Legionella pneumophila, o agente etiológico da doença dos Legionários, é conhecida por desencadear a formação de poro em membranas de macrófagos derivados de medula óssea (BMMs) por mecanismos dependentes do sistema de secreção do tipo IV conhecido como Dot/Icm. Neste trabalho, foram utillizados vários mutantes de L. pneumophila em combinação com camundongos nocautes para investigar os fatores bacterianos e do hospedeiro envolvidos na formação de poro em BMMs. Observamos que apesar da atividade do Dot/Icm, a formação de poro não ocorre em BMMs deficientes para caspase-1 e Nlrc4. A formação de poro foi temporalmente associada com a secreção de IL-1b e precedeu a lise celular e a piroptose. A formação de poro foi dependente do Dot/Icm, mas independente de várias proteínas efetoras, da multiplicação bacteriana e da síntese de novo de proteínas. A flagelina, a qual é conhecida em ativar o inflamassoma de Nlrc4, foi necessária para a formação de poro; a bactéria mutante flaA falhou em induzir a permeabilização celular. Consequentemente, a transfecção da flagelina purificada foi suficiente para desencadear a formação de poro independente da infecção. Utilizando 11 diferentes espécies de Legionella, nós observamos alta formação de poro em resposta à L. micdadei, L. bozemanii, L. gratiana, L. jordanis e L. rubrilucens, e essa resposta estava correlacionada com a expressão de flagelina por essas espécies. Além disso, verificamos que as proteínas Asc e Caspase-11 apresentam fenótipo intermediário na formação de poro, sugerindo que outras vias podem estar envolvidas no processo. Observamos também que a formação de poro desencadeada por L. pneumophila difere daquela induzida pelo ATP. Em conjunto, nossos resultados sugerem que a formação de poro não é uma resposta específica de L. pneumophila nem o resultado de dano da membrana induzido pelo Dot/Icm. Ao invés disso, a formação de poro é uma resposta do hospedeiro altamente coordenada, dependente dos componentes do inflamassoma Nlrc4 e caspase-1 e é desencadeada em resposta a bactérias que expressam o sistema de secreção do tipo IV e flagelina. / Legionella pneumophila, the etiological agent of Legionnaires disease, is known to trigger pore formation in bone marrow-derived macrophages (BMMs) by mechanisms dependent on the type IVB secretion system known as Dot/Icm. Here, we used several mutants of L. pneumophila in combination with knockout mice to assess the host and bacterial factors involved in pore formation in BMMs. We found that regardless of Dot/Icm activity, pore formation does not occur in BMMs deficient in caspase-1 and Nlrc4/Ipaf. Pore formation was temporally associated with IL-1b secretion and preceded host cell lysis and pyroptosis. Pore-forming ability was dependent on bacterial Dot/Icm but independent of several effector proteins, multiplication and de novo protein synthesis. Flagellin, which is known to trigger the Nlrc4 inflammasome, was required for pore formation as flaA mutant bacteria failed to induce cell permeabilization. Accordingly, transfection of purified flagellin was sufficient to trigger pore formation independent of infection. By using 11 different Legionella species, we found robust pore formation in response to L. micdadei, L. bozemanii, L. gratiana, L. jordanis and L. rubrilucens, and this trait correlated with flagellin expression by these species. Furthermore, we found that Asc and Caspase-11 showed an intermediate phenotype in pore formation, suggesting that other pathways may be involved in this process. We also observed that the pore formation triggered by L. pneumophila differs from the pore induced by ATP. Together, the results suggest that pore formation is neither L. pneumophilaspecific nor the result of membrane damage induced by Dot/Icm activity; instead, it is a highly coordinated host cell response dependent on host Nlrc4 and caspase-1 and on bacterial flagellin and type IV secretion system.

