No description available.

Consumption of plastics has increased exponentially, in line with the world's population. Not surprisingly this is reflected in enormous growth of the plastic industry especially during the last five decades. Commensurate with this, waste produced from plastics consumption has created a major environmental problem. Many types of waste disposal methods have been used all over the world so far, but all of them have disadvantages. Furthermore, some methods are responsible for the generation of green house gases and further contribution to global warming. Recently, reduction of green house gas emission has become a target of most industries. Plastic recycling and reuse breaks the cycle of endless production of virgin polymer and thus contributes to a net reduction of green house gas emission. Recycling of plastics should produce materials with improved properties to replace virgin plastics for a variety of applications. Improvement in the properties of recycled plastics can be achieved by blending with other plastics, by filler addition and by modification using free radical initiators. Introduction of the free radical initiator (organic peroxide) during reprocessing of the recycled plastics has been found to offer significant property improvements to the recycled materials. Extremely small amounts of a free radical initiator (typically ranging between 0.01 wt% to 0.2 wt%) is capable of enhancing the properties of the recycled plastics to a great extent. This project investigates the use of free radical initiators in the recycling of post consumer recycled high density polyethylene using reactive extrusion. Both molecular and rheological characterisation of recycled and reprocessed materials was carried out and this was followed by tensile testing of the modified materials to satisfy end use applications such as packaging and drainage piping. Post consumer recycled high density polyethylene (R-HDPE) resin and virgin high density polyethylene (V-HDPE) were reactively extruded with low concentrations of dicumyl peroxide (DCP) and 1, 3 1, 4 Bis (tert- butylperoxyisopropyl) Benzene (OP2) respectively in a twin screw extruder in order to produce modified materials with varying composition (0.0 wt%, 0.02 wt%, 0.05 wt%, 0.07 wt%, 0.10 wt% and 0.15 wt%) of both organic peroxides. Morphological characterisation using modulated differential scanning calorimetry (MDSC) demonstrated that there is a decrease in the crystallinity level for all the modified samples. Shear rheological tests were carried out to study the structure of the modified materials within the linear viscoelastic region. Viscoelastic parameters, such as storage modulus (G'), loss modulus (G

The effective acyl flux between phospholipids and neutral lipids is critical for a high level of the biosynthesis of very long chain polyunsaturated fatty acids (VLCPUFAs) such as arachidonic acid (ARA,20:4-5,8,11,14), eicosapentaenoic acid (EPA, 20:5-5,8,11,14,17) and docosahexaenoic acid (DHA, 22:6-4,7,10,13,16,19) which are essential for human health and wellbeing. Three membrane-bound enzymes, phosphatidylcholine:diacylglycerol cholinephosphotransferase (PDCT), cholinephosphotransferase (CPT) and ethanolaminephosphotransferase (EPT) from VLCPUFA-producing fungi were selected as candidates for my thesis research based on the hypothesis that these enzymes play important roles in acyl trafficking between phosphatidylcholine (PCs) and diacylglycerols (DAGs) during the biosynthesis of VLCPUFAs. Two putative PDCT cDNAs (PiPDCT1 and PiPDCT2) were cloned from Phytophthora infestans which encode polypeptides with two conserved domains and about 15% of amino acid identity to an Arabidopsis PDCT. However, in vitro assays in yeast Saccharomyces cerevisiae showed they did not have any PDCT activity. Four putative CPT and EPT cDNAs (PiCPT1, PiCPT2, PiEPT and TaCPT) were cloned from P. infestans and Thraustochytrium aureum which encode proteins with a conserved CDP-alcohol phosphotransferase motif and 22% to 26% of amino acid identity to the yeast CPT. In vitro assays indicated PiCPT1 and TaCPT had CPT activity, PiEPT had EPT activity and PiCPT2 did not have either activity. Substrate specificity assays showed that all the three functional CPT and EPT preferred VLCPUFA-containing DAGs as substrates with PiCPT1 being the most specific towards ARA-DAG and DHA-DAG. Real-time qPCR analysis revealed that the expression of PiCPT1 was up-regulated in P. infestans fed with exogenous VLCPUFAs. These results lead us to conclude that PiCPT1 is a VLCPUFAs-specific CPT which may play an important role in shuffling VLCPUFAs from phospholipids to storage neutral lipids, would thus have potential use in metabolic engineering of VLCPUFAs in heterologous systems including oilseed crops.

