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The aim of this study was to investigate the surface topography and to compare the calcium and phosphorus ions concentration in dentine and cement following their contact with five acidic drinks in the presence or absence of saliva. 25 caries free extracted teeth were used in this study. All the teeth were longitudinally sectioned in three slices. One slice has been stored in distilled water (control group). The second slice has been continuously immersed for 12 h in one of the tested beverages: Red Bull, Lipton Green Tea, a commercial apple juice, a natural carbonated mineral water and lemon juice. The third slice has been subject to 3 cycles of immersion in one of the tested beverages for 1 min, followed by storage in artificial saliva (AFNOR NF S90-701) for 4 h. The samples were analyzed using a scanning electron microscope and an EDX detector. The specimens continuously stored in acidic beverages showed enlarged dentinal tubules. The specimens successively stored in acidic beverages and saliva showed a slightly eroded surface of dentine and cement. The calcium and phosphorus ions concentration in dentine and cement significantly decreased following continuous storage in all the tested beverages (mean calcium ion concentration (wt%) in dentine (D)/cement (C): 28.17/23.93 control group, 16.45/11.07 apple juice, 22.84/11.48 Lipton Green Tea, 24.01/21.46 natural carbonated mineral water, 15.06/9.22 lemon juice, 18.09/10.52 Red Bull; mean phosphorus ion concentration (wt%) in D/C: 10.80/ 9.92 control group, 7.84/6.55 apple juice, 8.70/6.98 Lipton Green Tea, 9.39/9.21 natural carbonated mineral water, 7.45/6.28 lemon juice, 7.85/6.79 Red Bull). The decrease of mineral ions concentrations in dentine and cement was significantly lower when saliva has been used as a storage medium between immersions in acidic beverages (p < 0.05, ANOVA and Bonferroni test). Under the conditions of this study, saliva offered to dentine and cement a protective effect against the acidic challenge of tested beverages. Keywords: dentine, cement, acidic beverages, SEM, calcium ions, phosphorus ions

The aim of our study was to obtain cellulose acetate composites based on hydroxyapatite and nystatin with increased local therapeutic effect in the therapy of candidiasis. The porous composites were obtained by phase inversion method. Antifungal susceptibility of the samples was investigated by the Kirby Bauer Disk Diffusion test. The method has demonstrated an antifungal effect of the samples against Candida albicans as well as the fact that the polyene antibiotic nystatin might be an optimal choice as active agent incorporated in a composite. Also we have studied the swelling and the degradation of the membranes. These measurements help us better understand the water and PBS absorption capacity of the polymer matrix. Keywords: Composite, cellulose acetate, hydroxyapatite, nystatin, antifungal activity

This paper presents the results of the author’s latest researches on lignocellulosic basic structure composites, which resort to wood fibres and chips, in admixture with mineral binders - cement and gypsum. The obtained products, shaped as boards and blocks, may be deemed “ecological products” with applicability in the field of Civil Engineering, both as plating materials and as filling material (for the sandwich-type structures). The obtained results may be reckoned for the theoretical and experimental basis for further development of the materials and products achievable in industrial systems and usable in the structure of constructions for various purposes. Keywords: composites, wood chips, wood fibres, adhesiveness, embedding

The research highlights the main trends and guidance in the design of products using plastics in conditions of sustainable development of society. Plastics have an important role in the configuration of the new products still in the phase of conception. Having in view the main advantages of the utilization of plastics the expectation is to see an increase of the weighting of these ones in the products development. The present work spotlights the positive influence of the covering of the alloys with polyester. Especially it aims to increase the wearing resistance and resistance to fragility that has a direct effect on the increase of the functioning time in the total life cycle of the product. Keywords: polyester graphite, wear resistance

In the industry of plastics and dyes, pharmaceuticals and agriculture, the toxic effects of heavy metals have been reported during prolonged professional exposure. Heavy metals in the environment can enter the body orally, inhaled or by skin absorption. Unlike other toxins present in the environment, heavy metals accumulate in tissues because the body has no ability to remove them. Heavy metals in excess cause numerous metabolic imbalances. In cancer, heavy metal overload could be a stimulus for secretion of chemokines, for promoting oxidative stress and antioxidants inactivation, for altering cell signaling, for promotion and progression of tumorigenesis. Strategies to prevent accumulation of toxic metals, to decipher the pathophysiological mechanisms by which heavy metals affect cell metabolism, to increase excretion of toxic metals without removing essential minerals in the body is the subject of current researches. Keywords: heavy metals, dyes, plastics, skin cancer

