Dimethylether is a non-toxic liquefied gas, which is projected to become one of the fundamental chemical feedstock in the future. Dimethylether can be produced from syngas via a two-step (indirect) process that involves synthesis of methanol by hydrogenation of CO/CO2 over a copper based catalyst and subsequent dehydration of methanol to DME over an acidic catalyst. Alternatively, DME can be produced in an one-step (direct) process using a hybrid (bifunctional) catalyst system that permits both methanol synthesis and dehydration in a single process unit. In the present research work the production of DME has been studied by applying both the indirect and direct processes. Firstly, the methanol synthesis and methanol dehydration reactions involved in the indirect process have been studied separately. Afterwards, these two reactions have been combined in the direct DME production process by using a hybrid catalyst comprising a methanol synthesis and a methanol dehydration component. The methanol synthesis by CO2 hydrogenation has been investigated over commercial and home-made CuO/ZnO/Al2O3 catalysts with the aim to identify optimal experimental conditions (CO2:H2 ratio, flow rate, temperature) that could be then used in the direct conversion of CO2/H2 mixtures into methanol/DME. Obtained results reveal that the conversion of CO2 and the yields of reaction products (CH3OH and CO) increase when the concentration of H2 in the feed and the reaction contact time are increased. It was found that both Cu+/Cu0 species are important for the conversion of CO2/H2, although the presence of Cuo seems to be more important for selectivity/yield of methanol. The stability of the CuO/ZnO/Al2O3 catalyst has been also investigated. It was observed that the main reason for the deactivation of catalyst is the water produced via the methanol synthesis and reverse water gas shift reactions. However, the catalytic activity and products selectivity were recovered slowly to their original levels after applying a regeneration procedure, indicating that deactivation by water is reversible. The dehydration of methanol to dimethylether (DME) has been investigated over a range of catalysts including alumina, silica-alumina and zeolites with different physicochemical characteristics. The effects of temperature and the presence of water vapour in the feed on catalytic performance have been studied in detail. The reactivity of catalysts has been evaluated by determining the reaction rates per gram of catalyst per acid site (total: Brönsted+Lewis) and per Brönsted/Lewis mole ratio. In addition, the reaction mechanism has been investigated over a selected catalyst, with the use of transient-MS and in situ DRIFTS techniques. Results obtained for alumina catalysts show that the catalytic activity and selectivity are determined to a large extent by the textural properties, degree of crystallinity and total amount of acid sites of catalysts. In particular, the methanol conversion curve shifts toward lower reaction temperatures with an increase of specific surface area. However, the enhanced catalytic activity of high-SSA samples cannot be attributed solely to the higher amount of surface acid sites, implying that the reaction rate is determined to a large extent from other parameters, such as textural properties and degree of crystallinity. Results of mechanistic studies indicate that interaction of methanol with the Al2O3 surface results in the formation of two kinds of methoxy groups of different adsorption strength. Evidence is provided that DME evolution is associated with methoxy species that are weakly adsorbed on the Al2O3 surface, whereas more strongly held species decompose to yield surface formate and, eventually, CH4 and CO in the gas phase. Results obtained over zeolite catalysts show that catalytic performance depends on the topology of zeolites due to differences in micropore structure and Si/Al ratio as well as on the number, strength and nature of active acid sites. The activity of zeolite catalysts for the methanol dehydration to DME follows the order ZSM-5 > Ferrierite > Mordenite ~ Beta ~ USY > H-Y. The strong Brönsted acid sites of ZSM-5 zeolites with relatively high Si/Al ratio represent the most active sites in methanol dehydration to DME reaction. However, the overall reactivity of the ZSM-5 zeolites is also affected by the balance of the Brönsted to Lewis acid sites. The activity of Beta and USY zeolites is determined by both Lewis and Brönsted acid sites. The moderate/low reactivity of Ferrierite, Mordenite and H-Y zeolite are determined by the abundant Brönsted acid sites of relatively weak/moderate strength. The direct CO2 hydrogenation to methanol/DME has been investigated using admixed catalysts comprising a methanol synthesis (commercial copper based catalyst: CZA1) and a methanol dehydration component (different alumia/zeolite catalysts: γ-Al2O3, ZSM-5, W/γ-Al2O3, USY(6), Ferrierite(10)). It has been revealed that the conversion of CO2 is always lower than the corresponding equilibrium values predicted by thermodynamics, indicating operation in the kinetic regime. The nature of the methanol dehydration component of the admixed catalysts was found to be important for both CO2 conversion and methanol dehydration. In particular, DME selectivity/yield, depends strongly on the nature of acid sites (both Lewis and Brönsted) as well as the textural (meso/macro porosity) and topological properties of methanol dehydration component of the admixed catalysts. The yield of DME obtained at a temperature of 250oC decreases following the order CZA1/ZSM-5, CZA1/USY(6) > CZA1/Ferrierite(10) > CZA1/ W/γ-Al2O3 >> CZA1/γ-Al2O3. The long-term stability experiments conducted over selected bifunctional catalytic systems revealed that the catalysts deactivate with time-on-stream, mainly due to water produced via methanol synthesis, methanol dehydration and reverse water gas shift reactions. In case of the CZA1/ZSM-5 admixed catalyst the catalytic activity and products selectivity were almost recovered after regeneration indicating that deactivation by water is reversible. / --

No description available.

