In light of the world‟s growing demand for energy that is environmentally friendly and sustainable, energy sources such as hydrogen have been considered potential contenders. Hydrogen, which can be used for energy storage, can be produced efficiently by the membrane based Hybrid Sulfur (HyS) thermo-chemical process consisting of a decomposition and an electrolysis step. During the HyS electrolysis step, SO2 and H2O are converted to H2 and H2SO4, which implies that the proton exchange membranes (PEMs) to be used for this process should have a high proton conductivity, limited SO2 cross-over and good H2SO4 stability. In order to find alternatives to the costly and high-temperature unstable Nafion®, the aim of this study was to evaluate the H2SO4 stability of various novel membranes. To structure the study, the novel PEM materials were grouped according to the PBI-type base component within the blend membranes, resulting in three groups comprising non-PBI based membranes, PBIOO based membranes and F6-PBI based membranes. Nafion®212 was included as reference PEM. By repeating the H2SO4 treatment with three different Nafion®212 samples, the obtained Nafion® data was also used to determine the experimental and analytical error margins for the study. The stability of all membranes was determined by submerging the membrane samples in 80 wt% H2SO4 at 80 °C for 120 hours. To determine the influence of the acid on the membranes, all samples were characterised before and after the H2SO4 treatment and compared in terms of their acid stability. Physical characterisation of the PEMs included the evaluation of weight and thickness changes, while IEC, SEM-EDX, FTIR and TGA were used to elucidate possible chemical changes due to the H2SO4 treatment. According to the Nafion®212 data, which had been obtained in triplicate for each of the analytical techniques, the experimental error of both the analytical and H2SO4 treatment remained below 10 %, except for the SEM-EDX sulfur-content where significantly larger errors were observed. In spite of the high error margins of the SEM-EDX data (S-content), its results, combined with the results from the other analytical techniques, resulted in a better understanding (both physical and chemical) of the effect the H2SO4 had on the membrane. This further facilitated the evaluation and comparison of the various blended PEM materials in terms of their H2SO4 stability, and the subsequent relation obtained between the observed stability and the chemical constitution and cross-linking of the membranes. After the 80 wt% H2SO4 treatment, significant weight losses were reported for the non-PBI based and PBIOO based membrane groups in comparison with the minimal changes noted for the F6-PBI based group and Nafion®212. Furthermore, significant thickness changes were reported for most of the PBIOO based membranes. The small weight and thickness changes observed for the F6-PBI confirmed the improved stability of this group of membranes in an H2SO4 environment, most likely due to the protective role of the partially fluorinated basic polymer and the known strength of the C-F bonds present. The results showed a clear correlation between the H2SO4 stability and the specific polymers present in the PEM blends investigated. Specific effects found included sulfonation, salt formation, hydrolysis and the accompanied dissolution of membrane fragments. Significant physical changes, for example ascribed to sulfonation of the concerned polymers, were supported by increased IEC measurements and peak intensities of the FTIR spectra, corresponding to the additional –SO3H groups present, while a variation in TGA signals served to further support the altered membrane composition and structure due to the H2SO4 treatment. In the case of dissolution, the corresponding chemical changes (analytical techniques) were supported by the decreased peak intensities of FTIR spectra, IEC measurements and TGA signals associated with degradation of the polymer backbone. It was shown that the stability of the blended membranes depended on the composition (blend components) of the membrane and the effective cross-linking (interaction) between the blend components. For all three groups examined, it became apparent that blend components sFS and sPSU were, for example, more stable than sPEEK and that ionical cross-linking seemed more effective than covalent cross-linking of blend components. When considering all membranes tested, the non-PBI based blend membranes consisting of (s)PSU and PFS copolymers in the presence of fluorinated cross-linkers and the PBIOO-sPSU blended membranes including most of the F6-PBI based membranes showed sufficient stability to be recommended for SO2 electrolysis. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

