The Cracking Behavior of Two Dental Composite Materials Validated through Multifractal Analyzes.

The aim of this in vitro study was to analyze, both experimentally and theoretically, the mechanical behavior of two types of composite materials used in restoring dental integrity. The samples of each composite resin, namely Filtek Supreme XT (3M ESPE, St. Paul, MN, USA) and Filtek Z250 (3M ESPE, St. Paul, MN, USA), were experimentally analyzed by determining their compressive strength and fracture behavior. The fractured fragments of the samples were subjected to surface evaluation by scanning electron microscopy. The compressive stress-compressive strain dependencies revealed stronger cracking of the Filtek Supreme XT composite than Filtek Z250 prior to fracture. Theoretically, the evaluation was made by means of holographic implementations of such types of composite materials. A Hooke-type equation in a differential form is presented, which links the proposed theoretical model with the experimentally obtained data.

Theoretical and Experimental Designs on Several Mechanical Properties of Cu-Al-Zn Shape Memory Alloys Used in the Processing Industry.

By assimilating shape memory alloys with mathematical multifractal-type objects, a theoretical model based on Scale Relativity Theory in the form of The Multifractal Theory of Motion, in order to explain the mechanical behavior of such material, is proposed. The model is validated by analyzing the mechanical behavior of Cu-Al-Zn shape memory alloy with various chemical compositions. More precisely, the multifractal tunnel effect can "mime" the mechanical hysteresis of such a material, a situation in which a direct correspondence for several mechanical properties of Cu-Al-Zn is highlighted (the chemical composition can be correlated with the shapes of the curves controlled through the multifractality degree, while the areas delimited by the same curves can be correlated with the multifractal specific potential, as a measure of the mechanical memory degree).

Polycyclic Aromatic Hydrocarbons (PAHs) Contamination in Chrysichthys nigrodigitatus Lacépède, 1803 from Lake Togo-Lagoon of Aného, Togo: Possible Human Health Risk Suitable to Their Consumption.

The Lake Togo-Lagoon of Aného is located in the coastal zone where phosphorite mining is carried out. This mining discharges all kinds of waste such as fuel oil into the surrounding environment without prior treatment. Moreover, the hydrosystem receives runoff and river inputs after having crossed and leached from mining and urban soils. This study aims to determine the polycyclic aromatic hydrocarbons (PAHs) contamination in commercially consumed fish species (Chrysichthys nigrodigitatus) from that hydrosystem and the associated health risks for consumers. For that, fish sample collection was performed during the dry season. Afterwards, their muscles, gills, and livers were cut and 12 PAHs were analyzed using gas chromatography coupled with a mass spectrometer (GC-MS). The total PAHs (tPAHs) concentrations in fish tissues ranged from 5.24 to 48.40 µg/kg with average concentration of 14.51 ± 8.95 µg/kg in muscles, from 5.90 to 28.20 µg/kg averaging 14.90 ± 5.19 µg/kg in gills, and from 43.20 to 149.00 µg/kg with an average of 80.74 ± 27.08 µg/kg in livers. The average concentrations of low molecular weight PAHs (LMW PAHs) were 10.82 ± 9.61 µg/kg in muscles, 8.25 ± 5.43 µg/kg in gills, and 47.97 ± 22.56 µg/kg in livers whereas those of high molecular weight of PAHs (HMW PAHs) were 4.10 ± 2.14 µg/kg in muscles, 7.98 ± 3.96 µg/kg in gills, and 32.77 ± 8.66 µg/kg in livers. An overall trend of decreasing concentrations with increasing fish size classes was observed for some PAHs (Naphtalene, Pyrene in muscles, for Pyrene, Benzo(a)Anthracene, Chrysene in gills and for Naphtalene, Phenanthrene in livers). The PAHs in these fish might have pyrogenic and petrogenic sources, with the dominance of pyrogenic, and all of the total hazard quotients (THQ) are less than 1. This situation must not be neglected for better planning sustainable management of the target ecosystem.

Drug-Loaded Polymeric Particulated Systems for Ophthalmic Drugs Release.

Drug delivery to the anterior or posterior segments of the eye is a major challenge due to the protection barriers and removal mechanisms associated with the unique anatomical and physiological nature of the ocular system. The paper presents the preparation and characterization of drug-loaded polymeric particulated systems based on pre-emulsion coated with biodegradable polymers. Low molecular weight biopolymers (chitosan, sodium hyaluronate and heparin sodium) were selected due to their ability to attach polymer chains to the surface of the growing system. The particulated systems with dimensions of 190-270 nm and a zeta potential varying from -37 mV to +24 mV depending on the biopolymer charges have been obtained. Current studies show that particles release drugs (dexamethasone/pilocarpine/bevacizumab) in a safe and effective manner, maintaining therapeutic concentration for a longer period of time. An extensive modeling study was performed in order to evaluate the drug release profile from the prepared systems. In a multifractal paradigm of motion, nonlinear behaviors of a drug delivery system are analyzed in the fractal theory of motion, in order to correlate the drug structure with polymer. Then, the functionality of a SL(2R) type "hidden symmetry" implies, through a Riccati type gauge, different "synchronization modes" (period doubling, damped oscillations, quasi-periodicity and intermittency) during the drug release process. Among these, a special mode of Kink type, better reflects the empirical data. The fractal study indicated more complex interactions between the angiogenesis inhibitor Bevacizumab and polymeric structure.

Complex Behavior in the Dynamics of a Polymeric Biocomposite Material-"Liquid Wood". Experimental and Theoretical Aspects.

The purpose of the present paper is to analyze, both experimentally and theoretically, the behavior of the polymeric biocomposite generically known as "liquid wood", trademarked as Arbofill. The experimental part refers to the mechanical performance in tension and compression, having as finality the possibility of using "liquid wood" as a material suitable for the rehabilitation of degraded wooden elements in civil structures (ex. use in historical buildings, monuments etc.). The theoretical part refers to computer simulations regarding the mechanical behavior of "liquid wood" as well as to a theoretical model in the paradigm of motion, which describes the same behavior. This model is based on the hypothesis that "liquid wood" can be assimilated, both structurally and functionally, to a multifractal object, situation in which its entities are described through continuous, non-differentiable curves. Then, descriptions of the behavior of "liquid wood", both in the Schrödinger-type and in hydrodynamic-type representations at various scale resolutions, become operational. Since in the hydrodynamic-type representation, the constitutive law of "liquid wood" can be highlighted, several operational procedures (Ricatti-type gauge, differential geometry in absolute space etc.) will allow correlations between the present proposed model and the experimental data. The obtained results, both practical (81% bearing capacity in compression and 36% bearing capacity in tension, compared to control samples) and theoretical (validation of material performance in virtual environment simulations, stresses and strains correlations in a theoretical model) indicate that "liquid wood" could be used in the construction industry, as a potential rehabilitation material, but with more development clearly needed.