Loline alkaloids, found in many grass-Epichloë symbiota, are toxic or feeding deterrent to invertebrates. The loline alkaloids all share a saturated pyrrolizidine ring with a 1-amine group and an ether bridge linking C2 and C7. The steps in biosynthesis of loline alkaloids are catalyzed by enzymes encoded by a gene cluster, designated LOL, in the Epichloë genome. This dissertation addresses the enzymatic, genetic and evolutionary basis for diversification of these alkaloids, focusing on ether bridge formation and the subsequent modifications of the 1-amine to form different loline alkaloids. Through gene complementation of a natural lolO mutant and comparison of LOL clusters in strains with different loline alkaloid profiles, I found that lolO, predicted to encode a 2-oxoglutarate-dependent nonheme iron (2OG/Fe) dioxygenase, is required in formation of the ether bridge. Through application of isotopically labeled compound to Epichloë uncinata culture, I established that exo-1-acetamidopyrrolizidine (AcAP) and N-acetylnorloline (NANL) are true pathway intermediates. Application of AcAP to yeast expressing lolO resulted in production of NANL, establishing that LolO is sufficient to catalyze this unusual oxygenation reaction. After ether formation, modifications on the 1-amino group give loline, N-methylloline (NML), N-formylloline (NFL) and N-acetylloline (NAL). A double knockout of lolN, predicted to encode an acetamidase, and lolM, predicted to encode a methyltransferase, produced only NANL. Complementation of the double knockout with wild-type lolN and lolM restored the loline alkaloid profile. These results indicate that LolN is involved in deacetylating NANL to produce norloline, which is then modified to form the other lolines. Crude protein extract of a yeast transformant expressing LolM converted norloline to loline and NML, and loline to NML, supporting the hypothesis that LolM functions as a methyltransferase in the loline-alkaloid biosynthesis pathway. The alkaloid NAL was observed in some but not all plants symbiotic with Epichloë siegelii, and when provided with exogenous loline, asymbiotic meadow fescue (Lolium pratense) plants produced N-acetylloline (NAL), indicating that a plant acetyltransferase converts loline to NAL. I further analyzed the basis for loline alkaloid diversity by comparing the LOL clusters in the Epichloë and Atkinsonella species with different loline alkaloid profiles, and found that LOL clusters changed position, orientation and gene content over their evolutionary history. Frequent, independent losses of some or all late pathway genes, lolO, lolN, lolM and lolP, resulted in diverse loline alkaloid profiles. In addition, phylogenetic analyses demonstrated transspecies polymorphism of the LOL clusters. Based on my findings, I established that in Epichloë and Atkinsonella species the ether bridge is formed on acetamidopyrrolizidine. My study of the loline alkaloid profile of Adenocarpus decorticans (Fabaceae) suggests that these plants probably use a similar strategy at least with respect to ether-bridge formation. Further diversification steps of loline alkaloids in grass-Clavicipitaceae symbiota are carried out by enzymes of both Epichloë species and the host plant. Finally, I present evidence that LOL clusters have evolved by balancing selection for chemical diversity.

