Thesis (Ph. D.)--University of Alabama at Birmingham, 2006. / Additional advisors: Andrei V. Stanishevsky, Derrick R. Dean, Gregg M. Janowski, Yogesh K. Vohra. Description based on contents viewed Feb. 11, 2009; title from PDF t.p. Includes bibliographical references (p. 132-151).

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 122-125).

Thesis (Ph. D.)--University of California, San Diego, 1999. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Canterbury, 2010. / Typescript (photocopy). Includes bibliographical references (p. 196-206). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 197-202). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 197-202). Also available on the Internet.

Orientadores: Telma Teixeira Franco, Cristiana Maria Pedroso Yoshida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-06T18:08:42Z (GMT). No. of bitstreams: 1 Reis_ArleteBarbosados_M.pdf: 1735903 bytes, checksum: de3ef62122076a76e44326331e797276 (MD5) Previous issue date: 2005 / Resumo: Um novo conceito de embalagens para alimentos vem sendo estudado, conhecido como embalagem ativa, combinando áreas da tecnologia de alimentos, biotecnologia, embalagem e ciência dos materiais. Estes sistemas consistem na incorporação de aditivos tais como, agentes antimicrobiano, antioxidantes, antiumectantes, microrganismos antagonistas, bactericidas, antibióticos, enzimas e outros, na embalagem ao invés de serem adicionados diretamente nos alimentos. Os filmes de quitosana vem sendo estudados para aplicação como embalagem ativa devido às suas propriedades antimicrobianas, elasticidade, flexibilidade, biodegradabilidade e por fornecerem uma boa barreira ao oxigênio. O objetivo deste trabalho foi agregar valor ao filme de quitosana incorporando aditivos e, a partir de então, a aplicação deste em coberturas de papelão, formando uma embalagem bioativa. De acordo com a atuação esperada, diferentes aditivos foram incorporados à matriz padrão (filme de quitosana). Com o intuito de reduzir a passagem de umidade para o interior das embalagens foi incorporado o agente sequestrante de umidade, sílica micronizada Siloyd FP244 (filme-sílica) e para atuar na oxidação no interior das embalagens foi incorporado ácido cítrico, um agente antioxidante. Após a obtenção dos filmes bioativos, estes foram aplicados em coberturas de papelão, dando origem ao sistema embalagem papelão-filme, o qual foi caracterizado quanto às propriedades de barreira (permeabilidade ao vapor d¿água, permeabilidade ao oxigênio e isotermas de sorção) e quanto às propriedades mecânicas (esmagamento de onda, compressão na coluna e absorção de água). A incorporação de sílica nos filmes de quitosana e consequente aplicação em coberturas de papelão reduziu a passagem de umidade através das coberturas de papelão, absorvendo a umidade. As propriedades mecânicas do sistema embalagem papelão filme-sílica demonstraram um decréscimo no esmagamento, quando comparado aos outros sistemas de embalagem, mas apresentou uma maior capacidade de absorção de água. O sistema embalagem papelão filme-cítrico atuou reduzindo a passagem de oxigênio através das coberturas de papelão e promoveu uma melhoria nas propriedades mecânicas, devido à maior rigidez do papelão / Abstract: Active packaging can be defined as a kind of packaging where package, product the environment interact to increase shelf life, maintaining the final quality. It combines advances in food technology, biotechnology, packaging and material science. These packaging systems are based on additives incorporation directly into polymeric matrix, such as antimicrobial agents, antioxidants, antiumectants, antagonists, bactericides, antibiotics, enzymes, etc. Chitosan is natural polymer derived by deacetylation of chitin. Chitosan presents a good film- form properties and has studied as a potential polymers of food packaging. This natural polymers are biodegradable, easily decomposable and environmentally friendly. This work studied a new package system formed by a bilayer of paperboard card and chitosan films containing different additives and moisture-absorbing agent (silica siloyd FP 244) were incorporated into chitosan matrix films. The barrier properties (water vapor and oxygen permeabilities) and mechanical properties were characterized. WVP reduced as silica was incorporated into chitosan films. The water absorbing capacity increased, indicating that the silic acted as a moisture absorbing agent. The mechanical properties of active moisture package systems decreases in comparisom of paperboard cards without coating. The active package systems containing citric acid reduced the oxygen permeability and increase the rigidity / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds. Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.