Point defects are an inherent part of crystalline materials and they influence important physical and chemical properties, such as diffusion, hardness, catalytic activity and phase stability. Increased understanding of point defects enables us to tailor the defect-related properties to the application at hand. Modeling and simulation have a prominent role in acquiring this knowledge. In this thesis thermodynamic and kinetic properties of point defects in metals and ceramics are studied using first-principles calculations based on density functional theory. Phenomenological models are used to translate the atomic level properties, obtained from the first-principles calculations, into functional materials properties. The next paragraph presents the particular problems under study. The formation and migration of vacancies and simple vacancy clusters in copper are investigated by calculating the energies associated with these processes. The structure, stability and electronic properties of the low-oxygen oxides of titanium, TiOx with 1/3 < x < 3/2, are studied and the importance of structural vacancies is demonstrated. We develop an integrated first-principles and Calphad approach to calculate phase diagrams in the titanium-carbon-nitrogen system, with particular focus on vacancy-induced ordering of the substoichiometric carbonitride phase, TiCxNy (x+y < 1). The possibility of forming higher oxides of plutonium than plutonium dioxide is explored by calculating the enthalpies for nonstoichiometric defect-containing compounds and the analysis shows that such oxidation is only produced by strong oxidants. For ceria (CeO2) doped with trivalent ions from the lanthanide series we probe the connection between the choice of a dopant and the improvement of ionic conductivity by studying the oxygen-vacancy formation and migration properties. The significance of minimizing the dopant-vacancy interactions is highlighted. We investigate the redox thermodynamics of CeO2-MO2 solid solutions with M being Ti, Zr, Hf, Th, Si, Ge, Sn or Pb and show that reduction is facilitated by small solutes. The results in this thesis are relevant for the performance of solid electrolytes, which are an integral part of solid oxide fuel cells, oxygen storage materials in automotive three-way catalysts, nuclear waste materials and cutting tool materials. / QC 20100622

The subject of this thesis relates to the design of new polymer electrolytes for battery and fuel cell applications. Classical Molecular Dynamics (MD) modelling studies are reported of the nano-structure and the local structure and dynamics for two types of polymer electrolyte host: poly(ethylene oxide) (PEO) for lithium batteries and perfluorosulfonic acid (PFSA) for polymer-based fuel cells. Both polymers have been modified by side-chain substitution, and the effect of this on charge-carrier transport has been investigated. The PEO system contains a 89-343 EO-unit backbone with 3-15 EO-unit side-chains, separated by 5-50 EO backbone units, for LiPF6 salt concentrations corresponding to Li:EO ratios of 1:10 and 1:30; the PFSA systems correspond to commercial Nafion®, Hyflon® (Dow®) and Aciplex® fuel-cell membranes, where the major differences again lie in the side-chain lengths. The PEO mobility is clearly enhanced by the introduction of side-chains, but is decreased on insertion of Li salts; mobilities differ by a factor of 2-3. At the higher Li concentration, many short side-chains (3-5 EO-units) give the highest ion mobility, while the mobility was greatest for side-chain lengths of 7-9 EO units at the lower concentration. A picture emerges of optimal Li+-ion mobility correlating with an optimal number of Li+ ions in the vicinity of mobile polymer segments, yet not involved in significant cross-linkages within the polymer host. Mobility in the PFSA-systems is promoted by higher water content. The influence of different side-chain lengths on local structure was minor, with Hyflon® displaying a somewhat lower degree of phase separation than Nafion®. Furthermore, the velocities of the water molecules and hydronium ions increase steadily from the polymer backbone/water interface towards the centre of the proton-conducting water channels. Because of its shorter side-chain length, the number of hydronium ions in the water channels is ~50% higher in Hyflon® than in Nafion® beyond the sulphonate end-groups; their hydronium-ion velocities are also ~10% higher. MD simulation has thus been shown to be a valuable tool to achieve better understanding of how to promote charge-carrier transport in polymer electrolyte hosts. Side-chains are shown to play a fundamental rôle in promoting local dynamics and influencing the nano-structure of these materials.

No description available.

No description available.

