<p dir="ltr">Corn, a vital cereal grain extensively used in various industries, exhibits viscoelastic properties when subjected to compressive forces. The effect of moisture content on the mechanical behavior of corn is crucial for understanding its storage, processing, and transportation requirements. Understanding the mechanical properties of bulk corn is crucial for ensuring a smooth flow of grains from the bin, thereby helping to prevent confined space-related accidents such as grain bin entrapment and engulfment, which can occur when workers enter the bin to facilitate grain flow. The objective of this study is to investigate the stress and strain relaxation of different bulk corn kernels qualities. In the first study various qualities of bulk corn, including clean corn, corn with impurities, and moldy corn samples were compressed at 42, 77, 106, and 130 N force levels. The compressive behavior of samples was measured at 13.22, 16.16, 18.93, and 21.70% wet basis moisture contents. The samples were compressed at a strain rate of 1.25mm/min, and the strain was kept constant for 200 s to determine the stress relaxation properties. For moldy corn, the energy absorbed increased with force resulting in clump formation irrespective of the force level. In the clean corn, the energy absorbed increased with moisture content, and formation of clumps was observed at 21.70% moisture content. Solidity decreased with moisture content, resulting in high cohesion at moisture contents 18.93% and 21.70% for clean corn. In corn with impurities, even though the energy absorbed increased with moisture content, no clump formation was observed. This study provides insights into the mechanical behavior of bulk corn under compression, such as solidity and compressive strength. An increase in the compressive strength or a decrease in the solidity of stored shelled corn in a grain bin increases compaction, cohesion, and the formation of clumps, and thereby affects the flow of grains during discharge from the bin. The study also highlights potential risks in grain bins when the kernels are moldy and stored at high moisture content.</p><p dir="ltr">The second study investigates the creep behavior of bulk corn kernels and its relationship with moisture content. Clean corn reconditioned to 16.23%, 19.02%, and 21.63% from the initial moisture content of 10.81% were compressed at 42, 77, 106, and 130 N. The viscoelastic behavior of the sample was measured by fitting the experimental data to a four-element Burgers model to obtain the model parameters E₀, E₁, η₀, and η₁. The results showed that the ranges of the elastic modulus (E₀) increase with an increase in moisture content, indicating an increase in compaction and elastic deformation of the sample. Retarded elastic modulus (E₁) values were also high at high moisture content, implying a high absorption of energy. The viscous component shows a dominance of the elastic component due to the low value of η₁ at high moisture content. The findings highlight the importance of considering moisture content in optimizing the handling of corn to enhance safety and efficiency in agricultural operations. Increase in the elastic modulus, retarded elastic modulus, and decrease in the viscous component leads to poor discharge of grains from the bin due to grain bridging or crust, or formation of clump due to out-of-conditioned grain, leading to a potential risk of grain entrapment and engulfment when the grain bin workers get inside the bin. This research contributes to the ongoing efforts to improve grain storage conditions.</p>

Made available in DSpace on 2014-12-17T14:16:25Z (GMT). No. of bitstreams: 1 AcariliaES_Dissert_01.pdf: 1640327 bytes, checksum: 9c4568aff953d538d26000691eb0407d (MD5) Previous issue date: 2009-03-10 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Colon-specific drug delivery systems have attracted increasing attention from the pharmaceutical industry due to their ability of treating intestinal bowel diseases (IBD), which represent a public health problem in several countries. In spite of being considered a quite effective molecule for the treatment of IBD, mesalazine (5-ASA) is rapidly absorbed in the upper gastrointestinal tract and its systemic absorption leads to risks of adverse effects. The aim of this work was to develop a microparticulate system based on xylan and Eudragit? S- 100 (ES100) for colon-specific delivery of 5-ASA and evaluate the interaction between the polymers present in the systems. Additionaly, the physicochemical and rheological properties of xylan were also evaluated. Initially, xylan was extracted from corn cobs and characterized regarding the yield and rheological properties. Afterwards, 10 formulations were prepared in different xylan and ES100 weight ratios by spray-drying the polymer solutions in 0.6N NaOH and phosphate buffer pH 7.4. In addition, 3 formulations consisting of xylan microcapsules were produced by interfacial cross-linking polymerization and coated by ES100 by means of spray-drying in different polymer weight ratios of xylan and ES100. The microparticles were characterized regarding yield, morphology, homogeneity, visual aspect, crystallinity and thermal behavior. The polymer interaction was investigated by infrared spectroscopy. The extracted xylan was presented as a very fine and yellowish powder, with mean particle size smaller than 40&#956;m. Regarding the rheological properties of xylan, they demonstrated that this polymer has a poor flow, low density and high cohesiveness. The microparticles obtained were shown to be spherical and aggregates could not be observed. They were found to present amorphous structure and have a very high thermal stability. The yield varied according to the polymer ratios. Moreover, it was confirmed that the interaction between xylan and ES100 occurs only by means of physical aggregation / Sistemas c?lon-espec?ficos t?m atra?do o interesse da ind?stria farmac?utica devido ? possibilidade de tratarem enfermidades, como as doen?as inflamat?rias intestinais (DII), que compreendem um problema de sa?de p?blica em muitos pa?ses. Apesar de ser considerada uma mol?cula bastante eficiente para o tratamento das DII, a mesalazina (5-ASA) ? rapidamente absorvida no trato gastrintestinal superior e sua absor??o sist?mica leva ? incid?ncia de s?rios efeitos adversos. Este trabalho teve como objetivos produzir um sistema polim?rico microparticulado ? base de xilana e Eudragit? S-100 (ES100) para libera??o c?lon-espec?fica de 5-ASA e avaliar a intera??o entre os pol?meros constituintes do sistema, al?m de aprofundar a caracteriza??o f?sico-qu?mica e tecnol?gica da xilana. A xilana foi extra?da a partir de sabugos de milho e caracterizada quanto ao rendimento, granulometria, cristalinidade, propriedades reol?gicas e comportamento t?rmico. Em seguida, 10 formula??es contendo 5-ASA foram preparadas em diferentes propor??es de xilana e ES100 atrav?s da secagem por aspers?o das solu??es polim?ricas com NaOH 0,6N ou tamp?o-fosfato pH 7,4, como solvente. Al?m disso, 3 formula??es constitu?das de microc?psulas de xilana produzidas por reticula??o polim?rica interfacial foram revestidas por ES100 atrav?s de secagem por aspers?o em diferentes propor??es polim?ricas e empregando-se NaOH 0,6N ou tamp?o-fosfato pH 7,4, como solvente. As micropart?culas foram avaliadas quanto ao rendimento, morfologia, granulometria, homogeneidade, aspecto visual, cristalinidade e comportamento t?rmico. A intera??o entre os pol?meros foi investigada atrav?s da espectroscopia na regi?o do infravermelho e de an?lises t?rmicas. A xilana extra?da apresentou-se como um p? muito fino, com tamanho m?dio inferior a 40&#956;m, e com colora??o opaca levemente amarelada. A avalia??o das propriedades reol?gicas da xilana permitiram a caracteriza??o desse pol?mero, em seu estado original de p?, como um material de baixa densidade, fluxo restrito e bastante coesivo. Foram obtidas micropart?culas esf?ricas e sem presen?a de agregados, com estrutura amorfa, em sua maior parte, e bastate est?veis a temperaturas elevadas. Al?m disso, confirmou-se que a intera??o entre xilana e ES100 ocorre apenas por agrega??o f?sica