Magnetic resonance (MR) is a highly versatile technique with great potential for use in industrial applications; from the in situ study of unit operations to the optimisation of product properties. This thesis, concerned with the latter, is divided into two parts. Firstly, dynamic MR is applied to characterise the flow behaviour, or rheology, of process fluids. Such characterisation is typically performed using conventional rheometry methods operating offline, with an online, or inline, method sought for process control and optimisation. Until recently, MR was an unlikely choice for this application due to the requirement of high-field MR hardware. However, recent developments in low-field MR hardware mean that the potential of MR in such applications can now be realised. Since the implementation of MR flow imaging is challenging on low-field MR hardware, two new approaches to MR rheometry are described using pulsed field gradient (PFG) MR. A cumulant analysis of the PFG MR signal is first used to characterise the rheology of model power-law fluids, namely xanthan gum-in-water solutions, accurate to within 5% of conventional rheometry, the data being acquired in only 6% of the time required when using MR flow imaging. The second approach utilises a Bayesian analysis of the PFG MR signal to characterise the rheology of model Herschel--Bulkley fluids, namely Carbopol 940-in-water solutions; data are acquired in only 12% of the time required for analysis using MR flow imaging. The suitability of the Bayesian MR approach to study process fluids is demonstrated through experimental study on an alumina-in-acetic acid slurry used by Johnson Matthey. Secondly, MR imaging is used to provide insights into the origins and mechanisms of colloidal gel collapse. Many industrial products are colloidal gels, a space-spanning network of attractive particles with a yield stress. Colloidal gels are, however, known to undergo gravitational collapse after a latency period, thus limiting the shelf-life of products. This remains poorly understood, with a more detailed understanding of both fundamental interest and practical importance. To this end, MR imaging is applied offline to investigate the phase behaviour of colloidal gels. In particular, a comparison of the simulated and experimental phase diagrams suggests gravitational gel collapse to be gravity-driven. Furthermore, measurement of the colloid volume fraction using MR imaging indicates the formation of clusters of colloids at the top of the samples. Whether such clusters initiate gravitational gel collapse is yield stress-dependent; the gravitational stress exerted by a cluster must be sufficient to yield the colloidal gel.

Made available in DSpace on 2014-06-11T19:27:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-21Bitstream added on 2014-06-13T19:56:30Z : No. of bitstreams: 1 danelon_m_me_araca.pdf: 771559 bytes, checksum: e2cac1c49604512ad384ef716b5f196f (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O objetivo foi avaliar a capacidade de géis com baixa concentração de F suplementados com trimetafosfato de sódio (TMP), em reduzir a desmineralização (in vitro) e promover a remineralização (in situ) de esmalte dentário. No estudo in vitro, blocos de esmalte bovino (n = 160) selecionados pela dureza de superfície (SHi) foram divididos em oito grupos de géis (n=20): sem F e TMP (Placebo); TMP3%, TMP5%; 4500 μg F/g (4500); 4500 μg F/g + TMP3% (4500 TMP3%), 4500 μg F/g + TMP5% (4500 TMP5%), 9000 μg F/g (9000) e 12300 μg F/g (Gel ácido). Os blocos foram submetidos a ciclagem de pH durante cinco dias, após aplicação tópica dos géis. A seguir, determinou-se a dureza de superfície final (SHf), perda integrada de dureza de subsuperfície (ΔKHN), CaF2, F, Ca, P formados e retidos no esmalte. Os resultados foram submetidos à análise de variância e teste de Bonferroni (p<0,05). Os grupos 4500 TMP5% e Gel ácido apresentaram a menor perda mineral (SHf e DKHN) e similares entre si (p>0,05). O Gel ácido apresentou a maior concentração de CaF2 formado. O grupo 4500 TMP5% apresentou o maior valor de F formado (p<0,05). O Gel ácido apresentou maiores valores de Ca retido (p<0,05), seguido pelos grupos 4500 TMP5% e 9000, que foram similares entre si (p>0,05). O P formado foi semelhante entre os grupos (p>0,05) e o Gel ácido apresentou a maior concentração de P retido no esmalte. Concluiu-se que é possível inibir a desmineralização do esmalte com gel fluoretado de baixa concentração suplementado-o com TMP. Para o estudo in situ, blocos de esmalte bovinos (n=240) foram selecionados pela dureza de superfície (SH1), após desmineralização, e divididos