Thesis (Ph. D.)--University of Rhode Island, 2006. / Typescript. Includes bibliographical references (leaves 129-143).

O objetivo do presente trabalho foi estudar, por meio da técnica de titulação colorimétrica e análise da microdureza dentinária, o shelf life da solução de quitosana 0,2% armazenada em frascos de vidro e plástico. Trinta caninos superiores humanos tiveram as coroas desprezadas e a porção cervical das raízes seccionada, obtendo-se 3 cortes. O segundo e terceiro cortes foram divididos ao meio e incluídos em resina acrílica resultando em 4 corpos de prova por dente. A solução de quitosana 0,2% (pH 3,2) foi preparada e distribuída em 3 frascos iguais de vidro (v1, v2 e v3) e em 3 de plástico (p1, p2 e p3) para realização dos testes em triplicata. Os testes de microdureza e colorimetria foram realizados durante seis meses nos períodos de 0, 7, 15, 30, 45, 60, 90, 120, 150 e 180 dias após o aviamento da solução. Para a mensuração da microdureza Knoop utilizou-se carga de 10 gramas por 15 segundos. O corpo de prova recebeu 50 &mu;L da solução teste por 5 minutos e, após lavagem e secagem foi levado para mensuração. A análise foi realizada com as soluções v1, p1, EDTA 17% e água destilada (controle); v2, p2, EDTA 17% e controle; v3, p3, EDTA 17% e controle, para cada tempo proposto. Foram realizadas 3 endentações com espaço de 200 &mu;m. As mensurações foram anotadas e arquivadas em um banco de dados. Para o teste da colorimetria utilizou-se uma solução padrão de carbonato de cálcio 0,3%, na qual gotejava-se por meio de micropipeta a solução de quitosana com volume pré determinado. A alteração da coloração da solução de carbonato, do violeta para azul, indicava quelação dos íons cálcio, detectada por meio de espectrofotometro Ultravioleta Visivel. O aparelho emitia um valor da absorbância para cada análise da coloração, expressa por meio de gráfico (comprimento de onda/absorbância). Empregou-se Análise de Variância (one-Way ANOVA) (&alpha; = 0,05) para comparar a microdureza entre as soluções, os diferentes tempos para cada solução, bem como a interação microdureza/tempo para cada solução. Houve semelhança entre as soluções testadas no que se refere ao tempo de estudo (p=0,113), bem como em relação à interação microdureza/tempo (p=0,329). As soluções testadas apresentaram, individualmente, o mesmo efeito sobre a microdureza da dentina, desde o tempo zero até os 180 dias. Quando comparadas entre si foram diferentes (p<0,0001). O teste de Tukey evidenciou que a quitosana (v1, v2, v3, p1, p2 e p3) e EDTA reduziram a microdureza de forma semelhante entre si (p>0,05) e diferente do controle (p<0,001). Os gráficos da análise colorimétrica mostraram que tanto a quitosana em vidro como a em plástico apresentaram valores médios de absorbância no mesmo comprimento de onda (234nm) para todos os tempos, enquanto que para a solução padrão de carbonato de cálcio o comprimento de onde foi de 206nm. Concluiu-se que independentemente da forma de armazenamento a quitosana apresenta propriedade quelante por um período mínimo de 6 meses. / The aim of this study was evaluate, through the colorimetric titration method and analysis of the dentine microhardness, the shelf life of the solution of chitosan 0,2% stored in flasks of glass and plastic. Thirty human superior canines had their crown discarded and the cervical portion of the root sectioned, obtaining 3 sections. The second and the third sections were divided in half and included in acrylic resin resulting in 4 specimens per tooth. The chitosan solution 0,2% (pH 3,2) was prepared and distributed in 3 flasks of glass (v1, v2, v3) and in 3 of plastic (p1, p2, p3) to perform the test in triplicate. The tests of microhardness and colorimetry were performed during 6 months in the period of 0, 7, 15, 30, 45, 60, 90, 120, 150 and 180 days after the preparation of the solution. For the measurement of microhardness Knoop, it was used a load of 10 grams for 15 seconds. The test object received 50 &mu;L of the test solution for 5 minutes and after washing and drying, it was taken out for measurement. The analysis was performed with the solutions v1, p1, EDTA 17% and distilled water (control); v2, p2, EDTA 17% and control; v3, p3, EDTA 17% and control, for each proposed time. Three indentations were performed with a 200&mu;m space. Measurements were noted and filed in a database. For the colorimetric test, a standard solution of calcium carbonate 0.3% was used and a predetermined volume of chitosan solution was inserted to it by using a micropipette. The color changes observed in the carbonate solution, from violet to blue, indicated the chelation of calcium Ions, detected through visible ultraviolet absorbance spectrophotometry. The instrument generated a specific value of absorbance for each coloring solution analyzed, expressed through the graphic (wavelength/absorbance). Variation of analysis was used (One-Way ANOVA) (&alpha;= 0,05) to compare the microhardness among the solutions, the different time for each solution, as well as the interaction microhardness/time for each solution. The time of study was similar among the tested solutions (p=0,113), as well as the interaction between microhardness/time (p=0,329). The tested solutions showed, individually, the same effect over the dentine microhardness, from time zero until 180 days. When compared among each other the results were different (p<0,0001). The Tukey test demonstrated that chitosan (v1, v2, v3, p1, p2 and p3) and EDTA reduced the microhardness in a similar pattern among them (p>0,05) and different from the control (p<0,001). The graphics of the colorimetric analysis showed that either chitosan in glass or plastic presented medium values of absorbance in the same wave length (234nm) for all the different times, meanwhile the standard solution of calcium carbonate wavelength was 206 nm. It was concluded that independently of storing methods, the chitosan presents chelating property for a minimum period of six months.

Ocean warming near the Antarctic ice shelves has critical implications for future ice sheet mass loss and global sea level rise. A global climate model with an eddying ocean is used to quantify the mechanisms contributing to ocean warming on the Antarctic continental shelf in an idealized 2xCO(2) experiment. The results indicate that relatively large warm anomalies occur both in the upper 100 m and at depths above the shelf floor, which are controlled by different mechanisms. The near-surface ocean warming is primarily a response to enhanced onshore advective heat transport across the shelf break. The deep shelf warming is initiated by onshore intrusions of relatively warm Circumpolar Deep Water (CDW), in density classes that access the shelf, as well as the reduction of the vertical mixing of heat. CO2-induced shelf freshening influences both warming mechanisms. The shelf freshening slows vertical mixing by limiting gravitational instabilities and the upward diffusion of heat associated with CDW, resulting in the buildup of heat at depth. Meanwhile, freshening near the shelf break enhances the lateral density gradient of the Antarctic Slope Front (ASF) and disconnect isopycnals between the shelf and CDW, making cross-ASF heat exchange more difficult. However, at several locations along the ASF, the cross-ASF heat transport is less inhibited and heat can move onshore. Once onshore, lateral and vertical heat advection work to disperse the heat anomalies across the shelf region. Understanding the inhomogeneous Antarctic shelf warming will lead to better projections of future ice sheet mass loss.

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Strawberries are a popular fruit with a pleasing color and flavor. However, its delicate tissue and high sugar content makes it highly perishable with visible mold. In this study, we have attempted to test feasibility of different edible coatings for extending shelf life of ‘Chandler’ strawberries subjected to simulated vibrations of local transportation. Six types of coatings were compared based on the quality of treated berries. Curcumin and limonene were used as natural antimicrobials and coatings were prepared from their liposomes and were over-coated with methyl cellulose. One set of each coating type were subjected to the simulated vibration of local transportation. The vibrated samples had lower shelf life than non-vibrated samples, indicating a robust coating which remains intact during road vibrations is required. Based on the number of berries with visible mold, limonene liposomes showed significantly lower fungal growth compared to the control on the 14th day of storage. Titratable acidity and total phenolic contents were also found to be higher in limonene-coated strawberries compared to other coatings. From the findings, further study of liposome coatings of limonene with different particle size and concentration of the lipid bilayer was necessary to characterize the liposome for an effective application in strawberries. To this regard, another study was done with the aim to develop and characterize alginate and limonene liposomes as edible coating materials and to determine their efficacy in shelf life extension and maintaining quality parameters of ‘Chandler’ strawberries. Alginate solution (1.5% w/v) and limonene liposomes prepared from 80% lecithin and 20% PDA were used as edible coating materials. Fungal decay percentage, total yeast and mold counts, headspace atmosphere analysis, total soluble solids, pH, titratable acidity, total anthocyanin content and total phenolics were analyzed to assess fruit quality during 14 days at 4ºC of storage. Days of storage were found to be significant in maintaining the quality of the strawberries. Among the coating types, strawberries coated limonene liposomes were found to be significantly effective in maintaining the lesser respiration rate, lower the change in pH (3.9), and had higher total anthyocyanin (43.849) content during storage. Thus, limonene liposomes were found to be useful for extending the shelf life and maintaining quality of strawberry fruits.