Science (Faculty of)
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Item Gaits and Their Development in the Infraorder Pecora(University of Waterloo, 1967-02) Dagg, Anne InnisThe gaits of twenty-eight species of the Infraorder Pecora are analyzed from motion picture sequences comprising over 45,000 frames. For each gait the percentage time spent on the various supporting legs during each stride and the order in which the combinations of supporting legs were used are tabulated. When possible the times for the strides are calculated. The walk patterns of each of the four families studied are shown to be statistically distinctive. Within each family, those members that live where the vegetation is so dense that they must rely on hearing to warn them of danger use a more stable walk than those species that inhabit open grasslands. A stable walk is that in which diagonal legs are used in preference to lateral legs and three or four supporting legs are used rather than two. With a more stable walk, a species is able to pause quickly and to flee instantly if danger threatens. The data for these species suggest that the antelopes, giraffids and pronghorns evolved in an open environment while the cervids, including the caribou, evolved in a woodland habitat. The variability in the walking strides of members of these species is assessed for the first time. The walk pattern varies with the nature of the terrain and with the speed at which the walk is executed. It also depends upon the age of an individual of a species and on the weight of its antlers or horns. A trotting gait is shown to be the predominant one of the constantly moving caribou. This species has evolved anatomically in ways that ensure an effective trot. The preferred fast gait of several other species is found to be a trot rather than a gallop, owing to their large size, their wooded environment, the swampy nature of the ground underfoot or their heavy antlers or horns. The type of gallop of the Pecoran species is shown to be closely related to their environment and to their anatomy. Light Pecoran species use both flexed and extended suspensions in their fast gallops. The white-tail and the mule deer alone use the extended suspension primarily, since it is in this phase of their gallop that they leap over the bushes and logs that occur throughout their brush environment. Heavy Pecoran species do not use extended suspensions, nor generally do those animals with backs sloping downward posteriorly to relatively short hind legs. A symmetrical bound is shown to be used by both cervids and antelopes either to navigate steep and rough slopes or to increase the field of vision. The times taken for walking, trotting and galloping strides are shown to be longer in larger animals. The reason for this is discussed in terms of the leg considered as a pendulum.Item The electrostatic potential in a finite ionic crystal(University of Waterloo, 1972-11-01) Redlack, AustinThis thesis is written in two parts. In Part One, we develop a new method for evaluating three dimensional lattice summations and apply it to the evaluation of the electrostatic potential of a finite ionic crystal. We then compare our expression with those obtained using infinite crystals. Some of the effects which are not obtainable using an infinite crystal are: i. the electrostatic potential depends on the shape of the sample when a dipole or quadrupole moment is present, and 2. the electrostatic potential at the surface of a crystal changes rapidly near the surface. In Part Two, we use the method developed in Part One to evaluate the electrostatic potential in a deformed crystal and use the resulting expression to define the macroscopic electric field and the electric displacement field. For the case of uniform fields, the expressions for these fields reduce to those in common use.Item Electric-field-dependent variable-range hopping conductance in quasi-two-dimensional systems: Application to PrBa2Cu3O7-y-based superconductor–normal-metal–superconductor junctions(American Physical Society, 1996-03) Singh, M.; Thompson, Russell B.; Dumas, O.We have calculated the hopping conductivity of quasi-two-dimensional systems by using the variable-range hopping conduction mechanism in the presence of an electric field. We considered that the localized states are randomly distributed both in energy and space coordinates. Localized carriers hop from one state to another in both coordinates. We also considered that at a particular temperature the localized carriers are distributed according to the Fermi distribution function both below and above the Fermi level. The expression of the conductivity for the constant density of states was calculated. After some approximations, the expression of the conductivity was shown to reduce to expressions found in the literature. We also compared our theory