In light of the world‟s growing demand for energy that is environmentally friendly and sustainable, energy sources such as hydrogen have been considered potential contenders. Hydrogen, which can be used for energy storage, can be produced efficiently by the membrane based Hybrid Sulfur (HyS) thermo-chemical process consisting of a decomposition and an electrolysis step. During the HyS electrolysis step, SO2 and H2O are converted to H2 and H2SO4, which implies that the proton exchange membranes (PEMs) to be used for this process should have a high proton conductivity, limited SO2 cross-over and good H2SO4 stability. In order to find alternatives to the costly and high-temperature unstable Nafion®, the aim of this study was to evaluate the H2SO4 stability of various novel membranes. To structure the study, the novel PEM materials were grouped according to the PBI-type base component within the blend membranes, resulting in three groups comprising non-PBI based membranes, PBIOO based membranes and F6-PBI based membranes. Nafion®212 was included as reference PEM. By repeating the H2SO4 treatment with three different Nafion®212 samples, the obtained Nafion® data was also used to determine the experimental and analytical error margins for the study. The stability of all membranes was determined by submerging the membrane samples in 80 wt% H2SO4 at 80 °C for 120 hours. To determine the influence of the acid on the membranes, all samples were characterised before and after the H2SO4 treatment and compared in terms of their acid stability. Physical characterisation of the PEMs included the evaluation of weight and thickness changes, while IEC, SEM-EDX, FTIR and TGA were used to elucidate possible chemical changes due to the H2SO4 treatment. According to the Nafion®212 data, which had been obtained in triplicate for each of the analytical techniques, the experimental error of both the analytical and H2SO4 treatment remained below 10 %, except for the SEM-EDX sulfur-content where significantly larger errors were observed. In spite of the high error margins of the SEM-EDX data (S-content), its results, combined with the results from the other analytical techniques, resulted in a better understanding (both physical and chemical) of the effect the H2SO4 had on the membrane. This further facilitated the evaluation and comparison of the various blended PEM materials in terms of their H2SO4 stability, and the subsequent relation obtained between the observed stability and the chemical constitution and cross-linking of the membranes. After the 80 wt% H2SO4 treatment, significant weight losses were reported for the non-PBI based and PBIOO based membrane groups in comparison with the minimal changes noted for the F6-PBI based group and Nafion®212. Furthermore, significant thickness changes were reported for most of the PBIOO based membranes. The small weight and thickness changes observed for the F6-PBI confirmed the improved stability of this group of membranes in an H2SO4 environment, most likely due to the protective role of the partially fluorinated basic polymer and the known strength of the C-F bonds present. The results showed a clear correlation between the H2SO4 stability and the specific polymers present in the PEM blends investigated. Specific effects found included sulfonation, salt formation, hydrolysis and the accompanied dissolution of membrane fragments. Significant physical changes, for example ascribed to sulfonation of the concerned polymers, were supported by increased IEC measurements and peak intensities of the FTIR spectra, corresponding to the additional –SO3H groups present, while a variation in TGA signals served to further support the altered membrane composition and structure due to the H2SO4 treatment. In the case of dissolution, the corresponding chemical changes (analytical techniques) were supported by the decreased peak intensities of FTIR spectra, IEC measurements and TGA signals associated with degradation of the polymer backbone. It was shown that the stability of the blended membranes depended on the composition (blend components) of the membrane and the effective cross-linking (interaction) between the blend components. For all three groups examined, it became apparent that blend components sFS and sPSU were, for example, more stable than sPEEK and that ionical cross-linking seemed more effective than covalent cross-linking of blend components. When considering all membranes tested, the non-PBI based blend membranes consisting of (s)PSU and PFS copolymers in the presence of fluorinated cross-linkers and the PBIOO-sPSU blended membranes including most of the F6-PBI based membranes showed sufficient stability to be recommended for SO2 electrolysis. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

