Previous studies have shown that marine drug propylene glycol alginate sodium sulfate (PSS) plays important roles in human diseases. This study mainly explored the effects of PSS on hyperglycemia and hyperlipidemia in diabetic db/db mouse models. The db/db mice were randomly divided into 5 groups (n=12), which were model control group (distilled water), positive control group (metformin), PSS low, medium, and high dose groups (PSS25, PSS50, PSS100) and normal control group (C57/BL, distilled water). The mice in each group had free diet and water for 90 days. During the experiment, food intake was recorded every day and body weight was recorded weekly. In addition, fasting blood glucose and glycosylated hemoglobin levels were measured regularly. Finally, the contents of triglyceride (TG), low-density lipoprotein (LDL-c), high-density lipoprotein (HDL-c) and total cholesterol (TC) in the serum of mice were determined. PSS can significantly reduce fasting blood glucose and glycosylated hemoglobin levels in db/db mice, and improve insulin sensitivity. Moreover, PSS can reduce the fat accumulation of db/db mice and significantly improve the blood lipid level of db/db mice. PSS can significantly improve the symptoms of glucose and lipid metabolism disorders in db/db mice.
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An original functionalization strategy is proposed here to design chitosan (CS)-based cryogels with ethylenediaminetetraacetic acid (EDTA) moieties. Cryogels with aligned micro-sized tubular structures were further engineered through an unidirectional freezing approach. Attachment of EDTA groups onto CS chains was proved by 1H-RMN and FT-IR spectroscopy. The formation of EDTA-functionalized 3D porous CS-based cryogels was demonstrated by several methods of characterization (FTIR spectroscopy, optical microscopy, SEM, porosity measurements, swelling behavior, copper (II) retention capacity). The sorption tests pointed out the high potential of EDTA-functionalized CS-based cryogels for heavy metal ions retention.
The purpose of this research is to study and develop the formulation of a rheological law for composite materials with elasto-plastic behaviour in cold compression. Starting from the generally known relationships in literature, the hypoelastic model proposed for the composite materials behaviour (as powder materials) has been developped/explained, ensuring the understanding of the research. The hypolastic theory has been used for modeling the continuous transition from elastic to plastic state for a powder material. The material behaviour is described through an isotropic tensor relationship between the deformation speed tensor, Cauchy’s stress tensor and its derivative in relation to time (the Jaumann’s derivative). Only the linear part has been used from the general form of the law which depends on scalar functions. The calculations lead to relationships depending on five parameters which are identified according to experimental data. A numerical simulation of the stress-strain evolution during the simple compression of a diepressed powder sample is made; the numerical simulation has been validated by the experimental results.
The paper presents the study on the static mechanical properties of PLA (Polylactic Acid) produced with entry-level additive technologies using three printing directions. During the experimental work were tested a total of 15 “dog bone” ASTM D638-14 standard specimens made from additively manufactured polymer (PLA) through FDM (Fused Deposition Modelling) technique, where the material and rectilinear pattern infill geometry and infill percentage of 100% were constant and the printing orientation was varied. Usually technical data sheets that are delivered by filament materials producers include the most satisfactory data which are valid for only one specific printing direction. The printing direction is deliberately selected, in such way that the best material characteristics are achieved. In addition to this matter, as the additive manufacturing market grew significantly in the past couple of years, the filament production market showed a consequential growth. The aftermath of this expansion had a direct impact towards the quality and costs of the filaments used for 3D printing, in order to satisfy both the low-end and high-end users. Therefore, in this frame, the present research provides entry-level additively manufactured PLA performances showing significant changes depending on the different printing directions and determine the build orientation influence on the mechanical properties, in the aim of providing aid for both mechanical designer and product manufacturer at the stage of the printed product mechanical properties.
This article aims to identify the behavior of light and heavy micro-plastics on the southern shore of the Caspian Sea during different seasons of the year. For this purpose, data from 15 sampling stations were gathered in four seasons, and subjected to various analyses after the samples were prepared. To separate light and heavy micro-plastics, the samples were washed with water. Analysis of TGA-DSC and FTIR imaging was used to quantitatively and qualitatively identify microplastic samples and optical microscope images were used to quantify the number of particles. According to the results, the amount of light microplastics in the spring and winter is less than in the summer and autumn. In the spring, the highest levels of pollutants are PVC, PES, PET and PU. In the summer and autumn, the values of PE, PP, PA, PAT, PU and PVC are at a relatively equal range. In the winter, most pollutants are PVC, PES, and PU. In conclusion, PE, PP, PPA, and PET should be removed from the environment before they can be modified by physical and chemical processes.
A biomaterial must be biologically compatible, mechanical, functional, corrosion resistant and easily adapt to clinical and laboratory technologies. Dental biomaterials are materials used to replace a part of a living system or to work closely with living tissue. Many scientific articles present different polymeric biocomposites with possible application in dentistry and this is a proof of the opportunity of a research in a field in full ascent and with great availability in the promotion of materials destined to “work under biological constraint” and which must also meet the functional requirements of a dental implant. The objectives of this research were to obtain and to comparatively evaluate different polymeric microparticles that can be used in dentistry. The samples based on poly(lactic-co-glycolic acid) and respectively polyurethane microparticles were characterized by pH and Zetasizer measurements, and in vitro cytotoxicity assays. The results indicate the obtaining of particles with a neutral pH, medium homogeneity, and with different tendencies to form agglomerations. Their low cytotoxicity, tested on the primary human gingival fibroblasts by MTT and LDH techniques, indicates that these microparticles are safe to be tested in further clinical evaluations.
Polypropylene (PP) has a wide range of applications in the automobile bumpers due to its many excellent properties. Mechanical properties of PP for automobile bumpers are investigated through an artificial accelerated aging test. The aging rules after different years of normal use and the artificial accelerated aging test are analyzed. The correlation between natural and artificially accelerated aging is also explored. It provides a reference for the study of the aging properties of polymers for automotive applications. Results show that the UV aging test can effectively simulate changes in tensile and bending strengths after natural aging and can be used to evaluate the weathering resistance of PP materials used in automotive bumpers. The tensile and bending strengths of these materials remain good during aging, and elongation is sensitive to aging. The short-term artificial accelerated aging test does not exert a significant influence on the impact strength of materials, and artificial accelerated aging does not completely reproduce the aging process of the material.
Since the commercialization of Li-ion batteries by Sony in 1990, the performance of cathode materials used in Li-ion batteries has improved significantly. However, Li-ion batteries cannot respond to the needs of the energy storage market in terms of energy density. In order to increase theoretical energy density of active materials, molar mass of the active material should be decreased, or electron number participating per reaction or reaction potential should be increased. In this study, it was aimed to produce cathode materials for Li-ion batteries in the form of composite nanofibers via electrospinning method. For this purpose, porous LiFexMn1-xPO4/C composite nanofibers (1 > x > 0) were synthesized with a scalable, two-step method (electrospinning and subsequent heat treatment). The morphological, structural and electrochemical properties of the LiFexMn1-xPO4/C composite nanofibers were determined by scanning electron microscope, X-ray diffraction and galvanostatic charge/discharge tests. Cathodes made of LiFexMn1-xPO4/C composite nanofibers showed various advantages such as long cycle life, improved electrochemical performance etc. due to the presence of carbon and LiFexMn1-xPO4 in the composite structure. With the addition of Mn to the structure of LiFePO4/C composite nanofibers, electrochemical performance was improved. LiFe0.8Mn0.2PO4/C composite nanofibers showed the best performance in terms of energy density among the samples. Further increment in Mn/Fe ratio resulted declining electrochemical capacity and energy density.
The thermoset polymers and the thermoplastic polymers matrix composites require different forming techniques due to the different properties of two classes of polymers. While the forming technique for thermoset polymer matrix composites does not require the use of special equipment, the thermoplastic polymer matrix composites imposes the rigorous control of temperature and pressure values. Each type of polymer transfers to the composite a set of properties that may be required for a certain application. It is difficult to design a composite with commonly brittle thermoset polymer matrix showing properties of a viscoelastic thermoplastic polymer matrix composite. One solution may consist in mixing a thermoset and a thermoplastic polymer getting a polymer blend that can be used as matrix to form a composite. This study is about using PMMA solutions to obtain thermoset-thermoplastic blends and to mechanically characterize the obtained materials. Three well known organic solvents were used to obtain the PMMA solutions, based on a previous study concerning with the effect of solvents presence into the epoxy structure.
A significant part of the research and production activities is represented in the field of bioengineering by the biomaterials used in hard tissue restorations. They are of great interest in dental science, intending to improve technological aspects, monitoring their biological responses to the living organisms, but also to redesign economic aspects, beginning with the choice of raw materials. In the present work, light-curing composite biomaterials were made from a composite polymer matrix consisting of specific concentrations of bisphenol A-glycidyl methacrylate base monomer (Bis-GMA), a mixture of two co-monomers, triethylene glycol dimethacrylate and ethoxylated bisphenol A-dimethacrylate (TEGDMA/BisEMA), and two alumina nanopowder concentrations (5 wt.% and 10 wt.%). These materials were mechanically tested for flexural strength and compressive strength. The structural analysis of these materials consisted of SEM microscopy and EDX elementary mapping. In order to extract 3D projections of sample surfaces, but also to produce indicative values of their roughness, the SEM micrographs were processed with open-source software. In order to observe a clear evolution of the mentioned properties, the composite biomaterials were compared with materials formed only with the Bis-GMA/TEGDMA/BisEMA composite, and with a commercial composite resin, Filtek™ Supreme Ultra Universal Restorative, also. The findings showed an increase in the mechanical properties of the materials manufactured concerning the concentration of nanoparticles of aluminum. EDX analyzes confirmed the good homogeneity of nanoparticles in the polymer matrix. Mechanical properties of the manufactured nanocomposite biomaterials were reported 28.8 % higher than the control biomaterial. The comparison results with the commercial resin composite are encouraging.