<p>S. 1-96: sammanfattning, s. 97-134: 5 uppsatser</p> / digitalisering@umu

Ces travaux ont permis d'approfondir les connaissances du mécanisme de déchargepeu conventionnel de l'accumulateur Li/S et de ses limitations. L'ensemble desrésultats a convergé vers une unique conclusion, à savoir que le système Li/S estprincipalement limité par le phénomène de passivation de l'électrode positive en finde décharge. Les polysulfures de lithium à chaines courtes précipitent à la surface del'électrode positive de soufre. Isolants électroniques, ils sont responsables de la perteprogressive de surface active de l'électrode et de la fin prématurée de la décharge.Ainsi, les performances électrochimiques ont pu être significativement améliorées entravaillant sur la morphologie de l'électrode positive, et sur la composition del'électrolyte. En augmentant la surface spécifique de l'électrode, la quantité depolysulfures de lithium qui peut précipiter en fin de décharge est augmentée, et lapassivation totale de l'électrode est retardée. En augmentant la solubilité despolysulfures de lithium dans l'électrolyte, la précipitation des espèces est retardée etla décharge prolongée. Dans cette optique, les solvants de type PEGDME semblentêtre les plus prometteurs à ce jour. Enfin, un mécanisme possible de réduction dusoufre en électrolyte de type éther a pu être proposé.

Thesis (MNutr)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Objectives: The objectives of this study were to determine the nutritional content/ contribution of intravenous (IV) fluid and electrolyte administration on the total feeding prescription of intensive care unit (ICU) patients. Methods: Retrospective review of ICU charts of consecutive patients (>18 years) with APACHE II scores ≥10 and on ≥72 hours nutrition therapy (NT) admitted to a medical/surgical ICU. Total fluid, electrolyte, energy and macronutrient intake from nutritional and non-nutritional sources were reviewed from ICU admission until discharge, discontinuation of NT or death for ≤7 days. Energy and protein delivery were compared to calculated targets of 25.4 – 28.6kCal/kg and 1.3 – 1.5g/kg respectively. Summary statistics, correlation coefficients and appropriate analysis of variance were used to describe and analyse the data. Results: A total of 71 patients (49% male), average age 49.2 ± 17.1, average APACHE II score 21.0 ± 6.1, 68% medical and 32% surgical, were included. Fluid and nutrient intake were reviewed over a mean of 5.7 ± 1.1 days. Mean daily fluid delivery was 3.2 ± 0.6L. IV fluid therapy (IVFT) contributed 32.0 ± 12.0% to total fluid delivery (TFD), whereas IV drug administration, including fluids used for reconstitution and dilution purposes, contributed 20.7 ± 8.1% to TFD. Balanced electrolyte solutions (BES) were the crystalloid of choice, prescribed in 91.5% of patients with a mean daily volume (MDV) of 0.5 ± 0.4L. Hypertonic low molecular weight (LMW) 130/0.4kD hydroxyethyl starch (HES) was the colloid of choice, prescribed in 78.9% of patients with a MDV of 0.2 ± 0.1L. Potassium salts were the most frequently prescribed IV electrolyte supplement (IVES), prescribed in 91% of patients (±20 – 60mmol per administration). NT was initiated within 14.5 ± 14.1 hours. The majority (80%) received enteral nutrition (EN). The mean daily energy delivered was 1613 ± 380kCal (25.1kCal/kg), meeting 93.6 ± 17.7% of mean target range (MTR). Mean daily protein delivery (PD) was 72 ± 22g (1.1g/kg), meeting 82.8 ± 19.9% of MTR. Non-nutritional energy sources (NNES), mostly derived from carbohydrate-containing IV fluids, contributed 10.1 ± 7.5% to total energy delivered (156kCal/d). Mean cumulative energy and protein balance was -674.0 ± 1866.1kCal and -86.0 ± 106.9g respectively. The majority (73%) received >90% of the minimum energy target but only 49% >90% of minimum protein target; 59% of those with energy intake 90-110% of target had adequate protein intake. A significant negative correlation was found between cumulative energy/protein balance and the time to