Master thesis deals with the influence of polyvinylacetate, polycaprolactone, poly(butylene-adipate-co-terephtalate) and talc, ethylenevinylacetate, polyethylene glycol and monosodium citrate on the flow properties, mechanical properties and crystallization ability of PLA. The flow properties were studied using the melt flow index and mechanical properties were studied using a tensile test. The crystallinity was studied by differential scanning calorimetry and on a polarization optical microscope equipped with hot stage. Isothermal crystallization was performed at 95 and 105 °C for 3 h and non-isothermal crystallization was performed with a calorimeter at two cooling rates (1 and 10 °C/min). Upon the isothermal crystallization at 95 °C, the formation of denser crystalline structure was observed and the content of crystalline phase increased in most of the samples. The formation of spherulitic structure was observed at 105 °C in samples with 30 % PVAc, 30 % EVA and PEG. Reducing the cooling rate to 1 °C/min at non-isothermal crystallization had nearly no effect on the crystallization process of the most samples; the content of crystalline phase increased in the samples containing PBAT and PEG, which revealed double melting peak during subsequent heating. The crystalline fraction was the most significantly affected by the addition of PEG. All added polymers except PVAc affected the mechanical properties; PBAT, PCL, EVA and PEG increased the strain and decreased the strength and modulus of elasticity. The samples containing monosodium citrate showed unsatisfactory mechanical properties and could not be measured. The samples containing higher concentration of EVA copolymer showed the phase separation.

Drought is the major environmental factor affecting crop growth, yield and quality. Two experiments were conducted to understand rice genotypic variability responses to drought stress conditions during seed germination and early-seedling growth. In Experiment I, the influence of wide range of osmotic stress on seed germination properties of 15 rice cultivars were studied using polyethylene glycol media. In Experiment II, seedling morph-physiological parameters including root traits were quantified by subjecting rice seedlings to three different soil moisture treatments, 100, 66 and 33% field capacity. Rice cultivars differed in their response to drought at both the stages. Cultivars were classified into different drought tolerant groups based cumulative drought response indices. Based on seed- and early-season growth and developmental responses, RU1104122, Rex, CL111 and RU1304154 were identified as drought tolerant among the rice cultivars tested. The identified tolerant cultivars will be a source for rice breeders to develop new drought tolerant cultivars.

No description available.

[pt] O grafeno é formado por uma monocamada de átomos de cabono ligados entre si formando uma rede hexagonal. Ele tem sido bastante estudado por pesquisadores e atraído investimentos de vários setores da economia por apresentar excelentes propriedades mecânicas, térmicas, elétricas e ópticas. O presente trabalho tem como objetivo principal a caracterização reológica das suspensões de óxido de grafeno (GO) dispersas em polietileno glicol (PEG 400), com diferentes tempos de oxidação (2 e 96 horas), através do uso da reometria rotacional. O óxido de grafeno foi obtido pelo método de Hummers e caracterizado por várias técnicas. Este método é baseado na esfoliação química do grafite através de ácidos fortes, como o ácido sulfúrico. Uma vez que o óxido de grafite (GrO) é obtido, ele é esfoliado em um banho ultrassônico em PEG para a formação da suspensão com óxido de grafeno. A caracterização reológica foi realizada através de medições em escoamento de cisalhamento em regime permanente, transiente e oscilatório. A caracterização do GO foi realizada utilizando técnicas como: Difração de Raios-X (DRX), Espectroscopia Raman, Infravermelho por Transformada de Fourier (FTIR), Microscopia de Força Atômica (AFM) e Análise Termogravimétrica (TGA). Os resultados servirão de base para a compreensão da interação entre o GO e o polímero, e o comportamento reológico dos nanofluidos de polímeros à base de GO. / [en] Graphene is formed by a monolayer of cabon atoms linked together forming a hexagonal network. It has been extensively studied by researchers and attracted investment from various sectors of the economy, because it presents excellent mechanical, thermal, electrical and optical properties. The present work has as main objective the rheological characterization of the suspensions of graphene oxide (GO) dispersed in poly(ethylene) glycol (PEG 400), with different oxidation times (2 and 96 hours), through the use of rotational rheometry. Graphene oxide was obtained by Hummers method and characterized by various techniques. This method is based on the chemical exfoliation of graphite using strong acids such as sulfuric acid. Once the graphite oxide (GrO) is obtained, it is exfoliated in an ultrasonic bath in PEG to form the suspension with graphene oxide. The rheological characterization is fulfilled through measurements in steady shear flow, transient shear flow and oscillatory shear flow. The characterization of GO was performed using techniques such as: X-Ray Diffraction (XRD), Raman Spectroscopy, Fourier Transform Infrared (FTIR), Atomic Force Microscopy (AFM) and Thermogravimetric Analysis (TGA). The results will serve as a basis for understanding the interaction between the GO and the polymer, and the rheological behavior of GO-based polymer nanofluids.