Orientador: Kenneth Elmer Collins / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-07T03:06:42Z (GMT). No. of bitstreams: 1 Amgarten_DioneRodrigues_M.pdf: 671991 bytes, checksum: cf94e99a89e166c1a60e3e1210bee361 (MD5) Previous issue date: 2006 / Resumo: A determinação do volume específico de poros (sV) de sílicas cromatográficas do tipo CLAE é importante porque o sV e uma característica fundamental da sílica que se relaciona diretamente aos parâmetros importantes (tamanho de poro e área superficial) para aplicações cromatográficas. A determinação do sV é normalmente feita por aparelhos de adsorção/dessorção de nitrogênio (baixas temperaturas: ~75K)) e de intrusão de mercúrio (alta pressão). A instrumentação usada nestes procedimentos é bastante cara e requer operadores bem treinados. Por isso, o objetivo deste projeto foi desenvolver um procedimento relativamente rápido, confiável, de baixo custo e que pudesse ser realizado, por estudantes e técnicos com um treinamento especial mínimo, em qualquer laboratório. Começando com um procedimento de adsorção volumétrica, publicado na literatura, um novo procedimento de dessorção gravimétrica que usa a mesma amostra várias vezes (reciclagem) para obter determinações estatisticamente confiáveis foi desenvolvido. As influências da umidade e da mudança do líquido volátil utilizado foram avaliadas. Os resultados mostraram que independente do líquido volátil utilizado, o valor de sV é preciso e se encontra bem próximo dos valores obtidos pelos procedimentos instrumentais convencionais. O procedimento requer aproximadamente de 6-8 horas para 1-5 determinações. O procedimento pode ser empregado no próprio ambiente do laboratório sem interferência da umidade do ambiente. Comparações com os outros procedimentos mostram que os valores de sV obtidos são precisos e provavelmente mais exatos do que os fornecidos por estes outros / Abstract: The determination of the specific pore volume (sV) of chromatographic silicas of the type used in HPLC is important because the sV is a fundamental characteristic of the silica which relates directly to parameters (pore size and surface area) important to chromatography applications. The determination of sV is usually made by means of adsorption/desorption of nitrogen at low temperature (~75K) or of intrusion of mercury at high pressure. The instrumentation for these procedures are quite expensive, and require well trained operators. Therefore, the objective this project was to developed a relatively fast and reliable procedure, of low cost that could be accomplished at any laboratory by students or technicians with a minimum of special training. Starting with a volumetric adsorption procedure published in the literature a new gravimetric desorption procedure was developed which uses the same sample several times (recycling) to obtain statistically confident determinations. The influences of the humidity and of the choice of volatile liquid used in the desorption from silica were evaluated. The results show that, independent of the volatile liquid used, the sV value is precise and in close agreement with values obtained by the conventional instrumental procedures. The procedure requires about 6-8 hours to make 1-5 determinations in parallel. The procedure can be employed in a laboratory environment with neglible interference from ambient humidity. Comparisons with the other procedures show thet the sV values obtained are at least as precise and are probably as accurate as they are / Mestrado / Quimica Analitica / Mestre em Química

Abstract This research examines the lower edge of arable land in cultivating littoral land and its effects on spring sowing Central Ostrobothnia and in the southern areas of Northern Ostrobothnia. This doctoral thesis develops methods to raise the lower edge of arable land in low littoral land. The methods are based on contribution margin, the gross profil of yield, the relocation of dry margin and the realigning of littoral land's area descriptor. In addition, outdated littoral land profil and loss evaluation criteria are renewed. The objective of the research is to decrease environmental damages and to improve cultivation. Another objective in raising the lower edge of arable land is to enhance the forming of protective noncultivated belts. Ten lakes from the hydrologic areas of the rivers Perhonjoki, Kalajoki and Pyhäjoki were chosen for the research, one half of them were in their natural state and the other half were regulated. The research consisted of comparing the sowing dates and patch yields (moisture content 14%) of the sample parcels (104 observations) chosen from littoral land around the lakes to the corresponding figures of sample