Statistical models of mixtures with a biaxial nematic phase

We consider a simple Maier-Saupe statistical model with the inclusion of disorder degrees of freedom to mimic the phase diagram of a mixture of rod-like and disc-like molecules. A quenched distribution of shapes leads to the existence of a stable biaxial nematic phase, in qualitative agreement with experimental findings for some ternary lyotropic liquid mixtures. An annealed distribution, however, which is more adequate to liquid mixtures, precludes the stability of this biaxial phase. We then use a two-temperature formalism, and assume a separation of relaxation times, to show that a partial degree of annealing is already sufficient to stabilize a biaxial nematic structure.Comment: 11 pages, 2 figure

Rheology of decane/water and triglyceride/water emulsions stabilized by β-casein and sodium caseinate

β-Casein and sodium caseinate stabilized emulsions were produced and had their rheological properties investigated as a function of the nature of the oil phase, ionic strength and pH. Oil phases of distinct structural characteristics, namely decane and vegetable oil of high triglyceride content, were assayed. The former was much more effectively emulsified than the latter. Effects of pH and ionic strength were minor. Emulsion rheological properties were strikingly distinct in each case, with viscoelastic, solid-like structures being formed with decane (G' >> G"), differently from what is observed for samples containing triglycerides as the oil phase, in which viscoelasticity was not even apparent. The relevance of the spatial features of the oil phase structure in the development of the emulsion viscoelastic character is discussed. Factors responding for the system distinct behaviour possibly reside at the emulsion droplet interface, unapproachable by optical microscopy, rather than on aspects related to particle size or shape.Emulsões estabilizadas por β-caseína e sódio caseinato tiveram suas propriedades reológicas investigadas em função da natureza da fase oleosa, da força iônica e do pH. Fases oleosas de características estruturais distintas, a saber, decano e óleos vegetais de alto teor triglicerídico, foram ensaiadas. A emulsificação dos sistemas contendo decano foi significativamente mais efetiva do que aquela das amostras contendo triglicérides. Efeitos de pH e força iônica mostraram-se relativamente pouco importantes sobre a capacidade emulsificante da proteína. As propriedades reológicas foram marcadamente distintas em cada caso, com estruturas de caráter sólido (G' >> G") sendo produzidas com decano, diferentemente do que foi observado para amostras contendo triglicérides, nas quais a viscoelasticidade não foi nem mesmo aparente. A relevância de aspectos espaciais da estrutura da fase oleosa no desenvolvimento do caráter viscoelástico é discutida. Propõe-se que os fatores responsáveis pelo comportamento distinto observado residam possivelmente na interface gotícula/meio dispersante, inacessível por microscopia óptica, e guardam pouca relação com tamanho ou forma da gotícula.FAPESPCNP

Effect of heat treatment on rheological properties of mixed nectars based on cashew apple, mango and acerola pulps

The purpose of this experiment was to evaluate the effect of heat treatment on the rheological properties of mixed nectars, based on cashew apple, mango, and acerola pulps. Ten different formulations with different mass fractions of cashew apple, mango, and acerola pulps were prepared using a simplex centroid design [with a total of 35% (w/w) pulp] and submitted to heat treatment at 90 °C for 1 min. Samples were collected before and after heat treatment and characterization of their rheological properties was carried out. The rheological behaviour was obtained at 25 °C, with shear rate ranging from 108 to 500 s−1 (upward curve) and from 500 to 108 s−1 (downward curve) for 1 min with 25 readings for each curve. The Ostwald de Waele model showed to be a good fit for all formulations studied, which showed a non-Newtonian behaviour and a pseudoplastic character. Results of apparent viscosity for the non-heated formulations were well fitted by the linear model and the heat treated formulations by the cubic model. The heat treated formulations had higher (P<0.05) values of consistency index and apparent viscosity, as well as lower (P<0.05) values of flow behaviour index compared to non-heated formulations. The rheological characterization of these formulations is a very useful tool during product development and processing control of mixed nectars of fruit juice

Effect of the saliva biomolecules on the interface zirconia/Ti6Al4V triboactivity

Abstract in proceedings of the Fourth International Congress of CiiEM: Health, Well-Being and Ageing in the 21st Century, held at Egas Moniz’ University Campus in Monte de Caparica, Almada, from 3–5 June 2019.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.info:eu-repo/semantics/publishedVersio

Smart capabilities of a laminated piezoelectric plate model

This paper focuses on the modelling and analysis of actuator and sensor effects for thin laminated plates, which are formed by stacking several layers of different piezoelectric materials. We first discuss features and properties of a two-dimensional asymptotic model for a piezoelectric anisotropic plate, whose unknowns are the Kirchhoff-Love displacement and the electric potential. We prove that the latter is a quadratic polynomial of the plate’s thickness. The polynomial’s coefficients depend on the tangential and transverse displacements of the plate’s middle plane and the material coefficients. The asymptotic laminated plate model is discretized using finite elements. To investigate its smart capabilities we use two discrete optimization problems: the first one, focusing on the actuator effect, aims at obtaining a maximum displacement of the plate’s middle plane; the second one that corresponds to the sensor effect intends to maximize the electric potential at a predefined thickness of the plate. The optimization variables are the thicknesses of the layers, their ordering as well as the location of the applied electric potential (for the actuator problem) or the location of the applied mechanical forces (for the sensor problem). Since we also want to minimize the number of these locations (besides maximizing the above objectives), we obtain a multi-objective optimization problem that we solve using genetic algorithms. Several numerical results are reported

Smart capabilities of a laminated piezoelectric plate model

This paper focuses on the modelling and analysis of actuator and sensor effects for thin laminated plates, which are formed by stacking several layers of different piezoelectric materials. We first discuss features and properties of a two-dimensional asymptotic model for a piezoelectric anisotropic plate, whose unknowns are the Kirchhoff-Love displacement and the electric potential. We prove that the latter is a quadratic polynomial of the plate’s thickness. The polynomial’s coefficients depend on the tangential and transverse displacements of the plate’s middle plane and the material coefficients. The asymptotic laminated plate model is discretized using finite elements. To investigate its smart capabilities we use two discrete optimization problems: the first one, focusing on the actuator effect, aims at obtaining a maximum displacement of the plate’s middle plane; the second one that corresponds to the sensor effect intends to maximize the electric potential at a predefined thickness of the plate. The optimization variables are the thicknesses of the layers, their ordering as well as the location of the applied electric potential (for the actuator problem) or the location of the applied mechanical forces (for the sensor problem). Since we also want to minimize the number of these locations (besides maximizing the above objectives), we obtain a multi-objective optimization problem that we solve using genetic algorithms. Several numerical results are reported