Most thin films of practical importance are composed of water as a primary solvent with dissolved ions. The major difficulty in developing a thermodynamic theory of ionic systems arises from the long-range nature of the electrostatic interaction potential between ions. The free energy for an ionic system cannot be represented as an analytic series expansion in powers of the particle number density. For more than half a century the approximations of Gouy-Chapman and Debye-Huckel have dominated our understanding of the interactions across the films that carry a surface charge. The Stern model gives a rather crude picture of the electric double layer, its main advantage being its simplicity. Hence the scientist trying to interpret experimental data involving electrostatic interactions is supplied with useful upper and lower bounds for the electrostatic forces in thin films even when the exact mechanism of charge regulation is obscure.

Chiral-magnetic/ferroelectric composite systems offer the possibility of electrically inducing magnetic Bloch skyrmions [Wang and Grimson, Phys. Rev. B 94, 014311 (2016)]. They are appealing for potential applications in spintronics due to their self-protection behavior. To realize skyrmion-based spintronic devices, it is essential to control the motions of the skyrmions. In this work, we propose a mechanical technique to manipulate skyrmions collinearly with a mobile external electric field that is imposed on the chiral-magnetic/ferroelectric system. The role of propagation velocity strongly impacts on the quality of magnetic skyrmions.

Magnetic skyrmions and multiferroics are the most interesting objects in nanostructure science that have great potential in future spin-electronic technology. The study of multiferroic skyrmions has attracted much interest in recent years. This article reports magnetic Bloch skyrmions induced by an electric driving field in a composite bilayer (chiral-magnetic/ferroelectric bilayer) lattice. By using the spin dynamics method, we use a classical magnetic spin model and an electric pseudospin model, which are coupled by a strong magnetoelectric coupling in the dynamical simulations. Interestingly, we observe some skyrmionlike objects in the electric component either during the switching process or by applying a magnetic field, which is due to the connection between the electric and the magnetic structures.

We investigate a mechanical method to manipulate magnetic Bloch Skyrmions by applying an electric field in a composite chiral-magnetic (CM)/ferroelectric (FE) bilayer. The magnetoelectric coupling at the interface allows the electric field to stimulate magnetic ordering. Therefore it offers the possibility to generate Skyrmions [Phys. Rev. B 94, 014311 (2016)]. Here, we design a movable and localized electric field source to drive skyrmion transport along the bilayer. A traveling velocity of the electric field source must be carefully chosen to show the stability and effciency of this process. The effects of high speed operation will be discussed.

Magnetic skyrmions and multiferroics are the most interesting objects in nanostructure science that have great potential in future spin-electronic technology. The study of the multiferroic skyrmions has attracted much interest in recent years. This paper reports on the magnetic skyrmions induced by an electric driving field on a composite multiferroic lattice. By using the spin dynamics method, we use a classical magnetic spin model and an electric pseudospin model, which are coupled by a strong magnetoelectric coupling in the dynamical simulations. Interestingly, we observe some skyrmion-like objects on the electric component during the switching process, which is due to the connection between the electric and the magnetic structures.

Theoretical investigation demonstrates that the composite bilayer (i.e., chiral-magnetic/ferroelectric bilayer) offers the possibility of electric-induced magnetic Skyrmions [Phys. Rev. B \textbf{94}, 014311 (2016)]. In this Article, we propose a micromagnetic model to physically manipulate magnetic Bloch Skyrmions propagating in a chiral-magnetic thin film with a polarized ferroelectric essential to drive the system through the converse magnetoelectric effect. Effects caused by different velocities of the propagation, sizes of the thin film, and strength of the magnetoelectric couplings strongly impact on quality and quantity of the magnetic Skyrmions.

