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Froth flotation is the most efficient method for phosphate separation, which is a physic-chemical separation process based on the difference of surface properties between the valuable minerals and unwanted gangue minerals. However, the presence of clay slimes in the slurry after grinding consumes a large amount of reagents, decreases the collision probability between bubbles and minerals, prevents phosphate particle attachment to air bubbles, and thus considerably reduces flotation recovery and concentrate grade. Georgia Pacific Chemical, LLC has recently developed novel depressants, i.e., clay binders, which are a series of low molecular weight specialty polymers to help improve phosphate flotation performance by selectively agglomerating and depressing clay particles, thus lowering their surface area and reducing the adsorption of surfactants. This thesis addresses the effects of clay binders on phosphate flotation performance and their adsorption behavior on different minerals in a sedimentary phosphate ore. Quartz Crystal Microbalance with Dissipation technique (QCM-D) was used to study adsorption characteristics of clay binders and batch flotation tests were performed under different conditions to investigate phosphate flotation performance. The experimental results have shown that clay binders significantly improved phosphate flotation selectivity and reduced the dosages of collector and sodium silicate used as dispersant in the industry.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O isopulegol à um monoterpeno Ãlcool presente no Ãleo essencial de diversas plantas aromÃticas, e tem sido utilizado na manufatura de perfumes com composiÃÃes florais. No presente estudo, inicialmente, foi realizado um screenig farmacolÃgico de aÃÃo central para a investigaÃÃo de possÃveis alteraÃÃes comportamentais induzidas pelo isopulegol. Camundongos Swiss machos foram tratados com isopulegol (25 e 50 mg/kg) ou veÃculo (salina a 0,9% em Tween 0,3%) 30 (i.p.) ou 60 min (v.o.) antes dos experimentos. Flumazenil foi utilizado 15 min antes dos tratamentos com o intuito de investigar a participaÃÃo dos receptores GABAA/BZD nas aÃÃes do isopulegol. A concentraÃÃo de monoaminas e seus metabÃlitos foi tambÃm verificada em corpo estriado apÃs a administraÃÃo aguda de isopulegol. Os resultados dos testes do LCE e hole board sugerem que o isopulegol apresenta provÃvel efeito ansiolÃtico, o qual està relacionado, pelo menos em parte, à modulaÃÃo positiva dos receptores GABAA/BZP. Esse efeito nÃo foi acompanhado de aÃÃo sedativa em baixas doses, o que foi evidenciado pela ausÃncia de diminuiÃÃo de ALE no teste do campo aberto. Os parÃmetros observados no teste do nado forÃado, suspensÃo da cauda e tempo de sono induzido por pentobarbital sugerem que o isopulegol apresenta possÃvel efeito depressor do SNC. Os efeitos centrais observados foram corroborados por uma reduÃÃo na concentraÃÃo de DA e NA, mas nÃo de 5-HT. Com o objetivo de investigar o potencial anticonvulsivante do isopulegol, camundongos foram prÃ-tratados com isopulegol (25, 50, 100 e 200 mg/kg, i.p. ou v.o.) ou veÃculo antes de serem expostos ao modelo de convulsÃo induzida por PTZ (99 mg/kg, s.c.). A participaÃÃo dos receptores GABAA/BZD (utilizando a administraÃÃo prÃvia de flumazenil), bem como se uma possÃvel atividade antioxidante estaria envolvida nas aÃÃes anticonvulsivantes do isopulegol, foram tambÃm investigadas. O isopulegol (100 e 200 mg/kg) apresentou significante atividade anticonvulsivante e bioprotetora contra convulsÃes induzidas pelo PTZ. Nessas doses, a administraÃÃo de isopulegol induziu acentuado efeito sedativo (diminuiÃÃo da ALE em campo aberto). A aÃÃo anticonvulsivante observada foi, possivelmente, relacionada à modulaÃÃo dos receptores GABAA/BZP, uma vez que o prÃtratamento com flumazenil reverteu o prolongamento da latÃncia para as convulsÃes induzidas pelo isopulegol. Propriedades antioxidantes tambÃm foram relacionadas ao efeito anticonvulsivante, desde que o isopulegol preveniu a peroxidaÃÃo lipÃdica, preservou a atividade da catalase e reverteu a reduÃÃo do conteÃdo de GSH induzida pelo PTZ. Com o objetivo de investigar o potencial gastroprotetor do isopulegol em modelo de Ãlcera gÃstrica induzida por etanol e indometacina, os animais receberam isopulegol (25, 50, 100 e 200 