Yes / Several contributions in answering granulation challenges including the use of computer simulation and well thought out experimental analyses are being researched. Using a twin screw granulator (TSG) by design of experiments (DoE), comparisons on 1) equipment similarities i.e., continuous and 2) shear forces, are made to previous literature on continuous equipment and a Cyclomix. This study proposes that equipment specific DoE, better explains the contribution of parameters than investigating an identified parameter from the experimental findings from a specific equipment. Granule strength and structure are presented together with the contribution of process parameters, speed, temperature, and binder content. Seeded structures are present in all but the Extrudomix. Longer residence times within the Cyclomix facilitates seeded structures. Granule crushing strengths are higher in TSG than all other continuous equipment. Optimum condition for the formation of stronger granules with least variation is around 65.4 °C. / The authors would like to acknowledge the support from the CCIP grant (Collaboration, Capacity and IP Development) fund from the University of Bradford for ordering cunsumables and equipment.

<p>PEGylation, referring to the covalent attachment of poly(ethylene glycol) or PEG to protein, has become the most established technology for improving pharmacokinetic behavior of native proteins, especially the prolongation of circulation half-life <em>in vivo</em>. This thesis focuses on the synthesis and purification of PEGylated proteins.</p> <p>The conventional way to synthesize PEGylated proteins is in liquid phase batch reaction, which usually causes the formation of significant amount and high diversity of by-products (i.e. di-, tri-, and/or higher-PEGylated forms of a protein). Many chemical and physical ways have been explored to increase the specificity of mono-PEGylated protein. Chemical ways involve manipulation of operating conditions towards site-specific PEGylation. Understanding reaction kinetics is helpful in optimizing conversion and specificity of mono-PEGylation. In this thesis, the PEGylation reaction kinetics between a model protein and PEG NHS ester under various operating conditions was investigated.</p> <p>In the physical perspective, the key point is to gain degree of control on reactant addition instead of one-time addition as in liquid phase batch reaction. Herein, two novel reactor systems were developed. One is solid phase PEGylation bioreactor, bringing free protein to react with immobilized PEG on a membrane surface; the other is Hollow-fiber Membrane Reactor (HMR), distributing PEG into the fiber lumen (where protein is flowing) through the pores on the fiber wall. Greatly improved conversion and specificity of mono-PEGylated protein were observed in both systems, compared to liquid phase batch reactor.</p> <p>An effective and efficient purification technique is very essential because purification step accounts for a significant portion of total cost. In this thesis, the use of hydrophobic interaction chromatography with environment-responsive microporous membranes was examined for the fractionation of different PEGylated proteins. The capability of this technique was demonstrated by obtaining mono-PEGylated protein in a pure form and observing well-resolved chromatographic peaks for different PEGylated proteins.</p> / Doctor of Philosophy (PhD)

