Discussion begins with a brief account of atomic level-pumping and reasons why atomic coherence is typically not considered in cw work on optical interactions. This dissertation is divided into four parts: semiclassical treatments of one-photon electric- dipole atom-field single-mode interactions and multimode interactions, and corresponding treatments for the two-photon interaction. We present the effects of injected atomic coherence on the polarization of the medium, the slowly varying envelope wave equation, the single- and multiwave mixing coefficients, and weak field propagation in a homogeneously broadened two-level medium. Spatial and temporal phase matching of the injected coherence to a field mode is crucial throughout, since the field may not be able to remain in phase with the induced and injected polarizations. One-photon injected coherence contributes directly to the polarization at the atomic resonance frequency. The perfectly phase-matched case leads to a linear superposition of an exponentially decaying field (Beer's law) and a constant field driven by the injected coherence. The interaction of an injected coherence with a detuned field produces frequency-symmetric sidebands about the pump field polarization. The sideband spacing equals the atom-field detuning. To probe the injected coherence we inject a weak resonant field. The resulting three-wave mixing leads to multiwave mixing coefficients that are unaffected to first-order in the weak sidemodes, but the injected coherence adds inhomogeneous terms to the coupled-mode equations. For both single- and multimode interactions the injected coherence does not affect the exponential growth/decay of the sidemodes, but it supports a weak field that may propagate if properly phase matched. For two-photon media the injected coherence requires at least one field interaction in order to produce a polarization, which then appears in the single- and multiwave mixing coefficients. The exponential growth/decay rate is modified by the injected coherence. For a centrally-tuned pump the injected coherence contributes the standard multiwave mixing terms as well as additional effects. Four-wave mixing is discussed as a means of relaxing the spatial phase matching constraint on the injected coherence.

No description available.

published_or_final_version / Electrical Engineering / Master / Master of Philosophy

Monomers, polymers, charge-transfer complexes of 2-benzylidene-1,3-dithioles (Dithiafulvenes), and 1,3-dithiolium (Dithiafulvenium) salts of dithioesters and poly(dithioesters) were synthesized. The infrared, nuclear magnetic resonance (NMR) and ultra violet spectra of these materials were also reported. Condensation polymerization of piperidinium tetrathio terephthalate with α-halocarbonyl compounds using phase-transfer techniques yielded poly(dithioesters) that upon dehydrative cyclization with sulfuric acid gave poly(1,3-dithiafulvenium) salts. Polymerization of substituted dithiafulvenes with diacid chlorides, p-phenylene diisocyanate or terephthalaldehyde yielded polymers with inherent viscosities of 0.10 dL/g to 0.21 dL/g. The electric resistivity of the charge-transfer complexes of several dithiafulvenes and the electron donors TCNQ and TNF measured by the two-probe method was found to be >10⁶ Ω.cm at room temperature, hence behaving like insulators. Polyesters and polyesterimides of 4,4'-sulfonyl diphenol were synthesized. The low molecular weight polymers had viscosities of 0.12 to 0.20 dL/g. The polymers formed brittle films and their IR and NMR spectra were reported.

This work involves a three part study concerning the synthesis and reactivity of quinodimethanes, the determination of reduction potentials of electrophilic olefins, and the crystal structure determination of a new charge transfer complex. Treatment of p-xylylene dicyanide (10) with NaH and dimethyl carbonate in glyme yielded a,a'-bis(methoxycarbonyl)-p-xylylene dicyanide (11a), 82% yield. Oxidation of 11a with N-chlorosuccinimide and triethyl amine in acetonitrile at 0° gave 7,8-di(methoxycarbonyl)-7,8-dicyanoquinodimethane (12a), 64% yield, d. 268°. This quinodimethane homopolymerizes spontaneously and forms a Wurster complex with tetramethyl-p-phenylenediamine and a blue-black CT-complex with tetrathiafulvalene. Cyclic voltammetry reduction potentials (E^(Red)(,p)) UV absorptions and ¹H-NMR chemical shift data of 22 olefins compounds were measured. The sequence for the ability to stabilize the ethylenic radical anion was found to be (diagram omitted) > -CN >-CO₂CH₃ > Cl > Br > H as expected. An inverse relationship between chemical reactivity and reduction potential was found for tetramethyl ethylenetetracarboxylate (25) and the triester derivative (33). Although 25 has a lower E^(Red)(,p) (-1.30v) than 33, it is less reactive toward polymerization. A linear correlation of E^(Red)(,p) and Hammett substituent constants was seen for the substituted maleic anhydrides and cyanofumarates. No correlations were seen for sterically crowded derivatives of 33. The crystal structure of tetrathiafulvalinium dimethyl dicyanofumarate was determined from a single crystal X-ray study. The crystal belongs to the monoclinic space group P2₁/C with two complexes per unit cell with cell constants a = 11.075(2) Å, b = 11.615(3) Å, c = 6.623(4) Å, α = 95.7°(16), V = 847.6(9) ų. The structural parameters have been refined to convergence, R = 0.0492 and R(,w) = 0.0614.

by So Koon Chong. / Bibliography: leaves 86-88 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984

Cardiac arrhythmias are caused by disordered propagation of electrical activity. Progress in understanding and controlling arrhythmias requires novel methods to characterize and control the spatiotemporal propagation of electrical activity. We used patterned illumination of cardiomyocytes derived from optogenetic human induced pluripotent stem cells to create dynamic conduction blocks, and to test spatially extended control schemes. Using this model, we demonstrated the ability to initiate, circumscribe, relocate, and terminate pathologic spiral waves that drive many arrhythmias. When cells were derived from patients with long QT syndrome, longer action potential durations made spiral waves more resistant to termination. This work lays the foundation for personalized models of cardiac injury and disease, and the development of tailored approaches to the management of arrhythmias.