mg/kg, v.o.) antes do etanol (0,2 mL, v.o.) ou indometacina (20 mg/kg, v.o.). Uma anÃlise histopatolÃgica de amostras dos estÃmagos foi realizada, bem como possÃveis mecanismos de aÃÃo foram tambÃm investigados. O isopulegol (100 e 200 mg/kg) apresentou significante efeito gastroprotetor em ambos os modelos de Ãlcera induzida por etanol e indometacina, aÃÃo esta corroborada pelo estudo histopatolÃgico. Observou-se que o prÃ-tratamento dos animais com indometacina e glibenclamida reverteu a gastroproteÃÃo induzida pelo isopulegol. O conteÃdo de GSH tambÃm foi preservado pela administraÃÃo prÃvia do isopulegol. Esses resultados sugerem que o efeito gastroprotetor do isopulegol parece ser mediado, pelo menos em parte, pelas prostaglandinas endÃgenas, pela abertura dos canais de KATP e por propriedades antioxidantes referentes ao aumento do conteÃdo de GSH. / Isopulegol is a monoterpene alcohol present in the essential oils of various plants, and has been used in the manufacture of fragrances with blossom compositions. In order to investigate its effects on animal models of CNS actions, isopulegol was administered to male Swiss mice at single doses of 25 and 50 mg/kg 30 (i.p.) or 60 min (p.o.) before the experiments. Control animals received vehicle (saline 0.9% in 0.3% Tween). For investigating the involvement of GABAA/BZP system, flumazenil was utilized 15 min before the treatments. Monoamines and their metabolites concentration were also investigated in striatum of mice after acute administration of isopulegol. The results in EMP and hole board tests suggest possible anxiolytic-like effects from isopulegol, which were reversed by flumazenil pretreatment, indicating probable positive modulation of benzodiazepine-sensitive GABAA receptors. The anxiolytic-like effects were not accompanied by sedation, as reduced locomotion was not observed in open field test. Parameters observed in the forced swimming, tail suspension and pentobarbital sleeping time tests support the idea that isopulegol possibly presents depressant activity on the CNS. The observed central effects were corroborated by DA and NE decreased levels (without changes in 5-HT levels). In order to verify whether isopulegol would be able to exert any protector effect in PTZ-induced convulsions, mice received isopulegol (25, 50, 100 and 200 mg/kg, i.p. or p.o.) or vehicle before PTZ (99 mg/kg, s.c.). The involvement of GABAA/BZP receptors was also investigated by flumazenil pretreatment. Also, it was evaluated whether antioxidant properties from isopulegol would be related to its possible anticonvulsant effect. Results showed that isopulegol (100 and 200 mg/kg) presented anticonvulsant and bioprotective effects against PTZ-induced convulsions. At 100 and 200 mg/kg doses, isopulegol induced marked sedative effect (decreased locomotion in open field test). Flumazenil pretreatment decreased the prolongation of convulsion latency induced by isopulegol, suggesting a possible involvement of direct activation of benzodiazepine site of GABAA. Isopulegol also significantly prevented PTZinduced increase in lipid peroxidation, preserved catalase activity in normal levels, and prevented the PTZ-induced loss of GSH in hippocampus of mice. In order to investigate whether isopulegol would be able to promote gastroprotective effects in ethanol- and indomethacin-induced gastric ulcer models, mice received isopulegol (25, 50, 100 and 200 mg/kg, p.o.) before ethanol (0.2 mL, p.o.) or indomethacin (20 mg/kg, p.o.). A histopathological assessment of stomachs was conducted, as well as possible mechanisms involved in gastroprotective action were also investigated. Isopulegol presented significant gastroprotective effect in both ethanol- and indomethacin-induced ulcer models. This effect was corroborated by the histopathological assay, which showed that pretreatment with isopulegol was able to inhibit the ethanol-induced microscopically alterations. The pretreatment with indomethacin and glibenclamide was able to reverse the gastroprotection induced by isopulegol. The PTZ-induced loss of GSH in stomachs and liver was also preserved by pretreatment with isopulegol. These results suggest that the gastroprotective effects induced by isopulegol appear to be mediated, at least in part, by endogenous prostaglandins, K+ATP channel opening and antioxidant proprieties related to GSH increased.

Submitted by Stéfany Moreira (stemellra@yahoo.com.br) on 2013-02-25T18:42:27Z No. of bitstreams: 1 DISSERTAÇÃO_EstudoDepressoresFlotação.pdf: 2366097 bytes, checksum: 9beeb25612b4624e59d30fb2c2743275 (MD5) / Approved for entry into archive by Neide Nativa (neide@sisbin.ufop.br) on 2013-02-27T15:01:23Z (GMT) No. of bitstreams: 1 DISSERTAÇÃO_EstudoDepressoresFlotação.pdf: 2366097 bytes, checksum: 9beeb25612b4624e59d30fb2c2743275 (MD5) / Made available in DSpace on 2013-02-27T15:01:23Z (GMT). No. of bitstreams: 1 DISSERTAÇÃO_EstudoDepressoresFlotação.pdf: 2366097 bytes, checksum: 9beeb25612b4624e59d30fb2c2743275 (MD5) Previous issue date: 2010 / Neste trabalho foram efetuados estudos de depressores na flotação de uma amostra de finos de minério sílico-carbonatado de manganês (estocados como rejeito) da Unidade Morro da Mina / RDM, localizada em Conselheiro Lafaiete-MG. Foram realizados testes de microflotação em tudo de Hallimond modificado, curvas de potencial zeta dos minerais puros na presença e ausência de reagentes e ensaios de flotação em bancada com amostra do resíduo do minério deslamado. Os reagentes estudados foram: fluorsilicato de sódio, metasilicato de sódio, amido de milho, dextrina branca e alguns tipos de quebracho (Floatans T0, T1, T5 e M3) utilizando-se oleato de sódio como coletor. A eficiência dos depressores testados na microflotação em relação à seletividade para a separação do quartzo dos minerais de manganês foi: floatan M3 > floatan T1> fluorsilicato de sódio > metassilicato de sódio > amido de milho > floatan T0 > dextrina > floatan T5. Os pontos isoelétricos dos principais minerais de Mn e ganga presentes neste minério foram determinados: rodonita (pH 2,8), rodocrosita (pH 10,5) e quartzo (pH 1,8). O estudo da adsorção que caracteriza a interação dos reagentes com as superfícies dos minerais mostrou ser de caráter específico. Os depressores mais eficientes na flotação em bancada entre os minerais de Mn e de ganga foram: floatan M3, floatan T1 e fluorsilicato de sódio, onde foram obtidos concentrados com teores de Mn, SiO2 e Al2O3 de aproximadamente 30, 17 e 10 %, respectivamente, para os três depressores testados. No entanto, a recuperação metalúrgica de Mn foi de 72,5 % para o floatan M3, 51 % para o floatan T1 e 45,2 % para o fluorsilicato de sódio. Posteriormente, efetuaram-se estudos preliminares de calcinação desse minério deslamado. O mais alto teor de Mn encontrado foi de aproximadamente 30 % com perda de massa de 11,2 % para temperatura de 1000 °C. ____________________________________________________________________________________________________ / ABSTRACT: Flotation depressants were studied from silicate-carbonate manganese ore samples (waste) at RDM – Morro da Mina, in Conselheiro Lafaiete – MG, Brazil. Micro-flotation tests were conducted in a modified Hallimond cell, also zeta potential curves for pure minerals in the presence or lack of reagents and bench-scale flotation tests for deslimed ore waste sample. The following reagents were studied: sodium fluorosilicate, waterglass, starch, white dextrin, some quebracho kinds (Floatans T0, T1, T5 e M3) and sodium oleate as a collector. The efficiency of the depressants during the micro-flotation regarding the selection for separation of quartzo from manganese mineral was as it follows: floatan M3> floatan T1> sodium fluorosilicate > waterglass > starch > floatan T0 > dextrin > floatan T5. The isolectric points (pl) of the main ore were also determined as rhodonite (pH 2.8), rhodochrosite (pH 10.5) and quartz (pH 1.8). The adsorption test, characterized by the interaction of reagents and mineral surfaces, indicates its specific nature. The most efficient depressants in bench-scale flotation test among Mn ore and ganga were floatan M3, floatan T1 and sodium fluorosilicate containing Mn, SiO2 and Al2O3 concentrations of approximately 30, 17 and 10%, respectively, for all depressants herein mentioned. However, the metallurgical recovery for Mn was 72,5 % when using floatan M3, 51 % for floatan T1 and 45,2% for sodium fluorosilicate. Furthermore, calcination preliminary studies were conducted and the highest concentration of Mn found was approximately 30%, with an 11.2% weight loss for a 1000°C temperature.

In the heart, the existence of an electrical memory was firstly reported by Rosenbaum et al. (1982), but Rios et al. (1975) and Garcia Moreira (1977) were those that firstly described the existence of contractile memories in the amphibian myocardium. These authors developed a mathematical model for representing such phenomenon. In the present study, we aimed to characterize two kinds of contractile memories occurring in the mammalian myocardium. One of them, depresses the tissue (the depressant memory, DM) and the other one acts by stimulating it (the excitatory memory, EM). The pivotal rationale guiding this work was: when the heart is challenged by changing the environment sources like nutrients, chemicals, temperature, etc., its behavior changes in order to optimize the energy expenditure associated with its contractility. This adaptation process allows to be reached a new state of dynamic equilibrium. In order to express such behavior, the tissue creates contractile memories for adjusting the amplitude of myocardial forces. This is provided by balancing the load of DM and EM available at each myocardial beat. The expression and accumulation of these memories were studied in the guinea pig atria submitted to the experimental protocols described previously by Seed & Walker (1988), Shimizu (2000), and Conde-Garcia (not published). The expression and accumulation of myocardial memories were described by employing two static descriptors, LODMmax and LOEMmax. They stand for the maximum load of depressant memory and the maximum load of excitatory memory, respectively. Furthermore, another pair of dynamic descriptors was also used to measure the maximum rate of erasing of the depressant memory (MREDM) and the other one to measure the maximum rate of erasing of the excitatory memory (MREEM). The static descriptors represent the transference of load of both memories but the dynamic descriptors were related to the rate of erasing of such memories. Our results brought us onto the following conclusions: 1. contractile memories are a phenomenon apart from the electrical memory because rising the external potassium from 2.7 to 7.0 mM did not modify (n n = 4) LODMmax that changed from 82,09 ± 1,58 to 81,56 ± 2,01% (p > 0,05), LOEMmax from 83,36 ± 0,56 to 90,12 ± 17,92% (p > 0,05), MREDM changed from -1,36 ± 0,67 to -1,13 ± 0,42gf/s (p > 0,05), and MREED from -2,09 ± 1,65 to -1,56 ± 1,41gf/s (p > 0,05). 2. However, the expression and accumulation of DM and EM are affected by the intracellular calcium transient. The increase of extracellular calcium from 1,37 to 5,47mM (n = 3) reduced LODMmax: from 87,56 ± 2,33 to 63,83 ± 3,78% (p < 0,05); LOEMmax from 84,36 ± 0,54 to 13,91 ± 0,11% (p < 0,05); MREDM from -2,58 ± 0,71 to -1,20 ± 0,37gf/s (p < 0,05) and MREEM from -0,90 ± 0,13 to -0,34 ± 0,05 gf/s (p < 0,05). Adding 5mM cafeine to the bath solution also reduced LODMmax from 79,88 ± 3,48 to 56,68 ± 6,62% (p < 0,05); LOEMmax from 77,14 ± 1,02 to 28,54 ± 2,11% (p < 0,05); MREDM from -1,78 ± 0,50 to -0,60 ± 0,10 gf/s (p < 0,05), and MREED from -1,74 ± 0,64 to -0,33 ± 0,14 gf/s (p < 0,05); 3. In the experimental condition employed in this work, a given beat receives both depressant and excitatory information built by the last ten beats. / A capacidade de o miocárdio memorizar foi estudada inicialmente por Rosenbaum (1982), que, entre outros, relataram uma memória elétrica no coração. Todavia, Rios e cols. (1975) e Moreira (1977) foram os primeiros a descrever a existência de memória contrátil no miocárdio de anfíbio. Eles propuseram um modelo matemático para representar esse fenômeno. A nossa proposta, contudo, visou caracterizar dois tipos de memórias contráteis. Uma delas inibe o inotropismo (memória depressora, MD) e a outra, o estimula (memória excitadora, ME). A hipótese central deste trabalho propõe que, quando o coração é desafiado por um novo ambiente (nutrientes, químicos, pH etc.), ele redefine sua atividade contrátil para que possa alcançar um novo estado de equilíbrio. Para expressar tal comportamento, o miocárdio cria memórias, visando ajustar a amplitude das forças geradas. Isto se dá por meio do balanço entre a carga de MD e de ME de cada batimento. Neste trabalho, a expressão e a acumulação destas memórias foram estudadas em átrio de cobaia, utilizando-se dois descritores para cada uma delas um estático, o IKMDmax e IKMEmax, que representam o incremento máximo de carga de MD e ME, respectivamente, e outro dinâmico VmedAMD e VmedAME - que está associado à velocidade de apagamento de cada memórias. As preparações foram ensaiadas com diferentes protocolos experimentais como os descritos por Seed & Walker (1988), Shimizu, et al. (2000) e Conde-Garcia (não publicado). Os resultados mostraram que a memória contrátil difere do fenômeno relativo à memória elétrica do miocárdio, porque, elevando-se o potássio externo de 2,7 para 7,0 mM, não houve variação significativa dos descritores, pois, para n = 3, o IKMDmax passou de 82,09 ± 1,58 para 81,56 ± 2,01% (p > 0,05), o IKMEmax passou de 83,36 ± 0,56 para 90,12 ± 17,92% (p > 0,05), a VmedAMD variou de -1,36 ± 0,67 para -1,13 ± 0,42gf/s (p > 0,05) e a VmedME foi alterada de -2,09 ± 1,65 para -1,56 ± 1,41gf/s (p > 0,05). A expressão e a acumulação das memórias são fenômenos que dependem do transiente intracelular de cálcio nas células miocárdicas. A elevação do cálcio extracelular de 1,37 para 5,47mM, para n = 3, alterou o IKMDmax: de 87,56 ± 2,33 para 63,83 ± 3,78% (p < 0,05); IKMEmax: 84,36 ± 0,54 para 13,91 ± 0,11% (p < 0,05); VmedAMD: -2,58 ± 0,71 para -1,20 ± 0,37gf/s (p < 0,05) e VmedME: -0,90 ± 0,13 para -0,34 ± 0,05 gf/s (p < 0,05). A adição de 5mM de cafeína à solução controle do banho fez o IKMDmax variar de 79,88 ± 3,48 para 56,68 ± 6,62% (p < 0,05); o IKMEmax de 77,14 ± 1,02 para 28,54 ± 2,11% (p < 0,05); a VmedAMD de -1,78 ± 0,50 para -0,60 ± 0,10 gf/s (p < 0,05) e a VmedME -1,74 ± 0,64 para -0,33 ± 0,14 gf/s (p < 0,05). Nas condições experimentais deste estudo, uma dada contração recebe informações depressoras e excitadoras que foram geradas pelos últimos dez batimentos.

The hydrophobicity of a surface is an important property in many areas of science and engineering. This is especially the case in mineral processing, where differences in surface hydrophobicity lie at the heart of the separation process of flotation. Chemicals are used to increase and decrease the natural hydrophobicity of minerals to attain a better separation between valuable and worthless material. Polymers are often used to reduce mineral surface hydrophobicity. Decades of empirically based decision making have produced a list of effective depressants. However the detailed study of how these polymer depressants affect surface hydrophobicity and mineral recovery lags behind applied investigations. The aim of this thesis was to study the adsorption of commonly used depressants on model surfaces and to interrogate the action of these polymers in reducing surface hydrophobicity. We have modelled the degree of hydrophobicity of common minerals in order to study polymer depressants with methods not commonly used in studies of surface characterisation in flotation. The model surfaces (self-assembled monolayers, SAMs) allowed us to use the quartz crystal microbalance with dissipation monitoring (QCM-D) to study the adsorption of polymers. The QCM-D can be used to obtain adsorption isotherms, adsorption kinetics, water content of adsorbed layers, and information on the conformation of the adsorbed polymer. The results from the QCM-D were correlated with the contact angle data from the captive bubble measurements, with which we assessed the hydrophobicity of the surface before and after polymer adsorption. Three of the polymers layers were probed with dynamic dewetting studies, in order to test other modes of depressant action. Three types of polymers were studied - a polyacrylamide (Polymer-H), a polyelectrolyte CMC (carboxymethyl cellulose) and a group of dextrins (Dextrin-TY, a phenyl succinate substituted dextrin (PS Dextrin) and a styrene oxide substituted dextrin (SO Dextrin)). These polymers are commonly used or have potential to be used in the depression of talc and graphite. Polymer-H was used to investigate the hydrophobic bonding between a non-ionic polymer depressant and chemically inert and non charged surfaces by probing the influence of substrate hydrophobicity on polymer adsorption and reduction of contact angle. Three different model surfaces were used (mixed self-assembled 0.5 SAM, 0.7 SAM or single self-assembled 1.0 SAM monolayers) with advancing contact angles between 75?? and 119??. The study of Polymer-H found that the substrate hydrophobicity is an important factor in adsorption of this polymer and the change in contact angle upon adsorption depends on adsorbed amount. The effectiveness of Polymer-H to reduce surface hydrophobicity was established to correlate with its conformation and morphology. CMC was investigated to find out how a stimulus responsive polymer depressant can be used in flotation. It was established that the adsorbed amount and rate of adsorption of CMC increase with decreasing of pH or increasing of ionic strength. It was shown that the surface hydrophobicity of a CMC pre-adsorbed layer changes with the environment and these alterations are fully reversible. A switch of ionic strength (from 10-2 M KCl to 10-1 M KCl) caused partial dehydration of the adsorbed layer and a decrease of the receding contact angle by 20??. A pH switch (pH = 9 to pH = 3) resulted in a 40?? change in receding contact angle. The CMC investigation showed that the use of a stimulus responsive polymer presents opportunities for exploiting solution conditions as a means to effect a better mineral separation in flotation The adsorption of three dextrin-based polymers on a model hydrophobic surface has been characterized using the quartz crystal microbalance with dissipation monitoring (QCM-D). The three polymers (one standard dextrin and two dextrins with different aromatic group substitutions) exhibited varying affinities and capacity for adsorption on the hydrophobic substrate. The effect of the three polymers on the static contact angle of the surface was studied using captive bubble contact angle measurements. The three polymers were seen to reduce the receding contact angle by similar amounts (approximately 14 degrees) in spite of having varying adsorbed amounts and differences in adsorbed layer water content. Although no differences were observed in the ability of the polymers to reduce the static contact angle, measurements of the dewetting dynamics between a rising air bubble and the polymer covered substrate yielded stark differences between the polymers, with one polymer slowing the dewetting dynamics by an order of magnitude more than the other two polymers. The differences in dewetting behaviour correlate with the adsorbed layer characteristics determined by QCM-D. / Thesis (PhD)--University of South Australia, 2010