with experimental results of PrBa2Cu3O7-y based S/N/S junctions. Good agreement between theory and experiment was found.Item The Tracing of a Contaminant (Tritium) from Candu Sources: Lake Ontario(University of Waterloo, 1997) King, Karen JuneIn any research program we begin with a hypothesis and when our expected results do not concur with the observed results we must try and understand the dynamics behind the changed process. In this study we were trying to understand the flux between regional groundwater systems, surface waters and sedimentation processes in order to predict the fate of contaminants entering one of the larger bodies of water in the world- Lake Ontario. This lake has increased levels of tritium due to anthropogenic inputs. Our first approach to the problem was to look at tritium fluxes within the system . Hydrological balances were constructed and a series of sediment cores were taken longitudinally and laterally across the lake. The second approach was to quantify the sediment accumulation rate (SAR) within the depositional basins and zones of erosion in order to improve the linkage between erosion control (sedimentation) and the water quality program. In the last chapter the movement of tritium, by molecular diffusion, through the clayey-silts of Lake Ontario is quantified in terms of an effective diffusion coefficient. In these sediments effective diffusion equals molecular diffusion. In a laboratory experiment four cores of lake sediment were spiked with tritium . The resulting concentration gradient changes in the sediment porewaters after six weeks could be modeled by an analytical one- dimensional diffusive transport equation. Results calculated the average lab diffusion coefficient to be 2. 7 x 10 - 5cm 2. sec -1 which is twice that determined by Wang et al, 1952 but still reasonable. Short cores (50 cm) from lake Ontario had observed tritium concentrations with depth that reflected a variable diffusive profile. The increases and decreases in tritium with depth could be correlated between cores. Monthly tritium emission data was obtained and correlations between peaks in the tritium profile and emissions were observed. Monthly variations in release emissions corresponded to approximately a one centimeter slice of core. An average calculated diffusion coefficient of theses cores was 1. 0 x 10 -5 cm 2. sec -1 which compares to Wang's coefficient of 1. 39 x 10 -5 cm 2. sec -1. This implies that tritium is moving through the sediment column at a rate equal to diffusion. The results were obtained for smoothed values. It was not possible to model the perturbations of the data with a one dimensional model. The dynamics of the system imply that tritium could be used as a biomonitor for reactor emissions, mixing time and current direction scenarios and that a better understanding of this process could be gained by future coring studies and a new hypothesis.Item Electric-field-dependent variable-range hopping conduction in PrBa2Cu307-y(Taylor & Francis, 1997-02) Thompson, Russell B.; Singh, M.The variable-range hopping conductivities of quasi-two-dimensional systems in electric fields were calculated for the cases of both constant and energy-dependent densities of states. The localized states were considered to be randomly distributed in space and energy coordinates, and the carriers were considered to be distributed according to the Fermi distribution. Approximations yielded analytic results valid for most temperatures and electric fields and included localized states both above and below the Fermi level. We hypothesized that the localized states of PrBa2Cu3O7-y (PBCO) are distributed in the CuO planes, making that compound behave as a quasi-two- dimensional material. We compared our theory with experiments of PBCO-based junctions and found good agreement between theory and experiment.Item Magnetoconductance due to variable-range hopping in quasi-two-dimensional systems: Application to PrBa2Cu3O7-delta(American Physical Society, 1998-01) Thompson, Russell B.; Singh, M.In this paper, we have developed a theory of magnetoconductance (magnetoresistance) due to variable-range hopping for quasi-two-dimensional systems. We have included the effect of electric fields on the calculation of the magnetoconductance. The effects of scattering and electron-electron interactions have also been included in our theory. We found analytical expressions for the conductivity for both the scattering and nonscattering cases, and obtained electric- and magnetic-field-dependent power laws in certain approximations. We found that the electric and magnetic-field dependences of the magnetoconductance had different power laws for the scattering and nonscattering cases. We tried to explain the van Ancum et al. magnetoconductance experiments of PrBa2Cu3O7-delta (PBCO) thin films by using our theory. A