Green–Naghdi type III viscous fluids

We investigate constitutive theory for a new type of thermoviscous fluid. Equations are derived which reduce to the classical heat conduction equation under Fourier’s law when the new parameters tend to zero. Basic solutions for parallel flows are found and a travelling wave analysis is presented.     

Harvesting Lost Photons: Plasmon and Upconversion Enhanced Broadband Photocatalytic Activity in Core@Shell Microspheres Based on Lanthanide‐Doped NaYF4, TiO2, and Au

Efficiently harvesting solar energy for photocatalysis remains very challenging. Rational design of architectures by combining nanocomponents of radically different properties, for example, plasmonic, upconversion, and photocatalytic properties, offers a promising route to improve solar energy utilization. Herein, the synthesis of novel, plasmonic Au nanoparticle decorated NaYF₄:Yb³⁺, Er³⁺, Tm³⁺‐core@porous‐TiO₂‐shell microspheres is reported. They exhibit high surface area, good stability, broadband absorption from ultraviolet to near infrared, and excellent photocatalytic activity, significantly better than the benchmark P25 TiO₂. The enhanced activity is attributed to synergistic effects from nanocomponents arranged into the nanostructured architecture in such a way that favors the efficient charge/energy transfer among nanocomponents and largely reduced charge recombination. Optical and energy‐transfer properties are modeled theoretically to support our interpretations of catalytic mechanisms. In addition to yielding novel materials and interesting properties, the current work provides physical insights that can contribute to the future development of plasmon‐enhanced broadband catalysts.     

ON A THEORY OF INTERACTING CONTINUA WITH MEMORY

A linear theory is developed for thermoviscoelastic composites modeled as interpenetrating solid continua with memory. The response functionals are considered to depend on the past history of displacement fields, displacement gradients, temperature field, and temperature gradient. A uniqueness result and a variational characterization of solutions in the context of the dynamical theory are also established.     

ON A THEORY OF THERMOELASTICITY WITH MICROTEMPERATURES

The article is concerned with a linear theory for elastic materials with inner structure whose particles, in addition to the classical displacement and temperature fields, possess microtemperatures. In the first part of the article we derive an existence result for the dynamical theory and establish the continuous dependence of solutions on the initial data and body loads. Then we consider the equilibrium theory and present a uniqueness result and a solution for the field equations. The theory is illustrated with the solution of the problem of thermal stresses in an elastic space with a spherical cavity.     

Colloidal aggregation induced by the reduction in pH and the synthesis of new molecular structures during the milk fermentation process

The use of different inocula in the milk‐to‐yoghurt transformation influences the kinetics of the fermentation process. The aim of this work was to study the kinetics induced by Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (Lb–St). The milk‐to‐yoghurt transformation showed no delay in the production of lactic acid for yoghurt produced using Lactobacillus johnsonii with S. thermophilus (La1–St) or Lactobacillus casei with S. thermophilus (Lc1–St); the delays were 20–70 min and 40–80 min, respectively. The absence of delay was 1.0/min (Lb–St) as compared with 0.015/min (La1–St) and 0.7/min (Lc1–St). The kinetics was fitted using second‐order reaction.     

Microstructure and properties of random heterogeneous materials: A review of theoretical results

We present an overview of some theoretical results that have been obtained to rigorously bound the effective conductivity and effective elastic moduli of random heterogeneous materials. These bounds are obtained through the appropriate use of integrals over certain microstructure functions that capture essential morphological information about random materials. Such a characterization has been obtained analytically for several models, including fully penetrable spheres, totally impenetrable spheres, and the “cherry-pit” model. These analytical techniques—characterizing the microstructure and using this information to bound the effective properties—will undoubtedly be useful in obtaining sharper bounds on the effective properties of polymers. While we present some advanced ideas and methods, an attempt will be been made to elucidate these methods for the nonexpert.     

A note on stability in three-phase-lag heat conduction

In this note we consider two cases in the theory of the heat conduction models with three-phase-lag. For each one we propose a suitable Lyapunov function. These functions are relevant tools which allow to study several qualitative properties. We obtain conditions on the material parameters to guarantee the exponential stability of solutions. The spectral analysis complements the results and we show that if the conditions obtained to prove the exponential stability are not satisfied, then we can obtain the instability of solutions for suitable domains. We believe that this kind of results is fundamental to clarify the applicability of the models.