Although the regulation of proteins functions by allosteric interactions has been identified in many subcellular processes, long-range conformational changes in proteins are also known to be induced by molecular switches. A molecular switch based on the cis-trans isomerization of a peptidyl-prolyl bond is capable of inducing a conformational change directly to the protein backbone, which is then propagated throughout the system. However, these switches are elusive and difficult to identify due to their intrinsic dynamics in the biomolecules where they are found. Herein, we explore the conformational dynamics and free energy landscape of the SH2 domain of Interleukin-2-inducible T-Cell Kinase (ITK) to fully understand the conformational coupling between the distal cis-trans molecular switch, and its phosphotyrosine binding pocket. Using multiple microsecond-long all-atom molecular dynamics simulations in explicit water for over a total of 60 μs, we show that the cis-trans isomerization of the Asn286-Pro287 peptidyl-prolyl bond is directly correlated to the dynamics of the phosphotyrosine binding pocket, in agreement with previous NMR studies. While the cis state is localized to a single free energy basin and less dynamic, the trans state samples two distinct conformations of its binding pocket – one that recognizes the phosphotyrosine motif, and another that is similar the cis state. These results provide an atomic-level description of a less-well understood allosteric regulation by a peptidyl-prolyl cis-trans molecular switch that could aid in the understanding of normal and aberrant sub-cellular process and the identification of these elusive molecular switches in other proteins.

L’objectif de la thèse vise au développement d’architectures moléculaires et supramoléculaires commutables par contrôle rédox. La stratégie proposée repose sur l’exploitation du processus de π-dimérisation subi par les radicaux cations de dérivés du viologène comme force motrice pour la génération électro-induite de mouvements intramoléculaires. Nous décrivons la conception de nouvelles charnières organiques à squelette calixarène permettant d’accéder à des pinces moléculaires. Convenablement fonctionnalisée par des mâchoires de type pyridine-pyridinium, le mouvement de la pince est déclenché par la combinaison d’une activation chimique et électrochimique. Dans un deuxième exemple, nous montrons comment il est possible de verrouiller et déverrouiller les mouvements de la charnière calixarène en utilisant un réseau de liaisons hydrogène intramoléculaires. Nous décrivons également la conception d’une charnière inorganique originale fondée sur un complexe de palladium qui joue le rôle du pivot d’un carrousel moléculaire dont les bras à base de viologène sont mis en rotation sous l’effet d’une réduction électrochimique centrée sur les motifs viologènes. Le contrôle rédox des phénomènes d’auto-association au sein de polymères de coordination dynamiques est également abordé au travers de deux exemples de pinces moléculaires aux mâchoires fonctionnalisées soit par des briques auto-complémentaires, soit par des ligands bidentés. Dans un dernier exemple, un centre métallique palladium est utilisé à la fois comme vecteur de polymérisation et comme charnière pour la π-dimérisation intramoléculaire de ligands ditopiques à base de viologènes. / The aim of the thesis is to develop new concepts in the design of redox-switchable molecular and supramolecular architectures. The strategies which have been implemented rely on the π-dimerization of viologen radical cations as a driving force for the generation of electron-triggered intramolecular movements. Upon studying a series of viologen-appended calixarenes, we have established that bipyridinium radicals can be reversibly -dimerized under the joined effects of chemical (proton transfer) and electrochemical (electron transfer) stimulus. Our investigations also led to the discovery that a bis-pyridinyl appended calixarene intermediate is involved in a fully reversible redox-triggered sigma-dimerization process. We have also established that the ability of a phenol-containing calixarene to dimerize in its two electron reduced state depends on a subtle balance of weak interactions associated with hydrogen bond formation on the lower rim and orbital overlap between -radicals on the upper rim.We also demonstrate that inorganic hinges based on palladium complexes can be used as pivots in viologen-containing π-dimerizable architectures. The redox-controlled self-assemby of dynamic coordination polymers is also addressed through two examples of molecular tweezers, whose arms are functionalized by self-complementary complexing units or by bidentate ligands. In a last example, a palladium metal center is used both as a carrier of polymerization and as a hinge enabling the intramolecular π-dimerization of ditopic viologen-based ligands.

The issue of increasing unfunded pension liabilities of state and local governments has drawn increasing attentions in the last few years, especially after the 2008 stock market downturn. To maintain sustainability many state and local governments have put public pension reform at the top of their priority list. Previous research and practices provide two strategies to reform the current pension systems: Incremental changes to amend the existing defined benefit plans (DB plans), and the pension model switch from the DB model to defined contribution plans (DC plans). This study aims to uncover reform strategies to cope for public pension systems. It first examined the appropriateness of the incremental reform strategies by identifying the determinants of the financial solvency of DB plans, utilizing the existing panel data of 151 local DB plans in Florida municipalities. Second, it gathered the primary data through the surveys and interviews with the Finance and HR directors in Florida local governments to analyze their perceptions of public pension reform and reveal their readiness to conduct the public pension paradigm switch. These approaches revealed the critical interperiod equity issue along with the impact of the two-tier benefit structure during the recent pension reform. The results suggest that incremental reform strategies that reduce benefits and increase contributions are not effective in improving the financial solvency of public DB plans. The alternative reform approach—the DB-to-DC transition—is attractive to local governments because it will relieve the employer of the pension cost burden and transfer the investment risk to employees themselves. The transition is also politically palatable because the taxpayer sentiment is not supportive of what are perceived to be generous retirement benefit of public employees. Meanwhile, local governments are hesitant to implement the paradigm switch due to prohibitive transition costs, political pressure, and perhaps more importantly, the potential negative impacts to public recruitment and retention. Local officials do not perceive a reduction of morale with the two-tier benefit structure at the present time; they believe this issue will solve itself along the retirement of senior employees.

No description available.

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.

Radio-frequency (RF) switches are widely used in electrical systems, telecommunications, and wireless applications. In RF systems, it is often desirable to change the signal path effectively, by us-ing couplers, duplexers, and RF switches for signal division and combining. Typically, in modern RF systems, the RF switch is mostly capitalized in order to reduce the RF footprint but with efficient switch characteristics. A simple method to reduce transceiver space requirement is to integrate RF switches with the frontend module on a single chip. Recent advances in Gallium Nitride (GaN) technology allows RF designers to design faster, smaller, and efficient components using this technology. With high data rates in demand for wireless communication systems, wideband characteristics are needed in modern systems [1]. Therefore, it is desirable to design wideband circuits; such as, mixers, amplifiers, and switches. In this work, a comprehensive study of NRC GaN150 HEMT is conducted to design broadband RF switches. Single pole and double pole switch topologies operating at 1-12 GHz are designed to evaluate GaN 0.15μm RF switches. The main objectives were to design compact sized switches, while having high power handling, low insertion loss, high isolation and high return loss. Additionally, a transmit-receive switch is designed for integration into a frontend module and further fabricated to operate at 10 GHz. There are many applications of RF switches in an RF transceiver, one of which is an impedance tuner. Impedance tuner are attractive for many applications where mobile devices are used for wireless communications. As mobile technology continues to evolve, they are designed to be com-pact, leaving minimal space for the antenna. Consequently, the radiating element is often electrically small and sensitive to near-field coupling requiring tuning. Matching networks aim to tune matching conditions; for example, loading effects due to human hand [2]. For such situations, specialized matching networks can be designed to account for specific loading environmental effects. However, for mobile systems, the environment is unknown; thereby, yielding unpredictable antenna loading, especially for electrically small antennas that have rapidly changing real and imaginary impedance. As a result, it is necessary to design a reconfigurable impedance-matching network to account for possible load impedances. In this work, a 16-bit reconfigurable impedance tuner design comprising of passive microwave components and NRC GaN 0.15μm FET operating at X-band is presented to evaluate its performance for integration with the frontend module on a single chip to reduce cost and increase efficiency of the system.

In this thesis we present pvFPGA, the first system design solution for virtualizing an FPGA - based hardware accelerator on the x86 platform. The accelerator design on the FPGA can be used for accelerating various applications, regardless of the application computation latencies. Our design adopts the Xen virtual machine monitor (VMM) to build a paravirtualized environment, and a Xilinx Virtex - 6 as an FPGA accelerator. The accelerator communicates with the x86 server via PCI Express (PCIe). In comparison to the current GPU virtualization solutions, which primarily intercept and redirect API calls to the hosted or privileged domain’s user space, pvFPGA virtualizes an FPGA accelerator directly at the lower device driver layer. This gives rise to higher efficiency and lower overhead. In pvFPGA, each unprivileged domain allocates a shared data pool for both user - kernel and inter-domain data transfer. In addition, we propose the coprovisor, a new component that enables multiple domains to simultaneously access an FPGA accelerator. The experimental results have shown that 1) pvFPGA achieves close-to-zero overhead compared to accessing the FPGA accelerator without the VMM layer, 2) the FPGA accelerator is successfully shared by multiple domains, 3) distributing different maximum data transfer bandwidths to different domains can be achieved by regulating the size of the shared data pool at the split driver loading time, 4) request turnaround time is improved through DMA (Direct Memory Access) context switches implemented by the coprovisor.