The hydrophobicity of a surface is an important property in many areas of science and engineering. This is especially the case in mineral processing, where differences in surface hydrophobicity lie at the heart of the separation process of flotation. Chemicals are used to increase and decrease the natural hydrophobicity of minerals to attain a better separation between valuable and worthless material. Polymers are often used to reduce mineral surface hydrophobicity. Decades of empirically based decision making have produced a list of effective depressants. However the detailed study of how these polymer depressants affect surface hydrophobicity and mineral recovery lags behind applied investigations. The aim of this thesis was to study the adsorption of commonly used depressants on model surfaces and to interrogate the action of these polymers in reducing surface hydrophobicity. We have modelled the degree of hydrophobicity of common minerals in order to study polymer depressants with methods not commonly used in studies of surface characterisation in flotation. The model surfaces (self-assembled monolayers, SAMs) allowed us to use the quartz crystal microbalance with dissipation monitoring (QCM-D) to study the adsorption of polymers. The QCM-D can be used to obtain adsorption isotherms, adsorption kinetics, water content of adsorbed layers, and information on the conformation of the adsorbed polymer. The results from the QCM-D were correlated with the contact angle data from the captive bubble measurements, with which we assessed the hydrophobicity of the surface before and after polymer adsorption. Three of the polymers layers were probed with dynamic dewetting studies, in order to test other modes of depressant action. Three types of polymers were studied - a polyacrylamide (Polymer-H), a polyelectrolyte CMC (carboxymethyl cellulose) and a group of dextrins (Dextrin-TY, a phenyl succinate substituted dextrin (PS Dextrin) and a styrene oxide substituted dextrin (SO Dextrin)). These polymers are commonly used or have potential to be used in the depression of talc and graphite. Polymer-H was used to investigate the hydrophobic bonding between a non-ionic polymer depressant and chemically inert and non charged surfaces by probing the influence of substrate hydrophobicity on polymer adsorption and reduction of contact angle. Three different model surfaces were used (mixed self-assembled 0.5 SAM, 0.7 SAM or single self-assembled 1.0 SAM monolayers) with advancing contact angles between 75?? and 119??. The study of Polymer-H found that the substrate hydrophobicity is an important factor in adsorption of this polymer and the change in contact angle upon adsorption depends on adsorbed amount. The effectiveness of Polymer-H to reduce surface hydrophobicity was established to correlate with its conformation and morphology. CMC was investigated to find out how a stimulus responsive polymer depressant can be used in flotation. It was established that the adsorbed amount and rate of adsorption of CMC increase with decreasing of pH or increasing of ionic strength. It was shown that the surface hydrophobicity of a CMC pre-adsorbed layer changes with the environment and these alterations are fully reversible. A switch of ionic strength (from 10-2 M KCl to 10-1 M KCl) caused partial dehydration of the adsorbed layer and a decrease of the receding contact angle by 20??. A pH switch (pH = 9 to pH = 3) resulted in a 40?? change in receding contact angle. The CMC investigation showed that the use of a stimulus responsive polymer presents opportunities for exploiting solution conditions as a means to effect a better mineral separation in flotation The adsorption of three dextrin-based polymers on a model