<p>In recent decades there has been great interest to produce novel bio-based composites to reduce carbon footprint without sacrificing the necessities that society demands. To achieve a more sustainable future, research in cellulose biopolymers has risen to the forefront. Impressive mechanical, thermal and optical properties along with its abundant biomass has made nanocellulose (NC) the subject of intense research in the area of electronics, drug delivery, sensors, selective filters, and structural materials, to name a few. The practical utility of any cellulose-based materials requires a more complete understanding of how the fundamental structure affects final performance. This thesis examines several avenues to obtain novel materials by considering processing parameters and preparation methods for working with raw nanocellulose materials, and mechanochemical approaches for surface grafting to obtain modified CNs with improved dispersion in organic media. Lastly, the synergy between the two studies and its impact on advanced materials and nanocomposites is discussed.</p> <p>The low cost and wide availability of cellulose nanofibers (CNF), a refined form of cellulose microfibrils, make these an ideal starting material for our studies. However, the aggregated states of freeze-dried CNFs hinder its use as an additive for reinforcing polymer blends or functional films. The use of <i>tert</i>-butyl alcohol (TBA) as a stabilizer in pharmaceutical drugs has been well studied for its effectiveness in facilitating redissolution and extending product shelf life. Lyophilization of aqueous CNF slurries treated with various amounts of TBA produced a more porous material that could be redispersed with superior colloidal stability relative to untreated freeze-dried CNFs. Furthermore, CNFs lyophilized from aqueous TBA mixtures could be subjected to mild mechanochemical reactions (horizontal ball milling) to produce esterified nanofibers with high degrees of substitution (DS) and good dispersibility profiles in organic solvents. This solventless technique allowed for a variety of carboxylic acids to be grafted onto CNF surfaces. Finally, investigations of new materials with technological utility have been explored using networks of CNFs modified with oleic acid. These can be cast into superhydrophobic (SHP) films having a hierarchical structure characteristic of a self-similar material, with a wettability comparable to that of the lotus leaf. The SHP surface can also be regenerated after surface fouling or physical damage. </p>

Made available in DSpace on 2015-04-11T13:54:25Z (GMT). No. of bitstreams: 1 jessyca dos reis.pdf: 2629785 bytes, checksum: 664a61966469b33065e128fef56d7900 (MD5) Previous issue date: 2013-10-29 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Environmental isolates of filamentous fungi are widely studied for their ability to secrete metabolites of great commercial value, including pigments. These, in turn, find application to color textile raw materials, foods and medicines. In this context, the aim of this work was to select fungi from soil samples Amazon with potential for the production of pigments. For this, samples were collected from surface soil and colonies were isolated by serial dilution technique. The macro and microscopic characteristics of colonies grown within 72 hours were used for determining the gender of the isolates and the ITS region of the ribosomal DNA of fungal pigment producers was sequenced for identification to the species level. A cryopreservation technique and conservation at -70 C was employed to preserve the lines with biotechnological potential. A bioprocess performed in broth Czapeck enabled the selection of fungi which produce colored compounds. Fractions containing the pigments were extracted by use of solvents of different polarity and selection of the pigment of interest was due to the color intensity of the substance present in the