Introduction: Excitability in cardiomyocytes is dependent on the subthreshold current required to raise transmembrane potential to the activation threshold and subsequent recruitment of voltage gated sodium channels to trigger an action potential. Conduction in cardiomyocytes is dependent on the robustness and speed of action potential propagating through tissue. Both are equally important for normal heart function and claim to be linear correlated (i.e if conduction decreases, excitability decreases) Cardiac sodium channels are densely expressed in the intercalated disc within the perinexus, which is two orders of magnitude narrower than bulk extracellular interstitium. The biphasic relationship between conduction and perinexus is well-researched and consistent between computations models. We hypothesized a biphasic relationship between Excitability and perinexal width (Wp). In addition, we hypothesize that the relationship between excitability and conduction is not linear but dependent on the original width of the perinexus. Methods/and Results: Ex vivo guinea pig hearts were epicardially paced and optically mapped to assess ventricular conduction and excitability. Strength-duration curves were constructed for pacing stimuli to measure rheobase (inversely correlated to excitability). Computation models incorporating ephaptic coupling and sodium channel localization to cleft widths between cardiomyocytes demonstrate these findings. Conclusion: Models and experiments reveal that the excitability and perinexus relationship is biphasic where narrowing and widening perinexus decreases conduction and excitability thus showing a linear relationship between excitability and conduction. However, the excitability and conduction become overly complex in the transition phase from release of self-attenuation to reduced self-activation. Therefore, targeting ephaptic coupling and monitoring plasma ions may be a novel strategy for increasing the efficacy and efficiency of cardiac pacemakers. / Doctor of Philosophy / The heart is a muscular organ that uses electrical impulses to function. The heart is made of cells called cardiomyocytes that allow for electricity to flow through the cells. They are connected via different junctions such as gap junctions, adherens, etc. Any loss of electrical coordination leads to irregular heartbeats which can lead to heart death. There are two ways to study electrical coordination, excitability, how easy is for the current to start in the tissue, and conduction, how easy can that current travel through the tissue. Since the 1900s researchers have stated that if excitability decreases conduction decreases. In other words, if you need more current to start the heart (excitability decreases) then that current will travel slower through the tissue (conduction decreases) thus increasing one chances of irregular heartbeats. However, the understanding of how conduction works has changed but not of excitability. For example, originally current was thought to travel through channels called gap junctions. If you have limited availability of gap junctions, current increases (aka excitability decreases) and conduction decreases. However, other species such as frogs, fishes have limited number of gap junctions and can survive. Therefore, a new mechanism was proposed called ephaptic coupling. There is space next to the gap junctions called perinexus which is rich in a channel called Na channels, which is the main driving force for excitability and conduction. The lab has shown that if you change that space between cells, you can change the conduction response. In other words, if you decrease the space between the cells, conduction will not change therefore reducing the chances of irregular heartbeats. Therefore, my project is to understand if by changing this space between cells, is excitability and conductions are still correlates of each other. Using mathematical and animal models, this dissertation shows excitability and conduction have a very complicated relationship.

Yes / The present work investigates the operation performance of 2-element configuration multiple input Multiple Output (MIMO) antennas system using Cylindrical Dielectric Resonator (CDR). The MIMO antenna arrays achieve 22.2% impedance bandwidth at S11 ≤ -10 covering the bandwidth from 10GHz to 12.5GHz that meets the essential requirements of wide band communications applications. The first array gives a maximum isolation of 27dB at an element spacing of 22mm, whereas the second array presents a maximum isolation of 42.55dB at element spacing of 12.25mm.

A rise in the need for dynamic energy allocation has been associated with the saturation of available portable wireless electronic devices. Currently, the methods for transmitting this energy efficiently have been limited to a number of options, including near field resonant magnetic coupling. Previous research with mid-range (dâ 4r) wireless power transfer has resulted in coupling efficiencies of close to 40%. In order to increase efficiency in transfer a more directive transmission system was developed using a phased array. Coupling networks were used to shift the resonance of the coupling device, leading to a tightly coupled network by array phasing. Coupling networks for the phased array were optimized using a hybrid combination of a full wave Method of Moments simulation with circuit simulation. Results were validated in a full wave simulator, and field results were shown during resonance. S-parameter results show simulated transfer efficiencies of 70% (-1.5dB) for a phased array structure and 62.3% (-2.4dB) for a single feed structure. Single feed prototyping S-parameter results show coupling efficiencies of 25% (-5.9dB). All coupling measurements are at a distance 4r with reference to the largest transmitting coupler. / Master of Science

No / A new method for the synthesis of meso-substituted porphyrins is described: reaction of 5,10,15,20-tetrabromoporphine magnesium complex with aryl or heteroaryl boronic acids in the presence of Pd(PPh3)4 gave meso-substituted porphyrins in yields up to 70%.

Many technologically important problems are coupled in nature. For example, blood flow in deformable arteries, flow past (flexible) tall buildings, coupled deformation-diffusion, degradation, etc. It is, in general, not possible to solve these problems analytically, and one needs to resort to numerical solutions. An important ingredient of a numerical framework for solving these problems is the coupling algorithm, which couples individual solvers of the subsystems that form the coupled system, to obtain the coupled response. A popular coupling algorithm widely employed in numerical simulations of such coupled problems is the conventional staggered scheme (CSS). However, there is no systematic study on the stability characteristics of the CSS. The stability of coupling algorithms is of utmost importance, and assessment of the stability on real problems is not feasible given the computational costs involved. The main aim of this thesis, is to address this issue - assess the accuracy and stability characteristics of CSS using various canonical problems. In this thesis we show that the stability of CSS depends on the relative sizes of the domain, disparity in material properties, and the time step.