initiation of NT (energy: r=-0.28, p=0.02; protein: r=-0.32, p=0.01). Conclusion: In this ICU BES are the crystalloid of choice and hypertonic LMW 130/0.4kD HES the colloid of choice for IVFT. Potassium salts are the most frequently prescribed IVES. NNES added significantly to energy delivery and should be included in the calculation of feeding prescriptions to avoid the harmful effects of overfeeding. Early initiation of EN with conventional products which are energy rich is insufficient to achieve adequate PD. EN formulae with a more favorable nitrogen to non-protein energy ratio could help to optimise PD during the first week of ICU care. / AFRIKAANSE OPSOMMING: Doelwitte: Die doelwit van hierdie studie was om die voedingswaarde/ bydrae van intraveneuse (IV) vog en elektroliet toediening tot die totale voedings voorskrif van pasiënte in ‘n intensiewe sorg eenheid (ISE) te bepaal. Metodes: Retrospektiewe bestudering van die ISE kaarte van agtereenvolgende pasiënte (>18 jaar) opgeneem in ‘n mediese/chirurgie ISE en met APACHE II tellings ≥10 en ≥72 ure voedingsterapie (VT). Totale vog, elektroliet, energie en makronutriënt inname vanaf voedingsverwante en nie-voedingsverwante bronne is vanaf ISE opname tot en met ontslag, staking van VT of sterfte, vir ≤7 dae hersien. Energie en proteiën inname is vergelyk met berekende doelwitte van 25.4 – 28.6kKal/kg en 1.3 – 1.5g/kg onderskeidelik. Beskrywende statisitiek, korrelasie koeffisiënte en toepaslike analises van variansie is gebruik vir data analise. Resultate: 71 pasiënte (49% mans), gemiddelde ouderdom 49.2 ± 17.1, gemiddelde APACHE II telling 21.0 ± 6.1, 68% medies en 32% chirurgie, is ingesluit. Vog en voedingstof inname is hersien oor ‘n gemiddelde tydperk van 5.7 ± 1.1 dae. Gemiddelde vog inname was 3.2 ± 0.6L/dag. IV vog terapie (IVVT) het 32.0 ± 12.0% bygedra tot totale vog inname (TVI). IV medikasie toediening, insluitende die herkonstruksie en verwatering van medikasie, het 20.7 ± 8.1% bygedra tot TVI. Die mees voorgeskrewe kristalloiëd en kolloiëd vir IVVT was gebalanseerde elektroliet oplossings (GEO), voorgeskryf in 91.5% van pasiënte (gemiddeld 0.5 ± 0.4L/dag), en hipertoniese lae molekulêre gewig (LMG) 130/0.4kD hidroksie-etiel stysel (HES), voorgeskryf in 78.9% van pasiënte (gemiddeld 0.2 ± 0.1L/dag), onderskeidelik. Die mees voorgeskrewe IV elektroliet supplement was kalium soute, voorgeskryf in 91% van pasiënte (±20 – 60 mmol per toediening). VT is binne 14.5 ± 14.1 ure geinisieër. Die meerderheid (80%) het enterale voeding (EV) ontvang. Die gemiddelde daaglikse energie inname van 1613 ± 380kCal (25.1kKal/kg) het 93.6 ± 17.7% van die gemiddelde doelwit rykwydte (GDR) bereik. Die gemiddelde daaglikse proteiën inname van 72 ± 22g (1.1g/kg) het 82.8 ± 19.9% van die GDR bereik. Nie voedings-verwante energie bronne (NVEB), meestal vanaf koolhidraat-bevattende IV vloeistowwe, het 10.1 ± 7.5% tot totale energie inname (TEI) bygedra (156kKal/d). Die gemiddelde kumulatiewe energie en proteiën balans was -674.0 ± 1866.1kKal en -86.0 ± 106.9g onderskeidelik. Die meerderheid (73%) het >90% van die minimum energie doelwit (ED) bereik. Slegs 49% het >90% van die minimum proteiën doelwit (PD) bereik. Opsomming: Die kristalloiëd en kolloiëd van keuse vir IVT is GEO en hipertoniese LMG 130/0.4kD HES onderskeidelik. Kalium soute word mees algemeen voorgeskryf. NVEB dra beduidend by tot TEI en moet inaggeneem word tydens die berekening van voedingsvoorskrifte ten einde oorvoeding te voorkom. Vroeë inisiëring van EV met konvensionele energie-ryke EV produkte is onvoldoende om genoegsame proteiën inname te verseker. EV produkte met ‘n gunstiger stikstof tot nie-proteiën energie verhouding sal help om proteiën inname gedurende die eerste week van intensiewe sorg te optimaliseer.Slegs 59% van pasiënte met genoegsame energie inname (90-110% van ED) het hul minimum PD bereik. Daar was ‘n beduidende negatiewe korrelasie tussen kumulatiewe energie/proteiën balans en die tyd tot inisiëring van VT (energie: r=-0.28, p=0.02; proteiën: r=-0.32, p= 0.01).

