Starch and pectin solubilization and texture modification during pre-cooking and cooking of cassava root (Manihot esculenta Crantz)

Physico-chemical alterations of cell-wall constituents and of substances stored in the cell characterize the behavior of fresh vegetables during cooking. Pre-cooking for 1 h at three different temperatures was used to identify alterations in hydration, pectin and starch solubilization and the relation to texture determination by a compression and a shear test. Samples of cassava (Catarina amarela) harvested 8 months after planting date were used. Soluble galacturonic acid in the treatment water varied from 0.07 to 0.2.1 mg/100 ml while soluble solids varied from 271.3 to 599.6 mg/100 ml. Soluble starch varied from 114.3 to 437.7 mg/100 ml and total solids varied from 292.4 to 611.4 mg/100 ml during pre-cooking from 55 to 75 °C. There was weight reduction of 4 and 2 g/100 g of material and reduction of compression force in the treatments at 55 and 65 °C in relation to the raw sample and weight gain of 6.7 g/100 g and increase in compression force at 75 °C. Shear force decreased from the raw sample to the 65 °C treated sample while pectin solubility increased up to 75 °C. Samples cooked in boiling water had weight gain of 6.8 g/100 g of material, 493.3 mg/100 ml of soluble solids and 588 mg/ 100 ml of total solids of which 507.6 mg was starch.     

A parametric analysis of the patch load behaviour using a neuro-fuzzy system

This work presents a parametric analysis to evaluate the behaviour of steel beams subjected to concentrated loads. A neuro-fuzzy system was trained and tested [Fonseca ET. Comportamento de Vigas de Aço Sujeitas a Cargas Concentradas Através de Técnicas de Inteligência Computacional. D.Sc. thesis. Civil Eng. Dept., PUC-Rio. 2003 [in Portuguese]; Fonseca ET, da S. Vellasco PCG, de Andrade SAL, Vellasco MMBR. A neuro-fuzzy system for patch load prediction. In: 7th international conference on the application of artificial intelligence to civil and structural engineering. Egmond aan Zee; 2003 [published in CD-ROM — 18 pages]] to predict patch load results and classify this behaviour. In preceding studies [Fonseca ET, Vellasco MMBR, da S. Vellasco PCG, de Andrade SAL, Pacheco MAC. A neural network system for patch load prediction. Journal of Intelligent and Robotic Systems 2001;31:185-200; Fonseca ET, da S. Vellasco PCG, de Andrade SAL, Vellasco MMBR. A patch load parametric analysis using neural networks. Journal of Constructional Steel Research 2003;59(2):251-67; Fonseca ET, da S. Vellasco PCG, de Andrade SAL, Vellasco MMBR. Neural network evaluation of steel beam patch load capacity. Advances in Engineering Software 2003;34(8):680-705] the performance of neural networks was significantly more accurate than patch load prediction formulae [Lyse I, Godfrey HJ. Investigation of web buckling in steel beams. In: ASCE Transactions, vol. 100, 1935, p. 675-95 [paper 1907]; Bergfelt A. Patch loading on slender web. Influence of horizontal and vertical web stiffeners on the load carrying capacity, Chalmers University of Technology, Publication. S79:1, Goteborg, 1979, p. 1-143; CISC, Canadian Institute of Steel Construction. Limit states design of steel structures. CAN/CSA -S16-01; 2001; Eurocode 3, ENV-1993-1-1. Design of steel structures. CEN, European Committee for Standardisation; 1997 [Doc. CEN/TC 250/SC3-N419E]; Roberts TM, Newark ACB. Strength of webs subjected to compressive edge loading. Journal of Structural Engineering, American Society of Civil Engineers 1997;123(2):176-83], although the system did not consider the difference in the beam ultimate limit state. Therefore this paper applies a neuro-fuzzy system to evaluate the ultimate load physical phenomena (yielding, buckling or crippling) as well as the critical load related to each collapse type.     

A MIS transistor using the nucleation surface of polycrystalline diamond

In this work, the nucleation surface of a polycrystalline diamond film was used for the first time to fabricate a MISFET structure using standard photolithographic procedures, with a channel length of 100 μm. The resulting structure works as an enhancement-type p-type MOSFET. The I_ON/I_OFF ratio is about three orders of magnitude. The saturation of the current is clearly observed, with I_DS currents of about 20 nA for V_DS of 20 V. The smoothness of the nucleation surface allows a higher control of the electrodes, as well as their size decrease. The results show that, even though in an early stage, this investigation opens the door for a new generation of devices built on free-standing diamond films.     