em cinco grupos experimentais: Placebo, 4500, 4500 TMP5%, 9000 e Gel ácido. Doze voluntários utilizaram dispositivos palatinos, com quatro blocos de esmalte desmineralizados, durante três... / The aim of this study was to evaluate the capacity of gels with low concentration of F supplemented with sodium trimetaphosphate (TMP) to reduce the dental enamel demineralization (in vitro) and remineralization (in situ). In the in vitro study blocks of bovine enamel (n=160) were selected through surface hardness (SHi) and divided into eight groups (n = 20): gel without F and TMP (Placebo), TMP3%, TMP5%, 4500 μg F/g (4500), 4500 μg F/g + TMP3% (4500 TMP3%), 4500 μg F/g + TMP5% (4500 TMP5%), 9000 μg F/g (9000) and 12.300 μg F/g (acid gel). The blocks were submitted to pH cycling during five days after topical application of gels. After that, the surface hardness (SHf), the subsurface hardness integrated loss (ΔKHN), CaF2, F, Ca and P formed and retained in enamel were determined. The results were submitted to analysis of variance and Bonferroni tests (p <0.05). Groups 4500 TMP5% and acid gel were similar and showed the best results for SHf and ΔKHN. The acid gel showed the highest concentration of CaF2 formed. The 4500 TMP5% group presented the highest values of F formed (p <0.05). The acid gel had the highest Ca retention (p <0.05), followed by 4500 TMP5% and 9000 groups, which were similar (p> 0.05). The P formed was similar between the groups (p> 0.05) and the acid gel showed the highest concentration of P retained in enamel. It was concluded that it is possible to inhibit enamel demineralization with low F concentration gel by supplementing it with TMP 5%. In the in situ study bovine enamel blocks (n=240) were selected through surface hardness (SH1) after demineralization and divided into five groups: Placebo, 4500, 4500 TMP5%, 9000 and Acid gel). Twelve volunteers wore palatal appliances with four demineralized blocks, during three days after topical application of F (ATF). Two blocks were removed immediately after the ATF to ... (Complete abstract click electronic access below)

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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Lipases, triacilglicerol Ãster hidrolases E.C. 3.1.1.3, sÃo enziÂmas que atuam nas ligaÃÃes Ãsteres de triacilglicerÃis, liberando Ãcidos orgÃnicos e glicerol. Podendo, em condiÃÃes microaquosas, catalisar a reaÃÃo reversa. Uma limitaÃÃo da utilizaÃÃo destas enzimas em processos industriais reside na falta de estabilidade operacional e na impossibilidade de sua reutilizaÃÃo na forma livre. O uso do sistema de organo-gÃis consiste em uma alternativa para a imobilizaÃÃo de enzimas, e para sua utilizaÃÃo na catÃlise enzimÃtica em meio orgÃnico. Neste sistema a enzima està localizada no centro micelar (centro aquoso) do organo-gel, eliminando o problemas como de estabilizar a enzima contra inativaÃÃo por um solvente nÃo-aquoso. O objetivo deste trabalho foi desenvolver derivados de lipases de Rhizomucor miehei imobilizadas em organo-gÃis à base de polÃmeros, visando à sÃntese de Ãsteres etÃlicos a partir de reaÃÃes de esterificaÃÃo de matÃrias-primas com elevado teor de Ãcidos graxos livres. Os suportes foram obtidos atravÃs de diferentes combinaÃÃes entre os componentes. Utilizaram-se polÃmeros gelatina (Gel), alginato (Alg) ou quitosana (Qui), fases orgÃnicas hexano (Hex) ou heptano (Hep) e os tensoativos dodecilsulfato de sÃdio (SDS) ou brometo de acetilmetilamÃnio (CTABr). Verificou-se a estabilidade tÃrmica da enzima na sua forma livre, determinando seu tempo de meia-vida. Na primeira etapa, foram produzidos derivados com e sem ativaÃÃo via glutaraldeÃdo 2% (v/v). A atividade enzimÃtica foi avaliada atravÃs hidrÃlise do p-nitrofenilbutirato (pNPB). Os derivados foram caracterizados quanto: fator de estabilidade a 60ÂC em relaÃÃo à enzima livre, eficiÃncia e rendimento de imobilizaÃÃo para assim determinar os melhores biocatalisadores. Dentre os catalisadores obtidos, os melhores apresentaram eficiÃncia de 4,1% e fator de estabilidade 30 vezes (Gel/SDS/Hex), eficiÃncia de 6,0% e fator de estabilidade 1,3 vezes (Alg/SDS/Hep) e eficiÃncia de 1,0% e fator de estabilidade de 2,3 vezes (Qui/SDS/Hep). Os suportes produzidos ativados com glutaraldeÃdo 2% (v/v) apresentaram baixas atividades e eficiÃncias, apesar de obterem valores bons de tempo de meia-vida e fator de estabilidade. Os derivados produzidos com o tensoativo CTABr apresentaram baixas atividades, eficiÃncias, tempo de meia-vida e fator de estabilidade. Na segunda fase, os derivados selecionados foram estudados quanto à carga mÃxima (50 U.g-1 