Identification, monitoring and quantification of biomolecules in the CNS is a field of growing interest for identifying biomarkers of neurological diseases. In this thesis, silicon needle-shaped multi-molecules sensing microprobes were developed. Our microelectrode array design comprises a needle length of 6mm with 100x50 µm2 cross-section bearing three platinum electrodes with a size of 40x200 µm and 200µm spacing between them. We have used these microprobes for simultaneous glucose and lactate monitoring, using the third electrode for control of non-specific current variations. Local microdroplet protein deposition on the electrode surface was achieved using a pneumatic picopump injection system. Enzyme immobilization on the electrode surface is a key step in microelectrode biosensor fabrication. We have developed a simple, low cost, non-toxic enzyme immobilization method employing poly(ethyleneglycol) diglycidyl ether (PEGDE). Successful biosensor fabrication was demonstrated with glucose oxidase, D-amino acid oxidase, and glutamate oxidase. We found that these biosensors exhibited high sensitivity and short response time sufficient for observing biological events in vivo on a second-by-second timescale. PEGDE-based biosensors demonstrated an excellent long-term stability and reliably monitored changes in brain glucose levels induced by sequential administration of insulin and glucose solution. We then carried out a comparative study of five enzyme immobilization procedures commonly used in Neuroscience: covalent immobilization by cross-linking using glutaraldehyde, PEGDE, or a hydrogel matrix and enzyme entrapment in a sol-gel or polypyrrole-derived matrices. Enzymatic microelectrodes prepared using these different procedures were compared in terms of sensitivity, response time, linear range, apparent Michaelis-Menten constant, stability and selectivity. We conclude that PEGDE and sol-gel techniques are potentially promising procedures for in vivo laboratory studies. The comparative study also revealed that glutaraldehyde significantly decreased enzyme selectivity while PEGDE preserved it. The effects that immobilization can have on enzyme substrate specificity, produce dramatic consequences on glutamate detection in complex biological samples and in the CNS. Our biosensor's results were systematically controlled by HPLC or capillary electrophoresis. The highly selective PEGDE-based biosensors allowed accurate measurements glutamate concentrations in the anesthetized and awaked rats at physiological conditions and under pharmacological and electrical stimulations. The microfabricated multielectrodes based on silicon needles coupled to the simple, non-toxic and mild immobilization method based on PEGDE, open new possibilities for specific neurotransmitter detection in the central nervous system and the study of cell-cell communication in vivo.

The developing brain goes through a number of developmental periods during which it displays an increased sensitivity to exogenous disturbances. On such period is the so called “Brain growth spurt” (BGS) which in humans takes place starting from the third trimester of pregnancy and throughout the first few years of life. The corresponding period in rats and mice is the first postnatal weeks. Exposure to relatively modest concentrations of the brominated flame retardant PBDE-99 during the second week of life in mice causes a more or less permanent impairment in the ability of the animals to adjust properly to environmental changes at adulthood. This “late response on early exposure” reflects the long-term consequences of disrupting the developing brain during a sensitive time period. The cellular mechanisms underlying the behavioral effects are far from clear. To address the initial damage occurring around the time of exposure, the approach used in this thesis is to use proteomics to analyze the effects of PBDE-99 on protein expression soon (24 hours) after exposure of the neonatal mouse on postnatal day (PND) 10.The thesis comprises the effects on the proteome in three distinct brain parts: cerebral cortex, striatum and the hippocampus. In addition, an in vitro model was developed and used to evaluate the PBDE-99 effects on cultured cerebral cortex cells from embryonic rat brains. Gel-based proteomics (2D-DIGE) coupled to MALDI- or ESI-MS has been used throughout for the proteomics experiments, but other techniques aimed at analyzing both proteins and mRNA have also been used to better characterize the effects. Even if the protein complements expressed by the different brain parts and separated with 2D-DIGE are seemingly similar, the effects are apparently specific for the different brain regions. In hippocampus, PBDE induces effects on proteins involved in metabolism and energy production, while the effects in striatum point towards effects on neuroplasticity. PBDE-99 changes the expression of cytoskeletal proteins in the cerebral cortex 24 hours after exposure. Interestingly, in vitro exposure of cerebral cortex cells to a PBDE-99 concentration in the same order of magnitude as in the in vivo neonatal brain also induces cytoskeletal effects, in the absence of cytotoxicity. This may suggest effects on regulatory aspects of cytoskeletal dynamics such as those involved in neurite sprouting. This thesis also addresses the problems involved in presenting proteomics data. Many of the available methods and approaches for presenting transcriptomics data are not suitable for isoform rich protein data. Modifications of existing methods and the development of a new approach (DEPPS) is also presented. Most importantly, the thesis presents the application and usefulness of proteomics as hypothesis generating techniques in neurotoxicology.