fractions. The techniques used for the isolation and structural elucidation of the sample of interest involved chromatographic fractioning (Sephadex LH-20 column and microcrystalline cellulose column), recrystalization and NMR (Nuclear Magnetic Resonance). The influence of carbon sources and nitrogen on the yield of the isolated substance was also studied in this work. From samples collected was possible to isolate 50 soil fungi. Of these five strains were able to produce pigments during fermentation. Producing fungi were identified as Penicillium sclerotiorum 2AV2, Penicillium sclerotiorum 2AV6, Aspergillus calidoustus 4BV13, Penicillium citrinum 2AV18 e Penicillium purpurogenum 2BV41. Penicillium sclerotiorum 2AV2 produced fractions very colorful and was chosen to continue the activities of the chemical characterisation. After isolation of the substance was obtained as a yellow-orange powder, which was identified by NMR as sclerotiorin, a major metabolite that has not been previously described by synthesis by fungi from the Amazon. The influence of carbon and nitrogen sources for production of sclerotiorin was analised and it was found that rhamnose and peptone increased yield when used separately. These results indicate that Amazonian fungi bioprospecting is an alternative to search for new sources of natural dyes, since it allows to exploit the biotechnological potential of our region while allowing knowledge of species of microorganisms producers. / Isolados ambientais de fungos filamentosos são amplamente estudados por sua capacidade de secretar metabólitos de grande valor comercial, entre eles os pigmentos. Estes, por sua vez, encontram aplicação como corantes de matérias-primas têxteis, alimentos e medicamentos. Nesse contexto, o objetivo deste trabalho foi selecionar fungos de amostras de solo Amazônico com potencial para a produção de pigmentos. Para isso, foram coletadas amostras de solo superficial e colônias foram isoladas pela técnica da diluição em série. As características macro e microscópicas das colônias crescidas em até 72 horas foram utilizadas para a determinação do gênero dos isolados e a região ITS do DNA ribossomal dos fungos produtores de pigmentos foi sequenciada para permitir a identificação em nível de espécie. Para conservar as linhagens com potencial biotecnológico foi empregada uma técnica de criopreservação e armazenamento a -70 C. Um bioprocesso realizado em caldo Czapeck possibilitou a seleção dos fungos produtores de compostos coloridos. Frações contendo os pigmentos foram extraídas pelo uso de solventes de diferentes polaridades e o pigmento de interesse foi selecionado pela intensidade da cor da substância presente nas frações. A metodologia para isolamento e caracterização química da amostra envolveu técnicas de fracionamento cromatográfico (coluna Sephadex LH-20 e coluna de celulose microcristalina), recristalização e análises de RMN (Ressonância magnética nuclear). A influência das fontes de carbono e nitrogênio sobre o rendimento da substância isolada também foi estudada nesse trabalho. A partir das amostras coletadas foi possível isolar 50 fungos do solo. Desses, 5 cepas foram capazes de produzir pigmentos durante a fermentação. Os fungos produtores foram identificados como Penicillium sclerotiorum 2AV2, Penicillium sclerotiorum 2AV6, Aspergillus calidoustus 4BV13, Penicillium citrinum 2AV18 e Penicillium purpurogenum 2BV41. Penicillium sclerotiorum 2AV2 produziu frações muito coloridas e foi escolhido para prosseguir as atividades de caracterização química. Após o isolamento da substância, obteve-se um pó amarelo-alaranjado, que foi identificado por RMN como esclerotiorina, um importante metabólito que ainda não havia sido descrito pela síntese por fungos da Amazônia. A influência das fontes de carbono e nitrogênio para a produção de esclerotiorina foi analisada, e verificou-se que ramnose e peptona aumentaram o rendimento quando utilizadas separadamente. Estes resultados indicam que a bioprospecção de fungos Amazônicos é uma alternativa para a pesquisa por novas fontes de corantes naturais, pois permite explorar o potencial biotecnológico da nossa região, ao mesmo tempo em que possibilita o conhecimento das espécies de micro-organismos produtores.