Synthesis and characterisation of organo-silica hydrophobic clay heterostructures for volatile organic compounds removal

Mesostructured materials belonging to a new class of solid acids known as porous clay heterostructures (PCHs) have been prepared by chemical modification of a natural clay, by using a cationic surfactant, a neutral amine, and an equimolar mixture of bis(triethoxysilyl)benzene (BTEB) and tetraethyl orthosilicate (TEOS). The effect of different polymerisation times of the silica sources and of the hydrocarbon chain length of the neutral amine was studied. The materials retained their layered structure after the formation of stable pillars by the polymerisation of hydrolysed TEOS and BTEB. All materials were characterised by low temperature nitrogen adsorption isotherms, ¹³C CP MAS, ²⁹Si MAS and CP MAS NMR spectroscopy, thermal analyses and infrared spectroscopy. The specific surface BET areas of the materials were in the range 550–800 m² g⁻¹ and the corresponding microporous volume were near 0.2–0.3 cm³ g⁻¹. The reduction of the reaction time from 12 to 4 h avoids the extra-gallery polymerisation, contributing for a larger specific surface area. The increase of two carbon atoms in the neutral amine chain does not show much effect on the available surface area.

These materials were very effective as adsorbents of volatile organic compounds (VOCs), according to tests on methanol, methyl ethyl ketone, toluene and trichloroethylene. The water adsorption isotherms proved the hydrophobicity of the materials, suggesting their capabilities for VOC adsorption in the presence of water.     

Evaluation of a numerical method to predict the polyphenols content in monovarietal olive oils

Three monovarietal virgin olive oils obtained from olives grown under biological agricultural system, in Portugal, with different ripening stages, were studied in what concerns the parameters usually related with oxidation status (total polyphenols, tocopherols, chlorophylls and carotenoids, peroxide values, oxidative stability, specific extinction coefficients K₂₃₂ and K₂₇₀ and titratable acidity). A total of 18 samples were analyzed: seven from Cv. Cobrançosa (maturation indices 1–7), five from Cv. Madural (maturation indices 3–7) and six from Cv. Verdeal Transmontana (maturation indices 1–6). Oxidative stability and polyphenols profile presented high correlation coefficients. Given this high correlation, a numerical method was developed and evaluated to predict total polyphenols contents in olive oil. The method is based on the kinetic equation of the oxidation process in the presence of antioxidants and on Rancimat profiles. Total polyphenols contents obtained with this method were similar to those obtained by the Folin-Ciocalteau method.     

A test method for measuring chloride diffusion coefficients through partially saturated concrete. Part II: The instantaneous plane source diffusion case with chloride binding consideration

A test method is proposed for measuring chloride diffusion coefficients through partially saturated concrete specimens with well characterized water contents. It includes an experimental procedure for supplying a limited amount of Cl⁻ to the tested concrete surface, and two mathematical models for processing the experimental Cl⁻ content profiles obtained at selected diffusion times. The use of the more refined model, taking into account the chloride binding by concrete, allows to increase the reliability of the determined diffusion coefficients. For the two tested Portland cement concretes, (water/cement ratios 0.6 and 0.5), the Cl⁻ diffusion coefficient decreases about two orders of magnitude, from 6 · 10^− 12 to 2 · 10^− 14 m²/s, when the relative humidity of the atmosphere in equilibrium with concrete is lowered from 95% to 54% approximately.     

Power plant multistage investment under market uncertainty

Power plants whose production will be sold in a market context must be evaluated, taking into account market variables such as fuel, emissions and electricity prices. These variables have a stochastic behaviour, and therefore the power plant's present value is also stochastic. Using a stochastic process to estimate the power plant's present value, the best plan for investment can be devised to extract the maximum project value. This is achieved by considering multiple investment stages together with the possibility of postponing or abandoning the project when market conditions are unfavourable. The focus of the paper is on establishing the market-based value of a power plant and on determining the best execution of investment when it is done in multiple, modular stages. A comprehensive methodology is developed to establish a process for the plant present value, and to derive the optimal execution policy for investment.