In this thesis, we did a forensic analysis of a Nintendo Switch gaming console. It is both a portable and a stationary device, which makes it so that it could contain valuable information about the usage of the console at home and elsewhere. Multiple methods of data extraction were used, including using an exploit to obtain storage memory, extracting the contents of the SD card and capturing network traffic. The findings from the analysis of these data sources were compared to the information on the user interface. Any information that could not be found on the user interface was reported. The main findings of memory analysis were a detailed log file of user interactions, JSON files with personal information such as email addresses, and crash logs with information about the state of the console during the crash. The SD card mainly contains screenshots with embedded timestamps, and the network capture does not contain any forensically relevant information. The combination of these different types of information could makethe Nintendo Switch a useful source of evidence during an investigation.

The objective of this doctoral thesis is to develop, engineer and investigate an amorphous metal tungsten nitride (aWNx) and to study its functionality for applications focused on electromechanical system at the nano-scale. Charge transport based solid state device oriented complementary metal oxide semiconductor (CMOS) electronics have reached a level where they are scaled down to nearly their fundamental limits regarding switching speed, off state power consumption and the on state power consumption due to the fundamental limitation of sub-threshold slope (SS) remains at 60 mV/dec. NEM switch theoretically and practically offers the steepest sub-threshold slope and practically has shown zero static power consumption due to their physical isolation originated from the nature of their mechanical operation. Fundamental challenges remain with NEM switches in context of their performance and reliability: (i) necessity of lower pull-in voltage comparable to CMOS technology; (ii) operation in ambient/air; (iii) increased ON current and decreased ON resistance; (iv) scaling of devices and improved mechanical and electrical contacts; and (v) high endurance. The “perfect” NEM switch should overcome all the above-mentioned challenges. Here, we show such a NEM switch fabricated with aWNx to show (i) sub-0.3-volt operation; (ii) operation in air and vacuum; (iii) ON current as high as 0.5 mA and ON resistance lower than 5 kΩ; (iv) improved mechanical contact; and the most importantly (v) continuous switching of 8 trillion cycles for more than 10 days with the highest switching speed is 30 nanosecond without hysteresis. In addition, tungsten nitride could be the modern life vine by fulfilling the demand of biodegradable material for sustainable life regime. Transient electronics is a form of biodegradable electronics as it is physically disappearing totally or partially after performing the required function. The fabricated aWNx suites this category very well, despite not being a universal bio-element. It has been found that aWNx dissolves in ground water with a rate of ≈ 20-60 nm h-1. This means that a 100 nm thick aWNx disappears in ground water in less than a day and three days are enough to dissolve completely a 300 nm thickness device.

With the world’s increasing usage of electronic devices such as mobile devices and batteries, improving the reliability and performance of these devices has become more and more important. Besides the common overheating issues, low-temperature environments can also cause performance degradation or failure to these devices. Research on thermal switches and thermal regulators aims to improve the thermal management of electronic devices across a range of operating conditions. However, continuous tuning of thermal transport with all-solid-state systems is still challenging. The primary purpose of this work is to propose and demonstrate compressible foams as novel variable thermal resistors and thermal regulators to control device temperature under various input heat flux and ambient temperature. The graphene/PDMS foam is first tested in this work to demonstrate promising performance as a thermal regulator, with continuous tuning capability and a system switching ratio over ~4. Then, the dependence of the thermal conductivity of polymer foams during compression is studied, where the thermal conductivity is measured using a customized system based on an infrared microscope. Unexpectedly, the thermal conductivity decreases slightly at a compression level of more than 10x, in contrast to common theories that the thermal conductivity would increase with the mass density. A simple “spring model” is proposed as a limit where the ligaments do not build contacts during compression. Our results now fall in between the “spring model” and other common theories and can be explained. To gain further insights, a molecular dynamic simulation is performed on a graphene random nanofoam on the nanoscale. The result also shows that the effective thermal conductivity along the compression direction is not sensitive to the mass density, consistent with our experimental data on the macroscopic scale. This work provides useful insights into dynamic thermal management of electronic devices.