A reactive distillation column for the alkylation of benzene with long chain linear olefin was studied. The study involved design, construction, experimentation, and simulation of the column. Establishing the design required study of reaction rates, thermodynamic relationships, and packing structures. A heuristic was developed for the design of such columns. This heuristic involved estimating an amount of catalyst loading and subsequently determining the operating parameters for a column. This method is particularly applicable to systems with high concentrations of inert feeds. A column was constructed following the design. Data was collected from the column and compared to simulations. The simulations were performed with Aspen Plus RADFRAC. In this manner, the data was used to validate the commercial steady state models for reactive distillation. In addition, dynamic simulations of the system were performed. These dynamic simulations provided insight into more design considerations. For example, steady state simulations indicated an optimal feed stage based on steady state conversion of the olefin. However, the dynamic simulations showed a potential disadvantage to the utilization of the optimal feed stage. With some disturbances, a column configured with the feed stage with the highest steady state conversion also deviated from the steady state faster and with greater amplitude than other configurations. These considerations were further explored in developing a control scheme for reactive distillation columns. Control of reactive distillation differs from traditional distillation in that one control variable is conversion. Traditional distillation generally focuses on production rates and product purity. To this end, control schemes were analyzed and dynamic simulations were performed. These simulations showed an advantage to a variable pairing in which duty is paired with conversion. The conversion was inferred from a stage temperature in the reactive zone. In addition, distillate rate may be paired with product composition. In conclusion, the reactive distillation column design for long chain olefin alkylation of benzene requires careful estimation of catalyst requirements and valid simulation tools. In addition, dynamic response should be considered in the design. Finally, a simple inferential control scheme may be adequate. / text

An investigation was carried out to study whether long-chain fatty acids (LCFAs) have an effect on digestion of waste sludge under anaerobic conditions. Four different kinds of LCFAs were used in this study. The 18 carbon series with 0, 1, 2 and 3 double bonds were studied to evaluate the degree of saturation on fatty acid degradation. Due to their molecular structure, unsaturated LCFAs are more soluble than saturated LCFAs. Oleic, linoleic, linolenic acid with an ascending number of double bonds were tested as representatives for three different degrees of saturation. In addition, stearic acid, a saturated fatty acid was also tested. LCFAs were added to sewage sludge at concentrations ranging from 5% to 20% on a weight basis and the pH, solids reduction and COD reduction were determined. The results suggested that in addition to degrading in the digesters, all unsaturated acids contributed additional solids removal, compared to the control group. In contrast, stearic acid did not affect the solids removal. The COD reduction was similar to solids reduction in that additional COD was destroyed when unsaturated LCFAs were added to the sludge. The mechanism for additional solids reduction is not known. / Master of Science

Yes / The present work deals with the flow-induced multiple orientations and crystallization structure of polymer melts under a complex flow field. This complex flow field is characteristic of the consistent coupling of extensional “pulse” and closely followed shear flow in a narrow channel. Utilizing an ingenious combination of an advanced micro-injection device and long chain aliphatic polyamides (LCPA), the flow-induced crystallization morphology was well preserved for ex-situ synchrotron micro-focused wide angle X-ray scattering (μWAXS) as well as small angle X-ray scattering (SAXS). An inverted anisotropic crystallization structure was observed in two directions: perpendicular and parallel to the flow direction (FD). The novel anisotropic morphology implies the occurrence of wall slip and “global” fountain flow under the complex flow field. The mechanism of structure formation is elucidated in detail. The experimental results clearly indicate that the effect of extensional pulse on the polymer melt is restrained and further diminished due to either the transverse tumble of fountain flow or the rapid retraction of stretched high molecular weight tails. However, the residual shish-kebab structures in the core layer of the far-end of channel suggest that the effect of extensional pulse should be considered in the small-scaled geometries or under the high strain rate condition.

No description available.

