High performance polyester-based materials

Biaxially oriented films produced from semi-crystalline, semi-aromatic polyesters are utilised extensively as components within various applications, including the specialist packaging, flexible electronic and photovoltaic markets. However, the thermal performance of such polyesters, specifically poly(ethylene terephthalate) (PET) and poly(ethylene-2,6-naphthalate) (PEN), is inadequate for several applications that require greater dimensional stability at higher operating temperatures. The work described in this project is therefore primarily focussed upon the copolymerisation of rigid comonomers with PET and PEN, in order to produce novel polyester-based materials that exhibit superior thermomechanical performance, with retention of crystallinity, to achieve biaxial orientation. Rigid biphenyldiimide comonomers were readily incorporated into PEN and poly(butylene-2,6-naphthalate) (PBN) via a melt-polycondensation route. For each copoly(ester-imide) series, retention of semi-crystalline behaviour is observed throughout entire copolymer composition ratios. This phenomenon may be rationalised by cocrystallisation between isomorphic biphenyldiimide and naphthalenedicarboxylate residues, which enables statistically random copolymers to melt-crystallise despite high proportions of imide sub-units being present. In terms of thermal performance, the glass transition temperature, Tg, linearly increases with imide comonomer content for both series. This facilitated the production of several high performance PEN-based biaxially oriented films, which displayed analogous drawing, barrier and optical properties to PEN. Selected PBN copoly(ester-imide)s also possess the ability to either melt-crystallise, or form a mesophase from the isotropic state depending on the applied cooling rate. An equivalent synthetic approach based upon isomorphic comonomer crystallisation was subsequently applied to PET by copolymerisation with rigid diimide and Kevlar®-type amide comonomers, to afford several novel high performance PET-based copoly(ester-imide)s and copoly(ester-amide)s that all exhibited increased Tgs. Retention of crystallinity was achieved in these copolymers by either melt-crystallisation or thermal annealing. The initial production of a semi-crystalline, PET-based biaxially oriented film with a Tg in excess of 100 °C was successful, and this material has obvious scope for further industrial scale-up and process development.

The land-atmosphere water flux in the tropics

Tropical vegetation is a major source of global land surface evapotranspiration, and can thus play a major role in global hydrological cycles and global atmospheric circulation. Accurate prediction of tropical evapotranspiration is critical to our understanding of these processes under changing climate. We examined the controls on evapotranspiration in tropical vegetation at 21 pan-tropical eddy covariance sites, conducted a comprehensive and systematic evaluation of 13 evapotranspiration models at these sites, and assessed the ability to scale up model estimates of evapotranspiration for the test region of Amazonia. Net radiation was the strongest determinant of evapotranspiration (mean evaporative fraction was 0.72) and explained 87% of the variance in monthly evapotranspiration across the sites. Vapor pressure deficit was the strongest residual predictor (14%), followed by normalized difference vegetation index (9%), precipitation (6%) and wind speed (4%). The radiation-based evapotranspiration models performed best overall for three reasons: (1) the vegetation was largely decoupled from atmospheric turbulent transfer (calculated from X decoupling factor), especially at the wetter sites; (2) the resistance-based models were hindered by difficulty in consistently characterizing canopy (and stomatal) resistance in the highly diverse vegetation; (3) the temperature-based models inadequately captured the variability in tropical evapotranspiration. We evaluated the potential to predict regional evapotranspiration for one test region: Amazonia. We estimated an Amazonia-wide evapotranspiration of 1370 mm yr(-1), but this value is dependent on assumptions about energy balance closure for the tropical eddy covariance sites; a lower value (1096 mm yr(-1)) is considered in discussion on the use of flux data to validate and interpolate models.

The game of contacts: Estimating the social visibility of groups

Estimating the sizes of hard-to-count populations is a challenging and important problem that occurs frequently in social science, public health, and public policy. This problem is particularly pressing in HIV/AIDS research because estimates of the sizes of the most at-risk populations-illicit drug users, men who have sex with men, and sex workers-are needed for designing, evaluating, and funding programs to curb the spread of the disease. A promising new approach in this area is the network scale-up method, which uses information about the personal networks of respondents to make population size estimates. However, if the target population has low social visibility, as is likely to be the case in HIV/AIDS research, scale-up estimates will be too low. In this paper we develop a game-like activity that we call the game of contacts in order to estimate the social visibility of groups, and report results from a study of heavy drug users in Curitiba, Brazil (n = 294). The game produced estimates of social visibility that were consistent with qualitative expectations but of surprising magnitude. Further, a number of checks suggest that the data are high-quality. While motivated by the specific problem of population size estimation, our method could be used by researchers more broadly and adds to long-standing efforts to combine the richness of social network analysis with the power and scale of sample surveys. (C) 2010 Elsevier B.V. All rights reserved.

