Stretch of cardiac muscle is known to activate various physiological processes that result in changes to cardiac function, contractility and electrophysiology. To date, however, the precise relationship between mechanical stretch and changes in the electrophysiology of the heart remain unclear. This relationship, termed mechanoelectric feedback (MEF), is thought to underlie many cardiac arrhythmias associated with pathological conditions. These electrophysiological changes are observed not only in the whole heart, but also at the single cardiomyocyte level, and can be explained by the presence of stretch-activated ion channels (SACs). Most investigations of the actions of stretch have concentrated on these sacrolemmal ionic currents thought responsible for the proposed MEF-induced changes in contractility. While these studies have provided some useful insight into possible mechanisms, the inappropriate use of solutions and non-physiological degrees of stretch, may have caused somewhat misleading results. Currently, little is known about the involvement or contribution of non-selective or K+ selective SACs to the normal cardiac cycle. Here, I investigate the concept that stretch-induced changes in cardiac electrophysiology (MEF) are important in normal cardiac cycle and demonstrate the effects of stretch on the Frank-Starling mechanism (stretch induced increases in cardiac contractility) while pharmacologically manipulating stretch-activated ion currents. Experiments were conducted using a number of agents known to influence stretch-activated channels either in a positive or antagonistic manner. Results proved somewhat negative toward MEF theory with only substantial or pathological levels of stretch being able to elicit any electrophysiological change in the heart. Furthermore, where electrophysiological changes were associated with pathological stretch they were not consistently modulated by stretch-activated ion channel activators or blockers. Of equal importance was the observation that smaller levels of myocardial stretch associated with positive changes in contractility via the Frank-Starling mechanism were not associated with any electrophysiological changes in the Langendorff perfused heart (as observed by monophasic action potentials) nor in isolated muscle preparations (as observed through transcellular membrane potential recordings). As such, the present research undertaken in this thesis confirms an absence of electrophysiological changes with stretch except under extreme conditions suggesting that MEF is not a robust and necessarily repeatable phenomenon in the mammalian heart. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1320476 / Thesis (Ph.D.) - University of Adelaide, School of Molecular and Biomedical Science, 2008

CuGaSe���/CuInSe��� tandem junction solar cell is currently being pursued to be a low cost and high efficiency renewable energy source. A reported theoretical efficiency of 33.9% solar cells has been the motivation to fabricate CuGaSe��� films in a simple and low cost method. Electrodeposition is a potentially suitable method to obtain the CuGaSe��� films. A better understanding of the electrodeposition process is required to optimize the process. Focusing on the manufacture of CuGaSe��� film, the reaction accompanying the electrodeposition of CuGaSe��� using rotating disk electrode from cupric sulfate, selenious acid and gallium chloride solution in sulphate medium were studied by voltammetry. Cyclic and rotating disk voltammetry in pure and binary systems were performed in order to understand the complexity of Cu + Ga + Se systems. Diffusion coefficients of Cu(II) and Se(IV) were determined using Levich equation to be 6.93x 10������ cm��/s and 9.69x 10������ cm��/s, respectively. The correlations between supporting electrolytes, flux ratios, working electrodes and films were investigated experimentally. The deposited films were characterized by Induced Couple Plasma Spectrometry, X-Ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-Ray. CuGaSe��� is formed via the reaction of CuSe compound reduction and Ga(III) and higher gallium concentration will favor the formation of CGS film. The incorporation of gallium is highly depending on the pH (higher is better). An impinging flow electrochemical reactor was built as an alternative approach for electrochemical deposition method. Preliminary experiments of copper and copper selenide electrodeposition were conducted, and the results were comparable to the rotated disk voltammetry. / Graduation date: 2004

Graduation date: 1997

David I. Kosowsky. / "June 1, 1955." "This report is based on a thesis submitted to the Department of Electrical Engineering, M.I.T., ... ." / Bibliography: p. 59-60. / Army Signal Corps Contract DA36-039 sc-42607 Project 102B Dept. of the Army Project 3-99-10-022

A computer model simulating the electrical activity of muscles of the upper arm during elbow motion is presented. The output of the model is an Electromyographic (EMG) signal. System identification is performed on the EMG signals using autoregressive moving average (ARMA) modelling. The calculated ARMA coefficients are then used as the feature set for pattern recognition. Pattern recognition is performed on the EMG signals to attempt to identify which of four possible motions is producing the signal. The results of pattern recognition are compared with results from pattern recognition of real EMG signals. The model is shown to be useful in predicting general trends found in the real data, but is not robust enough to predict accurate quantitative results. Simplifying assumptions about the filtering effects of body tissue, and about the size and position of muscles, are conjectured to be the most likely reasons the model is not quantitatively accurate. / Graduation date: 1992

