Emulsifying properties of β-lactoglobulin and Quillaja bark saponin mixtures: Effects of number of homogenization passes,pH, and NaCl concentration

The effects of number of homogenization passes, pH, and NaCl concentration on the formation and stability of oil-in-water emulsions comprising a mixture of a biosurfactant (Quillaja bark saponin) and a globular protein (β-lactoglobulin) were investigated. The emulsions were characterized as to visual appearance, droplet size, droplet surface charge, and rheology. The emulsions obtained by different conditions (4, 6, or 8 passes; pH 7, 8, or 9; and 0, 100, or 200 mmol L^?1 of NaCl) were polydisperse, presented relatively small average droplet sizes (z-average < 323 nm) as well as negative droplet charge (between –20 and –79.6 mV) in all evaluated conditions. Regardless of the number of homogenization passes, the emulsions exhibited low apparent viscosity and pseudoplastic behavior with small yield stress. Viscoelastic behavior was also observed, thus the emulsions were characterized as weak gels. Four homogenization passes were enough to obtain small droplets in the evaluated conditions. Droplet size was not significantly affected by NaCl concentration and pH (p > 0.05). On the other hand, the absolute ζ-potential values significantly decreased and increased upon increased NaCl content and pH, respectively. Regardless of the tested conditions, all emulsions had good stability against phase separation and droplet aggregation, since no significant changes in average droplet size were observed throughout storage (p > 0.05). In the presence of NaCl, in which droplet charge significantly decreased, emulsion was also stable. Thus, we can conclude that electrostatic repulsion as well as steric repulsion was responsible for stabilization.     

Borago officinalis oil: Fatty acid fractionation by immobilized Candida rugosa lipase

γ-Linolenic acid (Z,Z,Z-6,9,12-octadecatrienoic acid), a very important polyunsaturated fatty acid is found in the free fatty acid fraction prepared by the hydrolysis of borage oil. Our aim was to enrich this fraction in γ-linolenic acid using selective esterification. Candida rugosa lipase was used as catalyst after immobilization on the following ion-exchange resins: Amberlite IRC50, IRA35, IRA93, and Duolite A7, A368, A568. In every case, immobilization modified the lipae’s specificity: palmitic, stearic, oleic, and linoleic acids were preferentially esterified compared to γ-linolenic acid, thus allowing a γ-linolenic acid enrichment of 3.0.     

Prediction of corrosion-induced cover cracking in reinforced concrete structures

Usually, the time of repair/replacement of reinforced concrete structures due to corrosion is controlled by cracking of the concrete cover. Thus, it is important to be able to predict with sufficient accuracy the time from corrosion initiation to crack formation in the concrete cover. The paper presents a critical overview of existing empirical, analytical and numerical models for predicting the time to corrosion-induced cover cracking. A simple nonlinear finite element (FE) is then formulated and validated. The FE model is employed to investigate inaccuracies of analytical models arising due to simplified formulation of the nonlinear behaviour of concrete and inability to account for actual location of corroding reinforcing bars. Recommendations on the applicability of analytical models are provided. Finally, the FE model is used to estimate the amount of corrosion products penetrating into concrete pores and microcracks since this amount is an essential parameter for analytical and numerical models.     

A representative and comprehensive review of the electrical and thermal properties of polymer composites with carbon nanotube and other nanoparticle fillers

In this review we present the results of our literature investigation into the electrical and thermal properties of carbon nanotube polymer composites. A short selection of data relating to conductive polymer composites with various fillers is provided for comparison. The effects of filler properties such as type and size, the use of hybrid fillers, fabrication methods for polymer composites and the importance of the modeling of the electronic and thermal transport mechanisms are discussed, as are more general factors influencing the properties of these composites. This review represents a comprehensive survey and constructive study and should serve as a useful reference tool for industrial and academic researchers working in this field. © 2017 Society of Chemical Industry     

Model for thermodynamic point identification in laser cutting

In recent years, laser cutting has been introduced and developed to such an extent that it is now thought to be one of the leading and indispensable manufacturing tools. At the present time, dross‐free and accurately‐cut parts are basically regarded as the major targets to aim for, because the costs and efforts associated with dross removal by postprocessing cut parts are considerable. Therefore, control of dross formation during laser cutting is an important factor in maintaining edge quality. The initial aim of this paper is to describe the importance of physico‐mechanical material properties that need to be taken into account in modeling of laser material processing in order to control melting of the material.     

Heat and Mass Transfer in Capillary-Pumped Liquid Films in Square Cross-Section Minichannels

This study addresses heat and mass transfer during the vaporization of a liquid in a heated square cross-section mini-channel. A theoretical model is developed in steady state using the radius of curvature as a variable. One-dimensional simulations have been performed. An analysis of this model reveals that heat and mass transfer is governed by two main groups of non-dimensional numbers (i.e., Reynolds × Boiling and Weber × Boiling² numbers). Maps of heat transfer performance are thus proposed according to these non-dimensional numbers. A reduced model is finally derived, allowing the main parameters to be expressed (such as the extended meniscus length) analytically.     

Assessment of Cell Disruption and Carotenoids Extraction from Sporidiobolus salmonicolor (CBS 2636)

The increasing demand for carotenoids by industries has drawn attention to their bio-production. Since pigments are intracellular, extraction steps are then needed after cell cultivation. In this work, different strategies for extraction of carotenoid pigments from Sporidiobolus salmonicolor (CBS 2636) were studied. Different solvents (dimethyl sulfoxide, petroleum ether, hexane, ethyl acetate, chloroform, and acetone), liquid N₂, and diatomaceous earth were used to disrupt the cell and thus release the intracellular carotenoids. The results of this study showed that when multiple solvents were used, a synergistic effect on the extent of carotenoids recovery was obtained. Maximum concentration of total carotenoids (913 μg/L) was obtained in the treatment using liquid N₂ and dimethyl sulfoxide to disrupt the cell, followed by the extraction with a solution of acetone/methanol (7:3, v/v).     

On the coupling in molecular motions: A novel molecular micro-structure approach to the physical meaning of the Ngai's coupling parameter

Summary The dielectric behaviour through DETA system has been studied for six PVC samples of distinct molecular microstructure in terms of content and associated surroundings and conformation of the local configurations mmr termini of isotactic sequences. Both the dielectric studies and the microstructure of the samples, as obtained by stereospecific substitution reaction of an additive-free commercial PVC are to be published in detail separately. For purposes of clarity some of the results are mentioned in Experimental section. The phenomenological correlation between the β parameter as defined by Ngai's theory and the microstructure of the samples, quantities both issued from the above quoted work, is considered in the present paper with the objective of providing some novel ideas on the physical meaning, at molecular level, of the Ngai's coupling parameter, in the light of mobility constraints and local free volume associated with mmr structure at its likely conformations. Received: 16 March 2001/Revised version: 18 June 2001/Accepted: 24 July 2001