hydrophobic surface has been characterized using the quartz crystal microbalance with dissipation monitoring (QCM-D). The three polymers (one standard dextrin and two dextrins with different aromatic group substitutions) exhibited varying affinities and capacity for adsorption on the hydrophobic substrate. The effect of the three polymers on the static contact angle of the surface was studied using captive bubble contact angle measurements. The three polymers were seen to reduce the receding contact angle by similar amounts (approximately 14 degrees) in spite of having varying adsorbed amounts and differences in adsorbed layer water content. Although no differences were observed in the ability of the polymers to reduce the static contact angle, measurements of the dewetting dynamics between a rising air bubble and the polymer covered substrate yielded stark differences between the polymers, with one polymer slowing the dewetting dynamics by an order of magnitude more than the other two polymers. The differences in dewetting behaviour correlate with the adsorbed layer characteristics determined by QCM-D. / Thesis (PhD)--University of South Australia, 2010

Mise en contexte : Le décès neurologique correspond à la perte permanente des fonctions cérébrales. La validité de son diagnostic repose sur des conditions préalables et l’exclusion des facteurs confondants. L’objectif du mémoire est d’investiguer le rôle potentiellement confondant des médicaments sédatifs et analgésiques (MSA) sur le diagnostic de décès neurologique (DDN). Méthodes : 1) Nous avons réalisé une étude de la portée des recommandations mondiales s’intéressant au rôle des médicaments sédatifs et analgésiques lors du diagnostic de décès neurologique. Nous avons extrait les informations pertinentes à nos questions et les références qui les soutiennent. 2) Nous avons réalisé une étude transversale (étude Pinkie) nichée dans la cohorte INDex « CT-Perfusion for neurological diagnostic evaluation: a prospective Canadian multicenter diagnostic test study ». Nous avons comparé les concentrations plasmatiques de MSA lors du DDN et investigué l’association statistique entre MSA et DDN. Résultats : 1) La revue de la portée a démontré la variabilité des recommandations dans le domaine et le peu de preuves qui les soutiennent. Néanmoins, 67% des recommandations suggéraient de doser les MSA lors du DDN. 2) Nous avons observé dans l’étude Pinkie que les concentrations plasmatiques de MSA sont faibles et qu’elles ne sont pas associées à la probabilité de déclarer un patient en décès neurologique. Conclusion : Dans le cadre d’un diagnostic de décès neurologique effectué selon les guides de pratique au Canada, les médicaments sédatifs et analgésiques ne sont pas associés à la probabilité de diagnostic de décès neurologique. / Background: Neurological death is defined by the permanent loss of cerebral function. The validity of its diagnosis relies on prerequisite conditions and the exclusion of confounding factors. The goal of this work is to investigate the potential confounding role of sedatives and analgesics drugs (SAD) on the neurological death determination (NDD). Methods: 1) We conducted a scoping review of global guidelines addressing the role of sedative and analgesic drugs in the neurological death determination. We have extracted the information relevant to our questions and the references that support them. 2) We conducted a cross-sectional study (Pinkie study) nested in the INDex cohort “CT-Perfusion for neurological diagnostic evaluation: a prospective Canadian multicenter diagnostic test study”. We compared plasma concentrations of SAD during NDD and investigated the statistical association between SAD and NDD. Results: 1) The scoping review demonstrated the variability of recommendations in the field and the limited evidence supporting them. Nevertheless, 67% of recommendations suggested dosing SAD during NDD. 2) We observed in the Pinkie study that the plasma concentrations of SAD are low and that they are not associated with the probability of declaring a patient neurologically dead. Conclusion: In the context of a neurological death determination made according to the Canadian practice guidelines, sedative and analgesic drugs are not associated with the probability of neurological death diagnosis.