Dendrimers are synthetic macromolecules with branches-upon-branches structures, nanoscale dimensions and a high density of surface groups. Presence of multiple cationic sites in dendrimers permits their efficient nucleic acid complexation and cellular internalization through endocytic pathways. PETIM dendrimers of are characterized by tertiary amine branch points, and ether linkages. A third generation PETIM dendrimer, G3(NH2)24, with nitrogen at the core and twenty four peripheral primary amines was synthesized through alternate Michael addition and reduction reactions. The ability of G3(NH2)24 to interact with DNA was ascertained by spectroscopic and bio-physical techniques. These studies established the formation of dendrimer-DNA, and complex formation was also shown to protect the plasmid DNA from nucleases. Toxicity studies in cell culture, as well as, in female Balb/c mice established the non-toxic properties of the dendrimer. G3(NH2)24 was able to mediate efficient transfection in mammalian cells and in vivo. Targeted delivery of small interfering RNA (siRNA) to hepatocytes, in order to combat hepatitis C virus (HCV) infection was undertaken to expand the scope of PETIM dendrimer based gene delivery. Functionalization of the dendrimer periphery with galactose units ensured preferential delivery to the liver through multivalent interactions with the asialoglycoprotein receptors on the liver cell surface. The delivery of siRNA to the perinuclear region, in close proximity to the HCV RNA replication site resulted in ~75% decrease in viral RNA levels in replicon containing cells, as well as, JFH-1 infectious virus systems. The dendrimer-siRNA complexes were preferentially delivered to mice liver and were active in vivo. Physico-chemical studies of the protonation pattern of PETIM dendrimer indicated that the protonation of the dendrimer amines proceeded in a shell-wise pattern from the periphery to the core. The primary amines of the dendrimer as well as the outer shell tertiary amines with pKa values ~7-10 were protonated at physiological pH and were cationic sites for nucleic acid condensation. The inner shell tertiary amines with a pKa of ~4-6 were protonated at endosomal pH and aided ‘endosomal escape’ due to the high buffering capacity of 3.5. Work described in the Thesis establish a new synthetic dendrimer vector, namely, the series of PETIM dendrimers, as a high value gene delivery vector, making in-roads towards pre-clinical and possible clinical trials in future studies.

In this thesis, we investigated the generation of the higher derivative Chern-Simons term, as well as the ether-like term, both at finite temperature. We also examined the question of the large gauge invariance, with respect to the Chern-Simons term and the hight derivative one. We observed that the coefficient of the Chern-Simons term vanishes, when we taken into account the limit of high temperature. This happens to occur also for the other high derivative terms. With respects to the Chern-Simons term, we observed that the action of the Chern-Simons term and the high derivative one are invariant under the large gauge transformation. For this, we calculated the exactly effective action, however, for a specific gauge choice. Finally, with respects to the ether-like term, we observed that the calculation at finite temperature is ambiguous, as well as it is observed for the calculation at zero temperature. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nesta tese, investigamos a geração do termo de Chern-Simons de derivada superior, assim como o termo tipo éter, ambos à temperatura finita. Também estudamos a questão da invariância de gauge ampla, com o termo de Chern-Simons e Chern-Simons de derivada superior. Constatamos que o coeficiente do termo de Chern-Simons de derivada superior anula-se, quando tomamos o limite de altas temperaturas. Esse resultado parece se repetir para os demais termos de derivada superior. Dentro ainda do contexto de Chern-Simons, observamos que a ação de Chern-Simons e a ação de Chern-Simons de derivada superior são invariantes sob transformação de gauge ampla. Para isso, conseguimos calcular a ação efetiva exata, contudo, para uma escolha de gauge específica. Finalmente, com relação ao termo tipo éter, constatamos que o cálculo à temperatura finita e ambíguo, assim como observado no cálculo à temperatura zero.

