Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1980. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (DTech (Chemical Engineering))--Cape Peninsula University of Technology, 2009. / Highly concentrated emulsions (HCE) are classified as high internal phase ratio emulsions (or simply HIPRE), and the dispersed phase droplets are ranged In a hexagonal closely packed configuration. This closely packed configuration and the profound hydrodynamic interaction between neighbouring droplets induce mechanical interference between the droplets, thus prohibiting their free movement. Hence, while the highly concentrated emulsions consist of very low viscosity and inelastic components, they show gel-like behaviour with high elasticity and non-Newtonian flow response. It has been suggested in the literature that this behaviour originated from interfacial energy in terms of Laplace pressure. Therefore, the scaling of rheological properties with Laplace pressure is expected, but several publications show a deviation from this scaling behaviour. It seems that the source of deviation from this scaling is interdroplet interaction, which can contribute to the rheological behaviour of highly concentrated emulsions. The shear modulus of highly concentrated emulsions in the presence of interdroplet interaction was developed in this work. The prediction of model was verified by the data presented in the literature. It was shown that a small source of interdroplet interaction can result in deviation from scaling of shear modulus with Laplace pressure.

Made available in DSpace on 2014-06-11T19:29:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-12Bitstream added on 2014-06-13T19:25:35Z : No. of bitstreams: 1 moraes_jr_me_guara.pdf: 2408518 bytes, checksum: 50073dad1be607037f0eb398b2b0a8bc (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A Nanotecnologia é hoje um dos principais focos das atividades de pesquisa, desenvolvimento e inovação em todos os países industrializados. O uso da pele como alternativa para a administração sistêmica de fármacos constitui motivação e definição no investimento de novas pesquisas. Assim, veicular um fármaco pela via transdérmica apresenta inúmeras vantagens em relação a outras vias de administração de agentes terapêuticos. Muita atenção tem sido dada aos sistemas micro e nanoestruturados de tensoativos, por sua capacidade em aumentar a eficácia terapêutica de fármacos, permitindo a redução da dose administrada e minimizando os efeitos colaterais potenciais dos fármacos. A avaliação reológica e do comportamento fluidodinâmico de nanoemulsões tem sido pouco descrita na literatura, contudo, esta propriedade reveste-se de especial importância no seu desenvolvimento, pois pode representar uma limitação na administração de fármacos. Este trabalho pretende servir de fomento aos estudos de comportamento de nanofluidos, visando aplicações nessa interface de ciências farmacêuticas e engenharia / Nanotechnology is today one of the main focus of the activities of research, development and innovation in all industrialised countries. The use of the skin as an alternative to the systemic administration of drugs is motivation and definition of the investment of new researches. Thus, vehicular a drug by Transdermal administration offer numerous advantages in relation to other routes of administration of therapeutic agents. Much attention has been given to micro and nanostructure systems of tensoactives, by its capacity in increasing the therapeutic efficacy of drugs, allowing the reduction in the dose administered and minimizing the potential side effects of drugs. The evaluation rheological and behavior hydrodynamics of nanoemulsions has been little described in the literature, however, this property is of particular importance in their development, because it may represent a limitation in the administration of drugs. This work intends to serve to promote studies behavior nanofluidos, aiming at applications interface of pharmaceutical sciences and engineering

A method was developed for the preparation of slurries showing time dependent Theological properties, using artificial particles of constant shape and size, such that the effects of the slurry parameters, particle shape, size, concentration, and dispersing medium viscosity could be investigated separately. Two particle shapes were investigated, elliptical plate and rectangular plate. There were five sizes of elliptical plate particles with the surface area varied at nearly constant length to width ratio, and four sizes of rectangular plate particles with a length to width ratio varying from 1.92 to 4.85. Only one particle thickness was considered. The rheological state exhibited by the time dependent dispersions was found to be dependent on all the parameters investigated. The thixotropic state occurring with the smaller size particles became increasingly time dependent with the increase in particle surface area or length to width ratio. The transition to the false bodied state occurred with the largest size particles and the largest length to width ratios. Equilibrium apparent viscosity was found to increase linearly with particle surface area for thixotropic slurries with constant particle shape and dispersing medium viscosity. Also, equilibrium apparent viscosity was found to increase linearly with dispersing medium viscosity for thixotropic dispersions with constant particle shape, size, and concentration. The variation of the parameter of length to width ratio was found to have the greatest effect on the time dependency of the slurry. Ragged decay curves were obtained from the slurries made up from particles with the larger surface areas and length to width ratios. The ragged decay curves indicated a structural breakdown or that particle interference was taking place. The rate of decay of apparent viscosity of the slurries was shown to follow a curve which is approximated by the mathematical relationship for a second order-zero order reversible reaction mechanism. This theoretical model was found to fit regardless of slurry parameters or rheological state. The main determinants of the forward rate constant k₁ were found to be particle surface area, length to width ratio, concentration and dispersing medium viscosity. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Many pharmaceutical systems exhibit shear-thinning flow properties but the expression of these properties in terms of meaningful rheological parameters remains a problem. To be useful, the parameters must be rheometer-independent and either describe the fluid under application, processing and storage conditions, or specify the fluid structure and disposition of the molecules at negligible shear rates. Interlinked with this problem is the correct selection of rheological parameters and systems for applied studies, i.e. the determination of rheological effects on drug diffusion. The components of the model shear-thinning system, the nonionic cellulose polymer, hydroxyethylcellulose (HEC, Natrosol 250G), and the nonionic surfactant, polyoxyethylene (4) dodecyl ether (Brij 30), were characterized, physicochemically. The addition of Brij 30 to HEC dispersions provided a reliable means of obtaining a series of systems showing predictable increments in shear-thinning behaviour at each HEC concentration. Over a 5 year period, the rheological reproducibility and stability of aqueous HEC dispersions were determined and compared with corresponding data for 2% methylcellulose (MC, 1500 cP) dispersions. For similar consistencies, HEC and MC dispersions showed comparable reproducibility and stability. The power-law consistency index was observed to be related to both storage time and polymer concentration. Two methods of shear stress calibration were examined for the Rotovisko. The determination of a shear stress calibration constant for each shear rate provided a significant improvement for non-Newtonian shear-thinning fluids over the manufacturer's calibration method when both methods were compared with corresponding data generated with the cone-plate Weissenberg rheogoniometer. The limitations of shear rate equations and two Couette rheometers, Haake Rotovisko and Brookfield Synchro-lectric (with SC-4 spindles), to accurately represent shear stress-shear rate parameters were examined. The Krieger-Maron and the Mooney shear rate equations were found to yield the widest range of rheometer-independent results for the Rotovisko and Brookfield rheometers, respectively, when separately compared with similar data obtained with the rheogoniometer. Viscometric properties of polyoxyethylene (4) dodecyl ether in HEC dispersions were evaluated over a concentration range of 2.0 -3.5% HEC and 0 - 16% Brij 30. Three rheological models: the modified Shangraw structure equation, the Steiger-Trippi-Ory equation and the power-law model were fitted to the data and found to describe accurately the flow behaviour of the dispersions at 30.0°C between shear rates of 8.5 - 685 s⁻¹. Variation of model parameters with surfactant concentration was computed for each HEC dispersion. A shear-sensitive interaction between the surfactant and the cellulose polymer was noted. To determine the disposition of HEC in solution and the nature of the viscous interaction noted for the HEC - Brij 30 systems, low shear rate and dynamic measurements were made. From storage and loss moduli, dynamic viscosities and loss tangents, HEC was determined to be a molecule with intermediate flexibility and the HEC - Brij 30 systems were composed of a loose three dimensional network. The effect of increased limiting viscosity at low shear rates was measured on the diffusion of hydrocortisone through nylon membrane and human autopsy epidermis. The absence of drug-vehicle interactions was demonstrated and the similarity in the results for the two membranes indicated that the observed decrease in steady state flux was due to the alteration of vehicle viscosity. The solubility, partition coefficient and diffusion coefficients were measured for hydrocortisone. / Pharmaceutical Sciences, Faculty of / Graduate

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