The objectives of this study are to synthesize sub-micron sized zinc borate and to use them with other flame retardant additives in poly(ethylene terephthalate) (PET) based composites. The study can be divided into two parts. In the first part, it was aimed to synthesize sub-micron sized zinc borate (2ZnO.3B2O3.3.5H2O) with the reaction of zinc oxide and boric acid. For this purpose, low molecular weight additives or surfactants were used in the syntheses to prevent the agglomeration and to decrease particle size. Effect of type of surfactant and its concentration / effect of using nano-sized zinc oxide as reactant on the synthesis, properties and morphology of 2ZnO.3B2O3.3.5H2O were investigated. Synthesized zinc borates were characterized by X-Ray diffraction (XRD), Scanning Electron Microscope (SEM) and Thermogravimetric Analysis (TGA). The results were compared with a commercial zinc borate, Firebrake (FB). Characterization results showed that at least in one dimension sub-micron size was obtained and synthesized zinc borates did not lose their hydration water until the process temperature of the composites. In the second part of the study, PET based composites, which mainly included synthesized sub-micron sized zinc borates were prepared by using a co-rotating twin screw extruder and injection molding machine. Synergist materials such as boron phosphate (BP) and triphenyl phosphate (TPP) were also used in the composite preparation. The composites were characterized in terms of flammability and mechanical properties. Flammability of composites was determined by using a Limiting Oxygen Index (LOI) test. Mechanical properties such as tensile strength, elastic modulus, elongation at break and impact strength were also studied. According to LOI and impact tests, the composites containing 3 wt. % BP and 2 wt. % zinc borate which was modified with poly(styrene-co-maleic anhydride), 2PSMA05/3BP and 2PSMA1/3BP have higher LOI and impact values when compared to neat PET.

This work computationally investigates the partial oxidation of ethylene (i.e. ethylene epoxidation) using periodic Density Functional Theory (DFT) on slab models that represent the catalyst surfaces. The mechanical aspects of the reaction were investigated on silver surfaces, which are industrially applied catalysts, for a wide range of surface models varying from metallic surfaces with low oxygen coverage to oxide surfaces. For comparison, the metallic and oxide phases of copper and gold were also studied. On these surfaces, the reaction paths and the transition states along these paths for the selective and non-selective reaction channels were obtained using the climbing image nudged elastic band (CI-NEB) method. In order to answer the question &ldquo / what is the relation between the surface state and the ethylene oxide selectivity?&rdquo / metallic (100), (110) and (111) surfaces of Cu, Ag and Au / and, (001) surfaces of Cu2O, Ag2O and Au2O oxides were studied and compared. For the studied metallic surfaces, it was found that the selective and non-selective reaction channels proceed through the oxametallacycle (OMC) intermediate, and the product selectivity depends on the relative barriers of the these channels, in agreement with the previous reports. However for the studied metallic surfaces and oxygen coverages, a surface state that favors the ethylene oxide (EO) formation was not identified. The studied Au surfaces did not favor the oxygen adsorption and dissociation, and the Cu surfaces favored the non-selective product (acetaldehyde, AA) formation. Nevertheless, the results of Ag surfaces are in agreement with the ~50% EO selectivity of the un-promoted silver catalyst. The catalyst surface in the oxide state was modeled by the (001) surfaces of the well defined Cu2O, Ag2O and Au2O oxide phases. Among these three oxides, the Cu2O is found not to favor EO formation whereas Au2O is known to be unstable, however selective for epoxidation. The major finding of this work is the identification of a direct epoxidation path that is enabled by the reaction of the surface oxygen atoms, which are in two-fold (i.e. bridge) positions and naturally exist on (001) oxide surfaces of the studied metals. Among the three oxides studied, only Ag2O(001) surface does not show a barrier for the formation of adsorbed epoxide along the direct epoxidation path. Moreover, the overall heat of reaction that is around 105 kJ/mol agrees well with the previous reports. The single step, direct epoxidation path is a key step in explaining the high EO selectivities observed. Also for the oxide surfaces, the un-selective reaction that ends up in combustion products is found to proceed through the OMC mechanism where aldehyde formation is favored. Another major finding of this study is that, for the studied oxide surfaces two different types of OMC intermediates are possible. The first possibility is the formation of the OMC intermediate on oxygen vacant sites, where the ethylene can interact with the surface metal atoms directly. The second possibility is the formation of a direct OMC intermediate, through the interaction of the gas phase ethylene with the non-vacant oxide surface. This occurs through the local surface reconstruction induced by the ethylene. The effect of Cl promotion was also studied. Coadsorption of Cl is found to suppress the oxygen vacant sites and also the reconstruction effects that are induced by ethylene adsorption. Thus, by preventing the interaction of the ethylene directly with the surface metal atoms, Cl prevents the OMC formation, therefore the non-selective channel. At the same time Cl increases the electrophilicity of reacting surface oxygen. The direct epoxidation path appears to be stabilized by coadsorbed oxygen atoms. Thus, we carry the discussions on the silver catalyzed ethylene epoxidation one step further. Herein we present that the EO selectivity will be limited in the case of metallic catalyst, whereas, the oxide surfaces enable a direct mechanism where EO is produced selectively. The role of the Cl promoter is found to be mainly steric where it blocks the sites of non-selective channel.