This dissertation develops a systematic targeting method based on the C-H-O ternary diagram for the conceptual design of gasification-based biorefineries. The approach is applied using dimethyl ether (DME) as case study. A stoichiometric equilibrium model is presented for calculation of the C-H-O chemical equilibria to evaluate and predict equilibrium syngas composition, operating temperature, type and amount of oxidant required in biomass gasification. Overall atomic species balances are developed and process targets are plotted on the C-H-O ternary diagram. Sustainability metrics are incorporated to provide useful insights into the efficiency of biorefinery process targets. It was found that syngas at 1200 and 1500 K is predominantly H2 and CO. Moreover, DME biorefineries have two main process targets, based on the indirect and direct synthesis routes. Gasification at 1200 K and 1 atm. using H2O/CO2 = 2.642 (w/w) and H2O/CH4 = 1.645 (w/w) achieved syngas composition targets for the direct and indirect methods respectively. Comparatively, the integrated biorefinery based on indirect route was more efficient, producing 1.903 ton of DME per ton of biomass feedstock. The process is 100% carbon-efficient and recycles 1.025 tons of H2O. / Civil and Chemical Engineering / M. Tech. (Chemical Engineering)

O Pinguim-de-Magalhães, Spheniscus magellanicus, é o mais abundante dos pinguins que vivem em regiões temperadas da América do Sul, sendo um bom indicador de poluição ambiental. Poluentes orgânicos persistentes (POPs) foram detectados em fígado de Pinguins-de-Magalhães encontrados debilitados ou mortos nas praias do Brasil (Rio de Janeiro, São Paulo, Santa Catarina e Rio Grande do Sul) entre 2008 - 2012 e, do Uruguai e do Chile, em 2011. Os bifenilos policlorados (PCBs) predominaram em relação aos pesticidas organoclorados (DDTs ∼ HCB ∼ Drins) e aos éteres difenilos polibromados (PBDEs). O contaminante emergente fipronil não foi detectado apesar de seu uso na América do Sul. Entre os PCBs predominaram os congeneres penta, hexa e heptaclorados. Concentrações de POPs foram similares entre as áreas de migração e reprodução exceto para os PCBs que foram relativamente maiores na área de reprodução. Avaliação temporal (2008 - 2012) de POPs apresentou constância para os pesticidas organoclorados e tendência ao declínio para os PCBs. A glândula uropigiana de Pinguim-de-Magalhães mostrou-se um tecido alternativo adequado para análise de POPs em aves debilitadas. No geral, as regiões de reprodução e migração dos pinguins na América do Sul apresentam baixas concentrações de POPs com tendência constante ou indícios de declínio. / The Magellanic Penguin , Spheniscus magellanicus, is the most abundant penguin that live in temperate regions of South America and a good indicator of environmental pollution in that region. Persistent organic pollutants (POPs) were detected in the liver of Magellanic penguins found debilitated or dead on the beaches of Brazil (Rio de Janeiro, Sao Paulo, Santa Catarina and Rio Grande do Sul) between 2008 - 2012, and in Uruguay and Chile in 2011. Polychlorinated biphenyls (PCBs) were more prevalent than organochlorine pesticides (DDTs ∼ HCB ∼ Drins) and polybrominated diphenyl ethers (PBDEs). Fipronil, an emerging contaminant, was not detected despite its use in South America. Among PCBs, the congeners penta, hexa and heptaclorados were predominant. Concentrations of POPs are similar between the migration and reproduction areas except for PCBs that are relatively higher in the breeding area. At this time point (2008 - 2012) POPs showed constancy for organochlorine pesticides and PCBs tendency to decline. The Magellanic penguin uropygian gland has proved to be a suitable alternative for POPs tissue analysis in debilitated birds. Overall, southern South America has low concentrations of POPs with constant trend or decline evidence.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-10-22T16:54:02Z No. of bitstreams: 0 / Made available in DSpace on 2015-10-22T16:54:02Z (GMT). No. of bitstreams: 0 / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP