Odour‐active compounds in pineapple (Ananas comosus [L.] Merril cv. Red Spanish)

Application of solid‐phase microextraction, simultaneous distillation–extraction and liquid–liquid extraction combined with GC‐FID, GC‐MS, aroma extract dilution analysis, and odour activity value was used to analyse volatile compounds from pineapple (Ananas comosus [L.] Merril cv. Red Spanish) and to estimate the most odour‐active compounds. The analyses led to the identification of ninety‐four compounds, seventy‐two of them were positively identified. Twenty odorants were considered as odour‐active compounds, from which ethyl 2‐methylbutanoate, 2,5‐dimethyl‐4‐hydroxy‐3(2H)‐furanone, 1‐(E,Z,Z)‐3,5,8‐undecatetraene, ethyl 3‐(methylthio)propanoate, 1‐(E,Z)‐3,5‐undecatriene, ethyl hexanoate and methyl hexanoate were the most odour contributors and contribute to the typical pineapple aroma, while the others are responsible for fruity and sweet odour notes.     

Identification of multibody vehicle models for crash analysis using an optimization methodology

This work proposes an optimization methodology for the identification of realistic multibody vehicle models, based on the plastic hinge approach, for crash analysis. The identification of the design variables and the objective function and constraints are of extreme importance for the success of the optimization. The characteristics of the plastic hinges are used as design variables while the objective functions are formulated with measures of the difference between the dynamic response of the model and a reference response. The sequential application of genetic and gradient-based optimization methods is used to solve the optimization problem constituting a systematic approach to the automatic identification of vehicle multibody models. The methodology is demonstrated with the identification of the multibody model of a large family car for side and front crash. The vehicle model is developed in the MADYMO multibody code which is linked with the optimization algorithms implemented in the Matlab Optimization Toolbox.     

Comparisons of coherent systems using stochastic precedence

The comparisons of coherent systems is a relevant topic in reliability and survival studies. To this purpose, several techniques have been proposed including comparisons of expected lifetimes or comparisons using stochastic orderings. Recently, Samaniego (System Signatures and Their Applications in Engineering Reliability. International Series in Operations Research & Management Science, vol. 110. Springer, New York, 2007) proposed using stochastic precedence to compare the lifetimes of two independent coherent systems. He proved that if the components in both systems are independent and identically distributed (IID), then these comparisons are distribution free, while comparisons based on expected values are not. In the present paper, we obtain new expressions to compare systems using stochastic precedence without the assumption of IID components. In particular, we show that if the components in both systems are independent and satisfy the Cox proportional hazard rate (PHR) model with the same baseline hazard rate, then these comparisons do not depend on the baseline hazard rate function.     

Rheology of Cream-like Emulsions Prepared with Soybean Milk and Low Trans Vegetable Fat

The objective of this work was to study the effect of fat globule size and fat content on the rheological behavior of oil-in-water emulsions prepared with soybean milk, sunflower oil and low trans vegetable fat (LTF). Emulsions were prepared with 40 % w/w lipid phase (containing different proportions of LTF) and three different homogenization methods were used in order to obtain different globule sizes. Emulsions were subjected to controlled magnetic shaking until an increase in thickness. Partial coalescence was observed in all systems containing solid fat, which gave a rheopectic behavior and an increase in the viscoelastic parameters of the emulsions. Smaller particle sizes required higher shaking times to produce an increase in thickness, even though this did not lead to different final values of the viscoelastic parameters. The highest partial coalescence degree was observed at 50 % LTF in lipid phase, but the highest final viscoelastic parameters after shaking were observed at 100 % LTF in the lipid phase. The rheological behavior of these emulsions indicates that they could be a potential vegetable substitute for traditional dairy creams.     

Effect of Plant Sterols and Tannins on Phytophthora ramorum Growth and Sporulation

Elicitin-mediated acquisition of plant sterols is required for growth and sporulation of Phytophthora spp. This study examined the interactions between elicitins, sterols, and tannins. Ground leaf tissue, sterols, and tannin-enriched extracts were obtained from three different plant species (California bay laurel, California black oak, and Oregon white oak) in order to evaluate the effect of differing sterol/tannin contents on Phytophthora ramorum growth. For all three species, high levels of foliage inhibited P. ramorum growth and sporulation, with a steeper concentration dependence for the two oak samples. Phytophthora ramorum growth and sporulation were inhibited by either phytosterols or tannin-enriched extracts. High levels of sterols diminished elicitin gene expression in P. ramorum; whereas the tannin-enriched extract decreased the amount of ‘functional’ or ELISA-detectable elicitin, but not gene expression. Across all treatment combinations, P. ramorum growth and sporulation correlated strongly with the amount of ELISA-detectable elicitin (R ²?=?0.791 and 0.961, respectively).     

What goes up: Recent trends in Mexican residential energy use

Energy use in the Mexican residential sector is steadily increasing. Important factors contributing to the increase include changes in the types of housing built, heating, cooling, water-heating equipment and other appliances.     

Optimizing the search directions of a mixed DDM applied on cracks

Optimization and Engineering - Domain Decomposition Methods (DDM) are a set of numerical techniques that efficiently implement parallel computing for the structural analysis of large domains. This...