Este trabalho teve o objetivo de avaliar o uso de monensina, levedura e a interação destes aditivos no metabolismo digestivo e desempenho de animais Nelores. Foram realizados dois experimentos. Experimento 1. Foram utilizados quatro novilhos Nelores com cânulas no rúmen e no duodeno para avaliar a degradabilidade, digestibilidade, biohidrogenação, microrganismos ruminais e emissão de metano quando fornecidos monensina e/ou levedura na dieta contendo óleo de girassol em experimento quadrado latino e arranjo fatorial 2x2. Os tratamentos consistiram em com e sem levedura e com e sem monensina. A levedura utilizada foi a Sacharomyces cerevisiae cepa 1026. As variáveis estudadas foram degradabilidade in situ, digestibilidade in vivo avaliada pelo método de indicador interno FDNi, pH, nitrogênio amoniacal e ácidos graxos de cadeia curta do rúmen, protozoários ciliados, biohidrogenação ruminal, e estimativa do número das bactérias Anaerovibrio lipolyica, Butyrivibrio fibrisolvens e Megasphaera elsdenii, por PCR em tempo real. Experimento 2. Foi realizado ensaio para avaliar o desempenho e características de carcaça e carne de touros Nelores utilizando os aditivos supracitados. Foram utilizados cinquenta e dois touros Nelores com aproximadamente 233kg em delineamento em blocos ao acaso. O fornecimento de monensina reduziu o número de protozoários ciliados no rúmen, aumentou a eficiêcia alimentar e a porcentagem de C18:1 trans10-11 e de C18:2 t11c15 na carne. O uso de levedura aumentou a degradabilidade efetiva da MS, o NDT da dieta, os protozoários ciliados, o pH ruminal, a expressão relativa da bactéria B. fibrisolvens, a ingestão de MS dos animais confinados, os ácidos graxos insaturados no conteúdo duodenal e os ácidos graxos saturados na carne, e reduziu a eficiência alimentar, os ácidos graxos saturados no conteúdo duodenal e os ácidos graxos insaturados na carne. Houve interação para a digestibilidade da FDN, ingestão de matéria seca por quilo de peso metabólico, espessura de gordura subcutânea, e ácidos graxos insaturados na carne. O uso de monensina em dieta com óleo foi eficiente para melhora na conversão alimentar. A utilização de cultura de levedura mesmo em dieta com óleo favoreceu os microrganismos ruminais e a energia da dieta. / This work had the objective of evaluate the use of monensin, yeast and the interaction of these additives on Nellore digestive metabolism and performance. It were conducted two trials. Experiment 1. It were utilized four Nellore steers with rumen and duodenum cannulas to evaluate the diet degradability, digestibility, biohydrogenation, rumen microrganisms and methane emission when supplied monensin and/or yeast on the diet with sunflower oil in a latin square desing and a 2x2 fatorial arranjement.The treatments were with and without yeast and with and without monensin. The yeast utilized was the Sacharomyces cerevisiae 1026 strain. The variables studied were in situ degradability, in vivo digestibility evaluated by indicator method NDFi, pH, ammonia nitrogen and rumen short chain fatty acid, ciliate protozoa, biohydrogenation, and estimative of bactéria Anaerovibrio lipolyica, Butyrivibrio fibrisolvens e Megasphaera elsdenii, by real time PCR. Experiment 2. A trial was realized to evaluate the performance and carcass and meat characteristics of Nellore steers utilizing the additives above. It were utilized fifthty two Nellore bulls with 233kg live weight average in a random blocks design. The monensin supplied decreased the protozoa number, the relative efficiency of B. fibrosolvens, increased feed efficiency and the percentage of C18:1 trans10-11 and C18:2 t11c15 in the meat. The use of yeast increased the effective degradability of DM, the TDN, ciliate protozoa, rumen pH, DM intake, unsaturated fatty acid on the duodenal content, and the saturated fatty acid in the meat, and decreased the feed efficiency, saturated fatty acid on the duodenum content and the unsaturated fatty acid of the meat. There were interaction effect to NDF digestibility, dry matter intake per kg of metabolic weight, fat thickness, and unsaturated fatty acid in the meat. The use of monensin was efficient to get the feed efficiency better. The utilization of yeast culture, even in a oil diet, was favorable to rumen microorganisms and the diet energy.