Estudo teórico-experimental do processo de microfiltração de partículas de sílica em suspensão aquosa

Cada vez mais muitos processos industriais convencionais de separação, tais como destilação, centrifugação e extração com solventes, entre outros, estão sendo substituídos pelos processos de separação por membranas em virtude desses apresentarem vantagens em relação aos processos convencionais, além de serem considerados uma tecnologia limpa. Entre estas vantagens pode-se citar a economia de energia, pois não envolvem mudança de fase; a possibilidade de processamento de substâncias termolábeis, pois podem operar à temperatura ambiente; a maior seletividade; a facilidade de scale – up, pois são modulares e não extensivos em mão de obra, entre outros. Uma característica limitante destes processos é a existência de uma camada de elevada concentração de partículas ou moléculas que se forma próxima à superfície da membrana e que ocasiona uma redução no fluxo permeado, podendo modificar as características de retenção da membrana. Este fenômeno é conhecido como polarização por concentração. O entendimento dos mecanismos de polarização é considerado de grande importância neste campo e o estudo e validação de modelos matemáticos preditivos torna-se necessário para se obter sucesso na aplicação dos processos com membranas no meio industrial O objetivo geral deste trabalho consiste na análise teórico-experimental do processo de microfiltração tangencial com suspensão aquosa de partículas de sílica. O objetivo específico é a utilização de dados experimentais para a estimação de um parâmetro do modelo matemático que descreve o perfil de concentração na superfície da membrana ( membrana). A configuração tangencial implica que a alimentação, contendo as partículas a serem removidas ou concentradas, flui paralelamente à superfície da membrana reduzindo, assim, o fenômeno de polarização por concentração. Os experimentos foram efetuados em uma unidade de bancada de microfiltração tangencial, também conhecido como fluxo cruzado, em um módulo para membrana plana com canal de escoamento retangular sob condições de escoamento laminar. Os seguintes parâmetros foram variados durante os experimentos: pressão transmembrana, velocidade tangencial e concentração de partículas de sílica Os dados experimentais foram utilizados em uma modelagem matemática, baseada nas equações fundamentais da mecânica dos fluidos e da transferência de massa, que considera as propriedades físicas da suspensão, viscosidade dinâmica e difusividade mássica, variáveis com a concentração de sílica para se estimar a concentração máxima de sílica junto à superfície da membrana. Esta modelagem engloba os parâmetros operacionais, bem como as características da membrana nesta única variável. Com a finalidade de se verificar como a concentração máxima sobre a membrana é afetada pelas condições operacionais e, conseqüentemente, como esta afeta o fluxo permeado, a concentração máxima sobre a superfície da membrana é apresentada em função das condições operacionais variadas durante os experimentos de microfiltração. Finalmente, após a estimação desta variável, pôde-se concluir que ela é influenciada pelas condições operacionais típicas do processo de microfiltração tangencial, tais como velocidade tangencial de escoamento, pressão através da membrana e concentração da alimentação.

Integrated valorization of Anona Cherimola Mill. seeds

Agricultural and agro-industrial residues are often considered both an environmental and an economical problem. Therefore, a paradigm shift is needed, assuming residues as biorefinery feedstocks. In this work cherimoya (Annona cherimola Mill.) seeds, which are lipid-rich (ca. 30%) and have a significant lignocellulosic fraction, were used as an example of a residue without any current valorization. Firstly, the lipid fraction was obtained by solvent extraction. Extraction yield varied from 13% to 28%, according to the extraction method and time, and solvent purity. This oil was converted into biodiesel (by base-catalyzed transesterification), yielding 76 g FAME/100 g oil. The obtained biodiesel is likely to be incorporated in the commercial chain, according to the EN14214 standard. The remaining lignocellulosic fraction was subjected to two alternative fractionation processes for the selective recovery of hemicellulose, aiming different products. Empirical mathematical models were developed for both processes, aiming future scale-up. Autohydrolysis rendered essentially oligosaccharides (10 gL-1) with properties indicating potential food/feed/pharmacological applications. The remaining solid was enzymatically saccharified, reaching a saccharification yield of 83%. The hydrolyzate obtained by dilute acid hydrolysis contained mostly monosaccharides, mainly xylose (26 gL-1), glucose (10 gL-1) and arabinose (3 gL-1), and had low content of microbial growth inhibitors. This hydrolyzate has proven to be appropriate to be used as culture media for exopolisaccharide production, using bacteria or microbial consortia. The maximum conversion of monosaccharides into xanthan gum was 0.87 g/g and kefiran maximum productivity was 0.07 g.(Lh)-1. This work shows the technical feasibility of using cherimoya seeds, and materials as such, as potential feedstocks, opening new perspectives for upgrading them in the biorefinery framework.

