In this thesis we use three main approaches to enhance the performance of terahertz photoconductive switches (THz PC switches). We first propose two novel materials (GaBiAs and carbon nanotubes) for the substrate. The resulting enhancement in THz emission and reception are significant for GaBiAs. As thoroughly analyzed and addressed in Chapter 2, both the emission bandwidth and the emission amplitude of the device are improved by these materials. A systematic study of CNTs predicts 2 orders of magnitude enhancement in THz emission and one order of magnitude enhancement in THz reception. Experimental results for GaBiAs indicate 0.5 THz increase in bandwidth and 68% increase in the emitted THz wave amplitude. The bandwidth enhancement is in comparison to premium commercial devices. The optical excitation of the PC switch is studied and optimized next as the second enhancement approach (Chapter 3). The study presented in Chapter 3 provides an insight on the subwavelength dynamics of the optical excitation E-field at the edge of the electrodes. The study reveals that majority of the fast photocarriers are collected at the edge of the electrode in a subwavelength scale area. This insight leads to optimization of illumination profile and also the third enhancement approach, namely, the enhancement of electrode structure (Chapter 4). In Chapter 4 we have engineered the electrodes down to nanometer scale. This significantly enhances the optical excitation of the substrate and also overcomes the undesired properties of some substrate materials such as long carrier lifetime. Fabricated devices and fabrication processes are assessed in Chapter 5. Results (Chapter 6) highlight more than two orders of magnitude enhancement for nanostructures on GaAs. / Graduate / 0544

This dissertation investigates the structure of Internally Headed Relative Clauses (henceforth, IHRCs) within the framework of Government and Binding Theory. I propose that the structure of IHRCs involves a modifying clause predicted of a head. We provide empirical as well as conceptual arguments showing that the head of an IHRC is a pro licensed by coindexation with the internal head. Following Safir's (1986) LCR, this licensing must be mediated by A$ sp prime$-Binding, which is effected by operator-movement to COMP within the modifying clause. Island Constraints provide evidence for operator-movement in IHRCs. IHRCs pattern with other Wh-constructions in this way. Correlatively, if there are no Island effects in IHRCs, there are no Island effects with other Wh-constructions (cf. Lakhota, Mojave). In this case an Unselective Binding relation is established in the language. Other properties such as the Definiteness Effect and the occurence of Switch-reference markers in IHRCs in Choctaw are also shown to follow from independent parameters. / The consequences of our analysis for Baker's (to appear) theory of Configurationality are explored. We propose to expand Baker's theory to allow "discontinuous" constituents of the type (Wh$ sb1$ ... OP$ sb1$) to account for Island effects in IHRCs of pronominal languages like Mohawk and Navajo. / No special rules for the interpretation of IHRCs are required. The LF-Raising rule proposed in Williamson (1987), which raises the internal head at LF to the COMP of the IHRC is shown to derive from the LCR as it is required to create an operator-variable (A$ sp prime$-Binding) relation. We provide further independent evidence for this rule in Chapter 2.

The processes of secondary antibody diversification are initiated by the mutagenic, B cell specific enzyme, Activation-Induced Deaminase (AID). AID deaminates deoxycytosine (dC) that is located in single-stranded DNA (ssDNA) in actively transcribed DNA to initiate the processes of somatic hypermutation (SHM), gene conversion (GCV) and class switch recombination (CSR) at the antibody gene loci. These processes lead to high affinity antibodies and antibodies of various effector functions that are required to efficiently neutralize invading pathogens. It is currently unclear how the antibody genes are specifically targeted by AID over other genes. I found that AID is able to mutate a non-immunoglobulin (Ig) transgene independent of its chromosomal integration site at rates that were above background mutation rates, but were ~10-fold lower than at the antibody variable (V) region. This result suggests that AID can mutate non-Ig genes at low rates, which may explain AID’s role in oncogenesis, but nevertheless shows that AID preferentially mutates the Ig locus over other loci. While it is understood that AID specifically deaminates dC bases in ssDNA, the size, distribution and origin of these ssDNA substrates is unknown. By utilizing a unique in situ sodium bisulfite assay to detect regions of ssDNA in intact nuclei, I characterized ssDNA regions and found that they are accurate predictors of AID activity during the processes of SHM and CSR in mammalian B cells and E.coli. Importantly, with the use of E.coli models, I show that these ssDNA substrates are the product of transcription-induced negative-supercoiled DNA that correlates strongly with the mutagenic activity of AID. While several underlying mechanisms exist to prevent the mistargeting of AID, my findings suggest that by simply gaining access to ssDNA that is produced by transcription-induced negative supercoiling, AID has the potential to mutate non-Ig genes, albeit at lower rates than the antibody V-region.