good agreement between theory and experiment was found if we included the effect of scattering. In the above PBCO films, it was found that the approximate value of the concentration of localized states lies between 10^11 and 10^12 cm^-2.Item Small-polaron variable-range hopping in quasi-two-dimensional materials: application to PrBa2Cu3-xGax07-y(Taylor & Francis, 1999-01) Thompson, Russell B.; Singh, M.We have developed a theory for variable-rangehopping (VRH) due to small polarons in quasi-two-dimensionalsystems at high temperatures.We included the effects of temperature, electric fields, magnetic fields and scattering in the derivation of the conductivity. We found that the conductivity for quasi-two- dimensional systems depends on these factors differently from three- dimensional systems. We applied the theory to explain the resistivity data of PrBa2Cu3p,Ga,07-l, at high temperatures ( T > 150K). To explain the low- temperature data ( T < 150K), we used the pure electron VRH mechanisms. Good agreement between theory and experiment was found.Item Physical Hydrogeology and Impact of Urbanization at the Waterloo West Side: A Groundwater Modelling Approach(University of Waterloo, 2000) Radcliffe, AnthonyIn the last few decades protection of the environment has moved to the forefront of earth science research. Sustainable development is becoming more important to rapidly growing communities throughout southern Ontario including the City of Waterloo which has adopted an ecosystem planning approach toward future urban expansion. The City of Waterloo is located in the Regional Municipality of Waterloo which relies mainly on local groundwater resources for its drinking water supply. The Waterloo West Side is a collective name for several new developments occurring at the western limit of the City of Waterloo. Development of the Waterloo West Side is encroaching on a potential regional groundwater recharge area. Recent studies have recommended that some of these developments will require artificial infiltration facilities to augment the reduction in infiltration rates at the post-development stage. For this study, the pre-development groundwater flow system was characterized using a three-dimensional finite element model (WATFLOW). The regional Waterloo Moraine Model (approximately 750 km2) was refined in the study area (approximately 25 km2) so as to include the regional-scale influence on the local-scale groundwater flow. In addition, to approximate the complex groundwater flow system, within the study area, modifications were made to the current conceptual model. Several existing techniques were utilized in the numerical approach including three-dimensional parameterization and automated calibration methods. Simulations were completed to steady-state therefore results are averaged on a yearly basis. The potential impact of urbanization on the groundwater flow system was investigated by modifying the surficial boundary condition to simulate post-development infiltration rates (increased runoff) in areas where development will occur. The impact to local surface water was investigated for each post-development scenario. In addition, the effect on the regional and local groundwater flow systems were compared for each scenario.Item Supercooling and Freezing of HNO3/H2O Aerosols(University of Waterloo, 2000) Dickens, DustinThe freezing kinetics of binary nitric acid/water aerosols is of fundamental importance to the modelling of polar stratospheric clouds and the role they in ozone depletion over the Arctic/Antarctic regions. Cirrus clouds are also often composed of nitric acid solutions, hence an understanding of freezing process in these aerosols also aids in modelling the earth's radiation budget and global warming. This thesis explores the kinetic phase diagram of nitric acid/water aerosols with sizes ranging between 0. 2 and 1. 5 mm in radius and concentrations ranging between pure water and 0. 45 mole fraction HNO3. Although the kinetic phase diagram has now been studied between 0. 46 mole fraction HNO3 and pure water, more data is needed in the region between 0. 18 and 0. 25 mole fraction HNO3 to confirm the results reported. The project described in this thesis are a continuation of a project begun by Allan Bertram. The measurements involving aerosols with compositions greater than 0. 