a 500 U.g-1) de imobilizaÃÃo e eficiÃncia, nas temperaturas de 15ÂC e 25ÂC. Avaliou-se a aplicaÃÃo dos biocatalisadores na reaÃÃo de esterificaÃÃo do oleato de etila a partir de Ãcido oleico e etanol, variando a razÃo molar Ãcido/Ãlcool e utilizaÃÃo de agente dessecante (zeÃlitas). Verificou-se a estabilidade de estocagem sob 10ÂC por um perÃodo de 100 dias. Todos os derivados apresentaram melhores eficiÃncias utilizando carga de 50 U.g-1, apresentando valores de 4,2% e 4,8% (Gel/SDS/Hex), 2,0% e 2,3% (Alg/SDS/Hep) e 0,9% e 1,1% (Qui/SDS/Hep ) nas temperaturas de 15ÂC e 25ÂC, respectivamente. Nas reaÃÃes de esterificaÃÃo os derivados Gel/SDS/Hex e Alg/SDS/Hep obtiveram maiores conversÃes na razÃo molar Ãcido/Ãlcool 1:10, 72,9% e 16,9%, respectivamente. O derivado Qui/SDS/Hep obteve 80,0% de conversÃo na razÃo de 1:1. Com utilizaÃÃo de zeÃlitas o derivado Gel/SDS/Hex aumentou a conversÃo para 79,0% nas razÃes 1:1 e 1:5, os derivados Alg/SDS/Hep e Qui/SDS/Hep apresentaram decrÃscimo nas conversÃes. Durante os 100 dias de estocagem sob 10ÂC, os derivados Gel/SDS/Hex e Qui/SDS/Hep mantiveram atividade hidrolÃtica atà 40 dias, tendo um decrÃscimo ao longo do tempo. O derivado Alg/SDS/Hep obteve um tempo maior de 60 dias, apresentando tambÃm um decrÃscimo. / Lipases, triacylglycerol ester hydrolases EC 3.1.1.3, are enzymes that act on ester bonds of triacylglycerols, releasing organic acids and glycerol. May in microaquosas conditions, catalyze the reverse reaction. A limitation of using these enzymes in industrial processes is the lack of operational stability and the inability to re-use the free form. The use of organo-gels system is an alternative for the immobilization of enzymes and to their use in enzyme catalysis in organic media. In this system the enzyme is located in the micelle center (aqueous center) of the organo-gel, eliminating problems such as stabilizing the enzyme against inactivation by a non-aqueous solvent. The aim of this work was immobilize lipases from Rhizomucor miehei into organo - gels based on polymers for future application in ethyl esters synthesis through esterification of raw materials with high free fatty acids content. Supports were obtained using different combinations of components. It was used gelatin polymers (Gel), alginate (Alg) and / or chitosan (Chi), organic phases such as hexane (Hex) and heptane (Hep) and surfactants sodium dodecyl sulfate (SDS) or acetylmetylamonium bromide (CTABr). In the first step, derivatives were produced with and without glutaraldehyde 2% (v/v) activation. Enzymatic activity was measured by hydrolysis of p â nitrophenyl butyrate (PNPb). Biocatalysts were characterized as: stability at 60  C and compared to free enzyme, immobilization efficiency and yield factor, thus determining the best biocatalysts. Among the catalysts obtained, (Gel/SDS/Hex) showed the best efficiency of 4.1% , 30 âfold more stable; (Alg/SDS/Hep) with 6.0% efficiency , 1.3 âfold more stable and (Qui/SDS/Hep) with efficiency of 1.0 % , 1.3 âfold more stable than free lipase. Obtained supports activated with glutaraldehyde 2 % (v/v) showed lower activities and efficiencies, in despite of having good values for stability factor. Produced derivatives using surfactant CTABr presented low activity, efficiency and stability factor. In the second step, derivatives were analyzed as maximum load (50 U.g-1 a 500 U.g-1) enzyme immobilization and efficiency at 15  C and 25  C. It was evaluated biocatalysts application in ethyl oleate achievement in an esterification reaction, using oleic acid and ethanol, by varying molar ratio acid / alcohol with and without using of desiccant agent (zeolite) at 37  C and 24 h of reaction. Derivatives were submitted storage stability under 10  C studies, for a period of 100 days. All derivatives showed higher efficiencies using an initial enzyme loading of 50 U.g -1, with values of 4.2% and 4.8% (Gel/SDS/Hex), 2.0 % and 2.3 % (Alg/SDS/ Hep) and 0.9 % to 1.1% (Qui/SDS/Hep) at 15  C and 25  C, respectively. In esterification reactions, Gel/SDS/Hex and Alg/SDS/Hep derivatives showed higher conversions 72.9 % and 16.9 %, respectively, with molar acid / alcohol 1:10. The chemical derivative Qui/SDS/Hep presented 80.0 % conversion with molar acid / alcohol 1:1 ratio. Using zeolites, Gel/SDS/Hex conversion increased to 79.0 % using ratios of 1:1 and 1:5, the Alg/SDS/Hep and Qui/SDS/Hep presented a decreasing in conversions. During 100 days of storage at 10  C, Gel/SDS/Hex and Qui/SDS/Hep hydrolytic activity maintained up to 40 days and a decreasing during this period, however, Alg/SDS/ Hep achieved more than 60 days with activity.