Made available in DSpace on 2014-10-09T12:27:09Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:18Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

L'eau est partout et joue un rôle déterminant dans une multitude deprocessus. Cependant, on la trouve souvent au sein de minusculescellules, pores, ou canaux. En de tels cas, les proprietés“macroscopiques” de l'eau sont modifiées par les restrictions spatialeset les interactions entre les molécules d'eau et le matériau confinant.Elucider les propriétés de l'eau en confinement est crucial, et unecompréhension générale peut seulement être obtenue à traversl'utilisation de modèles. Alors que l'eau confinée dans des matériauxdurs tels que les nanotubes de carbone est bien documentée, nous n'avonspas trouvé de modèle général pour l'étude de l'eau confinée a desmatériaux mous, et ce en dépit de décénies de recherches sur de nombreuxmodèles spécifiques à une biomolécule ou un polymère en particulier.Dans cette thèse, nous présentons un modèle numérique d'eau confinéedans des géométries molles, générées par auto-assemblage. Nouscomprenons la manière dont les interactions réciproques entre l'eau etla matrice confinante déterminent la structure des assemblages et lespropriétés de transport de l'eau. Nous avons choisi un modèle desurfactant ioniques, matériaux très versatiles qui sont capables des'auto-assembler en diverses géométries confinantes.Nous nous concentrons sur l'effet des interfaces sur la formation de lananostructure et sur les propriétés de transport à l'échelle de lananoseconde. Nous nous distancons de l'approche traditionnelle auproblème du transport de l'eau dans des nanomatériaux. Nous montrons quel'hypothèse habituelle du transport diffusif est invalide car la matriceconfinante piège les molécules d'eau à l'interface. Nous proposons deremplacer cette hypothèse par celle du transport sous-diffusif, et nousmettons en évidence le rôle de l'échelle de taille et des propriétéstopologiques du confinement. Nous montrons que cette approche expliquedes résultats expérimentaux pour léau confinée dans des matériaux desynthèse, et qu'elle est compatible avec les développements récents liésà l'eau biologique. / Water is omnipresent and plays a decisive role in a myriad of processes.However, it is often found hidden in tiny cells, pores, or channels. Insuch cases, the usual “bulk” features of water are modified by thelimited available space and the interactions of individual moleculeswith the confining material. Elucidating the properties of water in suchconfined states is critical and general understanding can only beachieved through models. While water confined in model hard materialssuch as carbon nanotubes is well documented, we found that there existno general model to study water confined in soft materials, althoughthis has been an active research topic for decades and despite thenumerous models specific to one biomolecule or polymer that have beendeveloped. In this thesis, we present a numerical model of waterconfined in soft self-assembled environments, and we provide anunderstanding of how the interplay between water and the confiningmatrix affects the structure of the assemblies and transport propertiesof water. Our model confining matrix is composed of ionic surfactants.This versatile model is able to self-assemble to a wide variety ofconfining geometries.We focus on the role of interfaces in shaping the nanometer scalestructure, and nanosecond scale transport properties. This work is adeparture from the traditional approach to the problem of transport ofwater confined in soft nanomaterials. We show that the usual hypothesisof diffusive water transport does not hold due to trapping of moleculesat the interface with the confining matrix. Instead, we support apicture where transport is sub-diffusive, and we highlight the role ofthe length-scale of the confinement and of its topological features. Wefind that this rationale explains experimental results for waterconfined in synthetic materials, and that it is compatible with recentadvances in the understanding of biological water.