25 mole fraction HNO3 were carried out as part of Allan Bertram's Ph. D. thesis (see ref. 20) These data were later examined using a more comprehensive data analysis method (as presented in this thesis) in an effort to obtain a more complete understanding of this system.Item Numerical Simulation of Hydrocarbon Fuel Dissolution and Biodegradation in Groundwater(University of Waterloo, 2000) Molson, John W. H.The behaviour of hydrocarbon fuels in contaminated groundwater systems is studied using a multicomponent reactive transport model. The simulated processes include residual NAPL dissolution, aerobic and anaerobic biodegradation with daughter-product transport, and transport of a reactive carrier with mixed equilibrium/kinetic sorption. The solution algorithm is based on a three-dimensional Galerkin finite element scheme with deformable brick elements and capacity for a free watertable search. Nonlinearities are handled through Picard iteration. Convergence is rapid for most applications and mass balance errors for all phases are minimal. The model is first applied to simulate a pilot scale diesel fuel dissolution experiment in which humic acid is used as a natural organic carrier to enhance dissolution and to promote biodegradation of the aqueous components. The pilot scale experiment is described by Lesage et al. (1995) and Van Stempvoort et al. (2000). The conceptual model includes 8 unique components dissolving from 500 mL of residual diesel fuel within a 3D saturated domain. Oxygen-limiting competitive aerobic biodegradation with a dynamic microbial population is also included. A mixed 2-site equilibrium/kinetic model for describing sorption of the carrier to the aquifer solids was adopted to reproduce the observed breakthrough of the humic acid and organic components. Most model parameters were obtained independently with minimal calibration. Batch sorption data were found to fit well at the pilot scale, however biodegradation and dissolution rates were not well known and had to be fitted. Simulations confirmed the observed 10-fold increase in effective solubility of trimethylnaphthalene, and increases on the order of 2-5 for methyl- and dimethylnaphthalene. The simulated plumes showed almost complete attenuation after 5 years, in excellent agreement with observed data. A sensitivity analysis showed the importance of carrier concentrations, binding coefficients, dissolution and biodegradation rates. Compared to a dissolution scenario assuming no carrier, the humic acid-enhanced dissolution case decreased the remediation time by a factor of about 5. The second application of the model involves simulating the effect of ethanol on the persistence of benzene in gasoline-impacted groundwater systems. The conceptual model includes a 4-component residual gasoline source which is dissolving at the watertable into a 3D aquifer. Comparisons are made between dissolved plumes from a gasoline spill and those from an otherwise equivalent gasohol spill. Simulations have shown that under some conditions, a 10% ethanol component in gasoline can extend the travel distance of a benzene plume by at least 150% relative to that from an equivalent ethanol-free gasoline spill. The increase is due to preferred consumption of oxygen by ethanol and a corresponding reduction in the biodegradation rate of benzene while the two plumes overlap. Because of differences in retardation however, the ethanol and benzene plumes gradually separate. The impact therefore becomes limited because oxygen rapidly disperses behind the ethanol plume and benzene degradation eventually resumes. A sensitivity analysis for two common spill scenarios showed that background oxygen concentrations, and benzene retardation had the most significant influence on benzene persistence. A continuous gasohol spill over 10 years was found to increase the benzene travel distance by over 120% and a pure ethanol spill into an existing gasoline plume increased benzene travel distance by 150% after 40 years. The results are highly relevant in light of the forthcoming ban of MTBE in California and its likely replacement by ethanol by the end of 2002.Item Direct Fitting of Analytical Potential Functions to Diatomic Molecular Spectroscopic Data(University of Waterloo, 2000) Seto, JenningThe standard practice of spectroscopic data reduction is generally to fit data to level energy expansions in terms of the vibrational and rotational quantum numbers. However, the utility of such expressions is limited because they extrapolate poorly and they need very large sets of parameters, many of which have no independent physical significance. One method of addressing these problems is to fit the spectroscopic data directly to analytical potential energy functions incorporating the natural physical behaviour of the molecule in question. Although there have been a number of successful applications of this approach, there are still certain problems associated with the types of potential forms being used. This thesis will explore some of these problems and determine how effective the potential forms being used are for a number of specific cases.Item Effect of Fuel Ethanol on Subsurface Microorganisms and its Influence on Biodegradation of BTEX Compounds.