Abstract Aqueous solution containing tin chloride as precusor was traditionally added with NH3(aq) to promote hydrolysis and hence condensation. This results in a particulate sol which possesses little viscosity and the aggregation of precusor particles makes the subsequcently spin-coated thin film very rough in the surface and poorly-adhered with the substrate. One objective of this work is to improve the film quality by refluxing the sol to reduce precursor aggregation, enhance hydrolysis and promote HCl(g) evaporation. Experimtntal results show that, after refluxing the sol with DI-water or methanol as solvent, one obtains better films when basic sol (NH3(aq) added) and SnCl2 precursor is used instead of acidic sol (HCl(aq)added) and SnCl4 precursor. Moreover, to further reduce the effect of Cl¡Ð ion in aggregation and increase viscosity, ethylene glycol was used as solvent and two-stage heating-stirring of the sol in 80 oC and 130 oC ~150 oC was carried out to promote generation of H2O(g) and HCl(g). The evaporation of H2O(g) and HCl(g) enhances the polymerization of precursor and increase the viscosity of the sol. The aggregation caused by Cl¡Ð ions is thus reduced due to the steric effect present in the polymerical sol. XRD, SEM, FT-IR , TGA and DSC were used to examine the evolution from sol to films. FT-IR results show that absorbtion peaks of the xerogel appear at 636 cm-1(O-Sn-O) and 500 cm-1 (Sn-O). XRD results of the calcined (4 hr) powders show that rutile (SnO2) crystallization starts at 200 oC for that derived from the SnCl2-containing sol while powder derived from the SnCl4-containing sol starts crystallization at 250 oC. However, grain growth is faster in powder derived from SnCl4-containing sol as their XRD peaks become sharper than that corresponding to SnCl2 precursor as calcination temperature is raised. Based on the examination of the evolution process, it is concluded that SnCl2 polymerizes in ethylene glycol as a one dimensional chain while SnCl4 forming a 3-D network after polymerizing in ethylene glycol.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniversitet, 2009. / Härtill 4 uppsatser.