Novos sistemas de liberação de fármacos à base de xilana

The aim of this work was to perform the extraction and characterization of xylan from corn cobs and prepare xylan-based microcapsules. For that purpose, an alkaline extraction of xylan was carried out followed by the polymer characterization regarding its technological properties, such as angle of repose, Hausner factor, density, compressibility and compactability. Also, a low-cost and rapid analytical procedure to identify xylan by means of infrared spectroscopy was studied. Xylan was characterized as a yellowish fine powder with low density and poor flow properties. After the extraction and characterization of the polymer, xylan-based microcapsules were prepared by means of interfacial crosslinking polymerization and their characterization was performed in order to obtain gastroresistant multiparticulate systems. This work involved the most suitable parameters of the preparation of microcapsules as well as the study of the process, scale-up methodology and biological analysis. Magnetic nanoparticles were used as a model system to be encapsulated by the xylan microcapsules. According to the results, xylan-based microcapsules were shown to be resistant to several conditions found along the gastrointestinal tract and they were able to avoid the early degradation of the magnetic nanoparticles

Origem física das curvas sigmoidais respiratórias pressão-volume: recrutamento alveolar e elasticidade não-linear

An important unsolved problem in medical science concerns the physical origin of the sigmoidal shape of pressure volume curves of healthy (and some unhealthy) lungs. Such difficulties are expected because the lung, which is the most important structure in the respiratory system, is extremely complex. Its rheological properties are unknown and seem to depend on phenomena occurring from the alveolar scale up to the thoracic scale. Conventional wisdom holds that linear response, i.e., Hooke s law, together with alveolar overdistention, play a dominant role in respiration, but such assumptions cannot explainthe crucial empirical sigmoidal shape of the curves. In this doctorate thesis, we propose an alternative theory to solve this problem, based on the alveolar recruitment together with the nonlinear elasticity of the alveoli. This theory suggests that recruitment may be the predominant factor shaping these curves in the entire range of pressures normally employed in experiments. The proposed model correctly predicts the observed sigmoidal pressure volume curves, allowing us to discuss adequately the importance of this result, as well as its implications for medical practice

Produção e avaliação de nanoemulsão catiônica como possível vetor não-viral para pIRES2-EGFP

Gene therapy is based on the transfer of exogenous genetic material into cells or tissues in order to correct, supplement or silencing a particular gene. To achieve this goal, efficient vehicles, viral or non-viral, should be developed. The aim of this work was to produce and evaluate a nanoemulsion system as a possible carrier for no-viral gene therapy able to load a plasmid model (pIRES2-EGFP). The nanoemulsion was produced by the sonication method, after been choose in a pseudo-ternary phase diagram build with 5 % of Captex 355®, 1.2 % of Tween 80®, 0.8 % of Span 80®, 0.16% of stearylamine and water (to 100 %). Measurements of droplet size, polydispersity index (PI), zeta potential, pH and conductivity, were performed to characterize the system. Results showed droplets smaller than 200 nm (PI < 0.2) and zeta potential > 30 mV. The formulation pH was near to 7.0 and conductivity was that expected to oil in water systems (70 to 90 μS/s) A scale up study, the stability of the system and the best sterilization method were also evaluated. We found that the system may be scaled up considering the time of sonication according to the volume produced, filtration was the best sterilization process and nanoemulsions were stable by 180 days at 4 ºC. Once developed, the complexation efficiency of the plasmid (pDNA) by the system was tested by agarose gel electrophoresis retardation assay.. The complexation efficiency increases when stearylamine was incorporated into aqueous phase (from 46 to 115 ng/μL); regarding a contact period (nanoemulsion / pDNA) of at least 2 hours in an ice bath, for complete lipoplex formation. The nanoemulsion showed low toxicity in MRC-5 cells at the usual transfection concentration, 81.49 % of survival was found. So, it can be concluded that a nanoemulsion in which a plasmid model was loaded was achieved. However, further studies concerning transfectation efficiency should be performed to confirm the system as non-viral gene carrier

Avaliação preliminar da viabilidade de produção in vitro de um isolado brasileiro de baculovírus Spodoptera frugiperda MNPV