With the semiconductor industry racing toward a historic transition, nano chips with less than 45 nm features demand I/Os in excess of 20,000 with multi-core processors aggregately providing highest bandwidth at lowest power. On the other hand, emerging mixed signal systems are driving the need for 3D packaging with embedded active components and ultra-short interconnections. Being able to provide several fold increase in the chip-to-package vertical interconnect density is essential for garnering the true benefits of nanotechnology that will utilize nano-scale devices. Electrical interconnections are multi-functional materials that must also be able to withstand complex, sustained and cyclic thermo-mechanical loads. Device- to- system board interconnections are typically accomplished today with either wire bonding or solders. Both of these are incremental and run into either electrical or mechanical barriers as they are extended to higher interconnections densities. Downscaling traditional solder bump interconnect will not satisfy the thermo-mechanical reliability requirements at very fine pitches. Other approaches such as compliant interconnects require lengthy connections and are limited in terms of electrical properties. A novel chip-package interconnection technology is developed to address the IC packaging requirements and to introduce innovative design and fabrication concepts that will further advance the performance of the chip, the package, and the system board. The nano-structured interconnect technology simultaneously packages all the ICs intact in wafer form with quantum jump in the number of interconnections with the lowest electrical parasitics. The intrinsic properties of nano materials also enable several orders of magnitude higher interconnect densities with the best mechanical properties for the highest reliability and yet provide higher current and heat transfer densities. This thesis investigates the electrical and mechanical performance of nano-structured interconnections through modeling and test vehicle fabrication. Test vehicles with nano-interconnections were fabricated using low cost electro-deposition techniques and assembled with various bonding interfaces. Interconnections were fabricated at 200 micron pitch to compare with the existing solder joints and at 50 micron pitch to demonstrate fabrication processes at fine pitches. Experimental and modeling results show that the proposed nano-interconnections could enhance the reliability and potentially meet all the system performance requirements for the emerging micro/nano-systems.

It is generally believed that the Si technology is going to hit a road block soon. Amongst all the potential candidates, graphene shows the most promise as replacement material for the aging Si technology. This has caused a tremendous stir in the scientific community. This excitement stems from the fact that graphene exhibits unique electronic properties. Physically, it is a two-dimensional network of sp₂bonded carbon atoms. The unique symmetry of two equivalent sublattices gives rise to a linear energy dispersion for the charge carriers. As a consequence, the charge carriers behave like massless Dirac particles with a constant speed of c/300, where c is the speed of light. The sublattice symmetry gives rise to unique half-integer quantum hall effect, Klein's paradox, and weak antilocalization. In this research work, I was able to successfully study the growth and electronic structure of EG on SiC(0001), in ultra-high vacuum and low-vacuum furnace environment. I used STM to study the growth at an atomic scale and macroscopic scale. With STM imaging, I studied the distinct properties of commonly observed interface region (layer 0), first graphene layer, and the second graphene layer. I was able to clearly resolve graphene lattice in both layer 1 and 2. High resolution imaging of the defects showed a unique scattering pattern. Raman spectroscopy measurements were done to resolve the layer dependent signatures of EG. The characteristic Raman 2D peak was found to be suppressed in layer 1, and a single Lorentzian was seen in layer 2. Ni metal islands were grown on EG by e-beam deposition. STM/ STS measurements were done to study the changes in doping and the electronic structure of EG with distance from the metal islands.

Low-loss off-chip interconnects are required for energy-efficient communication in dense microprocessors. To meet these needs, air cavity parallel plate and microstrip lines with copper conductors were fabricated on an FR-4 epoxy-fiberglass substrate using conventional microelectronics manufacturing techniques. Copper transmission lines were separated by a composite dielectric of air and Avatrel 2000P and by a dielectric layer of air only. The composite dielectric lines were characterized to 10 GHz while the all air dielectric lines were characterized to 40 GHz. The transmission line structures showed loss as low 1.5 dB/cm at 40 GHz with an effective dielectric constant below 1.4. These novel structures show low loss in the dielectric due to the reduced relative permittivity and loss tangent introduced by the air cavity. Transmission line structures with a composite dielectric were built by coating the sacrificial polymer poly(propylene carbonate) (PPC) over a copper signal line, encapsulating with an overcoat polymer, electroplating a ground line, and decomposing PPC to form an air cavity. The signal and ground wires were separated by a layer of 15 µm of air and 20 µm of Avatrel 2000P. Air cavity formation reduced dielectric constant more than 30 percent and loss of less than 0.5 dB/cm was measured at 10 GHz. Residue from PPC decomposition was observed in the cavity of composite dielectric structures and the decomposition characteristics of PPC were evaluated to characterize the residue and understand its formation. Analysis of PPC decomposition based on molecular weight, molecular backbone structure, photoacid concentration and vapor pressure, casting solvent, and decomposition environment was performed using thermogravimetric analysis and extracting kinetic parameters. Novel interaction of copper and PPC was observed and characterized for the self-patterning of PPC on copper. Copper is dissolved from the surface during PPC spincoating and interacts with the polymer chains to improve stability. The improved thermal stability allows selective patterning of PPC on copper. Decomposition characteristics, residual metals analysis, and diffusion profile were analyzed. The unique interaction could simplify air-gap processing for transmission lines. Inorganic-organic hybrid polymers were characterized for use as overcoat materials. Curing characteristics of the monomers and mechanical properties of the polymer films were analyzed and compared with commercially available overcoat materials. The modulus and hardness of these polymers was too low for use as an air-gap overcoat, but may be valuable as a barrier layer for some applications. The knowledge gained from building transmission line structures with a composite dielectric, analyzing PPC decomposition, interaction with copper, and comparison of hybrid polymers with commercial overcoats was used to build air-gap structures with improved electrical design. The ground metal was separated from the signal only by air. The signal wire was supported from above using 60 µm of Avatrel 8000P as an overcoat. Structures showed loss of less than 1.5 dB/cm at 40 GHz, the lowest reported value for a fully encapsulated transmission line structure.