As saponinas são tensoativos naturais, caracterizadas principalmente por sua atividade espumógena. Ilex paraguariensis A. St. Hil, conhecida como "erva-mate", é uma espécie vegetal rica em saponinas e de importância econômica e cultural para este Estado. Estudos anteriores demonstraram que os frutos imaturos de I. paraguariensis, uma parte do vegetal sem valor comercial, apresenta teores mais elevados de saponinas que as folhas da erva-mate. O objetivo deste trabalho foi avaliar a potencialidade das saponinas dos frutos imaturos de I. paraguariensis como adjuvante espumógeno, sob o ponto de vista físico-químico e tecnológico, bem como a avaliação do potencial de irritação dérmica. Para isso, foram empregados um extrato bruto liofilizado (EXL) obtido por turbólise na proporção de 1:10 droga-solvente em etanol:água (40:60 v/v) como líquido extrator e dois produtos purificados ricos em saponinas, denominados Fr.7090 e P6, obtidos por um processo de fracionamento em fase sólida e eluição com metanol-água (método I) e por um processo de complexação com polímero polivinílico por contato direto (método II), respectivamente. Para a caracterização do perfil das saponinas e monitoramento de processos, foi desenvolvida uma metodologia analítica por CLAE em fase reversa C18, em sistema gradiente acetonitrila: ácido fosfórico 0,5 % com detecção em 205 nm. A atividade de superfície das saponinas foi avaliada através do abaixamento da tensão superficial, CMC, excesso de superfície e área superficial. Os perfis de espumabilidade e estabilidade da espuma das saponinas do EXL e da Fr. 7090 foram avaliados através de medidas da espumabilidade, drenagem, tempo de permanência da espuma e resistência. Como tensoativos de comparação foram utilizados o laurilsulfato de sódio (LSS) e polissorbato 80 (Poli. 80), empregados nas mesmas condições e concentrações que as soluções de saponinas. A influência de eletrólitos sobre os perfis espumógenos foi avaliado utilizando NaCl, KBr, KNO3, MgCl2 e Na2HPO4, mantendo a força iônica constante em 0,024 M. Para a análise das propriedades espumógenas das saponinas, a espuma foi gerada em coluna de vidro por insuflação de ar durante 20 segundos, mantendo um fluxo de 2 L min-1. O perfil de drenagem das espumas das saponinas na concentração de 10 CMC foi avaliado e expresso como percentual de volume de líquido retido na espuma (VLE %), no tempo zero e ao longo de 60 minutos. A estabilidade da espuma das saponinas de Fr.7090 e P6 foi avaliada considerando a altura da coluna de espuma em função do tempo e pelo registro e análise fotográficos da espuma até 480 minutos. Para avaliar a influência do tamanho micelar sobre as propriedades espumógenas dos tensoativos, o diâmetro efetivo das micelas foi determinado por medidas de espalhamento de luz dinâmica. Dados adicionais sobre a sua estabilidade foram obtidos mediante a análise fotográfica bidimensional, em câmara geradora de espuma projetada para esta finalidade. A resistência da espuma foi caracterizada mediante a velocidade de queda de uma esfera através da coluna de espuma, sob condições experimentais padronizadas. A Fr. 7090 apresentou um elevado grau de espumabilidade semelhante ao LSS e superior ao Poli. 80. Quanto ao perfil de drenagem, as saponinas apresentaram um valor de VLE % em 60 minutos (T1h) de 12,0 % e 15,2 %, para o EXL e Fr. 7090, respectivamente, em relação a 7,15 % para ambos tensoativos sintéticos. As saponinas apresentaram um perfil de estabilidade diferenciado, com maior estabilização estrutural com o tempo. As espumas das saponinas apresentaram uma resistência superior aos tensoativos sintéticos, porém, somente a 25 CMC. A adição de eletrólitos às soluções de saponinas influenciou negativamente os perfis espumógeno e de estabilidade da espuma das saponinas. As análises por espalhamento da luz sugerem micelas de dimensões maiores em relação aos tensoativos não-iônicos ou a possível formação de estruturas supramicelares, mesmo baixas concentrações. Pela análise bidimensional, a espuma do EXL apresentou menor alteração da forma e número das bolhas de ar com o tempo, comparado à espuma de LSS. O potencial de irritação dérmica das saponinas foi avaliado pelo teste de irritação primária dérmica de Draize in vivo, em coelhos machos albinos. A avaliação biológica classificou as saponinas como produtos não-irritantes. Pelos resultados, concluiu-se que as saponinas dos frutos imaturos de Ilex paraguariensis apresentam um potencial emprego tecnológico, tanto