Thesis (MScAgric (Soil Science)--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: A number of chemical and physical features of Namibian soils in a 22 790 km2, two degree-square block between 17 – 19 oE and 22 – 23 oS in eastern central Namibia, had been investigated, and the fertility status established. In 80 % of samples the nitrate, nitrite, and sulfate concentrations of the saturated paste extract are 0 – 54.6 mg l-1 NO3 -, 0 – 24.7 mg l-1 NO2 -, and 5.4 – 20.9 mg l-1 SO4 2- respectively. In 90 % of samples the plantavailable phosphorus is below 12 mg kg-1, which is low for a soil under natural grassland, but in line with the prevailing semi-arid climate and low biomass production of the study area. In 80 % of samples the extractable calcium, magnesium, potassium, and sodium concentrations are 0.61 – 5.73 cmolckg-1 Ca (122 – 1 146 mg kg-1 Ca), 0.12 – 2.28 cmolckg-1 Mg (15 – 278 mg kg-1 Mg), 0.13 – 0.54 cmolckg-1 K (51 – 213 mg kg-1 K) and 0.05 – 0.38 cmolckg-1 Na (11 – 87 mg kg-1 Na) respectively, while the exchangeable calcium, magnesium, potassium, and sodium concentrations are 0.21 – 6.02 cmolckg-1 Ca, 0.12 – 2.01 cmolckg-1 Mg, 0.12 – 0.49 cmolckg-1 K and 0 – 0.13 cmolckg-1 Na respectively. The mean ± 1 standard deviation is 3.57 ± 3.57 cmolckg-1 for cation exchange capacity, 3.48 ± 3.61 for sum of exchangeable bases and 4.53 ± 4.39 for sum of extractable bases. The cation exchange capacity and the sum of exchangeable bases are virtually identical, which indicate the almost complete absence of exchangeable H+ and Al3+ in the soils of the study area, as expected from a semi-arid climate. None of the profiles were classified as saline or sodic. In 80 % of samples the plant-available iron, manganese, zinc and copper concentrations are 7.2 – 32.8 mg kg-1 Fe, 13.6 – 207.5 mg kg-1 Mn, 0 – 1.80 mg kg-1 Zn and 0 – 4.0 mg kg-1 Cu respectively. Soil organic matter content of the study area soils ranges between 0.05 – 2.00 %, with most (80 % of samples) containing 0.25 – 1.20 % organic matter. This is considerably lower than values reported in literature, even for other southern African countries. The reason lies with the hot, semi-arid climate. The pH distribution is close to normal, with 80 % of samples having pH (H2O) of 5.54 – 8.18, namely moderately acid to moderately alkaline. Sand, silt and clay content of most (80 %) samples varies between 60.3 – 89.7 % sand, 4.6 – 25.2 % silt and 3.5 – 19.1 % clay. The soils of the study area are mainly sandy, sandy loam and loamy sand. In 80 % of samples the coarse sand fraction ranges from 3.5 – 34.5 %, the medium sand fraction from 20.5 – 37.3 %, the fine sand fraction from 38.7 – 54.5 % and the very fine sand fraction from 0.0 – 12.9 % of all sand. The fine sand fraction, thus, dominates, with very fine sand being least abundant. The topsoil contains relatively more coarse sand and less very fine sand than the subsoil. Instances of sealing, crusting and hardening occur sporadically in the study area. Cracking is only found in pans, while self-mulching is not evident. No highly instable soils were encountered in the study area. The water-holding capacity is generally low, with depth limitations in the western highlands, the Khomas Hochland, and texture limitations in the eastern Kalahari sands. The central area has soils with a somewhat better water-holding capacity, but it is still very low when compared to arable soils of temperate, sub-humid and humid zones elsewhere in southern Africa. Soil characteristics are perceptibly correlated with climate, parent material, topography, degree of dissection of the landscape and position in the landscape. The most obvious differences are between soils formed in schistose parent material of the Khomas Hochland in the west and those of the Kalahari sands in the east. The soils of the study area are unsuitable to marginally suitable for rainfed crop production, due to low iv fertility. The study area is climatologically unsuited for rainfed crop production, so the present major land use is extensive livestock production on large farms. The natural vegetation is well adapted to the prevailing conditions. The methodology followed to delineate terrain units, with a combination of procedures involving digital elevation data and satellite imagery, seems to work well in the Namibian landscape. This study thus served as a successful proof-of-concept for the methodology, which can in future be rolled out for the remainder of the country. The site and analytical information is available in digital format as spreadsheets and in a geographical information system, as well as in a variety of digital and printed maps. / AFRIKAANSE OPSOMMING: ‘n Aantal chemiese en fisiese eienskappe van Namibiese gronde in ‘n 22 790 km2, 1o x 