No description available.

Luo Yun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / 论文摘要 --- p.ii / Acknowledgements --- p.iii / Table of Contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.xi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Conjugated Polymers --- p.1 / Chapter 1.1.1 --- Overview --- p.1 / Chapter 1.1.2 --- Conducting Polymers --- p.2 / Chapter 1.2 --- Electrochemical Doping of Conjugated Polymers --- p.5 / Chapter 1.2.1 --- Doping Conjugated Polymers --- p.7 / Chapter 1.2.2 --- Doping Level --- p.8 / Chapter 1.3 --- Charges in Conjugated Polymers --- p.10 / Chapter 1.3.1 --- Electronic and Geometric Configurations --- p.10 / Chapter 1.3.2 --- Charge Carriers --- p.10 / Chapter 1.4 --- Effects of Localization and Structural Disorder on Conductivity --- p.18 / Chapter 1.5 --- Cyclic Voltammetric Behavior of Conjugated Polymers --- p.18 / Chapter 1.6 --- PEDOT: PSS Systems --- p.21 / Chapter 1.7 --- Motivation --- p.25 / References --- p.27 / Chapter Chapter 2 --- Instrumentation --- p.32 / Chapter 2.1 --- X-ray Photoelectron Spectroscopy --- p.32 / Chapter 2.1.1 --- Introduction --- p.32 / Chapter 2.1.2 --- Basic Principles and Theory --- p.32 / Chapter 2.1.3 --- Qualitative Analysis Using XPS --- p.35 / Chapter 2.1.4 --- Angular Effect on XPS --- p.35 / Chapter 2.1.5 --- Chemical Shifts --- p.35 / Chapter 2.1.6 --- Valence Band Investigation --- p.37 / Chapter 2.1.7 --- Quantitative Analysis Using XPS --- p.37 / Chapter 2.1.8 --- Instrumental Setup for XPS --- p.40 / Chapter 2.2 --- Scanning Probe Microscopy --- p.40 / Chapter 2.2.1 --- General Introduction --- p.40 / Chapter 2.2.2 --- Atomic Force Microscopy and Conducting Atomic Force Microscopy --- p.40 / Chapter 2.2.3 --- Instrumental Setup for Conducting AFM --- p.44 / Chapter 2.3 --- Cyclic Voltammetry --- p.44 / Chapter 2.4 --- Kelvin Probe --- p.46 / Chapter 2.5 --- a-step Profilometer --- p.48 / References --- p.49 / Chapter Chapter 3 --- Cyclic Voltammetric Characterization of PEDOT:PSS --- p.51 / Chapter 3.1 --- Film Preparations --- p.51 / Chapter 3.2 --- Electrochemistry --- p.52 / Chapter 3.3 --- Results and Discussions --- p.53 / References --- p.56 / Chapter Chapter 4 --- Electronic Structure of Doped and Dedoped PEDOT:PSS Systems --- p.57 / Chapter 4.1 --- Introduction --- p.57 / Chapter 4.2 --- Sample Preparations --- p.58 / Chapter 4.3 --- Results and Discussions --- p.60 / Chapter 4.3.1 --- XPS of C 1s Core Level of PEDOT:PSS --- p.61 / Chapter 4.3.2 --- XPS of S 2p Core Level of PEDOT:PSS --- p.66 / Chapter 4.3.3 --- XPS of O Is Core Level of PEDOT:PSS --- p.71 / Chapter 4.3.4 --- XPS of Valence Band of PEDOT:PSS --- p.77 / Chapter 4.3.5 --- Further Explanations and Discussions --- p.77 / Chapter 4.4 --- Kevin Probe Measurement --- p.83 / Chapter 4.5 --- Conclusions --- p.83 / References --- p.85 / Chapter Chapter 5 --- Morphology and Nano-scale Electrical Properties of PEDOT:PSS Thin Film --- p.87 / Chapter 5.1 --- Introduction --- p.87 / Chapter 5.2 --- Sample Preparations --- p.87 / Chapter 5.3 --- Results and Discussions --- p.88 / Chapter 5.3.1 --- CAFM on as Prepared PEDOT.PSS and Ar+ Sputtered Thin Film --- p.88 / Chapter 5.3.2 --- CAFM on pH Dedoped PEDOT:PSS (pH=6.6) --- p.95 / Chapter 5.3.3 --- CAFM on Electrochemically Dedoped PEDOTrPSS --- p.98 / Chapter 5.4 --- Conclusions --- p.105 / References --- p.106 / Chapter Chapter 6 --- Concluding Remarks and Future Work --- p.107 / Chapter 6.1 --- Concluding Remarks --- p.107 / Chapter 6.2 --- Future Work --- p.108

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