Poly (Ethylene Oxide) (PEO, with a general formula (CH₂-CH₂-O)[subscript pi] ) is completely soluble in water at room temperature over an extremely wide molecular weight range and has been widely studied by experiment and theory. The objective of our work is to study the solubility behavior by the method of Monte Carlo simulation. The insertion factor lnB, which is equivalent to the infinite dilute Henry's Law Constant, is used to represent the solubility of various molecules in water. Our research started with simple fluid and aqueous solutions of small molecules including hard spheres, inert gases, hydrocarbons and dimethyl ether (DME, as a precursor for PEO). Solubility consists of a favorable energy term and an unfavorable entropy term. Against the common belief of entropy-dominating-hydrophobicity effect, it is actually the ability of the solute to interact with solvent (or the energetic factor) that dominates solubility. The solubility minimum appearing for both hydrophobic and hydrophilic solutes along the water coexistence curve is the result of competition between the favorable energy contribution and the unfavorable entropy contribution. Normal alkanes with carbon number from 1 to 20 have been modeled by LJ chains to study the solubility of non-polar polymer chains in water. Various constraints have been put on the LJ model to evaluate their effect on solubility. No significant difference was observed for LJ chain with or without fixed bond angles, but torsional interaction changed the chain solubility dramatically. The temperature and chain-length effect on chain solubility has been examined and it can be explained by the balancing between the intra-chain interaction and entropy penalty. By choosing the right torsional interaction parameters we may be able to reproduce by simulations the solubility minimum of normal alkanes at C₁₁. PEO was modeled by united atom chains with length up to 30. The most probable distance between two nearest ether oxygens in both vacuum and aqueous solutions matches the hydrogen bond length in bulk water. Hydrogen bonding plays an important role in the unique water solubility behavior of PEO since the water-PEO interaction effectively increases the total number of hydrogen bonds and results in a favorable change in energy. A trans-gauche-trans conformation along the O-C-C-O bonds does enable hydrogen bond formation between one water molecule and two nearest or next nearest ether oxygens. A helix structure is not required for the PEO to have favorable interactions with water. Two polymers with similar structure as PEO but are insoluble in water: Poly (methylene oxide) (PMO) and Poly (propylene oxide) (PPO) have been studied to compare with PEO. Their difference in structure from PEO, though slight, reduces the chance of hydrogen bond forming between water and chains so as to decrease the solubility. / text

Studies of biomolecular interactions are of interest for several reasons. Beside basic research, the knowledge gained from such studies is also very valuable in for example drug target identification. Medical care is another area where biomolecules may be used as biomarkers to aid physicians in making correct diagnosis. In addition, the highly specific interactions between antibodies and almost any substance opens up the possibilities to design systems for detection of trace amounts of both biological and non-biological substances within environmental restoration, law enforcement, correctional care, customs service and national security. A biochip, which contains a biologically active material, offers a means of monitoring the molecular interactions in the above applications in a sensitive and specific manner. The biochip is a key component of a biosensor, which also includes components for transforming the interaction events into a human-readable signal. This thesis describes the use of poly(ethylene glycol) (PEG) in biochip design. Two different approaches are presented, the first based on ethylene glycol (EG)-containing alkyl thiol self-assembled monolayers (SAMs) on flat gold and the second on photo-induced graft copolymerisation of PEG-containing methacrylate monomers onto various substrates. The former is a two dimensional system where EG-terminated thiols are mixed with similar thiols presenting tail groups that mimic the explosive substance 2,4,6-trinitrotoluene (TNT). In an immunoassay, the detection limit for TNT was determined to fall in the range 1-10 µg/L. In the second approach, a branched three dimensional biosensor matrix (hydrogel) is proposed. The carboxymethylated (CM) dextran matrix, which is commonly used within the biosensing community, is not always ideal for studies of biointeractions, due to the non-specific binding frequently encountered in work with complex biological solutions and various proteins. To employ PEG, which displays a low non-specific binding of such species, is therefore an interesting option worth investigating. The use of a branched graft polymerised PEG matrix in biosensor applications is novel as compared to previous reports which have focused on linear PEG chains. The latter approach provides, at maximum, one functional group, per surface anchoring point, for immobilisation of sensor elements. Thus, it has the inherited disadvantage that it limits the number of available immobilisation sites. The present PEG matrix contains a large number of functional groups, for immobilisation of sensor