The processes of secondary antibody diversification are initiated by the mutagenic, B cell specific enzyme, Activation-Induced Deaminase (AID). AID deaminates deoxycytosine (dC) that is located in single-stranded DNA (ssDNA) in actively transcribed DNA to initiate the processes of somatic hypermutation (SHM), gene conversion (GCV) and class switch recombination (CSR) at the antibody gene loci. These processes lead to high affinity antibodies and antibodies of various effector functions that are required to efficiently neutralize invading pathogens. It is currently unclear how the antibody genes are specifically targeted by AID over other genes. I found that AID is able to mutate a non-immunoglobulin (Ig) transgene independent of its chromosomal integration site at rates that were above background mutation rates, but were ~10-fold lower than at the antibody variable (V) region. This result suggests that AID can mutate non-Ig genes at low rates, which may explain AID’s role in oncogenesis, but nevertheless shows that AID preferentially mutates the Ig locus over other loci. While it is understood that AID specifically deaminates dC bases in ssDNA, the size, distribution and origin of these ssDNA substrates is unknown. By utilizing a unique in situ sodium bisulfite assay to detect regions of ssDNA in intact nuclei, I characterized ssDNA regions and found that they are accurate predictors of AID activity during the processes of SHM and CSR in mammalian B cells and E.coli. Importantly, with the use of E.coli models, I show that these ssDNA substrates are the product of transcription-induced negative-supercoiled DNA that correlates strongly with the mutagenic activity of AID. While several underlying mechanisms exist to prevent the mistargeting of AID, my findings suggest that by simply gaining access to ssDNA that is produced by transcription-induced negative supercoiling, AID has the potential to mutate non-Ig genes, albeit at lower rates than the antibody V-region.

Modern switch-mode power supplies (SMPS) used for point-of-load (PoL) applications need to meet increasingly stringent requirements on voltage regulation, while minimizing physical volume and optimizing conversion efficiency. The focus of this thesis is the voltage regulation capability of low-power PoL converters during load transients. The main objective is to investigate converter topologies and control techniques that can achieve fast and smooth transient performance without significant penalty in volume and efficiency. The digital control method is used due to its ability to implement sophisticated control algorithms. The first part of this thesis investigates a dual output stages converter, with a small auxiliary output stage connected in parallel with the main output stage. While the main output stage is responsible for steady-state operation and designed to achieve optimum efficiency, the auxiliary stage is activated when a load transient occurs, to help suppress voltage deviation. Experimental results on a 6 V-to-1 V, 3W buck converter shows 35% improvement in peak transient voltage deviation while maintaining the same efficiency profile, compared to an equivalent buck converter. The second part of this thesis introduces a flyback-transformer based buck (FTBB) converter. In this topology, the conventional buck inductor is replaced with the primary winding of the flyback transformer, an extra switch, and a set of small auxiliary switches on the secondary side. During heavy-to-light load transients the inductor current is steered away from the output capacitor to the input port, achieving both energy recycling and savings due to reduced voltage overshoots. The light-to-heavy transient response is improved by reducing the equivalent inductance of the primary transformer winding to its leakage value. Compared to an equivalent buck converter, experiment results on a 6 V-to-1 V, 3 W prototype show three times smaller maximum output voltage deviation during load transients and, for frequently changing loads, about 7% decrease in power losses.

The purpose of this thesis is to introduce a family of interactive Switch Mode Power Supplies (SMPS) for reducing the overall volume of the conventional converter topologies in low-to-medium power (up to 60W) applications. As shown in this thesis, the interaction between power supplies and electronic devices can be incorporated with emerging digital controllers for SMPS, to implement flexible converter topologies. These flexible topologies dynamically change the converter configuration, based on the load requirement, to provide near ideal transient response and/or improved efficiency over a wide range of operating conditions. This interaction relaxes the energy storage requirement for the converter reactive components and results in a low volume implementation. The interaction with the SMPS can be between the electronic load and the power supply or different conversion stages of a multi-stage converter. The effectiveness of the introduced family of SMPS is verified on digitally controlled dc-dc and ac-dc converter topologies.

Modern switch-mode power supplies (SMPS) used for point-of-load (PoL) applications need to meet increasingly stringent requirements on voltage regulation, while minimizing physical volume and optimizing conversion efficiency. The focus of this thesis is the voltage regulation capability of low-power PoL converters during load transients. The main objective is to investigate converter topologies and control techniques that can achieve fast and smooth transient performance without significant penalty in volume and efficiency. The digital control method is used due to its ability to implement sophisticated control algorithms. The first part of this thesis investigates a dual output stages converter, with a small auxiliary output stage connected in parallel with the main output stage. While the main output stage is responsible for steady-state operation and designed to achieve optimum efficiency, the auxiliary stage is activated when a load transient occurs, to help suppress voltage deviation. Experimental results on a 6 V-to-1 V, 3W buck converter shows 35% improvement in peak transient voltage deviation while maintaining the same efficiency profile, compared to an equivalent buck converter. The second part of this thesis introduces a flyback-transformer based buck (FTBB) converter. In this topology, the conventional buck inductor is replaced with the primary winding of the flyback transformer, an extra switch, and a set of small auxiliary switches on the secondary side. During heavy-to-light load transients the inductor current is steered away from the output capacitor to the input port, achieving both energy recycling and savings due to reduced voltage overshoots. The light-to-heavy transient response is improved by reducing the equivalent inductance of the primary transformer winding to its leakage value. Compared to an equivalent buck converter, experiment results on a 6 V-to-1 V, 3 W prototype show three times smaller maximum output voltage deviation during load transients and, for frequently changing loads, about 7% decrease in power losses.

The purpose of this thesis is to introduce a family of interactive Switch Mode Power Supplies (SMPS) for reducing the overall volume of the conventional converter topologies in low-to-medium power (up to 60W) applications. As shown in this thesis, the interaction between power supplies and electronic devices can be incorporated with emerging digital controllers for SMPS, to implement flexible converter topologies. These flexible topologies dynamically change the converter configuration, based on the load requirement, to provide near ideal transient response and/or improved efficiency over a wide range of operating conditions. This interaction relaxes the energy storage requirement for the converter reactive components and results in a low volume implementation. The interaction with the SMPS can be between the electronic load and the power supply or different conversion stages of a multi-stage converter. The effectiveness of the introduced family of SMPS is verified on digitally controlled dc-dc and ac-dc converter topologies.

Rapid changes in population distribution across Canada and the introduction of new telecommunication services to the consumer market have resulted in a number of significant challenges for existing network infrastructure. Fast growing populations in metropolitan regions require high density access networks to meet the growing need for bandwidth that results. Furthermore, new services such as high definition TV, online gaming and real-time video teleconferencing are becoming increasingly popular among consumers. These services require higher bandwidth to be available to end users. Changes in the Canadian economy will soon lead to a transition in Canadian industry from manufacturing to services and exploration of natural resources. This will create opportunities for new industrial development and growth in northern regions. Expanding industrialization towards northern Canada will require deployment of reliable telecommunication infrastructure. The combination of open source software, Linux operating system and Personal Computer (PC) based hardware platform is proposed to become the foundation for low cost and flexible technology that will provide transition towards all-optical infrastructures. An innovative prototype of a low-cost optical gigabit Ethernet switch is presented and its benchmark results are discussed. Scalability of the switch and its future applications in optical networks are studied. A prototype of a software based data encapsulation system was designed and implemented in a PC based platform, and its performance was evaluated using real data that was captured in commercial LAN. Semiconductor optical amplifiers (SOA) are studied as a building block in next generation switching devices for all-optical access networks. A prototype of an SOA-based low-cost optical switching device with implemented FPGA based controlling mechanism is presented and its characteristics are discussed. SOA is also studied as an energy efficient optical amplifier that can be deployed in end user facilities. The presented results provide proof of concept of a low cost flexible platform that can be used to design and build network devices to facilitate the transition of existing telecommunication networks towards next generation optical access infrastructure.

Doctor of Philosophy(PhD) / Menggwa Dla is a Papuan language spoken in Sandaun Province of Papua New Guinea and Kabupaten Jayapura of Papua Province, Indonesia. Menggwa Dla is a dialect of the Dla language; together with its sister language Anggor (e.g. Litteral 1980), the two languages form the Senagi language family, one of the small Papuan language families found in North-Central New Guinea. The main text of this thesis is divided into seven chapters. Chapter 1 introduces the linguistic, cultural and political landscapes of the Indonesia-Papua New Guinea border area where the Dla territory is located. Chapter 2 introduces the phonology of Menggwa Dla; described in this chapter are the phonemes, allophonic variations, phonotactics, morpho-phonological processes, stress assignment and intonation of the language. The inventory of phonemes in Menggwa is average for a Papuan language (15 consonants and 5 vowels). The vast majority of syllables come in the shape of V, CV or C1C2V where C2 can be /n/ /r/ /l/ /j/ or /w/. In C1C2V syllables, the sonority rises from C1 to V (§2.2.2). Nevertheless, there are a few words with word-medial consonant sequences like ft /ɸt/, lk /lk/, lf /lɸ/ or lk /lk/ where the sonority drops from the first to the second consonant; the first consonant in these sequences is analysed as the coda of the previous syllable (§2.2.3). Chapter 3 is an overview of the word classes in Menggwa Dla; the morphological, syntactic and semantic properties of the three major word classes (nouns, adjectives and verbs) and the minor word classes are compared in this chapter. Chapter 4 describes the properties of nouns and noun phrases; the person-number-gender categories, noun-phrasal syntax, nominal clitics and personal pronouns are outlined in this chapter. Menggwa Dla has a rich array of case, topic and focus markers which comes in the form of clitics (§4.5). Subject pronouns (‘citation pronouns’) only mark person (i.e. one for each of the three persons), whereas object and genitive pronouns mark person (including inclusive/exclusive first person), number, and sometimes also gender features (§4.6). Chapter 5 introduces various morphological and syntactic issues which are common to both independent and dependent clauses: verb stems, verb classes, cross-referencing, intraclausal syntax, syntactic transitivity and semantic valence. Cross-referencing in Menggwa Dla is complex: there are seven paradigms of subject cross-reference suffixes and four paradigms of object cross-references. Based on their cross-referencing patterns, verbs are classified into one of five verb classes (§5.2). There is often a mismatch between the number of cross-reference suffixes, the semantic valence, and the syntactic transitivity within a clause. There are verbs where the subject cross-reference suffix, or the object suffix, or both the subject and object suffixes are semantically empty (‘dummy cross-reference suffixes’; §5.3.2). Chapter 6 outlines the morphology of independent verbs and copulas. Verbal morphology differs greatly between the three statuses of realis, semi-realis and irrealis; a section is devoted to the morphology for each of the three statuses. Chapter 7 introduces the dependent clauses and verbal noun phrases. Different types of dependent verbs are deverbalised to various degrees: subordinate verbs are the least deverbalised, chain verbs are more deverbalised (but they mark switch-reference (SR), and sometimes also interclausal temporal relations), and non-finite chain verbs even more deverbalised. Further deverbalised than the non-finite chain verbs are the verbal nouns; verbal noun phrases in Menggwa Dla functions somewhat like complement clauses in English. In younger speakers speech, the function of the chain clause SR system has diverted from the canonical SR system used by older speakers (§7.2.2). For younger speakers, coreferential chain verb forms and disjoint-reference chain verb forms only have their coreferential and disjoint-referential meaning — respectively — when the person-number-gender features of the two subject cross-reference suffixes cannot resolve the referentiality of the two subjects. Otherwise, the coreferential chain verb forms have become the unmarked SR-neutral chain verb forms. At the end of this thesis are appendix 1, which contains four Menggwa Dla example texts, and appendix 2, which contains tables of cross-reference suffixes, pronouns, copulas and irregular verbs.