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A diabetic foot ulcer (DFU) is a serious complication in patients with diabetes mellitus (DM). A DFU is the most common cause of non-traumatic limb amputation, and patients with DFUs have increased mortality rates within 5 years after amputation. DFUs also increase the risk of cardiovascular and cerebrovascular diseases; therefore, with the increasing incidence and prevalence of diabetic foot wounds, DFUs are gradually becoming a major public health problem. The pathophysiology of DFUs is complicated and remains unclear. In recent years, many studies have demonstrated that the pathophysiology of DFUs is especially associated with neuropeptides, inflammation, and biofilms. Neuropeptides, especially substance P (SP) and calcitonin gene-related peptide (CGRP), play an important role in wound healing. SP and CGRP accelerate the healing of cutaneous wounds by promoting neovascularization, inhibiting the release of certain proinflammatory chemokines, regulating macrophage polarization, and so on. However, the expression of SP and CGRP was downregulated in DM and DFUs. DFUs are characterized by a sustained inflammatory phase. Immune cells such as neutrophils and macrophages are involved in the sustained inflammatory phase in DFUs by extracellular traps (NETs) and dysregulated macrophage polarization, which delays wound healing. Furthermore, DFUs are at increased risk of biofilm formation. Biofilms disturb wound healing by inducing a chronic inflammatory response, inhibiting macrophage phagocytosis and keratinocyte proliferation migration, and transferring antimicrobial resistance genes. To understand the relationships among neuropeptides, inflammation, biofilms, and DFUs, this review highlights the recent scientific advances that provide possible pathophysiological insights into the delayed healing of DFUs. [ABSTRACT FROM AUTHOR]

Dielectric nonlinearity is an important characteristic of ferroelectrics. Based on the characteristics of hysteresis loops and [variant_greek_epsilon]-E curves in ferroelectric materials, a model for dielectric nonlinearity of ferroelectrics is established. It is verified by the data of barium strontium titanate thin films. [ABSTRACT FROM AUTHOR]

Abstract: Ba0.6Sr0.4TiO3 thin films were deposited on Pt/SiO2/Si substrate by radio frequency magnetron sputtering. High-resolution transmission electron microscopy (HRTEM) observation shows that there is a transition layer at BST/Pt interface, and the layer is about 7–8nm thickness. It is found that the transition layer was diminished to about 2–3nm thickness by reducing the initial RF sputtering power. X-ray photoelectron spectroscopy (XPS) depth profiles show that high Ti atomic concentration results in a thick interfacial transition layer. Moreover, the symmetry ν of ɛ r–V curve of BST thin film is enhanced from 52.37 to 95.98%. Meanwhile, the tunability, difference of negative and positive remanent polarization (P r), and that of coercive field (E C) are remarkably improved. [Copyright &y& Elsevier]

Abstract: The microstructure and electrical properties of Ba0.6Sr0.4TiO3 thin films have been investigated. Nanometer-sized domains, ranging from 8 to about 30nm, were observed by piezoresponse force microscopy (PFM). The critical size, below which only single domains exist, is found to be about 31nm. The film exhibits ferroelectric behavior characterized by polarization hysteresis loop and capacitance–voltage curve. [Copyright &y& Elsevier]

Abstract: The microstructures and ferroelectric properties of Ba0.6Sr0.4TiO3 (BST) thin films prepared by RF magnetron sputtering were investigated. By adjusting deposition conditions, the ratio of Ba:Sr is near to the value of the ceramic target. Ninety degree domains in BST thin films were observed by piezoresponse force microscopy (PFM). It is found that the domain configuration of 28nm grain is different from that of 33nm grain. At 1kHz the dielectric constant and the tunability of the Ba0.6Sr0.4TiO3 film with thickness 500nm are 1267 and 29.5%, respectively. The remnant polarization (P r) and the coercive electric field (E c) of the BST film are 0.6μC/cm2 and 12.1kV/cm at room temperature, respectively. The results show that the ɛ r–E and P–E curves are asymmetric, and show an electric field shift toward the negative side. It is implied that there are asymmetric potential barriers at the upper and bottom interfaces. [Copyright &y& Elsevier]

Abstract: The crystalline structure and dielectric properties of Ba x Sr1−x TiO3 ceramics with x =0.45, 0.5, 0.6, 0.65, 0.8, 0.9 were investigated. The a- and c-axis lattice constants of Ba x Sr1−x TiO3 ceramics were calculated and it is found that the crystal structures are tetragonal phase when x ≥0.65 at room temperature. The Curie–Weiss temperature (T 0) is always lower than Curie temperature (T C) and the linear relation between the Curie temperature and the stoichiometric percentage of barium can be observed and expressed as T C (°C)=−195.0+322.2x. The values of coercive electric field (E C) and remanent polarization (P r) increase as Ba/Sr ratio of Ba x Sr1−x TiO3 ceramics increases except for x ≤0.5, which are due to the decrease in grain size and the difference between the radius of Ba2+ and that of Sr2+. [Copyright &y& Elsevier]

Abstract: Barium strontium titanate (BST) thin films were prepared by RF magnetron sputtering. The curves of dielectric constant–voltage, dissipation factor–voltage and the hysteresis loops of BST thin films with different grain sizes were investigated. The differences of the curves were analyzed. The voltage shift and an increase in the maximum dielectric constant were observed in ɛ–V curves as the grain size in the films increased. It is found that the dielectric loss of BST thin films does not change significantly with applied voltage. The origin of the asymmetric hysteresis due to asymmetrical potential barriers at the upper and bottom interfaces, residual elastic stress and incomplete compensation of depolarizing field was discussed. [Copyright &y& Elsevier]