elements, per grafting site and offers the potential of improved response upon binding to the analyte as demonstrated in a series of successful sensor experiments. Furthermore, the nature of the process enables easy preparation of matrix patterns and gradients. In a PEG matrix gradient, protein permeability is studied and the capabilities of immobilising proteins are demonstrated. By combining the patterning technique with different monomers in a two-step process, an inert platform, lacking chemical attachment sites, is provided with arrays of spots (with immobilisation capabilities), which are conveniently addressed via microdispensing and used for biosensor purposes. The EG-terminated thiols present another means of generating such inert platforms, a route which is also investigated. To further explore the sensor quality of these spots, the concepts of patterning and gradient formation are combined and studied. / Det är intressant att studera biomolekylära interaktioner av många anledningar. För att kunna bedriva framgångsrik läkemedelsutveckling är det oerhört viktigt att känna till hur olika molekyler samverkar i människokroppen. Inom sjukvården kan biomolekyler användas som biomarkörer, då närvaro av dem eller förändringar av deras koncentrationer är kopplade till sjukdomstillstånd, och därmed hjälper läkaren att ställa rätt diagnos. Dessutom kan de mycket specifika interaktionerna mellan antikroppar och (i princip) valfri substans användas för detektion av spårämnen vid miljösaneringsarbete, gränskontroller, polisarbete, fängelser och arbete med nationell säkerhet. Den här avhandlingen beskriver hur polymeren polyetylenglykol (PEG) kan användas vid design av biochip. Ett biochip är en liten anordning, som kan användas för att detektera specifika molekyler med hjälp av en biologisk interaktion. Traditionellt har PEG använts inom biomaterialsektorn, men återfinns även i hygienartiklar som tvål och tandkräm. Ett annat användningsområde är konservering av bärgade träskepp och i en del litiumjonbatterier ingår PEG som en komponent. Dessutom pågår utveckling av PEG-innehållande skyddsvästar. I det här arbetet används PEG framför allt på grund av sin förmåga att minimera ospecifik inbindning av proteiner, som utgör en stor del av gruppen biomolekyler, till ytor på biochip. Två olika typer av ytbeläggningar, som innehåller den här polymeren, har använts. Den första typen ger mycket tunna (~0.000003 mm), tvådimensionella filmer medan den andra ger en något tjockare (~0.00005 mm), tredimensionell struktur (matris). De tvådimensionella filmerna har använts för att utveckla en sprängämnesdetektor med mycket hög känslighet (detektionsgräns mellan 1-10 ppb). En viktig beståndsdel i detta system är antikroppar riktade mot sprängämnet trinitrotoluen (TNT). Den tredimensionella matrisen är mer generell och kan användas för att studera många olika molekylära interaktioner. Tillverkningsmetoden av matrisen är baserad på belysning med ultraviolett ljus och är därmed lämpad för att skapa mönstrade ytor. Genom att blockera delar av ljusflödet begränsas tillväxten av matrisen till de belysta delarna. På så sätt har bland annat så kallade mikro-arrayer, bestående av mikrometerstora (tusendels millimeter) strukturer i ett regelbundet mönster, tillverkats. Tekniken tillåter även tillverkning av gradienter, där matrisens tjocklek varierar längs med provet, genom att belysa olika delar av provytan olika länge. Genom att undersöka dessa gradienter har information om matrisens genomsläpplighet för proteiner kunnat extraheras. Gradientkonceptet har även kombinerats med mikro-arraytillverkningen och gett möjlighet att studera interaktioner mellan flera olika modellproteiner och deras motsvarande antikroppar i olika tjocka matriser på en och samma yta. Det finns ett stort antal sätt att utnyttja interaktionerna mellan olika molekyler på ett biochip. Ett tilltalande tillvägagångssätt är exempelvis att i en mikro-array binda in olika molekyler som kan fånga kliniskt intressanta biomolekyler, i syfte att skapa en hälsoprofil. Ett sådant biochip skulle ge möjlighet att parallellt detektera eller bestämma koncentrationen av ett stort antal biomolekyler i till exempel en droppe blod. På så sätt kan en diagnos snabbt ställas, kanske till och med utan att patienten behöver uppsöka sjukvården. Den utvecklade PEG-matrisen har god potential att fungera i en sådan applikation.

The current study represents the first application of commercial laser-induced incandescence (LII) instrumentation at the University of Toronto Combustion Research Laboratory, for the characterization of soot in atmospheric laminar co-flow diffusion flames. An experimental apparatus was designed to accommodate the optical diagnostic, and to provide the means to probe various regions of the flames. An experiment with a well-characterized non-smoking ethylene-air diffusion flame was carried out to validate the performance of the LII instrument. Three measurement heights were analyzed; those at 40, 50, and 60 mm above the fuel exit. The soot volume fraction results were found to be in good agreement with those from the literature. The highest value was found to be 8.3 ppm at a height of 40 mm. While the instrumentation could report primary particle diameters, it was determined from the validation trial that the results were still premature. Further work is needed to validate the results of the instrument, especially for the particle size data.

