The presence of Ca(OH)2 (or free lime) in lime mud can cause many problems in the recovery process of kraft pulp mills. Conventional free lime analyses require extensive laboratory work and give inconsistent results. A systematic study was performed to determine if zeta potential, a quickly measurable dispersion characteristic, can be used to indicate the presence of free lime in the recovery process. Measurements were made on synthetic wet lime mud to simulate samples collected after the white liquor clarifier in pulp mills. The results show that zeta potential increases from negative to positive when the free lime content in the lime mud exceeds a critical threshold. This change from negative to positive zeta potential of the lime mud slurry can be used as a basis for developing an on-line monitoring system that effectively detects free lime in the lime mud in order to avoid problems associated with overliming in the recovery process.

Made available in DSpace on 2014-12-17T15:41:55Z (GMT). No. of bitstreams: 1 IdyllaST_DISSERT.pdf: 1649846 bytes, checksum: b16782ef605bdc7a1d3225b281a6f2b3 (MD5) Previous issue date: 2011-11-08 / Chitosan nanoparticles have been used in several systems for the controlled release of drugs. The aim of this study was to obtain and characterize chitosan nanoparticles prepared by the method of coacervation / precipitation using sodium sulfate at different concentrations as the crosslinking agent. The characterization was done using zeta potential and small angle Xray scattering, SAXS. The dispersions of chitosan were obtained at pH 1 and pH = 3. The results of zeta potential at pH = 1 ranged from +64.8 to +29.27 mV and for pH = 3 they varied from +72.4 to +23.48 mV, indicating that the chain of chitosan is positively charged in acidic pH and the behavior of nanoparticles in terms of surface charge was independent of pH. However, the results indicated a dependence of particle size in relation to pH. This difference in behavior was explained by the influence of enthalpic and entropic components / Nanopart?culas de quitosana t?m sido utilizadas em v?rios sistemas destinados a libera??o controlada de f?rmacos. O objetivo desse trabalho foi a obten??o e caracteriza??o de nanopart?culas de quitosana atrav?s do m?todo de coacerva??o/precipita??o utilizando o sulfato de s?dio em diferentes concentra??es como agente reticulante. A caracteriza??o foi feita utilizando potencial zeta e espalhamento de pequenos ?ngulos, SAXS. As dispers?es de quitosana foram obtidas a pH=1 e pH=3. Os resultados do potencial zeta variaram no pH = 1 de +64,8 a +29,27 mV e no pH = 3 de +72,4 a +23,48 mV, indicando que a cadeia de quitosana fica carregada positivamente em pH ?cido e que comportamento das nanopart?culas em termos de carga superficial foi independente do pH. Entretanto, os resultados indicaram depend?ncia do tamanho de part?cula em rela??o ao pH. Essa diferen?a em termos de comportamento foi explicada pela influ?ncia dos componentes ent?lpicos e entr?picos

Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2007.

In the past three decades, a new group of concrete admixtures, termed &ldquo / superplasticizers&rdquo / , were introduced to the concrete industry. They have gained wide acceptance because of their many advantages. The addition of superplasticizers to concrete improves the workability and strength of concrete. In this study, the effect of the chemical structure of poly (4-styrenesulfonic acid-co-maleic acid) sodium salt (SSAMA), which contains both sulfonic and carboxylic acid groups, which is a new superplasticizer, was analyzed. Two different molecular weights of PEG (polyethylene glycol monomethyl ether) were grafted to this water-soluble copolymer at different weight compositions. The structures of synthesized copolymers were verified by FTIR and NMR analyses. The molecular weight difference of the grafted copolymers with different side chain lengths was determined by dilute solution viscosimetry. The effects of chemical structure of grafted copolymers on the fluidity of cement paste and the mechanical properties of the mortars were investigated. The zeta potential measurements revealed the interactions between the cement particles and polycarboxylate type superplasticizers. The maximum fluidity was achieved for the PEG grafted copolymer with the weight ratio 3:3. The mechanical properties of this copolymer showed the highest flexural and compressive strength compared to other copolymers. The addition of various Li salts to SSAMA affected the ionic medium, therefore, the dispersion performance of cement paste and the mechanical properties of the mortars improved. The mixture of LiCl: SSAMA in 1:1 mol ratio exhibited the maximum fluidity compared to other Li salts and their compositions. This mixture gave the highest flexural strength but the mixture of Li2CO3 in 1:1 composition gave the highest compressive strength in each salt mixtures.