parcels selected from outside the areas influenced by water level variation. The findings are from 1985–1991 and 1996–1998. The cultivated plants were barley, oats and hay. The sample area research was completed with interviews. Furthermore, the research examined the dependence of air pore space of the soil cultivation layer on the dry margin. The research result indicate that the lower edge of arable land has to be raised, for lakes in their natural state the rise would be on average 35 ± 4 cm (67 observations) and for regulated lakes on average 39 ± 4 cm (61 observations). The minimum dry margins required by soil cultivation and sowing will be 69 ± 5 cm (67 observations) and 78 ± 5 cm (61 observations). Thus, the lowest part of the waterfront will not be cultivated anymore. The contribution margin of the field is not changed. Sowing can be done earlier and air pore space and viability increase. The condensation detriment of the soil cultivation layer, the workload needed for cultivation and the nutrient load in hydrologic areas will be decreased. Measuring and locating protective non-cultivated belts becomes easier. The state of environment is improved. The evaluation of profit and loss is modernized. / Tiivistelmä Tutkimuksessa tarkastellaan rantamaiden viljelyksessä pellon alarajaa ja sen vaikutuksia kevätkylvöihin Keski-Pohjanmaalla ja Pohjois-Pohjanmaan eteläisellä osalla. Työssä kehitetään katetuottoon, sadon bruttotuottoon, kuivavaran siirtoon ja rantamaan pinta-alan kuvaajan oikaisuun perustuvat menetelmät pellon alarajan määrittämiseksi alavilla rantamailla. Samoin pyritään nykyaikaistamaan rantamaiden hyödyn- ja vahingonarviointia. Tutkimuksen tavoitteena on vähentää viljelyn aiheuttamia ympäristöhaittoja sekä parantaa samalla itse viljelyä. Pellon alarajan määrittämisen yhteydessä on tavoitteena edistää myös suojavyöhykkeiden perustamista. Kohdejärvinä oli Perhonjoen, Kalajoen ja Pyhäjoen vesistöjen kymmenen järveä, joista puolet oli luonnontilaisia ja puolet säännösteltyjä. Järvien rantatiloilta valittujen koelohkojen (104 kpl) kylvöaikoja ja ruutusatoja (kosteuspitoisuus 14 %) verrattiin vedenkorkeuksien vaihteluista riippumattomien vertailulohkojen vastaaviin arvoihin. Havaintovuodet olivat 1985–1991 sekä 1996–1998. Viljelykasveja olivat ohra ja kaura sekä heinä. Koealuetutkimuksia täydennettiin haastatteluina. Lisäksi tarkasteltiin muokkauskerroksen ilmahuokostilan riippuvuutta kuivavarasta määritettynä järven vedenkorkeudesta. Tutkimustulosten mukaan pellon alarajaa on korotettava nykyisestään luonnontilaisilla järvillä keskimäärin 35 ± 4 cm (n = 67) ja säännöstellyillä järvillä keskimäärin 39 ± 4 cm (n = 61). Kylvön vaatimat kuivavarat määritettyinä järvien vedenkorkeuksista tulevat olemaan vastaavasti 69 ± 5 cm (n = 67) ja 78 ± 5 cm (n = 61). Tällöin rantalohkon alavimmalta osalta viljely poistuu. Pellon katetuotto ei muutu. Kylvö aikaistuu, ilmahuokostila kasvaa ja kulkukelpoisuus paranee. Muokkauskerroksen tiivistymishaitta ja viljelyn työnmenekki sekä vesistöön kohdistuva ravinnekuormitus vähenevät. Suojavyöhykkeiden mitoitus ja sijoitus helpottuvat. Ympäristön tila paranee. Hyödyn ja vahingon arviointi nykyaikaistuu.

The present study deals with the physical characterization of macrodefect free cements produced by ICI. These materials are made through a specialized mixing technique which incorporates an organic polymer into the cement/water system. The high mechanical strength and low porosity of this class of hardened cement paste had been well documented, however, a detailed characterization of the physical nature of the microstructure had not previously been attempted. Two classes of macrodefect free material were studied, based on Ordinary Portland cement and High Alumina cement, respectively. The porosities of these two materials were determined in their original state and after various forms of heat treatment and conditioning. Samples based on Ordinary Portland cement had a well defined narrow pore size distribution, even after heat treatment, while the High Alumina cement samples displayed a very low total pore volume in their original state, but subsequent heat treatment led to the developement of porosity over a wide range of pore sizes. These fundamental differences in the pore size distributions had significant effects on the homogeneity and reproducibility of the microstructures of the samples. The porosity generated by heat treatment was found to be unstable in the presence of water. In general, reductions in the porosities and permeabilities were observed. This was due to the formation of fresh cement hydrate gel within the pore structure, which caused a shift in the pore size distributions towards smaller pores.