2o blok tussen 17 – 19 o Oos en 22– 23 o Suid in oostelike sentraal-Namibië is ondersoek en die grondvrugbaarheidstatus bepaal. In 80 % van monsters is die nitraat-, nitriet- en sulfaatkonsentrasies van die versadigde pasta ekstrak 0.0 – 54.6 mg l-1 NO3 -, 0.0 – 24.7 mg l-1 NO2 -, en 5.4 – 20.9 mg l-1 SO4 2-onderskeidelik. In 90 % van monsters is die plant-beskikbare fosfor minder as 12 mg kg-1, wat laag is vir gronde onder natuurlike grasveld, maar dit is verklaarbaar deur die heersende semi-ariede klimaat en lae biomassa produksie in die studiegebied. In 80 % van monsters is die konsentrasies van ekstraheerbare kalsium, magnesium, kalium en natrium 0.61 – 5.73 cmolckg-1 Ca (122 – 1 146 mg kg-1 Ca), 0.12 – 2.28 cmolckg-1 Mg (15 – 278 mg kg-1 Mg), 0.13 – 0.54 cmolc kg-1 K (51 – 213 mg kg-1 K) en 0.05 – 0.38 cmolckg-1 Na (11 – 87 mg kg-1 Na) onderskeidelik, terwyl die uitruilbare kalsium, magnesium, kalium en natrium konsentrasies onderskeidelik 0.21 – 6.02 cmolckg-1 Ca, 0.12 – 2.01 cmolckg-1 Mg, 0.12 – 0.49 cmolckg-1 K and 0.0 – 0.13 cmolckg-1 Na is. Die gemiddelde ± 1 standaardafwyking is 3.57 ± 3.57 cmolckg-1 vir katioonuitruilvermoë, 3.48 ± 3.61 vir die som van uitruilbare basisse en 4.53 ± 4.39 vir die som van ekstraheerbare basisse. Die katioonuitruilvermoë en som van uitruilbare basisse is feitlik identies, wat ‘n feitlik algehele afwesigheid van uitruilbare H+ and Al3+ in die gronde van die studiegebied aandui, soos verwag word weens die semi-ariede klimaat. Geeneen van die profiele is geklassifiseer as soutbrak of natriumbrak nie. In 80 % van monsters is die plant-beskikbare yster, mangaan, sink en koper konsentrasies onderskeidelik 7.2 – 32.8 mg kg-1 Fe, 13.6 – 207.5 mg kg-1 Mn, 0.0 – 1.80 mg kg-1 Zn en 0.0 – 4.0 mg kg-1 Cu. Grond organiese material inhoud in die studiegebied wissel tussen 0.05 – 2.00 %, met 80 % van monsters wat 0.25 – 1.20 % organiese material bevat. Dit is aansienlik laer as die waardes gevind in literatuur, selfs vir ander Suider-Afrikaanse lande. Die oorsaak is die warm, semiariede klimaat. Die pH verspreiding is feitlik normaal, met 80 % van monsters wat pH (H2O) van 5.54 – 8.18 het, met ander woorde matig suur tot matig alkalies. Sand, slik en klei inhoud van die meeste (80 %) monsters varieer tussen 60.3 – 89.7 % sand, 4.6 – 25.2 % slik en 3.5 – 19.1 % klei. Die gronde van die studiegebied is hoofsaaklik sand, sand-leem en leem-sand. In 80 % van monsters beslaan die growwe sandfraksie 3.5 – 34.5 %, die medium sandfraksie 20.5 – 37.3 %, die fyn sandfraksie 38.7 – 54.5 % en die baie fyn sandfraksie 0.0 – 12.9 % van die totale sandfraksie. Die fyn sandfraksie is dus dominant, terwyl die baie fyn sandfraksie die skaarsste is. Die bogronde bevat relatief meer growwe sand en minder baie fyn sand as die ondergronde. Gevalle van verseëling, korsvorming en verharding kom sporadies in die studiegebied voor. Krake kom net in panne voor en self-omkering is nie opgemerk nie. Geen hoogsonstabiele gronde is in die studiegebied gevind nie. Die waterhouvermoë is in die algemeen laag, met dieptebeperkinge in die westelike hooglande, die Khomas Hochland, en tekstuurbeperkinge in die oostelike Kalahari sande. Die sentrale gedeelte het gronde met ‘n ietwat beter waterhouvermoë, maar dis steeds baie laag in vergelyking met akkerbougronde van gematigde, sub-humiede en humiede sones elders in Suider- Afrika. Grondeienskappe is ooglopend verwant aan klimaat, moedermateriale, topografie, graad van gebrokenheid van die landskap en posisie in die landskap. Die duidelikste verskille kom voor in die gronde wat van vi skisagtige moedermateriaal van die Khomas Hochland in die weste en dié wat in die Kalahari sande in die ooste gevorm het. Die gronde van die studiegebied is ongeskik tot marginaal geskik vir droëland akkerbou, weens die lae vrugbaarheid. Aangesien die studiegebied klimatologies ongeskik is vir droëland akkerbou, is die huidige hoof landgebruik ekstensiewe veeproduksie op groot plase. Die natuurlike plantegroei is goed by die heersende omstandighede aangepas. Die metodiek wat gevolg is om terreineenhede af te baken, wat ‘n kombinasie van prosedures met digitale hoogtedata en satellietbeelde is, blyk goed te werk vir die Namibiese landskap. Hierdie studie dien dus as ‘n suksesvolle bewys-van-konsep van die metodiek, wat in die toekoms uitgebrei kan word na die res van die land. Die veld- en ontledingsinligting is beskikbaar in digitale formaat, in ‘n geografiese inligtingstelsel en ‘n verskeidenheid digitale- en gedrukte kaarte.