Le procédé par lequel des forces sont transformées en signaux chimiques joue un rôle fondamental dans de nombreux processus biologiques. Ce travail de thèse a permis de mettre au point de nouvelles surfaces fonctionnelles synthétiques permettant de mimer ce comportement. Il s’agit plus précisément de contrôler l’adsorption d’objets biologiques tels que des protéines ou des cellules sur un support élastique modifié par plasma et présentant des récepteurs spécifiques. Ces récepteurs sont masqués par de longues chaînes de poly(éthylèneglycol) (PEG) qui sont également greffées sur la surface. L'étirement de celles-ci permet d'exhiber les sites d’adsorption ou les sites d'adhésion et de rendre ainsi la surface adhérente. Notre méthode est basée sur la polymérisation plasma de l’anhydride maléique. Cette fonctionnalisation permet de greffer à la surface de films silicones des fonctions carboxylique qui servent de points d’ancrage aux chaînes de PEG. Sur le même principe, la biotine ou les peptides d’adhésion (RGD) sont greffés dans un deuxième temps sur ce substrat. Nous montrons, qu’à l’état non étiré, ces ligands ne sont pas accessibles pour leurs récepteurs. Par contre, à l’état étiré, la surface devient spécifiquement adsorbante pour la streptavidine, l’anti-biotine et adhérente pour les cellules. Ces phénomènes sont parfaitement réversibles. / The process by which forces are converted into chemical signals play a fundamental role in many biological processes. This thesis has to develop new functional synthetic surfaces to mimic this behavior. It is more precisely to control the adsorption of biological objects such as proteins or cells on an elastic support modified by plasma and presenting specific receptors. These receptors are masked by long chains of poly (ethylene glycol) (PEG) which are also grafted onto the surface. Stretching allows them to exhibit adsorption sites or adhesion sites and thus make the surface adhesive. Our method is based on the plasma polymerization of maleic anhydride. This functionalization can be grafted to the surface of silicone films carboxylic functions which serve as anchors points for the PEG chains. On the same principle, biotin or adhesion peptides (RGD) have been grafted in a second time on this substrate. We show that the non-stretched state, these ligands are not accessible to their receptors. On the other side, in the stretched state, the surface becomes specifically adsorbent to streptavidin, anti-biotin and also adherent for cells. These phenomena are perfectly reversible.

Ces travaux de thèse concernent l’étude du comportement thermo-physique de mélanges de polymères biosourcés chargés de poudre d’Inconel 718 mis en forme par Moulage par Injection de poudre Métallique. Des matériaux et procédés innovants pouvant permettre une amélioration du procédé ont été étudiés. L’utilisation de polyéthylène glycol (PEG), choisi pour ses propriétés de solubilité dans l’eau, et de polymères biosourcés, pour diminuer l’impact environnemental, ont été choisi. Les nuances de polymères biosourcés ont été choisies adaptées aux conditions du procédé de moulage par injection, il s’agit d’acide polylactique et de polyhydroalcanoates. De même, l’utilisation du CO2 à l’état supercritique comme solvant, a pour objectif de diminuer le temps de déliantage ainsi que d’augmenter la qualité des composants réalisés. Les résultats obtenus ont montré une dégradation du PEG et de l’acide stéarique lors des cycles de mélangeage de de moulage par injection dans les conditions d’utilisation des polymères biosourcés. L’utilisation des mélanges chargés composés de polymères biosourcés ont permis d’améliorer l’homogénéité des composants injectés, mais ont engendré des défauts lors de l’étape de déliantage. Ces défauts ont pu être éliminés par l’utilisation de CO2 à l’état supercritique comme solvant du PEG. Ce dernier procédé a permis une diminution importante du temps de déliantage ainsi qu’une amélioration de la qualité des composants finaux. Les composants densifiés possèdent les propriétés mécaniques correspondantes à l’Inconel 718. / The works done during this PhD focuses on the study of the thermo-physical behavior of bio sourced polymer blends loaded with Inconel 718 powder (feedstock) to be shaped by the Metal Injection Molding process (MIM). First, a review of the researches related to the MIM process was conducted to identify innovative materials and processes that can improve the MIM process. Thus, the use of polyethylene glycol (PEG), selected for its properties of solubility in water, and bio sourced polymers, in order to reduce the environmental impact, were selected. The bio sourced polymers have been selected in accordance with the conditions of the injection molding process, and the choice was made to use polylactic acid (PLA) and polyhydroalkanoates (PHA and PHBV). Similarly, the supercritical CO2 as solvent was chosen to reduce the time of binder removal as well as increasing the quality of components produced. Thermo-physical, mechanical and rheological characterizations were made to determine the behavior of the different feedstock formulations. The results showed a degradation of the PEG and of the stearic acid under the conditions of use of the biopolymers, during the mixing and the injection stages. The use of feedstock made of bio sourced polymers have improved the homogeneity of the injected components, but they have generated defects during the debinding step. These defects have been eliminated by the use of CO2 in the supercritical state as solvent of the PEG. This method has significantly decrease the time of binder removal and improved the quality of the final components. Finally, densified components have the mechanical properties corresponding to Inconel 718.