Composite multiferroics, heterostructures of ferromagnetic (FM) and ferroelectric (FE) materials, are characterized by a remarkable magnetoelectric effect at the interface. Previous work has supported the ferromagnetic structure with magnetic spins and the ferroelectric with pseudospins which act as electric dipoles in a microscopic model, coupled with a magnetoelectric interaction [J. Appl. Phys. 118, 124109 (2015)]. In this work, by solving the stochastic Landau-Lifshitz-Gilbert equation, the electric-field-induced magnetization switching in a twisted boundary condition has been studied, and a behavior of domain wall in the ferromagnetic structure is discussed.

Magnetic skyrmions are topologically swirling magnetic spin textures realised as quasiparticles in chiral magnets. They hold great potential for applications in spintronic memory devices, due to their self-protection behaviour. Composite multiferroics are heterostructures displaying both ferromagnetic (FM) and ferroelectric (FE) orders. They also exhibit the remarkable magnetoelectric effect which offers an opportunity to induce magnetization by electric polarization, or vice versa. In this Article, we propose micromagnetic simulations for physically manipulated magnetic skyrmions propagating in a chiral-ferromagnet with a polarised ferroelectric essential to drive the system due to the converse magnetoelectric effect in the composite multiferroic heterostructure. Effects caused by different propagation velocities, film sizes and magnetoelectric couplings strongly impact on the quality and quantity of magnetic skyrmions. This technique is useful to control skyrmions in the composite thin film by using the microelectromechanical systems.

Magneto-electric effect in a multiferroic heterostructure film, i.e. a coupled ferromagnetic-ferroelectric thin film, has been investigated through the use of the Metropolis algorithm in Monte Carlo simulations. A classical Heisenberg model describes the energy stored in the ferromagnetic film, and we use a pseudo-spin model with a transverse Ising Hamiltonian to characterise the energy of electric dipoles in the ferroelectric film. The purpose of this article is to demonstrate the dynamic response of polarisation is driven by an external magnetic field, when there is a linear magneto-electric coupling at the interface between the ferromagnetic and ferroelectric components.

A spin dynamics approach has been used to study the behavior of the magnetic spins and the electric pseudo-spins in a 1-D composite multiferroic chain with a linear magneto-electric coupling at the interface. The response is investigated with either external magnetic or electric fields driving the system. The spin dynamics is based on the Landau-Lifshitz-Gilbert equation. A Gaussian white noise is later added into the dynamic process to include the thermal effects. The interface requires a closer inspection of the magneto-electric effects. Thus, we construct a 2-D ladder model to describe the behavior of the magnetic spins and the electric pseudo-spins with different magneto-electric couplings.

A composite multiferroic chain with an interfacial linear magneto-electric coupling is used to study the magnetic and electric responses to an external magnetic or electric field. The simulation uses continuous spin dynamics through the Landau-Lifshitz-Gilbert equations of the magnetic spin and the electric pseudo-spin. The results demonstrate an accurate description of the distribution of the magnetisation and polarisation are induced by applied electric and magnetic field, respectively.

A microscopic view of the response of the electric dipoles to a dynamic external field in a ferroelectric (FE) chain has been studied by two spin dynamics methods. One is the prominent micromagnetic approach, and the other is the micromagnetic approach with a variable size of the pseudo-spin. The energy stored in the ferroelectric chain is described by the transverse Ising model (TIM) with electric pseudo-spins. The simulations are based on a modified Landau-Lifshitz-Gilbert (LLG) equation which is precession free. The results obtained are shown and compared with the result supplemented by Landau-Devonshire (L-D) theory in the Appendix.

A rheological creep test was used to investigate the viscoelastic failure of five edible fats. Butter, spreadable blend and spread were selected as edible fats because they belong to three different groups according to the Codex Alimentarius. Creep curves were analysed according to the Burger model. Results were fitted to a Weibull distribution representing the strain-dependent lifetime of putative fibres in the material. The Weibull shape and scale (lifetime) parameters were estimated for each substance. A comparison of the rheometric measurements of edible fats demonstrated a clear difference between the three different groups. Taken together the results indicate that butter has a lower threshold for mechanical failure than spreadable blend and spread. The observed behaviour of edible fats can be interpreted using a model in which there are two types of bonds between fat crystals; primary bonds that are strong and break irreversibly, and secondary bonds, which are weaker but break and reform reversibly.