The correlation between the carbon-proton and proton-proton coupling constants have been studied in various 13 systems. Isocrotonic acid-carboxyl-3C, crotonic acid- 13 13 carboxyl-3C, and 5-norbornene-2-carboxylic acid-carboxyl-3C- 1,5,6,7,7-hexachloro were synthesized and their carbonproton coupling constants were analyzed. Nmr studies showed the magnitudes of the carbon-proton coupling constants to correlate well with analogous protonproton coupling constants, although the values of the couplings were larger than expected. The geminal olefinic couplings were considerably larger than all other couplings, but they were self-consistent. The signs of the carbon-proton coupling constants also were in agreement without exception with the signs of analogous proton-proton coupling constants.

Phase oscillators are a common starting point for the reduced description of many single neuron models that exhibit a strongly attracting limit cycle. The framework for analysing such models in response to weak perturbations is now particularly well advanced, and has allowed for the development of a theory of weakly connected neural networks. However, the strong-attraction assumption may well not be the natural one for many neural oscillator models. For example, the popular conductance based Morris-Lecar model is known to respond to periodic pulsatile stimulation in a chaotic fashion that cannot be adequately described with a phase reduction. In this paper, we generalise the phase description that allows one to track the evolution of distance from the cycle as well as phase on cycle. We use a classical technique from the theory of ordinary differential equations that makes use of a moving coordinate system to analyse periodic orbits. The subsequent phase-amplitude description is shown to be very well suited to understanding the response of the oscillator to external stimuli (which are not necessarily weak). We consider a number of examples of neural oscillator models, ranging from planar through to high dimensional models, to illustrate the effectiveness of this approach in providing an improvement over the standard phase-reduction technique. As an explicit application of this phase-amplitude framework, we consider in some detail the response of a generic planar model where the strong-attraction assumption does not hold, and examine the response of the system to periodic pulsatile forcing. In addition, we explore how the presence of dynamical shear can lead to a chaotic response.

Wave-like phonons are often used to describe the heat capacity in materials. In this report the spin-phonon interaction between nuclei in a diatomic molecular structure is introduced by looking at the Hamiltonian in its ground state. The corresponding Green's functions are computed in order to investigate how this interaction affects the phonons. When calculating the spin, pseudo fermions and tensor products are introduced to make the calculation easier because the spin statistics could be a bit tricky to deal with. Three different cases of how the total interaction Hamiltonian behaves are investigated i.e. when the phonon is coupled to the spin. It turns out that in two of these cases an effect on the phonons can be seen but not in the other case.

Radio frequency inductive coupling is extensively employed for wireless powering of embedded devices such as low power passive near-field RFID systems and implanted sensors. The efficiency of low power inductive links is typically less than 1%and is characterised by very unfavourable coupling conditions, which can vary significantly due to coil position and geometry. Although, a considerable volume of knowledge is available on this topic, most of the existing research is focused on the circuital modeling of the transformer action between the external and implanted coils. The practical issues of coil misalignment and orientation and their implications on transmission characteristics of RF links have been overlooked by researchers. The aim of this work is to present a novel analytical model for near-field inductive power transfer incorporating misalignment of the RF coil system. In this thesis the influence of coil orientation, position and geometry on the link efficiency is studied by approaching the problem from an electromagnetic perspective. In implanted devices some degree of misalignment is inevitable between external and implanted coils due to anatomical requirements. First two types of realistic misalignments are studied; a lateral displacement of the coils and an angular misalignment described as a tilt of the receiver coil. A loosely coupled system approximation is adopted since, for the coil dimensions and orientations envisaged, the mutual inductance between the transmitter and receiver coils can be neglected. Following this, formulae are derived for the magnetic field at the implanted coil when it is laterally and angularly misaligned from the external coil and a new power transfer function presented. The magnetic field solution is carried out for a number of practical antenna coil geometries currently popular in RFID and biomedical domains, such as planar and printed square, and circular spirals as well as conventional air-cored and ferromagnetic solenoids. In the second phase of this thesis, the results from the electromagnetic modeling are embodied in a near-field loosely coupled equivalent circuit for the inductive link. This allows us to introduce a power transfer formula incorporating for the first time coil characteristics and misalignment factors. This novel power transfer function allows a comparison between different coil structures such as short solenoids, with air or ferromagnetic core, planar and printed spirals with respect to power delivered at the receiver and its relative position to the transmitter. In the final stage of this work, the experimental verification of the model shows close agreement with the theoretical predictions. Using this analysis a formal design procedure is suggested that can be applied on a larger scale compared to existing methods. The main advantage of this technique is that it can be applied to a wide range of implementations without the limitations imposed by numerical modeling and existing circuital methods. Consequently, the designer has the flexibility to identify the optimum coil geometry for maximum power transfer and misalignment tolerance that suit the specifications of the application considered. This thesis concludes by suggesting a new optimisation technique for maximum power transfer with respect to read range, coil orientation, geometry and operating frequency. Finally, the limitations of this model are reiterated and possible future development of this research is discussed.

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