modelled and studied mathematically as a dynamical system. This study employs pertinent topological methods and relationships, which follow centrally from the symmetry of the circle map interpretation of the error state space dynamcis. The main approach taken is to reduce the nonlinear system into local or special case linear systems. Systems of sufficient structure are shown to often possess structured random, or random-like behaviour. An adaptation of Devaney's definition of chaos is applied to the model, and an extensive investigation of the conditions under which the associated chaos conditions hold or do not hold is carried out. This seeks, in part, to address the unresolved research issues. Chaos is shown to hold if all zeros of the noise transfer function lie outside the unit circle of radius two, provided the input is either periodic or persistently random (mod delta). When the filter satisfies a certain continuity condition, the conditions for chaos are extended, and more clear cut classifications emerge. Other specific chaos classifications are established. A study of the statistical properties of the error in dithered quantizers and sigma-delta modulators is pursued using the same state space model. A general treatment of the steady state error probability distribution is introduced, and results for predicting uniform steady state errors under various conditions are found. The uniformity results are applied to RPDF dithered systems to give conditions for a steady state error variance of delta squared over six. Numerical simulations support predictions of the analysis for the first-order case with constant input. An analysis of conditions on the model to obtain bounded internal stability or instability is conducted. The overall investigation of this thesis provides a theoretical approach upon which to orient future work, and initial steps of inquiry that can be advanced more extensively in the future.

The use of the stable isotopes, 18O and 2H, has proven to be a valuable tool in determining the importance of various hydrological controls on the modern water balances of Slave River Delta lakes, NWT, Canada. Samples collected during the 2002 and 2003 field season have shown that delta lakes exhibit highly systematic isotopic variability over the entire delta. The major influences observed to be affecting Slave River Delta lakes include spring snowmelt runoff, flood events from the Slave River, seiche events from Great Slave Lake and thaw season precipitation events. An important component of Slave River Delta lake modern water balances is evaporation, the main controlling factor of water loss in the study lakes, as well as isotopic variability experienced throughout the entire delta during the ice-off season. Flood events from Great Slave Lake and the Slave River play a key role in controlling modern water balances and isotopic compositions of lakes in the delta. Levee height throughout the delta seems to strongly affect local hydrology, with areas having the greatest levee heights also having the most enriched lake water compositions, and areas having the lowest levee heights having the most depleted isotopic signatures. Outer delta and mid-delta lakes experience the greatest amount of flooding during the spring. Lakes that are affected by spring flood events have a more depleted isotopic signature than those lakes in the upper delta. Discrepancies between δ18O- and δ2H-derived E/I ratios have been effectively reconciled by incorporating site-specific information into the mass balance equations, and allowing mixing between Great Slave Lake (GSL) vapour δE, a large body of water adjacent to the delta and advected atmospheric vapour δA. The use of locally derived parameters also ensures a more accurate depiction of local conditions. Good correlation can be observed during July 2003, between mixing of GSL vapour and atmospheric moisture, when the lakes water balances were solely affected by evaporation. The mixing ratios obtained from two of the study lakes suggest that 5 – 16% of ambient atmospheric moisture was derived from Great Slave Lake.