Este trabalho visou investigar as interações entre enzimas e polímeros em solução e a adsorção das mesmas sobre superfícies sólidas e para isto foi dividido em duas partes distintas. Na primeira parte a influência do poli(etileno glicol) (PEG), polímero considerado inerte e utilizado em muitos processosbiotecnológicos, na atividade enzimática e na conformação estrutural de enzimas foi estudada através de medidas de espectrofotometria- UV, calorimetria e espalhamento de raio-X de baixo ângulo (SAXS). Foram escolhidas neste estudo as enzimas glicose-6-fosfato desidrogenase (G-6-PDH) e hexoquinase (HK), que são enzimas largamente aplicadas em análises clínicas na determinação de glicose no sangue, e também a enzima álcool desidrogenase (AD), utilizada para determinação de concentração de álcool. Foram obtidos resultados quantitativos, numa faixa de baixa concentração de enzima, que indicam uma forte influência de PEG na atividade das enzimas estudadas. Medidas de calorimetria revelaram que PEG interage não só com a enzima em estudo mas também com a coenzima NADP+. Numa faixa de concentração maior, os resultados de SAXS mostraram que PEG exerce também um efeito significativo no processo de agregação das enzimas. Acima de tudo, foi evidenciado neste estudo que PEG não pode ser tratado como um polímero inerte, pois ele interfere na atividade e conformação de enzimas. As enzimas são macromoléculas complexas e PEG interage de forma diferenciada com cada enzima, merecendo atenção especial caso a caso. Na segunda parte do trabalho, o estudo da adsorção de hexoquinase (HK) e creatina fosfoquinase (CPK) sobre lâminas de silício foi realizado através de medidas de ângulo de contato, elipsometria in situ e microscopia de força atômica (AFM) em água. A CPK é uma enzima bastante utilizada em kits de determinação de creatina no sangue e no diagnóstico de desordens musculares. Este trabalho revelou que o mecanismo de adsorção de CPK sobre silício depende fortemente do pH. Em pH 4, 7 ou 9 CPK adsorveu mantendo a mesma conformação que tinha em solução. Medidas de espectrofotometria UV-Vis revelaram uma mudança no pH ótimo para atividade enzimática de CPK de 6,8 para 9 após adsorção. A HK imobilizada em esferas de vidro mostrou atividade maior do que HK imobilizada nas placas. A reutilização das esferas e placas recobertas com HK foi testada e observou-se que as atividades das enzimas adsorvidas no substrato esférico foram mantidas. Entretanto, nas placas revestidas a atividade foi perdida. As enzimas imobilizadas sobre esferas puderam ser reutilizadas pelo menos 3 vezes, mantendo a atividade por um período de até 3 semanas. / This work aimed to investigate the interactions between enzymes and polymers in solution and also the adsorption behavior of these enzymes on solid surfaces. For that reason it was divided into two parts. In the first part, the influence of poly(ethylene glycol) (PEG), a polymer considered inert and utilized in several biotechnological processes, on the enzymatic activity and structure of the enzyme was studied by means of UV spectrophotometry, calorimetric titration, circular dichroism (CD) and small angle X-ray scattering (SAXS). Glucose-6-phosphate dehydrogenase (G-6-PDH) and hexokinase (HK) were chosen because of their large application in clinical analysis for determination of glucose in the blood strain. Alcohol dehydrogenase (AD), which is widely used to determine alcohol concentration in various samples, was also used. Quantitative results, in a low enzyme concentration range, indicated a strong influence of PEG on the enzymes activity. The calorimetric measurements revealed no favorable interactions between enzyme and polymer, but indicated favorable interactions between PEG and co-enzyme NADP+. In a higher concentration range, SAXS results showed that PEG also exerts a significant effect on the enzyme aggregation process. This work showed that PEG shall no longer be treated as an inert polymer since it interferes in the enzyme activity and structure. The enzymes are complex macromolecules and PEG interacts differently with each one, deserving special attention in each case. In the second part of the work, the adsorption behavior of creatine phosphokinase (CPK) and hexokinase (HK) onto silicon wafers was studied by means of contact angle measurements, in situ ellipsometry and atomic force microscopy (AFM) in water. CPK was chosen due to its large application on the diagnosis of several muscle disorders. This work revealed that the adsorption mechanism of CPK on silicon surfaces is strongly dependent on pH. At pH 4, 6.8 or 9, CPK adsorbed keeping the same conformation as in solution. pectrophotometric measurements revealed a shift on the optimum pH from 6,8 to 9 upon CPK adsorption. HK adsorbed onto glass beads showed higher activity than HK immobilized on silicon wafers. HK covered glass beads could also be reused three times and for a period of at least three weeks. In the contrary, HK covered silicon wafers could not be reused. For practical purposes, HK covered glass beads showed to be a better “biosensor" than HK covered silicon wafers.