In vivo production of viral biopesticides is the major source of viral insecticides currently in the marketplace. However, this system presents limitations during production scale-up. For the Spodoptera frugiperda nucleopolyhedrovirus (SfMNPV), the insect used for replication has cannibalistic characteristics, thus production is even more difficult. Insect cells are commonly used for in vitro baculovirus production. Most of these cell lines are derived from Lepidoptera species. The Sf21 cell line is derived from Spodoptera frugiperda caterpillar ovarian tissue, and its clonal isolate Sf9 has been used for biopesticide production due to its ease of growth in suspension cultures. In this work, the in vitro production capabilities of a Brazilian SfMNPV isolate obtained from cornfields was evaluated. Comparison of polyhedra production was carried out using both Sf21 and Sf9 cells, based on volumetric and specific yields. Both cell lines were cultivated in Hyclone medium supplemented with different fetal bovine serum concentrations (2,5 and 5%). The best results were obtained using Sf9 cells supplemented with 5% serum. These results were further confirmed quantitively through kinetic parameter estimation for both cells lines and different serum concentrations. After seven successive passages, this system still presented high specific polyhedra production

The dead core model applied to beads with immobilized cells in a fed-batch cephalosporin C production bioprocess

Viable cells immobilized in inert supports are currently studied for a wide range of bioprocesses. The intrinsic advantages of such systems over suspended cultures incite new research, including studies on fundamental aspects as well as on the industrial viability of these non-conventional processes. In aerobic culture of filamentous fungi, scale-up is hindered by oxygen mass transfer limitation through the support material and bioprocess kinetics must be studied together with mass transfer limitation. In this work, experimental and simulated data of cephalosporin C production were compared. Concentrations in the bulk fermentation medium and cellular mass profiles inside the bioparticles are focused. Immobilized cells were used in a tower bioreactor, operated in fed-batch mode. To describe the radial variation of oxygen concentration within the pellet, a dead core model was used. Despite the extremely low sugar concentrations, bioreaction rates in the pellets were limited by the dissolved oxygen concentration. Cell growth occurs only in the outer layers, a result also confirmed by scanning electron microscopy. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

An evaluation into the potential of biological processing for the removal of metals from sewage sludges

The use of sewage sludge in agricultural land as a means of sludge disposal and recycling has been shown to be economical and suitable because of the presence of nutrients such as nitrogen and phosphorus. However, municipal sludges often contain high quantities of toxic metals and other compounds that must be removed for its safe use in agricultural soils. The biological leaching of metals from sewage sludges has been shown to be a promising technique for metal detoxifying in such complex matrix. The process efficiency is dependent on several physico-chemical parameters, such as total solids concentration, metal forms, pH-ORP, and temperature. Scale-up of the process has not yet been defined and is still pursuing the correct operational design. Current research involving the bioleaching of metals from sewage sludge and its application to land, which affects soil physical properties, are presented and discussed.

Desenvolvimentos da biopolpação no Brasil

Biopulping is a technology which application can be advantageous to mechanical or chemical pulping. It presents benefits such as the creation of stronger pulp, as well as energy or chemicals savings. This paper gives an overview of the recent efforts to develop biopulping processes in Brazil as well as provides critical information on biopulping development worldwide. Eucalyptus grandis wood chips have been biotreated by Ceriporiopsis subvermispora in a 50-ton biopulping pilot-plant and used to produce TMP and CTMP pulps on a mill scale, Up to 18% and 27% energy savings have been observed for producing 450-470 CSFreeness TMP and CTMP pulps. Despite darker bio-TMP pulps are produced, one-stage bleaching with 5% H2O2 was sufficient to improve brightness values to 70% and 72% for bio-TMP and control pulps, respectively. Understanding biopulping mechanisms is also relevant because more resistant and competitive fungal species could be selected with basis on a function-directed screen-ing project. As far as the chemical changes induced by the fungus in wood are concerned, recent efforts have pointed out for two different types of wood transformations. One of them involves intense lignin depolymerization in short biotreatment periods, while the other indicates that esterification reactions of oxalate secreted by the Jungas on the polysaccharides chains increase the water saturation point of the fibers. Both transformations are expected to affect the fiber-fiber bonding and, consequently, the physical resistance of wood.

Trade, poverty and complementary policies in Latin America

Includes bibliography

Preparação e caracterização de casearinas de Casearia sylvestris como padrão fitoquímico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise técnica econômica de um gaseificador de biomassa de 100 kg/h para acionamento de um motor de combustão interna

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)