Please read the abstract in the section, 00front, of this document / Dissertation (MEng)--University of Pretoria, 2008. / Chemical Engineering / unrestricted

Orientador : Pilar Rodriguez de Massaguer / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-03T14:51:13Z (GMT). No. of bitstreams: 1 McKnight_IvanaCristinaSpolidorio_D.pdf: 5817991 bytes, checksum: 5c66ef125a481e35fe8dddcb00029844 (MD5) Previous issue date: 2003 / Resumo: Alicyclobacillus acidoterrestris, uma bactéria termoacidófila esporogênica, recentemente tem sido relacionada com problemas de deterioração em sucos de frutas pasteurizados. Devido a alta resistência térmica de seus esporos, sobrevivem aos tratamentos de pasteurização. A deterioração é descrita pela produção de odor desagradável, semelhante a desinfetante, não ocorre produção de gás e raramente há formação de sedimentos no suco. O objetivo deste trabalho foi o de estabelecer uma metodologia de isolamento para Alicyclobacillus acidoterrestris em suco de maracujá e suco de abacaxi, identificar as cepas isoladas e determinar a resistência térmica destes isolados nos sucos. Suspensões de esporos da cultura padrão A. acidoterrestris DSM 2498 foram submetidas a tratamentos térmicos 60°C/60min, 60°C/30min, 70°C/20min, 80°C/5,10 e 30 min e ebulição por 5 min, para determinar a melhor condição de ativação dos esporos em suco de maracujá e abacaxi, separadamente. O melhor tratamento para a ativação nos dois sucos estudados foi o de 70°C/20 min. Foi determinado o tempo de enriquecimento para o isolamento de esporos de A. acidoterrestris a partir de amostras de suco de maracujá e abacaxi experimentalmente contaminadas com a cepa padrão DSM 2498. O melhor tempo de enriquecimento varia com o suco, para o de maracujá foi de 48 hs e para o de abacaxi, 24hs. Um total de 57 amostras de suco de maracujá e 50 amostras de suco de abacaxi integrais e pasteurizados foram examinados para detectar a presença desta bactéria. Para a detecção as amostras inicialmente foram inoculadas em tubos com caldo BAM (Bacillus acidocaldarius medium) e foram ativadas conforme indicado acima. A quantificação dos esporos foi feita pela técnica do Número Mais Provável ( NMP), em caldo BAM(pH 4,5). Do conteúdo de cada tubo foi retirada uma alçada e inoculada em ágar BAM, com incubação a 50°C/7dias. Não foram obtidos isolamentos a partir do suco de abacaxi. No suco de maracujá foram constatadas 16 ( 28%) de amostras positivas para a presença de A. acidoterrestris. A contaminação variou entre 1,1 e > 2,3 NMP/100ml de suco, ocorrendo a maior incidência nos meses de junho e julho, época seca do ano, indicando que o grau de contaminação está relacionado com a sazonal idade. Dezesseis colônias típicas foram submetidas à caracterização bioquímica pelo sistema API CH 50, que não foi satisfatório para a identificação desta bactéria em suco de maracujá, e a caracterização genotípica pelo método do RAPD, que sugeriu uma elevada similaridade genética (maior que 95%) entre a maioria dos isolados do suco de maracujá e a cepa padrão A. acidoterrestris DSM 2498. Foi determinada a resistência térmica de 3 isolados e também da cepa padrão em suco de maracujá, pelo método TDT (Tempo de Destruição Térmica), em tubos selados. Os valores D para a cepa padrão e para a cepa 4 que demonstrou maior resistência térmica foram de 19,9 e 28,9 min para 87°C; 4,8 e 8,0 min para 90°C e 1,4 e 2,0 min para 95°C, e os valores z obtidos foram 7,3 e 7,1°C, respectivamente. Foi demonstrado que a pasteurização comercial aplicada ao suco de maracujá não foi suficiente para destruir os esporos de A. acidoterrestris . Um processo de 102,1 °C/ 36 s seria adequado para reduzir 3 ciclos logarítmicos da cepa mais termoresistente isolada neste estudo, sem afetar os atributos sensoriais do suco / Abstract: Alicyclobacillus aCidoterrestris, a thermoacidofilic sporogenic bacteria, has recently presented deterioration problems in pasteurized juices. Due to the elevated thermal resistance of its spores, they survive the pasteurization process. The deterioration is described as an unpleasant odor production, similar to that of a disinfectant. There is no gas production, but occasionally sediments form within the juice. The aim of this research was to establish an isolation method for Alicyclobacillus acidoterrestris in passion fruit and pineapple juices, to identify the strains isolated and evaluate their heat resistance in the juices. Spore suspensions of the typical strain A. acidoterrestris DSM 2498 were submitted to heat treatments of, 60°C/60min, 60°C/30min, 70°C/20min, 80°C/5, 10 and 30 min, and boiled 5 min, to determine the best activation conditions for the spores within the passion fruit juice and pineapple juice separately. The best activation treatment found for both juices was 70°C/20min. The enrichment time to isolate the spores of A acidoterrestris, was determined from passion fruit juice and pineapple juice samples experimentally contaminated with typical strain DSM 2498. The best enrichment time for passion fruit juice was 48hs, and for pineapple juice 24hs. A total of 57 samples of passion fruit juice, and 50 samples of pineapple juice, integral and pasteurized were examined in order to detect the presence of the quoted bacteria. For detection, the samples were initially inoculated in tubes with BAM (Bacillus acidocaldarius medium) broth, and were activated at 70°C/20min followed by enrichment at 50°C/48hs for the passion fruit juice, and 50°C/24hs for the pineapple juice. Spore quantification was done by the Most Probable Number (NMP) Technique. From each tube, a loopful was removed and inoculated into BAM agar, followed by incubation for 7 days/50°C. No isolation from pineapple was observed. From the passion fruit juice 16(28%) positive samples for the presence of A. acidoterrestris were obtained. The contamination varied between 1.1 and > 2.3 NMP/100ml of juice, the major incidence occurring in June/July, the dry season of the year, indicating that the level of contamination is related to season. Sixteen typical colonies were submitted to biochemical characterization by the API CH 50 system. This method was not satisfactory for identification and genotipical characterization by RAPD was applied. The results suggested an elevated genetic similarity (over 95%) between most of the isolates from passion fruit juice and typical strain A. acidoterrestris DSM 2498. The heat resistance of 3 isolates and the typical strain in passion fruit juice,was determined by the TDT sealed tube method. The D values for the typical strain and for the most heat resistant isolated strain were 19.9 and 28.9 min at 87°C, 4.8 and 8.0 min at 90°C and 1.4 and 2.0 min at 95°C ones, and the z values obtained were 7.3 and 7.1°C, respectively. It was demonstrated that the commercially applied pasteurization of passion fruit juices was not sufficient to destroy the A. acidoterrestris spores. A 102,1 °C/36sec process would be adequate to reduce 3 logarithmic cycles of the most thermally resistant strain isolated in this study, without affecting the sensory attributes of the juice / Doutorado / Doutor em Ciência de Alimentos