O nimodipino é um bloqueador de canais de cálcio usado principalmente na terapia da hemorragia subaracnóidea e no tratamento de distúrbios cognitivos. É praticamente insolúvel em água e, pelo Sistema de Classificação Biofarmacêutica (SCB), é qualificado como classe II e, portanto, sua dissolução é etapa limitante da absorção, podendo apresentar problemas de biodisponibilidade. Assim, o objetivo do trabalho foi desenvolver e caracterizar dispersões sólidas de nimodipino, obtidas com os carreadores PEG 6000 ou Poloxamer 407 e compará-las quanto à melhoria na solubilidade e na dissolução do nimodipino. As dispersões sólidas foram obtidas pelos métodos de fusão e de evaporação do solvente e foram caracterizadas pelas técnicas de calorimetria exploratória diferencial (DSC), espectroscopia de absorção na região do infravermelho (FT-IR) e difração de raios-X, cujos resultados comprovaram a obtenção das dispersões sólidas. As características de solubilidade e de dissolução do nimodipino nas dispersões sólidas e em misturas físicas foram comparadas. As dispersões sólidas contendo poloxamer 407 apresentaram maior eficiência em melhorar a solubilidade e a velocidade de dissolução do nimodipino, o que pode ser explicado pelo seu efeito tensoativo. O aumento da solubilidade das dispersões sólidas preparadas com PEG (DSPEG-10 = 13,2 g.mL-1) foi significativamente maior que aquele devido às misturas físicas de mesma composição (MFPEG-10 = 3,21 g.mL-1) que, por sua vez, apresentaram solubilidade maior que a do fármaco (2,19 g.mL-1). O mesmo ocorreu com a eficiência de dissolução dessas preparações (DSPEG-10 = 69,11% , MFPEG-10 = 15,61% e nimodipino = 11,68%). Maior incremento da solubilidade foi obtido com a dispersão sólida produzida pelo método de evaporação do solvente contendo poloxamer 407 como carreador (SOLVP407-10 = 75,61 g.mL-1). / Nimodipine is a calcium blocker, used in prevention and treatment of ischaemic neurological deficits after aneurismal subarachnoid hemorrhage and cognitive deficit. It exhibits a low solubility in water and it is classified as class two in the Biopharmaceutics Classification System (BCS), thereby dissolution is the ratelimiting step in absorption, which impact on bioavailability. Consequently, the objective of this study was to develop and characterize solid dispersions of nimodipine, prepared with PEG 6000 or Poloxamer 407 and to compare them in terms of nimodipine solubility and dissolution. Solid dispersions were obtained by fusion and solvent methods and they were characterized by differential scanning calorimetry (DSC), infra red spectroscopy (FT-IR) and X-ray diffraction, where results confirmed the formation of solid dispersions. Solubility and dissolution characteristics of nimodipine in solid dispersions and physical mixtures were compared. Solid dispersions containing poloxamer 407 showed better efficiency than PEG in increasing solubility and dissolution rate of nimodipine, and it can be explained due to its surfactant activity. The solubility results obtained with solid dispersions prepared with PEG 6000 (DSPEG-10 = 13,2 g.mL-1) were better than physical mixtures with the same composition (MFPEG-10 = 3,21 g.mL-1) which, in turn, showed increased solubility compared with nimodipine (2,19 g.mL-1). Similar results were observed for dissolution efficiency (DSPEG-10 = 69,11% , MFPEG-10 = 15,61% and nimodipine = 11,68%). The best solubility result was obtained by the formulation prepared by the solvent method with poloxamer 407 as carrier (SOLVP407-10 = 75,61 g.mL-1).