(University of Waterloo, 2000) Araujo, DanielaEthanol is used as fuel in neat form in some countries (Brazil and India) or blended with gasoline (Europe, Canada and the United States). The benefits of ethanol use include octane enhancement, a cleaner environment and a secure renewable energy supply. BTEX compounds (benzene, toluene, ethylbenzene, m-xylene, p-xylene and o-xylene) are aromatic hydrocarbons present in gasoline. The fate of these compounds in the environment is of great health concern due to their carcinogenic (benzene) and toxic properties, and due to their high solubility in water compared to the other gasoline hydrocarbons. Ethanol present in gasoline may affect BTEX degradation, in an event of a spill into the subsurface environment. To address the effects of ethanol on subsurface microorganisms, microbial activity and growth in the presence of ethanol (concentrations ranging 0 to 70% v/v) were assessed. Microcosms studies showed that ethanol at concentration ranging 0. 5 to3% (v/v) enhanced microbial activity and did not interfere inmicrobial growth at 10oC temperature, when another source of carbon was present (glucose). Ethanol at 0. 5% concentration enhanced microbial activity over water soluble gasoline components and R2A medium combined. Both microbialactivity and growth were not detected at ethanol concentrations equal and above 5%. Biodegradation study was conducted, in which subsurface material and ground water were exposed to BTEX and ethanol at 0. 5 and 1. 5% (v/v) concentration. The controls had BTEX alone and ethanol alone, sterile and nutrient-free. Total BTEX degradation was observed whenever ethanol was absent. Ethanol and BTEX were simultaneously degraded, however in microcosms containing 0. 5% ethanol, BTEX degradation was slowed, compared to microcosms without ethanol. Competition for inorganic nutrients was the major problem in slowed BTEX degradation in the presence of ethanol. In microcosms where 1. 5% ethanol was present, BTEX compounds and ethanol degradation were not observed.Item A Quasilocal Hamiltonian for Gravity with Classical and Quantum Applications(University of Waterloo, 2000) Booth, Ivan S. N.I modify the quasilocal energy formalism of Brown and York into a purely Hamiltonian form. As part of the reformulation, I remove their restriction that the time evolution of the boundary of the spacetime be orthogonal to the leaves of the time foliation. Thus the new formulation allows an arbitrary evolution of the boundary which physically corresponds to allowing general motions of the set of observers making up that boundary. I calculate the rate of change of the quasilocal energy in such situations, show how it transforms with respect to boosts of the boundaries, and use the Lanczos-Israel thin shell formalism to reformulate it from an operational point of view. These steps are performed both for pure gravity and gravity with attendant matter fields. I then apply the formalism to characterize naked black holes and study their properties, investigate gravitational tidal heating, and combine it with the path integral formulation of quantum gravity to analyze the creation of pairs of charged and rotating black holes. I show that one must use complex instantons to study this process though the probabilities of creation remain real and consistent with the view that the entropy of a black hole is the logarithm of the number of its quantum states.Item Methodologies for capture zone delineation for the Waterloo Moraine well fields(University of Waterloo, 2000) Muhammad, DawoodThe Region of Waterloo relies mainly (75 %) on local groundwater resources for its drinking water supply. The water demand is increasing with the growth of the population and there is a need to enhance the present water supplies. The Regional Municipality of Waterloo (RMOW), which is the governing body in charge of providing the drinking water supply, is conducting an extensive program to protect the groundwater resources of the Waterloo Moraine aquifer. The focus of that work is defining the wellhead protection areas of the existing production wells as well as the investigation of potential further water supply. The main goal of the work presented here is to delineate the capture zones for the major well fields of the Region. To achieve that goal, the flow for the expected pumping conditions is simulated using a fully 3D finite element model (WATFLOW) which has been proven to be highly flexible to represent the natural boundaries and the highly irregular stratigraphy by previous researchers and scholars. The modified version of this model which includes a pseudo-unsaturated module is used for the solution of flow equation. For the delineation of capture zones, a new particle tracking code (WATRAC) as well as two advective-dispersive transport models are used by using a probabilistic approach presented by Neupauer and Wilson [1999]. For the probabilistic approach (Wilson's method), two transport models, a conventional time-marching code (WTC) and a time-continuous code (LTG) are usedand their results are compared. The LTG is computationally more efficient than the WTC, but it gives oscillatory results close to the steady state condition. A combined used of LTG and WTC istherefore recommended to obtain the steady state capture zones. The 0. 