Polymer microstructures containing plant extracts are a novel technique used to increase the bioavailability of active agents with low aqueous solubility. Japanese knotweed (Reynoutria japonica) is an invasive plant with multiple biomedical properties. The aim of the present study was to obtain and characterize polyurethane microstructures used as a drug delivery system of a Japanese knotweed extract. The results indicate the obtaining of microstructures with an almost neutral pH, with sizes between 540 and 1134 nm, with a medium stability against the tendency to form clusters and a very good thermal stability. These first results present the potential of the obtained polyurethane microstructures as candidates for the transmembrane drug delivery of Japanese knotweed extracts, as a starting point for further bioactivity investigations.
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Microfibers were obtained from organic low molecular weight compounds based on heteroaromatic and aromatic rings connected by aliphatic spacers. The obtaining of microfibers was proved by scanning electron microscopy. The deciphering of the mechanism of microfiber formation has been elucidated by X-ray diffraction, infrared spectroscopy, and atomic force microscopy measurements. By exciting with light of different wavelength, florescence microscopy revealed a specific optical response, recommending these materials for light sensing applications.
Nanocomposite materials have attracted a high interest for biomedical applications because their special properties related with structure and composition. In this paper we synthesized novel hydrogel nanocomposite materials special designed for hard tissue engineering. The nanocomposite materials are able to promote hydroxyapatite formation by alternating soaking mineralization demanded for increasing of cells biocompatibility and adhesion.
The objective of this paper is to present the thermal behavior of various PMMA/TiO2 nanocomposite for complete dentures fabrication with 3D printing technology. There have been prepared and thermally characterized polymeric composites with varied nanofiller content ranging between 0.2% and 2.5% (w/w%). The nanocomposites proved a better thermal performance than that of pure copolymer PMMA-MMA or 3D printing PMMA polymer complex matrix. A small difference in glass transition (Tg) temperature for all compounds studied was recorded.
PLA-based composites containing CF in the range 0 to 10 wt. % were prepared by melt mixing technique. The prepared composites were investigated in terms of processability, chemical structure (by Attenuated total reflectance - Fourier Transform Infrared - ATR-FT-IR analysis), thermal (Differential Scanning Calorimetry - DSC), optical properties (using UV-Vis spectrometry), barrier and migration in distilled water. Also, the behaviour of PLA based composites at sterilization was performed by examination the changes in their chemical structure. This study shows the feasibility of improving of PLA properties by using cellulose fibres, designed for flexible food packaging.
The normal development of the placenta is a major factor in the fetus’s growth and development, whilst the maternal-fetal placental vasculature is essential in this regard. During placentation, there is an ongoing process, which combines angiogenesis with vasculogenesis, as demonstrated by numerous studies, which reveal important roles of various known angiogenic factors, while other studies show the roles of different classes of factors in vascular morphogenesis nonspecific to the placenta. The method used in the case of our study is a standardized method of the Laboratory of Anatomy and Embryology, Victor Babes University of Medicine and Pharmacy, Timiºoara, for over 50 years. The making of corrosion concoction followed the recipe of the laboratory using type AGO II plastic substances, differently colored and then subjected to the corrosive action of hydrochloric acid. During the routine check outs all the pregnant woman’s were diagnosed with thrombophilia. The examination of the placental parameters - shape, weight, thickness - is important as a preliminary stage for the study of the placental architecture. The normal placental development remains a major factor in the growth and development of the fetus, and the maternal-fetal placental vasculature is essential in this regard. Placental angiogenesis has a different local component of angiogenesis, found in other anatomical regions.
Sandwich panels with composite/steel skin sheets and foam core are very often used as lightweight structures in automotive, maritime and aerospace applications due to their performances like high bending stiffness and strength and also lightweight. As an alternative to classical structural reinforced panels, the sandwich structures are justifying their use in various industrial fields, making these structures less complex, by eliminating the need for secondary stiffening. In the paper are presented three models of sandwich, steel-foam-steel, composite-foam-composite or steel-foam-composite structures, of different thicknesses, with functional use in various fields depending on necessities. The mechanical characteristics of the materials used in their manufacture have been determined. The panels have been subjected to various load cases in order to determine an optimal combination of weight and strength. At the same time, the numerical models used in the finite element analysis of the sandwich structures with specific elements for layered composites or sandwich (SHELL 4L and SOLID L) are presented.
The aim of this study was to evaluate the influence of different finishing and polishing systems and of composite resins structure on surface state of the restoration. Cylindrical samples from two different composite resins (Filtek Z 550 and Filtek Z 250, 3M ESPE) were obtained. In group 1 the samples were not finished and polished. In groups 2-4 the samples were submitted to finishing procedure using two tungsten carbide burs, then polished using three different polishing systems: three steps diamond abrasive polishers (Kenda CGI, Lichtenstein) - group 2, one step silicon carbide abrasive particles brush (Occlubrush, KerrHawe SA, Switzerland) - group 3 and two steps Sof-Lex spiral wheels (3M ESPE) - group 4. Half of the samples in each group were subjected to surface microstructure evaluation using a scanning electron mycroscope. The other half of the samples was subjected to surface state assessment using profilometery. All the investigated finishing and polishing systems leaded to increased surface roughness when compared to the roughness of composite resins placed in direct contact to celluloid clear matrix. The surface roughness of both microfilled-hybrid and nanofilled-hybrid composite resins finished and polished with different systems were influenced mostly by the polishing system and less by the composite resin structure.
The process of welding armor steel is a complex process because of possible welding faults, appearing in the weld metal zone in the form of cracks and pores. Austenitic filler material is traditionally used for welding armor steels. For heavy structural engineering such as armored military vehicles, which are frequently under the effect of dynamic load, it is important to know the dynamic properties of the most sensitive area of welded joints, the weld metal zone. Due to a significant interest in quantification of material resistance to crack initiation and propagation, the fatigue crack growth rate was measured in the welded metal zone, while the resistance to crack growth in the weld metal was tested by the amount of austenite transformed into martensite. Accordingly, the threshold stress concentration factor was 10 MPa m1/2. XRD spectral analysis revealed direct transformation of g - austenite into a’ -martensite.
A validation study between finite element analysis and experimental testing considering an impact loading of Fiberglass, Carbon and Kevlar-Carbon composite panels of 150 x 100 mm2 was conducted by the authors. Using the design of experiments method and the Design Expert software tool, the data obtained in FEA environment is validated, through means of statistical distributions, by the experimental tests results.