Plant-wide communication between tissues and cells is organized, in part, by a suite of compounds called hormones. I have chosen to focus on the effects of one plant hormone, ethylene; how its synthesis is controlled and how its perception is mediated to differentially control cell development and response to pathogens. In the production of ethylene, one level of control is by modulating the levels of the immediate precursor to ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC). I characterize here a plant encoded gene homologous to bacterial ACC Deaminases, AtACD1, and show through up- and down-regulation of the gene that it can modulate the plants sensitivity to exogenous ACC. Once ethylene is produced, it is sensed in Arabidopsis thaliana by a family of 5 receptors. I show that ETR2 in Arabidopsis is responsible for modulation of the microtubule cytoskeleton assembly as loss-of –function mutations to this gene cause randomized microtubule assembly in trichomes and increase sensitivity to microtubule depolymerising drugs in root hairs. In studies of plant:pathogen interactions, ethylene is a central signaling agent required for plant resistance. While it has been shown that etr1 mutants show increased susceptibility to fungal pathogens, exogenous ethylene has also been shown to speed the progress of pathogenesis. Using Fumonisin B1 (FB1) to induce cell death I show that etr1-1 has accelerated cell death while ein4-1 has a reduced rate of necrosis. Further to this, mutations to the other three ethylene receptors do not have any effect on the rate of cell death. My interest in cell development led to the characterization of an activation tagged Populus tremula x P. alba line with increased trichome initiation. The gene responsible for these phenotypes was identified as PtMYB186, which also affected growth rate, transpiration rate, photosynthetic capacity, and resistance to the Tussock moth larvae. Together these studies provide a new framework for our understanding of how the ethylene signal is modulated in plants and the controls behind cellular development. This knowledge will help reconcile studies which show that ethylene has different effects on plant development and provide new avenues of research into trichome development. / Thesis (Ph.D, Biology) -- Queen's University, 2009-01-13 10:08:03.605

Transport and post-harvest handling of flowers both cut and potted is one of the greatest challenges in the horticulture industry (REDMAN et al., 2002). Ethylene-induced flower abscission is responsible for the loss of crops (KIM et al., 2007). Flower abscission is greater when plants are transported (ABEBIE et al., 2005). This limits the sale of flowers and potted plants to areas close to the site of production and prevents export opportunities. South Africa is home to many spectacular species with great horticultural potential (RICE et al., 2011). Unfortunately however, development of a number of these species for export is difficult due to transport-induced flower abscission. Transport-induced flower abscission is a problem experienced by Dr Gert Brits, a breeder of Plectranthus in Stellenbosch in South Africa. In this study a number of Dr Brits’s Plectranthus varieties were used as model plants to understand the process of transport-induced flower abscission and develop a protocol for the prevention of such abscission. Flow cytometry was used to determine the ploidy levels of each of the varieties. It was important to be aware of this during the experiments as varieties with different ploidy levels have been reported to behave differently under stressful environmental conditions. Of the eight varieties examined, three were diploid (2n), one was triploid (3n), three were tetraploid (4n) and one was a mixopliod (2n/4n) variety. To determine the effects of packaging plants during transport and the effects of darkness on flower abscission, plants were packaged into perspex chambers and kept either in a 16 h photoperiod or in darkness for 96 h. Every 24 h the number of open and unopened flowers that had abscised was recorded. Both packaging and darkness increased flower abscission of open and unopened flowers in all eight varieties. Four varieties preferentially abscised open flowers; while the remaining four preferentially abscised unopened flowers. All eight varieties were exposed to different concentrations of ethylene (0, 0.1, 0.25 0.5, 1 and 2 μll-1) to determine their level of ethylene sensitivity. All of the Plectranthus varieties were determined to be extremely sensitive to ethylene. With 100% flower abscission occurring within 24 h at 1 and 2 μll-1 in all varieties. In order to determine what internal changes were causing this increase in flower abscission under these conditions, the changes in the expression of key ethylene biosynthetic enzymes, cytokinin content and carbohydrates in the flowers were examined. ACS and ACO are the two key enzymes in the ethylene biosynthetic pathway (JOHNSON & ECKER, 1998). Changes in the levels of mRNAs coding for these two enzymes were examined when plants were packaged and put into the dark. In general there was an upregulation of the ethylene biosynthetic pathway and in turn this may have increased ethylene production by the plants under simulated transport conditions. However, the changes were not large enough to be solely responsible for the increased flower abscission observed under simulated transport conditions. The concentrations of 43 cytokinins were measured in pedicle tissue from plants which had been kept in the dark for 0, 24, 48, 72 and 96 h. Of the 43 cytokinins measured 21 were below the level of detection. Concentrations for the remaining 22 cytokinins at each of the time points were examined and it was found that in general cytokinin concentrations increase when plants are packaged and put into the dark. DHZ-type cytokinins remained stable during the 96 h continuous dark monitoring period, with most of the changes observed in the tZ and iP types. Peaks in cytokinin concentrations are often followed by an increase in flower abscission, indicating that an increase in cytokinin concentrations may be one of the factors causing the increase in transport-induced flower abscission. Only glucose and fructose were detected in peduncle tissue. Changes in glucose and fructose over 24 h in the greenhouse and over 0, 24, 48, 72 and 96 h in simulated transport conditions were measured. During the day, glucose and fructose levels increased towards the afternoon and evening and decreased in the early morning. This is consistent with studies conducted on other species (ALONI et al., 1996). When plants were put into the dark, glucose and fructose levels increased slightly at 24 h and then decreased to levels similar to those measured in control plants. Although there were changes in glucose and fructose level in simulated transport conditions, they were very slight and it is unlikely that these changes are not responsible for the transport-induced flower abscission. These results suggest that the observed transport-induced flower abscission is the result of increased cytokinin concentrations and expression of ACO and ACS genes when plants are packaged and put into the dark. These changes in turn cause an increase in ethylene production by the plants, and the build-up of ethylene in the transport container causes flowers to abscise. Ethylene perception by the plant is the step which could be targeted to prevent flower abscission. A number of ethylene antagonists block the ethylene receptors in the plant and in so doing prevent the receptors from binding ethylene and transducing the abscission signal. 1-MCP isone such ethylene antagonist. To test whether 1-MCP could be used for the prevention of flower abscission in Plectranthus, plants were placed in sealed perspex chambers in the light and in the dark and treated with 100 nll-1 1-MCP for a single 6 h treatment, or for 6 h every day prior to continuous exposure to ethylene. 1-MCP treatment greatly reduced ethylene- and transport-induced flower abscission when plants were treated continuously, but reduced flower abscission for the first 24 h when pre-treated with a single 6 h exposure to 1-MCP.Transport-induced flower abscission in Plectranthus is the result of exposure to ethylene. The increase in ethylene production by the plants in transport conditions is likely due to an upregulation of the ethylene biosynthetic pathway and an increase in cytokinin concentrations or movement in the pedicle tissue. This transport-induced flower abscission can be prevented by continuous treatment with 100 nll-1 1-MCP during the transport period. By using 1-MCP plants can be transported for up to 4 d and the opportunity for export is made possible. / Thesis (Ph.D.)-University of KwaZulu-Natal, Piertermaritzburg, 2013.

The current study represents the first application of commercial laser-induced incandescence (LII) instrumentation at the University of Toronto Combustion Research Laboratory, for the characterization of soot in atmospheric laminar co-flow diffusion flames. An experimental apparatus was designed to accommodate the optical diagnostic, and to provide the means to probe various regions of the flames. An experiment with a well-characterized non-smoking ethylene-air diffusion flame was carried out to validate the performance of the LII instrument. Three measurement heights were analyzed; those at 40, 50, and 60 mm above the fuel exit. The soot volume fraction results were found to be in good agreement with those from the literature. The highest value was found to be 8.3 ppm at a height of 40 mm. While the instrumentation could report primary particle diameters, it was determined from the validation trial that the results were still premature. Further work is needed to validate the results of the instrument, especially for the particle size data.