Activated carbons have been modif fed using reactive chemicals to produce adsorbents of enhanced hydrophobic character which will also be resistant to surface oxidation that results from exposure to humid air ("ageing"). The intention was that modification would not disrupt the carbon pore structure. The adsorptive properties of the modified carbons have been investigated using probe molecules Including nitrogen, water, hexane, and chloropicrin, and the ageing characteristics of the carbons, and the factors controlling the adsorption of a model hydrophobic vapour from high humidity air have been studied. Directly fluorinated carbons were unstable, probably due to weakly adsorbed fluorine. Treatment of these adsorbents with other chemicals indicated the potential of the technique for Introducing specific functional groups onto the carbon surface. Carbons modified using selective fluorinating reagents (hexafluoropropene and 1,1-difluoroethene) were more hydrophobic, and adsorbed hydrophobic vapours more efficiently from humid air in comparison to controls. These adsorbents aged, but at a reduced rate in comparison to control carbon. Carbons modified using chlorinating reagents (carbonyl chloride and chlorine) and treated with solvents to remove adsorbed reagent and/or reaction products were of improved hydrophobic character, and adsorbed hydrophobic vapours from humid air at least as efficiently as the control samples. More importantly, these carbons offered resistance to ageing effects. A study of the factors controlling the efficiency with which hydrophobic vapours; are adsorbed from humid air revealed that the surface chemistry of the carbon is important, but that under typical conditions of use, filter performance was limited by the rate at which water displaced by the organic vapour could be carried away by the airstream. The results illustrate that filters containing chemically modified activated carbon offer advantages when volatile hydrophobic contaminant vapours are present, and where ageing effects are an important mechanism by which filtration efficiency is degraded.

Acute myeloid leukaemia is a heterogeneous disease characterized by uncontrolled proliferation of neoplastic haematopoietic precursor cells, which leads to the disruption of normal haematopoiesis and bone marrow failure. Impaired haematopoiesis is often associated with balanced chromosomal translocations that involve the nucleoporin Nup98 fused to around 30 different partner genes, such as the homeobox genes HOXA9 and PMX1. Nup98-associated AML is characterized by poor prognosis and poor treatment outcome for the patients. The aim of the study was to elucidate the mechanisms underlying chemotherapy-resistance. Previous experiments showed that the expression of Nup98 fusion proteins leads to changes in nuclear organization. Based on these observations, we hypothesize that the expression of Nup98 fusion proteins affect DNA double-strand break (DSB) repair. Our work shows that the expression of Nup98-HoxA9 and Nup98-HHEX in U2OS cells does not induce any DSBs. Further, we examined the repair phenotype of exogenously induced DSBs. Experiments carried out using etoposide (ETO) or neocarzinostatin (NCS) revealed that Nup98 fusion proteins affect non-homologous end joining (NHEJ). The second major DSB repair pathway, homologous recombination (HR), remains unaffected by Nup98 fusion proteins. The repair phenotype showed that at most timepoints analyzed, cells expressing Nup98 fusion proteins present less DSBs that control cells. We further performed single cell gel electrophoresis assays, also called COMET assay. This assay determines the amount of broken DNA at the single cell level. COMET assays showed that cells expressing Nup98-HoxA9 get equally damaged as control cells. Taken together, these results show that Nup98-HoxA9 induces faster DNA repair by affecting NHEJ. Additional experiments, pointed toward a role of p53 in the effect of Nup98 fusion proteins on DSB repair. Monitoring the repair phenotype in a wild-type and p53 depletion background, revealed that the effect of Nup98-HoxA9 on NHEJ is partially p53 dependent. A further search for the potentially implicated factor in the accelerated NHEJ remained inconclusive so far. In conclusion, Nup98-HoxA9 induces accelerated NHEJ in a partially p53-dependent manner. / Option Biologie moléculaire du Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Poröse Kohlenstoffmaterialien zeichnen sich durch hohe spezifische Oberflächen und Porenvolumina, eine gute elektrische Leitfähigkeit sowie hohe mechanische und chemische Stabilität aus. Sie werden in Anwendungen wie der Gasspeicherung oder der elektrochemischen Energiespeicherung eingesetzt. Besondere Aufmerksamkeit erfährt momentan die Energiespeicherung, unter anderem durch die fortschreitende Verbreitung der Elektromobilität. Als besonders effizient haben sich elektrochemische Energiespeichermaterialien, zum Beispiel für Doppelschichtkondensatoren (EDLCs) und Batterien, herausgestellt. Ein vielversprechendes Batteriesystem ist die Lithium-Schwefel-Batterie (LiS-Batterie). Mit diesem System können wesentlich höhere gravimetrische Energiedichten als mit Lithium-Ionen-Batterien erreicht werden. Poröser Kohlenstoff stellt aufgrund der hohen Porosität, der guten elektrischen Leitfähigkeit und der chemischen Beständigkeit ein ideales Elektrodenmaterial für die Anwendung sowohl in EDLCs als auch in LiS-Batterien dar. Bei den im industriellen Maßstab am häufigsten eingesetzten Aktivkohlen ist nachteilig, dass während der Synthese nur begrenzte Kontrolle über das Porensystem vorhanden ist. Zudem sind die Poren oft flaschenhalsartig, was zu einer schlechten Zugänglichkeit des Porensystems führt und dadurch den Stofftransport limitiert. Eine verbesserte Kontrolle über das Porennetzwerk bieten das Templatverfahren oder die Synthese von Kohlenstoffen aus Carbiden. Diese Methoden ermöglichen es zudem, Poren unterschiedlicher Größe, das heißt, ein hierarchisches Porensystem, einzubringen. Dies ist vorteilhaft für Prozesse, in denen sowohl eine hohe Adsorptionskapazität als auch ein schneller Stofftransport notwendig sind. Die meisten dieser Synthesen haben die Nachteile, dass sie komplex sind und viel Abfall produzieren. Eine vergleichbar neue Methode zur Herstellung von hierarchischen Kohlenstoffen ist die Synthese von Kroll-Kohlenstoffen über eine reduktive Carbochlorierung. Dieses Verfahren ist dem Schlüsselschritt des Kroll-Prozesses zur Herstellung von Titan nachempfunden. Dafür werden oxidische Nanopartikel mit Kohlenstoff beschichtet und durch Behandlung mit heißem Chlorgas in Kohlenstoff überführt. Diese Synthese ermöglicht neben der Kontrolle der Mesoporengröße über die Größe der Nanopartikel gleichzeitig die Einbringung von Mikroporen durch das Ätzen von Kohlenstoff während der Carbochlorierung, sodass in wenigen Syntheseschritten ein hierarchisches Porensystem generiert werden kann. In dieser Arbeit wurde untersucht, ob sich der Ansatz der Carbochlorierung auf weitere Systeme übertragen lässt. Durch postsynthetische Aktivierung wurde die Porosität von Kroll-Kohlenstoff unter Erhalt der Porenstruktur gesteigert. So war es möglich, Kohlenstoffe mit spezifischen Oberflächen von mehr als 2700 m²/g und Porenvolumina von 3 cm³/g zu synthetisieren. Die Mesoporenstruktur konnte aufrechterhalten werden, während sowohl der Anteil von Meso- als auch Mikroporen erhöht werden konnte. Aktivierter Kroll-Kohlenstoff wurde in EDLCs als Elektrodenmaterial untersucht. Mit 1 M Schwefelsäure als Elektrolyt konnten spezifische Kapazitäten von 160 F/g über galvanostatische Lade-/Entlademessungen erreicht werden, wobei bei hohen Lade-/Entladeströmen von 10 A/g noch 87 % der Maximalkapazität abgerufen werden konnten. Weiterhin wurde der Frage nachgegangen, ob mittels Carbochlorierung