pelas suas propriedades espumógenas, como pela ausência de irritação cutânea. / Saponins are natural surfactants, characterized mainly for its foaming properties. Ilex paraguariensis A. St. Hil, known as "erva-mate", is a rich vegetal specie in saponins and of economic and cultural importance for this State. Previous studies had demonstrated that the immature fruits of I. paraguariensis, one has left of the vegetable without commercial value, presents higher concentrations of saponins that the leaves of "erva-mate". The objective of this work was to evaluate the saponins potentiality of the immature fruits of I. paraguariensis as adjuvant foaming, under the technological and physical-chemical point of view, as well as the evaluation of the cutaneous irritation potential. For this, it had been used a rude extract (EXL) obtained by tubo-extraction using ethanol 40% (v/v) as extractor liquid and two rich purified products in saponins obtained by a process in solid phase and elution with methanolwater (method I) and a complexation process with polyvinyl polymer (method II), respectively. For the characterization of saponins profile was developed an analytical methodology using HPLC in C18 reversed phase, with a system gradient composed by acetonitrile:phosphoric acid 0,5 % with detection in 205 nm. The surface activity of saponins was evaluated through the lower of the superficial tension, CMC, surface density and superficial area. Foambility and stability profiles of the saponins foam of the EXL and Fr. 7090 had been evaluated through foamability mensuraments, draining, permanence time of the foam and resistance of the films. As surfactants of comparison it had been used sodium dodecylsulphate (LSS) and polyssorbate 80 (Poli. 80). These had been analyzed in the same conditions and concentrations of saponins solutions. The electrolytes influence on the foaming profiles was evaluated using NaCl, KBr, KNO3, MgCl2 and Na2HPO4, keeping the constant ionic strenght in 0,024 M. For the analysis of the foams properties of the saponins, the foam was generated in glass column by air insufflation during 20 seconds, with a constant flow of 2 L min-1. The draining profile of the saponins foams in the concentration of 10 CMC was evaluated and expressed as percentile of volume of restrained liquid in the foam (VLE %), in time zero and throughout 60 minutes. The stability of the saponins foam of Fr.7090 and P6 was evaluated considering the height of the foam column in function of the time and for the photographic register and analysis of the foam till 480 minutes. To evaluate the influence of the micellar size on the foaming properties of the surfactants, the effective diameter of micelles was determined by dynamic light scattering mensuraments. Additional data on its stability had been obtained by means of the bidimensional photographic analysis, in generating foam chamber projected for this purpose. The resistance of the foam was characterized by means of the speed of a sphere fall through the foam column, under standardized experimental conditions. Fr. 7090 presented one high degree of similar foambility to the LSS and superior to Poli. 80. As much as to the draining profile, the saponins had presented a value of VLE % in 60 minutes (T1h) of 12,0 % and 15,2 %, for the EXL and Fr. 7090, respectively, in relation to 7,15 % for both synthetic surfactants The saponins showed a differentiated profile of stability, with bigger structural stabilization with the time. The saponins foams had presented a superior resistance to the synthetic surfactants, however, only 25 CMC. The addition of electrolytes had a negative influence on saponins foams profile and stability. The analyses for dynamic light scattering suggest bigger dimensions micelles in relation to the nonionic surfactants or the possible formation of highest micelles, even at low concentrations. To the bidimensional analysis, the EXL foam presented minor alteration of the form and number of the air bubbles with the time, compared with the LSS foam. The potential of the cutaneous irritation of the saponins was evaluated by the test of dermic primary irritation of the Draize test in albinic male rabbits. The biological evaluation classified the saponins as not-irritating products. For the results, it was concluded that the saponins of I. paraguariensis immature fruits presented a technologycal potential use, as for its foaming properties as for the absence of cutaneous irritation.