Thechnology's impact on strategy, performance and strategy-performance relationship : an investigation employing a taxonomic approach to model-building

Miller III, George Alexander UMI Disseration Service 1983 국내박사

Self-organization in systems of anisotropic particles

Miller, William Leneal, III Columbia University 2012 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation presents studies on self-organization in soft matter systems. A wide variety of systems is studied, with the goal of understanding both the nonequilibrium and the equilibrium properties of this important process. In Chapter 2, we study the self-assembly of asymmetric Janus colloidal particles. We identify and systematically describe the effect of the ratio of hydrophobic to hydrophilic surface area on the nonequilibrium processes and structure formation. In Chapter 3, we examine systems of hard, aspherical particles. We demonstrate that the thermodynamics of self-organization of a system of these aspherical particle (either a system of identical particles or a polydisperse system of different-shaped particles) is well-predicted by a simple relationship between the crystallization pressure and two measures of particle asphericity borrowed from other fields. In Chapter 4, we shift focus to systems of soft particles in two dimensions and on the surface of a sphere. Soft particles are particles with a nite interaction potential at zero distance; such particles exhibit a surprisingly large variety of ordered structures at equilibrium. A similar phenomenon is seen when the study is extended to soft particles on the surface of a sphere. In Chapter 5, we study the free energy of two-component polymer brush systems in which polymers of different length are patterned in alternating stripes of specified widths on the surface of a cylinder. We present the dependence of the free energy on the polymer lengths and stripe width and a qualitative explanation of its functional form. Finally, in Chapter 6, we approach the reverse self-assembly problem. That is, we describe an algorithm for answering the reverse (and much more difficult) question, "Given a specific desired target self-assembled structure, what interparticle interactions will yield a system which will self-assemble into that structure?" We also describe a new model of interparticle interaction which should be able to generate interparticle interaction geometries with a high degree of flexibility.

Rational design of protective agents and processes for the stabilization of biologicals (Cryopreservation)

Miller, Danforth Parker, III The University of Wisconsin - Madison 2000 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The work compiled in this thesis consists of a range of topics related to the stabilization of biological materials. The chief goal of this work is to further the fundamental understanding of the protection of biological systems under dry or low-temperature conditions. Contributions in this area would help advance the development of superior protective formulations and processes. Early work involved the measurement of many fundamental thermophysical properties of trehalose and its aqueous solutions. These data included: viscosity, glass transition temperature (T_g), molar volume, x-ray diffraction pattern, solubility, freezing point depression, and the heat of solution. The ubiquity of trehalose in examples of preservation found both in nature and in the literature of biostabilization posed the question as to why trehalose appears, in many cases, to have a greater protective efficacy than other disaccharides. The prevailing hypotheses of stabilization, known as the water replacement and vitrification hypotheses, imply that the most important chemical properties are the hydrogen bonding capacity and T_g, respectively. These quantities were calorimetrically determined for trehalose and other structurally similar saccharides. Results indicated a correlation between these quantities, thereby reconciling the aforementioned hypotheses for the disaccharides. Because of their physiological importance, studies of aqueous electrolytes were a natural extension of the work with trehalose. This work involved examination of a theoretical model that predicts the T_g of dilute electrolyte solutions. Experimental results here indicate that the increase in T_g was much less than that predicted by theory. Further studies on aqueous electrolytes showed that many electrolyte/saccharide systems were found to deviate significantly from Walden's rule. The deviation was rationalized by the concept of local heterogeneities in the solvent that permitted greater ionic mobility than that predicted by Stokes' Law. This unexpected molecular mobility has implications for the long-term stabilization of biomaterials. The synthesis of the results of the studies of trehalose and its mixtures with electrolytes resulted in the development of a superior protective formulation: trehalose/borate mixtures. The thermophysical properties of these mixtures were characterized and their feasibility was demonstrated on a labile enzyme, lactate dehydrogenase. In comparison with trehalose, dried enzyme formulations that included borate exhibited longer storage stabilities under conditions of high temperature and high relative humidity.

Influences of processing and composition on the grain boundary character distribution

Miller, Herbert M., III Carnegie Mellon University 2009 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Experiments were performed to observe the effects of processing and composition on the grain boundary character distribution (GBCD) of SrTiO 3, MgO, and Ni. Anisotropic interfacial energies and, in the case of nickel, crystallographic constraints, are expected to influence the evolution of the GBCD during processing. Interrupted grain growth experiments were performed with SrTiO3 to observe the evolution of the GBCD with grain growth. The GBCD was determined at three time steps during grain growth and quantitative comparisons were made. Guidelines for quantitative comparisons of grain boundary plane distributions (GBPDs) and GBCDs were established. Relative grain boundary energies were evaluated using two independent techniques to observe the relationship between grain boundary population and energy and the role that grain boundary energy has in determining the GBCD. It was found that anisotropic interfacial energies dictate an anisotropic GBCD which develops very early in the grain growth process for SrTiO 3. The GBPD remains constant even as the grain size increases. Relatively low energy {100} grain boundary planes are favored. The five parameter GBCD evolves during grain growth to eliminate relatively higher energy grain boundaries while lower energy grain boundaries are preserved. Doping was explored as a processing technique to alter the GBCD in MgO. The GBCDs of 3000 ppm Ca-doped MgO and undoped MgO were measured and quantitatively compared. Relative grain boundary energy anisotropy was determined for each material and compared to the anisotropy of the GBPD. Calcium doping in MgO increases the anisotropy of the GBPD and GBCD. Specifically, the relative population of {100} grain boundary orientations increases with doping. In the five parameter GBCD of the pure material, some misorientations favor {100} boundary plane orientations and in these cases, the doping increases this preference. For misorienations in the pure material that favor {111} boundary plane orientations, the preference for {111} is diminished or the preference switches to {100} orientations. The anisotropy of the grain boundary energy distribution increases with doping. Iterative thermomechanical processing was explored as a technique to alter the GBCD in nickel. GBCDs were determined before and after iterative thermomechanical processing for both commercially available "grain boundary engineered" (Integran) and high purity nickel. Triple junction analysis was performed in which triple junctions were classified according to the types of grain boundaries that formed the junction. The relative grain boundary energy distribution was also determined for high purity nickel. Grain boundary energy was also found to be a factor of influencing GBCD evolution during iterative thermomechanical processing. Boundaries with relatively higher energy decrease in population while lower energy boundaries increase in population. Specifically, random boundaries are preferentially eliminated while the population of Sigma3 boundaries increases. However, because the evolution mechanism is different than in grain growth, and relies more on local rearrangements of boundaries rather than large scale elimination of interfacial area, constraints placed on the resulting network of boundaries influence the GBCD as well. Thus, interfacial energy is not the sole factor that determines the GBCD in nickel. The population of incoherent Sigma3 boundaries increases more than the population of the much lower energy coherent Sigma3 boundaries. Sigma9 and Sigma27 boundaries are also observed to increase in population. These boundaries tend to be the result of interacting Sigma3 boundaries. This conclusion is supported by the triple junction populations that show an increase in triple junctions that are comprised of two or three Sigma3 n type boundaries, where n = 1, 2, or 3. A mechanism is proposed that accounts for the increased population of incoherent Sigma3 boundaries, the increased populations of Sigma9 boundaries, and the observed triple junction populations.