Ellipsoidal anisotropy in linear elasticity: Approximation models and analytical solutions

The concept of ellipsoidal anisotropy, first introduced in linear elasticity by Saint Venant, has reappeared in recent years in diverse applications from the phenomenological to micromechanical modeling of materials. In this concept, indicator surfaces, which represent the variation of some elastic parameters in different directions of the material, are ellipsoidal. This concept recovers different models according to the elastic parameters that have ellipsoidal indicator surfaces. An interesting feature of some models introduced by Saint Venant is the formation of analytical solutions for basic problems of linear elasticity. This paper has two main objectives. First, an accurate definition of the variety of anisotropy called ellipsoidal is provided, which corresponds to a family of materials that depends on 12 independent parameters, including varieties of orthotropic and non-orthotropic materials. An explicit nondegenerate Green function solution is established for these materials. Then, it is shown that the ellipsoidal model recovers a variety of phenomenological and theoretical models used in recent years, specifically for geomaterials and damaged or micro-cracked materials. These models can be used to approximate the elastic parameters of any anisotropic material with different fitting qualities. A method to optimize the parameters will be given.     

Naproxen-eudragit RS100 nanoparticles: preparation and physicochemical characterization

The objective of the present study was to formulate naproxen-eudragit RS100 nanoparticles and investigate the physicochemical characteristics of the prepared nanoparticles. The nanoparticles of naproxen with eudragit RS100 were formulated using the solvent evaporation/extraction technique (the single emulsion technique). The effect of several process parameters, i.e., drug/polymer ratio, aqueous phase volume and speed of homogenization were considered on the size of the nanoformulations. The physicochemical characteristics of nanoparticles were studied applying particle size analysis, differential scanning calorimetry, X-ray crystallography, Fourier transform infrared spectroscopy and scanning electron microscopy. The release rate of naproxen from various drug/polymer nanoparticles was investigated as well. All the prepared formulations using eudragit RS100 resulted in nano-range size particles with relative spherical smooth morphology. The nanoparticles of naproxen-eudragit RS100 displayed lower crystallinity. The intermolecular interaction between naproxen and eudragit RS100 was detected in the FT-IR spectrum of the nanoparticles. All the nanoparticles displayed a slowed release pattern with the reduced burst release in comparison with the intact drug powder and physical mixtures of drug and polymer. According of these findings, formulation of the naproxen-eudragit RS100 nanoparticles was able to improve the physicochemical characteristics of the drug and possibly will increase the anti-inflammatory effects of drug following its ocular or intra-joint administration.     

Investigation of coupling length in a semi-cylindrical surface plasmonic coupler

We have investigated the performance of a nano-optical directional coupler based on gap plasmon waveguides. The coupler consists of two waveguides having a localized coupled plasmon propagating between two semi-cylindrical surfaces. After introducing a fundamental mode of studied waveguides, effects of the structure parameters on the coupling length are shown. Simulation results of the coupler obtained by the compact-2D finite-difference time-domain (FDTD) method comply with those derived by an analytic method with the aid of the finite-element frequency-domain (FEFD) software package of COMSOL.     

Effective permeability of cracked unsaturated porous materials

This study focuses on a theoretical estimation of the effective permeability of unsaturated cracked porous media. The closed-form flow solution around and in a superconductive crack, embedded in an infinite porous matrix under a far-field condition, is recalled first. Then the solution of flow around a completely unsaturated (empty) crack that is considered as an obstruction against the flow is determined. The flow solution for partially saturated crack in special configurations is obtained by superposition of the two basic solutions for superconductive and empty cracks. The contribution of an unsaturated crack, with a given saturation degree, to the effective permeability is estimated by using dilute upscaling scheme. Numerical results obtained by Finite Elements Method, are in good agreement with the theoretical results for weak crack densities but show the additional effect of cracks interaction for higher densities.     

Synthesis, characterization, X-ray crystallography, acetyl cholinesterase inhibition and antioxidant activities of some novel ketone derivatives of gallic hydrazide-derived Schiff bases

Alzheimer's disease (AD) is the most common form of dementia among older people and the pathogenesis of this disease is associated with oxidative stress. Acetylcholinesterase inhibitors with antioxidant activities are considered potential treatments for AD. Some novel ketone derivatives of gallic hydrazide-derived Schiff bases were synthesized and examined for their antioxidant activities and in vitro and in silico acetyl cholinesterase inhibition. The compounds were characterized using spectroscopy and X-ray crystallography. The ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays revealed that all the compounds have strong antioxidant activities. N-(1-(5-bromo-2-hydroxyphenyl)-ethylidene)-3,4,5-trihydroxybenzohydrazide (2) was the most potent inhibitor of human acetyl cholinesterase, giving an inhibition rate of 77% at 100 μM. Molecular docking simulation of the ligand-enzyme complex suggested that the ligand may be positioned in the enzyme's active-site gorge, interacting with residues in the peripheral anionic subsite (PAS) and acyl binding pocket (ABP). The current work warrants further preclinical studies to assess the potential for these novel compounds for the treatment of AD.