Coatings based on mucin‐tannic acid assembled multilayers. Influence of pH

Although widely used as implantable materials due to their mechanical properties, metal devices show several disadvantages, such as the lack of cellular binding sites, antibacterial properties, or lubricant properties. To this end, the development of engineered surfaces through protein coatings has been largely investigated. Due to their natural origin and complex structure which allows the formation of hydrogels, mucins have been proposed and investigated as effective coatings for metallic implants. The present study evaluates the ability of porcine gastric mucin (PGM) to form stable coatings on a model metal surface, using three buffers with different pH values, ranging from acid to alkaline, as dispersion media. Considering its large number of hydroxyl groups and its ability to form hydrogen bonds with the protein, tannic acid (TA) was used as cross‐linker. In addition to coatings' thickness and elasticity assessed through Quartz Crystal Microbalance with Dissipation monitoring (QCM‐D), the study also evaluates the interactions between PGM and TA at various pH values of the dispersion media through DLS. The corroborated results show that the neutral pH allows the best interactions between PGM and TA leading to the formation of a stable, less elastic coating when compared with that obtained using as dispersion media the other two investigated buffers. Moreover, the hydrophilicity and mechanical properties of the dried coatings were assessed through contact angle measurements and nanoindentation, respectively.     

Fluorescence enhancement for the complex PAMAM-BSA in the presence of photonic crystal heterostructures

The paper presents the optical characterization of the multilayer film composed of styrene (ST)-poly(ethylene glycol) methyl ether methacrylate (PEGMA 1100)-gold nanoparticles (Au)-poly(amidoamine) PAMAM (G4)-bovine serum albumin (BSA). The addition of the last layer composed of BSA resulted in an unusual optical behaviour, i.e. increase of the fluorescence emission intensity, respectively the intensity of the UV-vis reflection, compared with the ST-PEGMA 1100-Au-G4 film. The explanation could be attributed to the presence of photonic crystal heterostructures. The multilayer film has been characterized by optical microscopy, AFM, UV-vis, and fluorescence.     

Experimental and micromagnetic first-order reversal curves analysis in NdFeB-based bulk “exchange spring”-type permanent magnets

In this paper we present the results of applying the first-order reversal curves (FORC) diagram experimental method to the analysis of the magnetization processes of NdFeB-based permanents magnets. The FORC diagrams for this kind of exchange spring magnets show the existence of two magnetic phases—a soft magnetic phase and a hard magnetic one. Micromagnetic modeling is used for validating the hypotheses regarding the origin of the different features of the experimental FORC diagrams.     

Gaussian effective potential for the U(1) Higgs model

In order to investigate the Higgs mechanism nonperturbatively, we compute the Gaussian effective potential of the U(1) Higgs model (“scalar electrodynamics”). We show that the same simple result is obtained in three different formalisms. A general covariant gauge is used, with Landau gauge proving to be optimal. The renormalization generalizes the “autonomous” renormalization for λ?⁴ theory and requires a particular relationship between the bare gauge coupling e _B and the bare scalar self-coupling λ _B. When both couplings are small, then λ is proportional to e⁴ and the scalar/vector mass-squared ratio is of order e², as in the classic 1-loop analysis of Coleman and Weinberg. However, as λ increases, e reaches a maximum value and then decreases, and in this “nonperturbative” regime the Higgs scalar can be much heavier than the vector boson. We compare our results to the autonomously renormalized 1-loop effective potential, finding close agreement in the physical predictions. The main phenomenological implication is a Higgs mass of about 2 TeV.     

The Discrete Planar L0-Minkowski Problem

In the discrete setting, the L₀-Minkowski problem extends the question posed and answered by the classical Minkowski's existence theorem for polytopes. In particular, the planar extension, which we address in this paper, concerns the existence of a convex polygonal body which contains the origin, whose boundary sides have preassigned orientations and each triangle formed by the origin with two consecutive vertices is of prescribed area.     

Single-domain particle hysteresis for a Random Anisotropy Ising System with exchange and magnetostatic interactions

In this paper we present an analysis on the hysteretic behaviour of magnetic nanoparticles described by a Random Anisotropy Ising Model. We have carried out an extensive study on the size, kinetics and inter-atomic interactions strength influences on the width and shape of the hysteresis loops of spherical particles composed by atoms situated in a cubic crystalline structure and interacting by the way of magnetostatic and exchange interactions.     

Influence of space charge related to water trees on the breakdown voltage of power cable insulation

A three-dimensional computation of the electric field and breakdown voltage in power cable insulation containing water trees and space charges is presented. The breakdown voltage and the conductivity of cylindrical samples of cable insulation containing water trees were measured. The samples have been aged in wet environment under ac voltages of frequencies comprised between 1 and 5 kHz. Exponential and parabolic spatial variations of permittivity and space charge density and the electrostatic, electro-kinetic and quasi-stationary regimes of the electric field were considered. The best correlation between the experimental breakdown voltage and the calculated one has been obtained in quasi-stationary regime.     

Preparation and dielectric properties of BaZr0.1Ti0.9O3 ceramics with different grain sizes

BaZr_0.1Ti_0.9O₃ ceramics with grain sizes of 0.75 and 2.60?µm have been prepared via solid-state reaction. Optimum parameters for calcination and sintering have been found in order to obtain pure perovskite phase, high density ceramics and homogeneous microstructures. The dielectric data show a diffuse phase transition with a mixed ferroelectric-relaxor character at a maximum at 87–92°C, with a small thermal hysteresis of 2–3°C. A tendency towards a more diffuse character of the ferro–para phase transition towards the full relaxor behaviour is observed as small in the ceramic grain size. Better dielectric properties in the coarse ceramics with higher permittivity up to 14,000 at the transition temperature by comparison with 5000 for the fine one, are observed as a consequence of higher tetragonal distortion and higher density. The differences in the dielectric spectra found for the two grain sizes were interpreted as a consequence of the higher degree of inhomogeneity in the fine ceramics and to different grain boundary properties induced by the different sintering temperatures.     

Microscopic and proximity nucleus-nucleus potentials

The energy functional of the Skyrme interaction is employed to calculate the real part of the interaction potential between magic nuclei in the sudden approximation. The use of an approximation introduced by Kirzhnits and others for the kinetic energy density produces improvements over the previous results. The mass dependence of the potential is analysed and its consistency with the proximity potential is discussed.     

The real part of the nucleus-nucleus interaction

The real part of the interaction potential for several pairs of magic nuclei has been derived from the Skyrme interaction density functional. The matter density of each nucleus is described by a Fermi distribution adjusted to reproduce the Skyrme-Hartree-Fock densities. Exchange effects due to antisymmetrization are taken into account in an approximate way. The tail of the resulting potential can be accurately approximated with a Woods-Saxon shape beyond the inflexion point of the calculated potential. The parameters of these Woods-Saxon potentials show regularities with respect to the masses of the target and projectile. We have tested the validity of the real part of the potential against elastic scattering data by choosing an imaginary part with the same geometry and a variable strength. For the energy range we consider the calculated grazing angles are somewhat larger than the experimental ones.