In recent years the application of single-molecule techniques to probe biomolecules and intermolecular interactions at single-molecule resolution has expanded rapidly. Here, I investigate a series of peptides and proteins in an attempt to gain a better understanding of nanopore sensing as a single-molecule technique. The analysis of retro, inversed, and retro-inversed isomers of glucagon and α-helical Fmoc-D2A10K2 peptide showed that nanopore sensing utilizing a wild-type α-hemolysin pore can distinguish between all four isomers while circular dichroism can only distinguish between chiral isomers, but not between directional isomers. The investigation of a series of proteins of different chemical and physical properties revealed important information about nanopore analysis of proteins. Contrary to some reports in the literature, all proteins analysed here induced large blockade events. The frequency of total events and the proportion of large blockade events were significantly reduced in tris(hydroxymethyl)aminomethane or 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid buffers and were only restored by the addition of ethylenediaminetetraacetic acid or the use of phosphate buffer, both of which can sequester metal ions. Furthermore, the results obtained with the proteins in the presence of ligands demonstrated that transient or partial unfolding of proteins can be detected by nanopore analysis confirming the usefulness of this technique for conformational studies or for protein/ligand interactions. Interestingly, while the blockade current histograms were different for each protein there was no obvious correlation between the properties of the proteins and the blockade current histograms. In an attempt to identify whether the large blockade events were translocation or intercalation, both an indirect and a direct approach were taken. The indirect approach which relies on the effect of voltage on the interaction of the molecule with the pore provided no conclusive answer to the question of protein translocation through the α-hemolysin pore. In contrast, the direct approach in which ribonuclease A is added to the cis side of the pore and then the trans side is tested for enzyme activity showed that ribonuclease A doesn't translocate through the α-hemolysin pore.

Pheroid is a patented system comprising of a unique submicron emulsion type formulation. Pheroid vesicles consist mainly of plant and essential fatty acids and can entrap, transport and deliver pharmacologically active compounds and other useful molecules. The aim of this study was to show that a modulation of components and parameters is necessary to obtain the optimum formula to be used in pharmaceutical preparations. Non-optimal or non-predictable stability properties of emulsions can be limiting for the applications of emulsions (Bjerregaard et al., 2001:23). Careful consideration was given to the apparatus used during the processing along with the ratios of the various components added to the formulation and the storage conditions of the Pheroid vesicles. A preliminary study was performed to optimize the most accurate processing parameters during emulsification. The effect of emulsification rate and time, the temperature of the aqueous phase, the number of days the water phase were gassed, the concentration of the surfactant, cremophor® RH 40, used and the concentration of Vitamin F Ethyl Ester CLR added to the oil phase of the o/w emulsion has been studied. Quantification of the mean particle size, zeta potential, turbidity, pH and current values were used to characterize the emulsions. The samples were characterised after 1, 2, 3, 7, 14, 21 and 28 days of storage. The emulsions were also characterised with confocal laser scanning microscopy (CLSM) to measure the number and size and size distribution of the vesicles. After determination of the processing variables influencing the emulsion stability an accelerated stability test was conducted on a final formula. In the present study, accelerated stability testing employing elevated temperatures and relative humidity were used with good accuracy to predict long-term stability of an o/w emulsion kept at both 5 and 25 OC with 60 % relative humidity and 40 OC with 75 % relative humidity. The results of the stability tests were presented in histograms of the physical properties 24 hours, 1 month, 2 months and 3 months after preparation of the emulsion. It was concluded that Pheroid vesicles demonstrate much potential as a drug delivery system. The high stability of this formula allows its use in a wide variety of applications in the pharmaceutical industry. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2007.

Pheroid is a patented system comprising of a unique submicron emulsion type formulation. Pheroid vesicles consist mainly of plant and essential fatty acids and can entrap, transport and deliver pharmacologically active compounds and other useful molecules. The aim of this study was to show that a modulation of components and parameters is necessary to obtain the optimum formula to be used in pharmaceutical preparations. Non-optimal or non-predictable stability properties of emulsions can be limiting for the applications of emulsions (Bjerregaard et al., 2001:23). Careful consideration was given to the apparatus used during the processing along with the ratios of the various components added to the formulation and the storage conditions of the Pheroid vesicles. A preliminary study was performed to optimize the most accurate processing parameters during emulsification. The effect of emulsification rate and time, the temperature of the aqueous phase, the number of days the water phase were gassed, the concentration of the surfactant, cremophor® RH 40, used and the concentration of Vitamin F Ethyl Ester CLR added to the oil phase of the o/w emulsion has been studied. Quantification of the mean particle size, zeta potential, turbidity, pH and current values were used to characterize the emulsions. The samples were characterised after 1, 2, 3, 7, 14, 21 and 28 days of storage. The emulsions were also characterised with confocal laser scanning microscopy (CLSM) to measure the number and size and size distribution of the vesicles. After determination of the processing variables influencing the emulsion stability an accelerated stability test was conducted on a final formula. In the present study, accelerated stability testing employing elevated temperatures and relative humidity were used with good accuracy to predict long-term stability of an o/w emulsion kept at both 5 and 25 OC with 60 % relative humidity and 40 OC with 75 % relative humidity. The results of the stability tests were presented in histograms of the physical properties 24 hours, 1 month, 2 months and 3 months after preparation of the emulsion. It was concluded that Pheroid vesicles demonstrate much potential as a drug delivery system. The high stability of this formula allows its use in a wide variety of applications in the pharmaceutical industry. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2007.