geordnete mesoporöse Kohlenstoffe synthetisiert werden können. Dafür wurden sowohl Harttemplat- als auch Weichtemplatmethoden eingesetzt. Im Harttemplatverfahren war es möglich, geordneten mesoporösen Kohlenstoff DUT-118 zu synthetisieren.7 DUT-118 weist eine höhere spezifische Oberfläche und ein höheres Porenvolumen im Vergleich zu Kohlenstoff auf, der über das klassische „Nanocasting“ hergestellt wird. Durch die Carbochlorierung kann zudem der Mikroporenanteil des Materials im Vergleich zur klassischen Templatentfernung gesteigert werden, was durch Präadsorptionsexperimente mit n-Nonan nachgewiesen wurde. In einer weichtemplatgestützten Synthese konnte geordneter mesoporöser Kohlenstoff DUT-119 aus Oxid/Kohlenstoff-Kompositen mittels Carbochlorierung synthetisiert werden. DUT-119 verfügt über eine spezifische Oberfläche von über 2200 m²/g, ein Porenvolumen von mehr als 2 cm³/g und ein hierarchisches Porensystem. Aufgrund des hierarchischen Mikro-/Mesoporensystems ist DUT-119 hervorragend als Kathodenmatrix in LiS-Batterien geeignet. Besonders hervorzuheben ist die geringe Menge an eingesetztem Elektrolyt von nur 5 μL/mgSchwefel. Die gefertigte Zelle ist über 50 Zyklen stabil und verfügt über eine herausragende Flächenkapazität von 3,7 mAh/cm² nach 50 Zyklen. Verstärkt im Fokus der Forschung stehen Kohlenstoffe, welche mit Heteroatomen dotiert sind. Durch Dotierung können die Eigenschaften der Kohlenstoffe hinsichtlich Polarität oder elektrochemischer Eigenschaften optimiert werden.8,9 Deshalb wurde untersucht, ob über die Carbochlorierung stickstoffdotierter Kohlenstoff synthetisiert werden kann. Dafür wurde ein metallorganisches Netzwerk (MOF) zu Kroll-Kohlenstoff DUT-127 umgesetzt. In Abhängigkeit von der Synthesetemperatur von 600–900 °C konnten spezifische Oberflächen von 1450–2750 m²/g und Porenvolumina zwischen 0,8 und 2 cm³/g erreicht werden. Da das eingesetzte MOF Aminogruppen enthielt, sind in DUT-127 Stickstoffdotierungen vorhanden, was zu einer verringerten Hydrophobie führt. DUT-127 wurde als Elektrodenmaterial in EDLCs eingesetzt. Mit 1 M Schwefelsäure konnten spezifische Kapazitäten von 165 F/g, ermittelt über galvanostatische Lade-/Entlademessungen, erreicht werden. Besonders bei hohen Lade-/Entladeströmen von 12,5 A/g konnten über 90 % der maximalen Kapazität abgerufen werden. Weiterhin ist die hohe Arbeitsfrequenz von über 25 Hz hervorzuheben. Beides wird durch die gute Benetzbarkeit, das ausgeprägte Transportporensystem sowie die geringe Partikelgröße ermöglicht. Der große Vorteil der Synthese von Kroll-Kohlenstoffen über die Carbochlorierung ist der Verzicht auf Lösemittel während der Templatentfernung. Wünschenswert ist es, zukünftig ebenfalls die Synthese der Präkursoren und Template möglichst lösemittelfrei zu gestalten. Die Porenstruktur (Textur) eines porösen Materials bestimmt in großem Maße die Leistungsfähigkeit in einer bestimmten Anwendung. Deshalb wird der exakten Charakterisierung des Porensystems viel Aufmerksamkeit gewidmet. Neben Methoden wie der Gasadsorption sind bildgebende Verfahren ein wichtiges Hilfsmittel, um Informationen über Porengröße, -geometrie und -konnektivität zu erhalten. In einem ersten „Proof of Concept“ wurden die Porensysteme nanoporöser Materialien mit definierter Porenstruktur durch Röntgenmikroskopie untersucht. Dabei konnten Poren bis zu einer Größe von etwa 60 nm aufgelöst werden. Weiterhin war es möglich, aus den aufgenommenen Bilderserien Rekonstruktionen zu erstellen, wodurch Einblicke in das Innere des Partikels möglich wurden. Für die erfolgreiche Rekonstruktion einer Bilderserie ist es notwendig, dass diese optimal ausgerichtet ist. Aufgrund der hohen Uniformität der untersuchten Proben ist dies ein anspruchsvoller Prozess, der noch weiter optimiert werden muss. Dadurch könnten weitere Einblicke in die untersuchten Proben, beispielsweise durch eine quantitative Diskussion der Porosität, gewonnen werden.