25 probability contour agrees very well with the particle tracks, except for somewhat greater transverse spreading due tothe dispersion which is not considered by the particle tracking algorithm. Both methods, backward particle tracking and probabilistic advective-dispersive modelling are clearly more informative and give better insight when considered together than each by itself.Item Pulse Flow Enhancement in Two-Phase Media(University of Waterloo, 2001) Zschuppe, RobertThis laboratory project has been done to evaluate pressure pulsing as an Enhanced Oil Recovery (EOR) technique. To perform the study, a consistent laboratory methodology was developed, including the construction of a Consistent Pulsing Source (CPS). Tests compared pulsed and non-pulsed waterfloods in a paraffin or crude oil saturated medium, which also contained connate water (an irreducible water saturation). Results revealed that pulsed tests had maximum flow rates 2. 5--3 times higher, greater oil recovery rates, and final sweep efficiencies that were more than 10% greater than non-pulsed tests. The CPS design has proven very successful, and has since been copied by a major oil corporation. However, there are two limitations, both caused by fluctuating water reservoir levels. Longer pulsed tests (reservoir-depletion tests) were periodically paused to refill the water reservoir, resulting in reservoir depressurization and lower flow rates. The final effect of this was impossible to quantify without correcting the problem. The second CPS limitation was the change in pulse shape with time. However, it is not expected that this had any major effect on the results. The pulse pressure and period studies were limited by early tests, which did not have the necessary time duration. Both increasing pulse pressure and decreasing pulse period were found to increase the final sweep efficiency. Slightly decreasing porosity (0. 4% lower) was found to lower sweep efficiencies. However, the 34. 9% porosity results were not done until reservoir depletion, so it is difficult to quantitatively compare results. An emulsion appeared after water breakthrough when using the CPS on light oils (mineral oil). This may have been the result of isolated oil ganglia being torn apart by the sharp pulses. Although it is difficult to apply laboratory results to the field, this study indicates that pressure pulsing as an EOR technique would be beneficial. Doubled or tripled oil recovery rates and 10% more oil recovery than waterflooding would be significant numbers in a field operation. A valuable application would be in pulsing excitation wells to both pressurize the reservoir and enhance the conformance of the displacing fluid over a long-term period. It would also be valuable for short-term chemical injections, where mixing with the largest volume possible is desirable.Item Noble Gas Collision Induced Vibrational Relaxation of (v=1) para-H2(University of Waterloo, 2001) Weir, DouglasClose coupling scattering calculations have been conducted for the para spin modification of H2-{He, Ne and Ar}. The XC(fit) potential energy surfaces for H2-Ne and H2-Ar have been used for calculations for these two systems, while a newly fitted version of the Schaefer and Kohler potential energy surface was used for the H2-He system. The fitting procedure employs nine modified Lennard-Jones oscillator functions to describe accurately 90% of the original tabulated potential energy surface to better than 12% error. The scattering calculations for H2-Arfailed at higher energies due to the presence of a previously undocumented potential energy surface turn-over at R less than 1. 0 Angstroms. Manifold-to-manifold v=1 vibrational relaxation calculations for each of these systems are compared with other experimental and theoretical calculations. These comparisons demonstrate a common discrepancy between previous calculations and the current calculations for each system. The current vibrational relaxation rate constants are generally too small when compared to low temperature values of Audibert et al. and Orlikowski, and the high temperature values obtained by Flower et al. and Dove andTeitelbaum. The current calculations indicate the presence of a dramatic up-turn in the low temperature H2-He rate constants. Other experimental and theoretical treatments do not exhibit this same up-turn, which is puzzling. A set of follow-up calculations featuring a larger basis set (such as the {16,12,10,8} Flower et al. basis set) and a larger manifold of included