Liquid dispersions of colloidal particles play a big role in nature and as industrial products or intermediates. Their material properties are largely determined by the liquid-mediated particle-particle interaction. In water-based systems, electric charge is ubiquitous and electrostatic particle interaction often is the primary factor in stabilizing dispersions against decomposition by aggregation and sedimentation. Very nonpolar liquids, by contrast, are usually considered free of charge, because their low dielectric constant raises the electrostatic cost of separating opposite charges above the available thermal energy. Defying this conventional wisdom, nonpolar solutions of certain ionic surfactants do support mobile ions and surface charges. Even some nonionic surfactants have recently been found to raise the conductivity of nonpolar oils and promote surface charging of suspended particles, but this counter-intuitive behavior is not yet widely acknowledged, nor is the mechanism of charging understood. The present study provides the first characterization of the electrostatic particle interaction caused by nonionizable surfactants in nonpolar oils. The methods used in this study are video microscopy experiments where particle positions of equilibrium ensembles are obtained and translated into particle interactions. Experimentally, equilibrium particle positions are monitored by digital video microscopy, and subjected to liquid structure analysis in order to find the energy of interaction between two particles. The observed interaction energy profiles agree well with a screened-Coulomb potential, thus confirming the presence of both surface charge and mobile ions in solution. In contrast to recently reported electrostatic particle interactions induced by ionic surfactants in nonpolar solution, the present study finds evidence of charge screening both above and below the surfactant's critical micelle concentration, CMC. Fitted Debye screening lengths are much larger than in aqueous systems, but similar to the Debye length in nonpolar oils reported for micellar solutions of ionic surfactants cite{hsu_charge_2005}. Radial distribution functions obtained from experiments are compared to Monte-Carlo simulations with input potentials obtained from a fit to the interaction measurement. The measured electrostatic forces and fitted surface potentials are fairly substantial and easily capable of stabilizing colloidal dispersions. Although few in number, surface charges formed on polymer particle surfaces submerged in nonpolar solutions of nonionizable surfactants create surface potentials comparable to those in aqueous systems.

In this thesis we study the effect of electron-electron interactions on Chiral two-dimensional electron gas (C2DEGs). C2DEGs are a very good description of the low-energy electronic properties of single layer and multilayer graphene systems. The low-energy properties of single layer and multilayer graphene are described by Chiral Hamiltoninans whose band eigenstates have definite chirality. In this thesis we focus on the effect of electron-electron interactions on two of these systems: monolayer and bilayer graphene. In the first half of this thesis we use the massless Dirac Fermion model and random-phase-approximation to study the effect of interactions in graphene sheets. The interplay of graphene's single particle chiral eigenstates along with electron-electron interactions lead to a peculiar supression of spin susceptibility and compressibility, and also to an unusual velocity renormalization. We also report on a theoretical study of the influence of electron-electron interactions on ARPES spectra in graphene. We find that level repulsion between quasiparticle and plasmaron resonances gives rise to a gap-like feature near the Dirac point. In the second half we anticipate interaction driven integer quantum Hall effects in bilayer graphene because of the near-degeneracy of the eight Landau levels which appear near the neutral system Fermi level. We predict that an intra-Landau-level cyclotron resonance signal will appear at some odd-integer filling factors, accompanied by collective modes which are nearly gapless and have approximate q[superscrit 3/2] dispersion. We speculate on the possibility of unusual localization physics associated with these modes. / text