A vast amount and variety of mine tailings are produced around the world each day. In the gold¬mining industry in South Africa the residue of crushed are is disposed of in large tailings or hydraulic fill dams. The outer walls of these dams are built up of layers of material, each of which is allowed to dry before the next layer is placed. In order to study the stability of these walls, the appropriate engineering properties of the tailings must be ascertained. Due to the construction technique used in tailings dam construction, the outer walls are in an unsaturated state, which also means that suctions are generated within the tailings. Various techniques exist to measure suction, most of which are indirect methods. The recent development of the mid-¬plane suction probe at the University of Pretoria created the opportunity of measuring suctions directly on desiccating samples of gold mine tailings. A test method has been developed from which soil mechanics parameters can be derived from suction measurements. The experimental programme consisted of a series of these newly developed tests on fine and coarse samples of gold mine tailings, as well as on different particle size ranges. The experimental results were used in the development of a new method of predicting the air-entry value, with only the grading of the tailings known. A new method of predicting the soil-water characteristic curve up to the air-entry value was also proposed. The results of the research showed that the tailings remain saturated up to the air-entry value. The clay, fine silt and medium silt sized tailings was found to be the controlling particle size ranges in the development of suctions. The vast amount of parameters and information gained through the use of the proposed test method clearly indicates its effectiveness in studying the performance and characteristics of a material drying from saturation. The results also indicated the effectiveness of the mid-plane suction probe for the direct measurement of suction. / Dissertation (M Eng (Geotechnical Engineering))--University of Pretoria, 2006. / Civil Engineering / unrestricted

No description available.

Natural gas is stored as compressed natural gas (CNG) in heavy steel cylinders under pressures of 200-250 atm. However, such a method of storage has certain disadvantages which include multistage compression costs, limited driving range and safety aspects. Hence, alternative methods of storage such as adsorbed natural gas (ANG) which involve adsorbing natural gas at moderate pressures and room temperatures in a suitable nanoporous material are currently being explored. In this thesis, we have isolated model carbon nanostructures and defect geometries most likely to be found in these materials and investigated their specific interactions with methane. The thesis is concerned with ab-initio density functional theory calculations on these various model carbon nanostructures in order to identify the potential candidates that enhance methane adsorption. The adsorption energies of methane on graphite and graphene sheets were similar, with a value of 12.3 kJ/mol for graphene. The Stone-Wales defect in graphene was found to increase the methane adsorption energy to 37.2 kJ/mol, and small surface undulations on the graphene sheet resulted in a smaller increase (16 kJ/mol) in the adsorption energy relative to graphene. The presence of an interstitial carbon was found to significantly reduce the adsorption energy to 5.2 kJ/mol. The enhanced adsorption energy in the case of the Stone-Wales defect was attributed to the significant charge redistribution in the vicinity of the defect. A variety of functional groups such as carboxylic acid (COOH), carbonyl (CO), phenol (OH), pyran (-O-), phenone (=O), peroxide (OOH) and amine (NH2) groups have been observed on carbon surfaces. Extensive density functional calculations of methane adsorbed on various chemically functionalized graphene nanoribbons were carried out to evaluate their methane adsorption energies. A significant finding in this study, is the increased adsorption energies (relative to graphene) that occur for the functional groups containing the OH moiety. The adsorption energies for edge functionalized graphene nanoribbons are 27.6 and 69.7 kJ/mol for COOH and OOH functionalization. Additional computations reveal a strong correlation between the induced dipole moment on methane and the strength of the adsorption energies obtained for the extended nanoribbons. Adsorption isotherms for methane were obtained using grand canonical Monte Carlo simulations for slit-like graphitic pores with and without functional groups. For both OH and COOH functionalized graphite, we observe more than a 40 % increase in the volumetric loading over bare graphite for the highest weight % of the functional group and smallest pore width considered. The maximum volumetric loading decreases with a decrease in the wt% of the functional groups and with an increase in the pore width.