<p>Curiosity is a powerful tool, and combined with the ability to observe the natural world, grants humankind an unique opportunity, the opportunity to wonder why. Why do things exist?, why do they do the things they do?, why is this even possible?</p> <p>Research in our lab is focused on the basic understanding and potential application of biological materials, in particular, biological adhesives produced by marine organisms such as oysters. Oysters produce a cement-like material that is able to withstand the dynamic conditions found in coastal environments. The focus of this dissertation is to lay the basis of the characterization of new biological materials by observing and analyzing its physical properties, to measure the performance of the material in natural conditions and finally to identify the basic components that give the material the properties that we observe. The end goal of this project is to understand the properties of this material so we are able to develop a synthetic system that is able to imitate, as close as possible, what we find in nature. These results, and more importantly, the new questions that emerge from this research, provide a first look at the adhesive system of oysters leading the way to new discoveries in the future.</p>

Une enquête ethnobotanique a été menée en Bosomtwi et Sekyere Est Districts de la Région Ashanti, au Ghana, en utilisant des questionnaires validés pour identifier les plantes traditionnellement utilisées pour gérer le paludisme. Cinq plantes avec une utilisation élevée ont été sélectionnés et une extraction préliminaire des matières végétales sélectionnées effectuées avec de l'eau, le methanol, l'acétate d'éthyle et d'éther de pétrole. Les extraits ont été dosés pour l'activité antiplasmodiale utilisant les méthodes antiplasmodiales in vitro. Les deux les plus prometteuses plantes, Phyllanthus fraternus (Phyllanthaceae) et Bambusa vulgaris (Pocea) ont été choisis pour l'isolement bio-guidée de constituants bioactifs en utilisant des méthodes chromatographiques (par exemple TLC, flash chromatographie, HPLC semi-préparative). Élucidation de la structure des composés isolés ont été effectuées en utilisant des méthodes spectroscopiques (par exemple 1D et 2D Magnétique Nucléaires Résonance (MNR), infrarouge et spectrométrie de masse et leur activité antiplasmodiale étudiés. / An ethnobotanical survey was conducted in Bosomtwi and Sekyere East Districts of the Ashanti Region, Ghana, using validated questionnaires to identify plants used traditionally to manage malaria. Five plants with high usage were selected and a preliminary extraction of the selected plant materials done using water, methanol, ethyl acetate and petroleum ether. The extracts were assayed for antiplasmodial activity using in vitro antiplasmodial methods. The two most promising plants, Phyllanthus fraternus (Phyllanthaceae) and Bambusa vulgaris (Pocea) were selected for bio-guided isolation of bioactive constituents using chromatographic methods (e.g. TLC, flash chromatography, semi-preparative HPLC). Structural elucidation of the isolated compounds were done using spectroscopic methods (e.g. 1D and 2D Nuclear Magnetic Resonance, Infrared and mass spectrometry) and their antiplasmodial activity studied.