relaxation pathways are needed to improve these calculations.Item Predicting the Mesophases of Copolymer-Nanoparticle Composites(American Association for the Advancement of Science, 2001) Thompson, Russell B.; Ginzburg, Valeriy V.; Matsen, Mark W.; Balazs, Anna C.The interactions between mesophase-forming copolymers and nanoscopic par- ticles can lead to highly organized hybrid materials. The morphology of such composites depends not only on the characteristics of the copolymers, but also on the features of the nanoparticles. To explore this vast parameter space and predict the mesophases of the hybrids, we have developed a mean field theory for mixtures of soft, flexible chains and hard spheres. Applied to diblock- nanoparticle mixtures, the theory predicts ordered phases where particles and diblocks self-assemble into spatially periodic structures. The method can be applied to other copolymer-particle mixtures and can be used to design novel composite architectures.Item Determining Analytical Potential Energy Functions of Diatomic Molecules by Direct Fitting(University of Waterloo, 2001) Huang, YiyeThe fully quantum mechanical 'direct-potential-fit' (DPF) method has become increasingly widely used in the reduction of diatomic spectra. The central problem of this method is the representation of the potential energy and Born-Oppenheimer breakdown (BOB) correction functions. There are a number of problems associated with the existing method and potential forms. This thesis delineates these problems and finds solutions to some of them. In particular, it is shown that use of a different expansion variable and a new treatment of some of the expansions resolves most of the problems. These techniques have been successfully tested on the ground electronic states of the coinage metal hydrides and the Rb2 molecule. To address the problem of representing 'barrier' potential curves, a flexible new functional form, the 'double-exponential long-range' (DELR) potential function, is introduced and applied to the B barrier state of Li2. In addition, the Lambda-doubling level splitting which occurs for singlet Pi electronic states has been taken into account by extending the effective Schrodinger equation. The computer program DSPotFit developed in our laboratory for performing DPF analyses has been extended to incorporate the ability to fit the analytical potential energy functions to tunneling predissociation line widths for quasibound levels. Finally, an attempt is made to investigate whether there exists a hump in the ground state rotationless potential curve of beryllium hydride.Item Effect of Nanoscopic Particles on the Mesophase Structure of Diblock Copolymers(American Chemical Society, 2002) Lee, Jae Youn; Thompson, Russell B.; Jasnow, David; Balazs, Anna C.Introduction. The fabrication of novel biomimetic photonic and electronic materials requires the manipulation of both organic and inorganic materials at the nanometer length scale. One possible means of achieving this level of control is to add inorganic nanoparticles to a melt of diblock copolymers. The microphase separation of the copolymers into nanoscopic, ordered domains could be harnessed to “template” the organization of the particles into nanoplanes, -wires, or -spheres within the polymer matrix. However, as we show below, the particles are not passive and can affect the overall morphology of the mixture. We also show that this effect is sufficiently robust that it can be found in both the strong and intermediate segregation limits of the diblock melts (i.e., both low and intermediate temperatures).Item Block Copolymer-Directed Assembly of Nanoparticles: Forming Mesoscopically Ordered Hybrid Materials(American Chemical Society, 2002) Thompson, Russell B.; Ginzburg, Valeriy V.; Matsen, Mark W.; Balazs, Anna C.Mixtures of diblock copolymers and nanoscopic spherical particles can yield well-ordered hybrid materials, which can be used for separation processes, catalysis, and optoelectronic applications. Predicting the morphologies of these systems is difficult because the final structures depend not only on the characteristics of the copolymer but also on the features of the particles. Combining self-consistent field and density functional theories, we develop a model that allows us to determine the equilibrium or metastable phases of diblock copolymer/spherical nanoparticle composites, without making a priori assumptions about the structure of the system. Using this model, we illustrate various examples where mixtures of diblocks and nanoparticles self-assemble into mesoscopically ordered phases. The model can be generalized to other types of copolymers and particles and can be modified to include homopolymers or solvent molecules. Thus, the technique constitutes a useful tool for determining the structures of a large class of nanocomposites.