ABSTRACT Pectins are polygalacturonic acids with varying degrees of methyl esterification and are widely used to create gels. The commercial pectins studied by the authors were high‐methoxyl esterified pectin, low‐methoxyl esterified pectin and low‐methoxyl amidated pectin. A puncture test was performed at 5 and 20C using a texture analyzer. The compression force was recorded as a function of displacement. The resulting force‐displacement measurements were converted to stress‐strain to calculate Young's modulus by assuming incompressibility of the materials in a linear viscoelastic region (LVR). A rheometer was used for the shear flow curve, frequency sweep, amplitude sweep and creep tests, at 5 and 20C. The effects of temperature on storage and loss moduli were obtained. Further to that, a differential scanning calorimeter was used to investigate the melting behavior of pectin gels. The shear elastic moduli of pectin gels in an LVR were compared with Young's modulus. PRACTICAL APPLICATIONSUnderstanding the rheological properties of high‐methoxyl esterified pectin (HM), low‐methoxyl esterified pectin (LM) and low‐methoxyl amidated pectin (LMA) pectin gels is useful in the food, pharmaceutical and cosmetic industries for the improvement of product quality. The results may be used to model the relationship between the microstructural and mechanical properties of HM, LM and LMA pectin gels.

ABSTRACT The texture of lipid‐based food materials is an important topic for investigation. In this study, the rheological properties of five edible fats were determined. A puncture test was performed to investigate the rheological properties of the food materials at 5C and at 19C using a texture analyzer. The force‐displacement measurements were converted to stress–strain by assuming incompressibility of edible fat food materials in a linear viscoelastic region (LVR). Young's modulus of each edible fat was calculated using stress–stain curves in a LVR. Shear elastic moduli of edible fats in a LVR were obtained using a rheometer. Further to that the effect of temperature on storage modulus and loss modulus and creep test were obtained using a rheometer. The tests showed good correlation between Young's modulus and shear elastic modulus for each material. The mechanical properties correlated well with the structural properties of each of the materials. PRACTICAL APPLICATIONSThe texture of butter, blends and spreads is determined by temperature, rheological properties, processing conditions and the composition of the material. Our research investigated the effect of temperature on the rheological properties of these foods. The results may be used to model the relationship between the microstructure and mechanical properties of the fat crystal network.

The enormous diversity among bacterial colonies of different species, and among colonies of the same species under different environmental conditions, has long interested microbiologists. Yet it is only comparatively recently that quantitative, rather than merely conceptual, models have been developed to explain the dynamics of bacterial colony formation and growth. Understanding the fundamental processes that drive these dynamics is still at a rudimentary level, though a number of advances have been made. This review traces the history of bacterial colony growth modelling, from the pioneering work of Pirt in the late 1960s, through experimental investigations by Wimpenny and his colleagues in the 1970s, and further models extending from that work to understand complex bacterial colony formations. It concludes with recent results which find that both diameter and height of the colony follow simple power-law behaviour over the entire active growth period (from a few hours to several days old), and that the results of Pirt, Wimpenny and their contemporaries can be re-interpreted.

The dynamic phase behavior of a classical Heisenberg spin system with a bilinear exchange anisotropy in a planar thin film geometry has been investigated by Monte Carlo simulations using different forms for the stochastic dynamics. In simulations of the dynamic phase transition (DPT) in films subject to a pulsed oscillatory external field with competing surface fields, both Glauber and Metropolis dynamics show a continuous DPT. But while the field amplitude dependence of the DPT is similar in both cases, the transition region for the DPT as a function of temperature is more extended with Metropolis dynamics. The difference arises from a decoupling of the surface and bulk responses of the film near the dynamic phase transition with Metropolis dynamics that is not evident for Glauber dynamics.