<p> Mass spectrometry (MS) has become one of the most powerful and versatile tools for chemical analysis due to its ultra-high sensitivity, high throughput, ease of automation, and the large amount of information obtained. Nowadays, MS is extensively used in many tasks, such as identification and quantitation of drug metabolites, analysis of the products of biomass pyrolysis, and study of reactive intermediates, to name a few. However, these mass spectrometric analyses are not without challenges. For example, the requirement for quantifying trace amounts of substances in a complex mixture constantly pushes the detection limit of mass spectrometers, and the increased sample complexity demands higher and higher mass resolution. Therefore, MS is constantly evolving to address more difficult analytical challenges. A variety of MS techniques have been developed over the years, including soft ionization methods that facilitate mass spectrometric analysis of macromolecules, such as proteins and antibodies that enables the development of new therapeutic agents, benchtop high-resolution mass spectrometers, such as the orbitraps that can be used to analyze some of the most complex mixtures, and portable mass spectrometers which can be used in the home and garden and even in cancer surgery. Besides its applications in chemical analysis, MS can serve as a unique tool for the fundamental study of gas-phase ion/molecule reactions, these gas-phase reactions can be used to better understand the reactivities of many reactive intermediates and to obtain structural information for unknown analytes.</p><p></p><p> This thesis is aimed at addressing challenges involved in mass spectrometric analyses of isomeric drug metabolites (Chapter 4), quantitation of drug metabolites by using tandem mass spectrometry coupled with liquid chromatography (LC-MS/MS) (Chapter 5), delineating cellulose depolymerization mechanisms upon fast pyrolysis by using pyrolysis-tandem mass spectrometry (py-MS/MS) (Chapter 6), and studying the reactivities of vinyl cation intermediates (Chapter 7). An overview of the dissertation research is given in Chapter 1, the instrumentation and principles of linear quadrupole ion trap (LQIT) mass spectrometer are discussed in Chapter 2, and the organic synthesis performed for several studies is detailed in Chapter 3.</p>

Cellulose Nanocrystals have been used in a wide range of applications including cement composites as a strength enhancer. This work analyses the use of CNC from several sources and production methods, and their effects on rheology and hydration of pastes made using different cement types with different compositions. Cement Types I/II and V were used to prepare pastes with different water to cement ratios (w/c) and measure the changes in rheology upon CNC addition. The presence of tricalcium aluminate (cement chemistry denotes as C3A) made a difference in the magnitude of CNC effects. At dosages under 0.5vol% to dry cement, CNC reduced the yield stress up to 50% the control value. Pastes with more C¡A reduced yield stress over a wider range of CNC dosages. CNC also increased yield stress of pastes with dosages above 0.5%, twice the control value for pastes with high C3A content at 1.5% CNC and up to 20 times for pastes without C3A at the same dosage.<br>All the CNCs used were characterized in length, aspect ratio, and zeta potential to identify a definitive factor that governs the effect in the rheology of cement pastes. However, no definitive evidence was found that any of these characteristics dominated the measured effects.<br>The CNC dosage at which the maximum yield stress reduction occurred increased with the amount of water used in the paste preparation, which provides evidence of the dominance of the water to cement ratio in the rheological impact of CNC.<br>14<br>Isothermal calorimetry showed that CNC cause concerning retardation effects in cement hydration. CNC slurries were then tested for sugars and other carbohydrates that could cause the aforementioned effect, then slurries were filtered, and impurities were detected in the filtrate, these impurities were quantified and characterized, however, the retardation appeared to be unaffected by the amount of the species detected, suggesting that the crystal chemistry, which is a consequence of the production method, is responsible of this retardation.<br>This work explores the benefits and drawbacks of the use of CNC in cement composites by individually approaching rheology and heat of hydration on a range of physical and chemical tests to build a better understanding of the observed effects.<br>Understanding the effect of CNCs on cement paste rheology can provide insights for future work of CNCs applications in cement composites.

New experimental strategies and algorithmic approaches were devised and tested to improve the analysis of pharmaceutically relevant materials. These new methods were developed to address key bottlenecks in the design of amorphous solid dispersions for the delivery of low-solubility active pharmaceutical ingredients in the final dosage forms exhibiting high bioavailability. <br>