Poly(ethylene terephthalate) PET was subject to a glycolysis process using diethylene glycol (PET/DEG = 1/1 molar ratio) and zinc acetate as trans-esterification catalyst. An unsaturated polyester resin was then prepared using the glycolysis product and maleic anhydride. The molecular weights of glycolysed PET products and polyester resin were investigated using gel permeation chromatography (GPC) analysis. A cross-linking reaction of the unsaturated polyester resin was performed in the presence of styrene (different amounts) at 80°C. The compression and impact strength/resistance properties of the cured resins were determined. Keywords: PET waste, glycolysis, GPC, unsaturated polyester resin, mechanical properties

The J integral method was used to characterize the dependence of stresses and strains in the vicinity of the crack tip in thermoplastic materials with nonlinear deformations. This method makes it possible to establish the correlation between crack growth resistance of the material based on the stable propagation and the crack extension by means of J-R curve, which is an indicator related to the toughness of the material. The paper presents the results of experimental researches carried out on three-point bending test specimens of thermoplastic high density polyethylene - type PE 100, taken from the pipes with 110 mm diameter. Keywords: J-integral, J-R curve, toughness, thermoplastic materials, polyethylene PE 100

An incompressible MHD flow of two-dimensional upper-convected Maxwell fluid over a porous stretching plate with suction is studied. The nonlinear differential equation is solved approximately by means of the Optimal Homotopy Asymptotic Method (OHAM). Multiple solutions are given, showing a very good agreement between the analytical and numerical solutions. This procedure is very efficient in practice, ensuring a very rapid convergence of the solutions after only one iteration. Keywords: Maxwell fluid, porous stretching plate, optimal homotopy asymptotic method

One of the biggest dangers to our environment today is the increasing number of unused synthetic rubber in the environment and these pose a big threat to nature, if it is not disposed properly. Typically, synthetic rubber is developed for specific applications, and is specifically for those applications due to the process used to make them, and the resulting properties. Dumping these synthetic rubber in dumpsites could contaminate nearby water sources. Heating these synthetic rubber with normal heat will generate harmful chemical substances, like carbon and lead, which are really dangerous for humans. Dealing with rubber properly is not only advantageous to nature, but also to humans. Recycling represents a best alternative to the disposal of post-consumer rubber in common landfills if it is possible to obtain new materials with good final properties compatible with practical application. In this study, characterization and properties of virgin acrylonitrile butadiene rubber/recycle acrylonitrile butadiene rubber (vNBR/rNBR) were examined. Three different size ranges of rNBR particles, i.e., 150 - 350 mm, 2.0 -15.0 mm, and 5 -10 cm were used in this study. The vNBR/rNBR blends with blend ratios of 95/5, 85/15, 75/25, 65/35, and 50/50 phr (part per hundred rubber) were prepared using a two roll-mill at room temperature. The vNBR/rNBR blends with smallest size of rNBR particles show better tensile properties (tensile, elongation-at-break and M100) compared with all other blend ratios. For physical properties, vNBR/rNBR blends with smallest size of rNBR particles exhibited the highest hardness and cross-linking density at all blend ratios whereas resilience decreased, accordingly. The cross-linking density of vNBR/rNBR blends also show an increasing trend with increasing rNBR content. A morphological study of tensile fracture surface of the blends was also carried out. The scanning electron microscopy study indicates that rNBR exhibited a weak rNBR-vNBR matrix interaction particularly when more than 25 phr of rNBR was used, thus decreasing the mechanical properties of vNBR/rNBR blends. Keywords: vNBR, rNBR, Curing characteristic, Mechanical properties, Morphological properties

For determining the optimal conditions of the cutting process (material and tool geometry, process parameters), quantitative data are necessary concerning the roughness of surfaces. Using experimental research methods, this work aims at determining equations between surface roughness and parameters of the milling, process for some polyamides samples (PA66, PA66 – GF30 and PA66 MoS2). PA66, PA66 – GF30 and PA66 MoS2 polyamides are technical thermoplastics with excellent mechanical and physical properties, increasingly used in industrial machinery. Keywords: surface roughness, milling, polyamides