Orientador: Valdir Augusto Neves / Banca: Edwil Aparecida de Lucca Gattás / Banca: Eduardo Purgatto / Resumo: Os frutos e vegetais apresentam-se fisiologicamente ativos após a colheita, dessa forma as perdas pós-colheita ocorrem pela influência de diferentes fatores onde se destacam a respiração, a temperatura, a umidade, a concentração de oxigênio e gás carbônico, a produção de etileno e a ação de enzimas endógenas associadas com processos de deterioração. As raízes de yacon têm sido cada vez mais consumidas devido à revelação de qualidades medicinais. A manutenção de sua qualidade in natura é um sério problema nos processos pós-colheita devido a inúmeras reações metabólicas. A peroxidase (POD, E.C.1.11.1.7) é largamente encontrada nos vegetais apresentando importante papel fisiológico/bioquímico embora uma precisa função não tenha ainda sido estabelecida. Sua importância para ciência dos alimentos evidencia-se pelas relações com alterações indesejáveis na qualidade e resistência dos vegetais, tornando interessante sua supressão parcial ou total no pós-colheita. Os objetivos desse trabalho foram isolar, purificar e caracterizar a peroxidase de raízes de yacon. Condições de extração para a POD de yacon foram estabelecidas e a enzima foi isolada por precipitação com sulfato de amônio, eluição em Sephadex G-25 e DEAE-celulose. Somente um pico de atividade foi eluído no processo de purificação com um fator de purificação de 222,33. O peso molecular determinado foi 34.8 kDa com valores de pH e temperatura ótima de 5,5 e 35°C, respectivamente. As constantes Km e Vmax foram de 14,227 mM e 17409 UA/mL, para s-dianisidina, e de 14,434 mM e 14830 UA/mL, para H2O2. Foram testados os efeitos inibidores de sais, quelantes, compostos sulfidrila, ácidos fenólicos e outros. Estudos de inativação térmica da POD foram realizados, nos quais se verificou o efeito protetor da sacarose na inativação enzimática e o efeito promotor de inativação pela ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The fruits and vegetables still continue physiologically active after the crop, in that way the postharvest losses occurs by the influence of different factors, like the respiration, temperature, humidity, concentration of oxygen and carbonic gas, ethylene production and the action of endogenous enzymes associated with deterioration processes. Yacon (Smallanthus sonchifolius) roots has been more and more consumed by the revelation of prebiotic and medicinal properties. The maintenance of its quality in the postharvest is a serious problem due to several metabolic reactions. Peroxidase (POD, E.C.1.11.1.7) is widely found in plants, having physiological/biochemical importance, although a precise function has not still been established. The POD importance for food science is due to its relationships with alteration of the quality and resistance of the vegetables to the postharvest factors. Its total or partial suppression by thermal inactivation or inhibitor compounds may be interesting for postharvest interests. The objectives of this work were to isolate, purify and characterize the POD from yacon roots. Extraction conditions for yacon POD were determined and the enzyme was isolated by precipitation with ammonium sulfate, elution on Sephadex G-25 and DEAE-cellulose. Only one peak of enzyme activity was eluted on the purification process with a 222.33 fold purification factor. The determined molecular weight was 34.8 kDa. The optimum pH and temperature values were pH 5.5 and 35°C, respectively. Km and Vmax for ï-dianisidine was 14.227 mM and 17409 UA/mL, and 14.434 mM and 14830 UA/mL for H2O2, respectively. The effects of metals, chelating agents, sulphidryl, phenolic acids and other compounds as POD inhibitors were evaluated... (Complete abstract, click electronic address below). / Mestre

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Decompositions of solids are typically of the form: A(s) ----> B(s) + gases. Symmetry-controlled routes (based on known and hypothetical crystal structures) for transforming the solid reactant into the solid product were devised as possible decomposition pathways. Lattice energies of the reactants, of the postulated transient intermediate structures and of the final solid products were then estimated by crystal modelling procedures. Profiles of lattice energy changes during the proposed decomposition routes were constructed and any energy barriers were compared with experimental activation energies reported for the thermal decompositions. The crystal modelling was performed with the computer program WMIN. Calculation of the lattice energies involved the development of a model potential for the perfect lattice and the evaluation of the interatomic parameters. The potential was based on the Born model of ionic solids using the Buckingham potential (Ø(r)= Ae⁻r/p - C/r⁶) to describe the short-range energy contribution. Empirical fitting was used to establish reliable interatomic energy parameters. The reliability of the interatomic potentials was assessed by calculating crystal structures and lattice energies (which were not included in the fitting). The particular reactions selected for modelling were the decompositions of the alkaline-earth metal (Ca, Sr, Ba) peroxides and carbonates: M0₂(s) ---> MO(s) + ¹/₂0₂(g) MC0₃(s) ---> MO(s) + CO₂(g)The lattice energies calculated for the known structures were in good agreement with reported values, (except for Ba0₂ and BaC0₃) which provided support for the adequacy of the potential model used. Activation energies calculated for the decomposition of the carbonates were in the correct order but hlgher than experimental values, i. e., 422, 422, 465 and 499 kJ mol̄̄⁻¹ compared to the experimental values of 205, 87(?), 222 and 283 kJ mol̄̄⁻¹ for CaC0₃ (calcite), CaC0₃(aragonite), SrC0₃ and BaC0₃. The values calculated for the peroxides (91 and 100 kJ mol⁻¹ compared to the experimental values of 119 and 185 kJ mol⁻¹ for Sr0₂ and Ba0₂ respectively) were less satisfactory but could be a reflection of the poor structural data used for the peroxides. The significance of this approach to the modelling of solid decompositions is discussed.

New methods in the fabrication of top coat and bond coat have been introduced to improve the efficiency and performance of advanced thermal barrier coatings (TBCs).i. Top coat. Thick yttria-stabilized-zirconia (YSZ) coatings (300-400 μm) have been fabricated by using electrophoretic deposition (EPD) method. The EPD coatings have more favorable microstructures with uniformly distributed porosity and stronger bonding, in comparison with conventional air-plasma spray (APS) coatings. ii. Bond coat. Pt-diffused single γ’-phase bond coat has been fabricated by applying selective etching prior to the electroplating of Pt on CMSX-4 single crystal superalloys. The concern on the compromised scale adhesion caused by the depletion of Pt is effectively avoided, as Pt remains stable in a coherent γ’-phase layer after long-term diffusion and oxidation. Considerable cost of Pt could also be reduced. Commercial TBCs, comprising an electron beam physical vapour deposition (EBPVD) top coat, a Pt-enriched intermetallic bond coat and a CMSX-4 single crystal superalloy, have also been investigated focusing on the failures that typically occurred at the scale/alloy interface. Advanced characterization techniques have been used to study the chemical factors (Al, Pt, S, Hf, etc.) that determine the durability of TBCs. Mechanisms have been discussed that control the TBCs behaviours of diffusion, oxidation, and adhesion. i. Diffusion. A depletion of Pt near the scale/alloy interface inevitably occurs at high temperatures, which significantly weakens the scale adhesion. Mechanisms controlling the diffusion of Pt in Ni-based single crystal superalloys at high temperatures have been investigated focusing on the evolution of phase, microstructure, and composition. It was found that Pt has negative chemical interactions with Al, Ti and Ta, all of which could stabilize Pt in β- and γ’-phases, and therefore avoid the depletion of Pt. ii. Oxidation. Selective oxidation behaviour of Ni-based superalloys has been studied by using thermodynamic calculations, which is mainly affected by alloy compositions, oxygen partial pressures and temperatures. It was found that the formation of a protective α-Al2O3 scale is more favoured under lower oxygen partial pressures and higher temperatures. The additions of Al and Pt in Ni-based superalloys could also promote the formation of Al2O3 and the exclusion of NiO and spinel. The additions of reactive elements (RE), however, are less effective and may even cause severe internal oxidations due to a competitive oxidation between Al and RE.iii. Adhesion. Sulphur effect in TBCs mainly refers to a segregation of sulphur at the scale/alloy interface, which significantly deteriorates the scale adhesion to alloys. High resolution secondary ion mass spectrometry (Nano-SIMS) was employed to trace sulphur in commercial TBCs. The undesired “sulphur effect” on scale adhesion was suggested to be caused by the formation of residual sulphides beneath the scale with weaker ionic bonding to alloy cations, rather than a segregation of sulphur atoms. Possible solutions have been suggested to alleviate the sulphur effect in TBCs.

The relationship between the fabric parameters, as independent variables, and the comfort related properties, as dependent variables, of commercial suiting fabrics, containing both natural and man-made fibres, have been studied. The fabric parameters measured in the study were mass, thickness, density, and air permeability. The comfort related properties, tested on a Permetest instrument, included water vapour permeability, water vapour resistance, and thermal resistance, with the moisture permeability index being derived. A total of 26 commercial suiting fabrics, covering a wide range of mass, as well as different fibre types and blends and fabric structures, was tested. The fibres covered, included wool, polyester, viscose, and cotton, while the fabric structures covered were 1x1 plain weave, 2x1 twill and 2x2 twill weave. The objectives of this study were to determine the empirical relationships between the measured fabric properties and the measured comfort related properties, and to determine the role, if any, of fibre type and fabric structure, since many claims are made in practice concerning the relative advantages, in terms of comfort, of a specific fibre type or blend, or fabric structure, over others, some of which being supported by research results. Since the fabrics covered, were commercial and were not engineered so that the different fabric parameters (independent variables) and fibre type and blend, as well as fabric structure could be varied independently of each other, the effects of the various fabric parameters on the fabric comfort related properties were determined and quantified by multiple regression analyses (multi-linear and multi-quadratic), and the best fit regression equations, and contribution of each parameter to the overall fit established. It was found that fabric thickness and fabric mass had the largest effect on the comfort related properties as measured here, fabric mass determining, to a large extent, water vapour permeability, and fabric thickness, thermal resistance. The rest of the fabric parameters included in the study had only a relatively small effect on the measured comfort related properties. The influence of fabric parameters, with particular reference to mass and thickness, on the measured comfort related properties, were much greater than that of fibre type or blend, or fabric structure. It was, therefore, concluded from this study, that the fabric parameters, as opposed to the intrinsic characteristics of a particular fibre, whether natural or man-made, largely determined those fabric comfort related properties measured here.