<p>This report defines a present problem with U.S. bridges and suggests several reasons for bridge infrastructure deterioration and degradation, such as traffic overload, expired life cycles, environmental and operational conditions, and budget cuts. The most commonly used nondestructive evaluation (NDE) methods for determining the health of bridge infrastructure are summarized and compared. Advantages and disadvantages of each NDE technique are provided, and the lack of an adequate method which can quantitatively monitor the structural integrity of bridges is noted.</p> <p>This report then discusses the possibility of health monitoring sensor systems for the quantitative NDE of bridge infrastructure. Several types of sensors that may be used to collect paSSlve and quantitative data related to the structural integrity of bridges are evaluated, and the extrinsic Fabry-Perot interferometric (EFPI) fiber optic sensor is suggested as the preferred sensor.</p> <p>The fabrication processes and operational principles of EFPIs are presented. Two case studies which demonstrate the performance of EFPI sensors when used in health monitoring sensor systems are provided. Finally, a design criteria checklist suggests several questions that need to be asked (or more thoroughly defined) concerning the usefulness, reliability, durability, and sensitivity of EFPI-based health monitoring sensor systems.</p> / Master of Science

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Yes / To develop high deterioration resistance concrete for marine infrastructures, two types of nano TiO2 (NT) including anatase phase NT and silica surface-treated rutile phase NT were incorporated into concrete. The fabricated NT modified concrete was then put into the marine environment for 21 months in this study. The effects and mechanisms of two types of NT on the deterioration of concrete in the marine environment were investigated from three aspects, including seawater physical and biological and chemical actions on concrete with NT. Under the seawater physical action, the exposed degree of coarse sand particles on the surface of control concrete is greater than that of concrete with NT. Owing to the microorganism biodegradation property of NT, the elimination and inhibition rates of concrete with NT on microorganisms can reach up to 76.98% and 96.81%, respectively. In addition, the surface biofilm thickness of concrete can be reduced by 49.13% due to the inclusion of NT. In the aspect of seawater chemical action, NT can increase the pH value inside concrete by 0.81, increase the degree of polymerization of C-S-H gel, and improve the interfacial transition zone between cement paste and aggregate in concrete. Compared to concrete with anatase phase NT, silica surface-treated rutile phase NT is more effective in improving the deterioration resistance of concrete in the marine environment. It can be concluded that incorporating NT can inhibit the deterioration of concrete in the marine environment.