Made available in DSpace on 2015-05-14T12:56:03Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2756793 bytes, checksum: 52c334e99949464b4e3237ddf1e202c6 (MD5) Previous issue date: 2014-02-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The transport of materials through the tooth enamel is conventionally derived from the diffusion process, which leads to a number of limitations, because the pores of the enamel are extremely small, requiring a certain extension, as occurs in adhesive techniques by the etching process. An alternative method to this technique is the electrokinetic flow (EKF), which promotes the unidirectional flow of substances through the pores of the enamel by applying an external electric field. Based on this premise it was promoted the infiltration of a composite resin with low viscosity (Icon DMG, Hamburg, Germany) on the surface of 20 extracted human teeth by EKF, using an electric field (1.5V) in two stages: (1) infiltration of potassium chloride 0.1M (KCl) during 3h and (2) infiltration of the resin during 2h. Longitudinal histological sections of &#8776; 100&#956;m were analyzed by fluorescence microscopy and polarized light microscopy associated with the "polscopesingle"system, after 24h of dehydration and along 50, 100, 150, 200, 250, 300, 350, 400, 450 and 500&#956;m deep. Electric voltage (&#956;A) presented to be positive during infiltration. Images from Fluorescence Microscopy revealed fluorescence of the infiltrated enamel areas for all samples, from the surface to the dentin-enamel junction (DEJ), indicating the formation of a hybrid layer with average depth of 1627.66 &#956;m and a standard deviation of 284.20 &#956;m. The records of the phase delay during dehydration of the infiltrated and non-infiltrated areas did not present changes in the infiltrated area. It was observed that the water was replaced by the resin (p<0.000001), with high effect size (>0.8). Based on these results, it was concluded that the EKF resulted in infiltration of the resin into the enamel nanochannels. / O transporte de materiais através do esmalte dentário é limitado já que convencionalmente depende do processo de difusão, em virtude do volume nanométrico dos poros do esmalte. Um método alternativo pode ser o uso do Fluxo Eletrocinético (FEC), que promove o fluxo unidirecional de substâncias através dos poros do esmalte pela aplicação de um campo elétrico externo. Por conseguinte, este estudo promoveu a infiltração de resina fluida na superfície de 20 dentes humanos extraídos através do FEC, utilizando um campo elétrico de 1,5 volt em duas etapas: (1) infiltração de Cloreto de Potássio (KCl) 0,1M por 3h (2) infiltração da resina Icon (DMG, Alemanha) por 2h. Cortes histológicos por desgaste com &#8776; 100&#956;m foram analisados por Microscopia de Fluorescência (MF) e por Microscopia de Luz Polarizada (MLP) associada ao sistema single polscope , durante a desidratação das amostras por um período de 24h e analisando pontos histológicos a 50, 100, 150, 200, 250, 300, 350, 400, 450 e 500&#956;m a partir da superfície de áreas infiltradas e não infiltradas. A variação da corrente elétrica (mA) mostrou-se positiva durante a infiltração. As imagens da MF demonstraram fluorescência do esmalte na região infiltrada desde a superfície até a junção amelo-dentinária (JAD), indicando a formação de uma camada híbrida com profundidade média de 1627,66 &#956;m e desvio padrão de 284,20 &#956;m. Comportamentos distintos foram identificados para as áreas infiltrada e não infiltrada durante a desidratação. A área não infiltrada perdeu água, conforme verificado através da redução do retardo de fase. A área infiltrada não perdeu água, uma vez que o retardo manteve-se constante, sugerindo que a água fracamente aderida foi substituída pela resina durante a infiltração. As diferenças estatísticas entre os pontos histológicos das duas áreas foram calculadas através do teste de Mann-Whitney, com nível de significância de 5%, confirmando que a água foi substituída pela resina (p< 0,000001), com alta magnitude do efeito (>0,8). Portanto, pode-se concluir que a utilização do FEC resultou na infiltração da resina nos nanocanais do esmalte, formando camada híbrida de grande profundidade.

Thesis is indirectly connected to many years of research in field of sulphate binders. Work is focused on modifying of properties of alfa and beta gypsum, mainly on reduction of water ratio. We monitored effect of addition of chloride salts, carbonates and sulphates on zeta potential and its measurement. Part of thesis is also focused on laboratory production of beta plaster from secondary materials and optimization of grinding process to achieve required criteria.

Charles University Faculty of Pharmacy in Hradcec Králové Department of Pharmaceutical Technology Supervisor: doc. RNDr. Milan Dittrich, CSc. Student: Simona Medviďová Title of thesis: Formulation and testing of branched polyesters siRNA-loaded nanoparticles The progression of development increases demand for new and more effective drug systems formulations. This diploma thesis is focused on the preparation of nanoparticles from biodegradable branched polyesters based on PLGA, which are suitable for the transport of an oligonucleotide of a small interfering nucleic acid, siRNA. The theoretical part focuses on the characteristics of usable polymers, their possible modifications, the methods of preparation with closer look at the selected nanoprecipitation method, the important parameters such as particles size, zeta potential, and polydispersity. The main part is also characterization of siRNA in terms of structure, properties, modifications, and its function. A more extensive experimental part deals with the appropriate choice of type and concentration of polyester and stabilizer, methods of preparation and characterization of nanoparticles, and the possibility of analyzing encapsulated siRNA. Chapters results and discussion compares polyesters branched on tripentaerythritol, and polyacrylic acid...