In both the legume symbiont Sinorhizobium meliloti and the mammalian pathogen Brucella abortus, the inner membrane BacA protein is essential for host persistence. In free-living S. meliloti and B. abortus loss of the BacA protein also results in an increased resistance to the glycopeptide bleomycin and a ~ 50% decrease in the lipopolysaccharide (LPS) very-long-chain-fatty-acid (VLCFA) content. Consequently, it was proposed that BacA may be involved in transport of peptides into the cell and/or that BacA may be involved in the VLCFA modification of the LPS. During this work it was determined that the increased resistance observed in an S. meliloti DbacA mutant to bleomycin and to the truncated eukaryotic peptide Bac7(1-16), is independent of the VLCFA modification. These data support a model for BacA having multiple non-overlapping functions. Using flow cytometry studies with fluorescently labelled forms of bleomycin and Bac7(1-16) it was found that the BacA protein plays a role in the uptake of bleomycin. However, BacA was shown to be essential for the uptake of Bac7(1-16). Additionally, it was determined that two symbiotically defective bacA site directed mutants with known reductions in their VLCFA could still take up Bac7, suggesting that the BacA function that leads to the VLCFA modification could also play a key role in host persistence. To investigate further the role of BacA in the VLCFA modification and where in the cell envelope the lipid A is modified with the VLCFA, the role of the putative lipid trafficking protein MsbA2 was investigated. Interestingly, it was discovered that S. meliloti lacking the MsbA2 protein, is unable to enter host cells and induces a plant defence response more characteristic of a pathogen. To investigate the importance of the VLCFA modification during the symbiosis S. meliloti mutants lacking either the AcpXL (VLCFA acyl carrier protein) or LpxXL (VLCFA acyl transferase protein) were characterized in the host. Although not essential for host persistence, loss of each of the proteins did result in distinct defects, suggesting the VLCFA modification is important during the symbiosis. Since there are hundreds of nodule specific cysteine-rich peptides produced by the host plant Medicago truncatula, the BacA mediated uptake of one of these peptides combined with the VLCFA modification may account for the essential role of the BacA protein in the legume symbiosis.

Very long chain polyunsaturated fatty acids (VLCPUFAs) such as arachidonic acid (ARA, 20:4ù6), eicosapentaenoic acid (EPA, 20:5ù3) and docosahexaenoic acid (DHA, 22:6ù3) have been shown to have many health benefits, some of which include lowering blood pressure, providing protection against cardiovascular diseases and improving brain and eye functions. Entomopathogenic fungi, a group of fungal pathogens able to infect insects, were previously reported to produce substantial amounts of VLCPUFAs, however the genes involved in the biosynthesis of these fatty acids have yet to be identified. This research started with fatty acid analysis of five entomopathagenic fungi, of which Conidiobolus obscurus and Conidiobolus thromboides were found to produce high levels of VLCPUFAs such as ARA and EPA. Thus, these two fungal species were selected as potential gene sources for the enzymes involved in the biosynthesis of VLCPUFAs. Using degenerate reverse transcriptase-polymerase chain reaction (RT-PCR) and rapid amplification of the cDNA ends (RACE) methods; we cloned two full-length putative ∆6 desaturase cDNAs (CoD6 and CtD6) from the two fungi.<p> Functional expression of CoD6 in Saccharomyces cerevisiae showed it codes for a functional Ä6 desaturase, which can introduce a Ä6 double bond into linoleic acid and á-linolenic acid, respectively. However, expression of CtD6 in S. cerevisiae showed it does not have any Ä6 desaturase activity. Using degenerate RT-PCR and RACE, we also cloned two full-length ∆6 elongase cDNAs (CoE6 and CtE6) from the C. obscurus and C. thromboides species. Functional expression of these genes in S. cerevisiae showed CoE6 and CtE6 code for functional ∆6 elongase. Substrate specificity analysis indicated that both preferentially elongate 18-carbon Ä6 desaturated fatty acids, such as ã-linolenic acid and stearidonic acid. In addition, CtE6 can also elongate 20-carbon VLCPUFAs, such as ARA and EPA. The entire eicosatetraenoic acid (ETA, 20:4ù3) biosynthetic pathway was reconstituted in yeast using four genes, CoD6 (a ∆6 desaturase) and CoE6 (a ∆6 elongase) from Conidiobolus obscurus, CpDes12 (a Ä12 desaturase) and CpDesX (a ù3 desaturase) from Claviceps purpurea. Yeast transformant expressing the four genes produced several new fatty acids. Among them, eicosatetraenoic acid (ETA) accounts for approximately 0.1% of the total fatty acids. Although the level of ETA in the transformant is low, this represents the first report describing the reconstitution of the entire ETA pathway in yeast without exogenous supplementation of any fatty acids.