Photodegradation of southern yellow pine, its mechanisms and means of prevention were studied. Changes in brightness and color were recognized when wood was exposed outdoors or to ultraviolet light. Scanning electron micrographs showed that most of the cell walls on irradiated transverse surface were separated at the middle lamella region. Half-bordered pits and bordered pits on irradiated longitudinal surf aces were found to be readily destroyed by ultraviolet light. It was also noted that progressively granular surfaces formed on the cell walls of latewood in response to irradiation with ultraviolet light. Spectrophotometric studies on the chemical changes of exposed wood, lignin, and cellulose revealed that photochemical reactions primarily took place in lignin, leading to the generation of carbonyl- and carboxylic-containing degradation products of low molecular weight. Formation of hydroperoxides, one of the mechanisms attributed to the photodegradation of wood, was illustrated from iodometry UV absorption studies. The hydroperoxide concentration at the wood surface increased when wood was irradiated in the presence of singlet oxygen generators. The hydroperoxide concentration decreased when wood was irradiated in the presence of singlet oxygen quenchers. These findings imply the participation of singlet oxygen and the formation of hydroperoxides at the photo-irradiated wood surfaces. It was found that the photodegradative effects on wood surfaces were mitigated by treating wood surfaces with aqueous solutions of chromic acid or ferric chloride, by treating with penetrating chemical agents such as trial, glycol and 1-octadecanol, or by coating with clear polymeric ultraviolet stabilizers such as homo- and copolymer of 2-hydroxy-4(3-methacryloxy-2-hydroxypropoxy)benzophenone. Experimental results showed that the polymeric ultraviolet stabilizers provided the best protection of the treatments tried, and were themselves stable and resistant to photodegradation. Possible chemistry and mechanisms of protection provided by organic and inorganic chemical agents are discussed. / Ph. D.

Polymer films are often pre-treated to alter surface properties resulting in improved adhesion and wettability. The objective of the present work was to demonstrate the applicability of surface-sensitive techniques in the analysis of polymer films coated with thin overlayers. The surface or interphase region of sodium oleate coated polyethylene terephthalate (PET) films was studied by angle dependent x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The effect of corona discharge pre-treatment on sodium oleate coating adhesion was of particular interest. The PET films were analyzed at five separate stages of production; between forward drawing of the PET and corona discharge pre-treatment, both prior to and after sodium oleate coating, after biaxially drawing of the coated film, and, as a final film, after annealing. A comparison was made between corona discharge pre-treated films and otherwise experimentally identical films, which has not been pre-treated. It was determined that corona discharge pre-treatment causes increased surface oxygen on the PET films. This effect disappears with time until XPS analysis shows no difference between treated and untreated films. However, PET films which had been forward drawn, corona discharge pre-treated, immediately coated with sodium oleate, biaxially drawn and then annealed, showed the enhanced surface oxygen after several months of storage. It has been proposed that the mechanism for this phenomenon includes the ionic interaction between the sodium of sodium oleate and the surface oxygen groups, as well as, the increased crystallinity of the PET brought about by the annealing process. Corona discharge processing of polymer films such as PET or polyethylene has been used previously as a means of enhancing adhesion minutes before an adhesion promoter was required. The process described above now allows long-term storage of films with enhanced adhesion properties which in turn makes these films more versatile and practical commercially. / M.S.

This study of nonequilibrium behavior in-network and pseudo network polymeric glasses has focused on linear and network epoxy systems, semicrystalline PET, and SBS and PC-PSX block copolymers. The aging behavior of polymers within each of these three classes was compared, and certain relationships between structure and aging behavior were found. These relationships will now be discussed with respect to each of the three classes of materials. / Master of Science

The objective of this research was to characterize the seawater transport and its effect on the transverse tensile strength of a carbon/vinylester composite. The moisture contents of neat vinylester and unidirectional carbon/vinylester composite panels immersed in seawater were monitored until saturation. A model for moisture up-take was developed based on superposition of Fickian diffusion, and Darcy’s law for capillary transport of water. Both the predicted and measured saturation times increased with increasing panel size, however the diffusion model predicts much longer times while the capillary model predicts shorter time than observed experimentally. It was also found that the saturation moisture content decreased with increasing panel size. Testing of macroscopic and miniature composite transverse tensile specimens, and SEM failure inspection revealed more fiber/matrix debonding in the seawater saturated composite than the dry composite, consistent with a slightly reduced transverse tensile strength. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection