Browse Articles

This paper is aimed to the identification of the plastics used in the insulation of the conductors and the electrical cables and depending on their characteristics , the influence exercised on power losses in the dielectric of the cables . Solid organic synthetic insulating materials that are used in electrotechnics , represents a sensitive group larger than natural materials . According to current statistics , it is clear that solid synthetic materials are implemented in a majority share in achieving equipment and electrical installations insulation being in the configuration of generation, transmission and distribution of electricity systems. Keywords: plastic , polyvinylchloride , insulation, electrical cable , thermal stability

During the daily activity the orthodontic systems are suffering various loadings which together with saliva lead to a depreciation of bonding material which is used to fix the brackets on the dental surfaces. For this study human incisive shaped bovine bone were used to simulate mastication in a media consisting in a mixture of sesame, poppy and sunflower seeds and water. The aim is to compare the shear resistance of the bond with the one evaluated for fresh mounted brackets. Also a qualitative analysis is aimed based on micro photos took before and after bracket debonding. There are not rare the cases when patients are returning to doctor immediately after orthodontic system installation despite the medical advice because it is almost impossible to inhibit natural habits developed. In the first period after the installation of the orthodontic systems the reflex of biting the food is present in all the cases and that produces the detachment of the incisive bonded brackets. However during the mastication components of the food are interacting with the brackets generating local loads over the brackets themselves and also over the bonding material which can be a polymer or a composite. These loadings together with the ones meant by the doctor are producing in time small fractures and cracks at the bonding level with consequences on shear resistance of brackets on the tooth. Keywords: orthodontics, adhesive, bracket, shear strength

To achieve a modeling of the epithesis as close as possible to the lost organ, information on its size and shape can be registered by using computed tomography and 3D reconstruction. This paper aims to investigate to what extent the recording geometry of facial regions using computed tomography and identify on the sections of computed tomography the contour of the region to be reconstructed for virtual modeling of future silicone epithelium can be achieved. The results were obtained by applying the algorithm described in C + + program and contour detection in computed tomography images recorded preoperatively in patients who were to receive resection surgery of a facial region followed by reconstruction of the defect by facial epithesis. Keywords: acrilic resins, contour detection

The poly (vinyl butyral)/silica (PVB/SiO2) composite fibers were produced by the electrospinning process. The experiments were performed with the PVB solution in concentration of 10 wt.% where ethanol was used as the solvent. The silica nanoparticles were added into the solution in different content of 1, 3 and 5 wt.% SiO2. The PVB fibers with 50 wt.% SiO2 nanoparticles were deposited on p-aramid fabrics which were coated with PVB solution. The effect of the processing parameters on the morphology of PVB/SiO2 composite fibers was analysed. Mechanical properties of the p-aramid fabrics were tested by dynamic mechanical analysis (DMA). Keywords: electrospinning, electrospun composite fibers, silica nanoparticles, p-aramid fabrics

Polyelectrolyte multilayers composed of chitosan and poly(acrylic acid) were constructed onto silicon wafers from solutions of different concentrations of polymer and NaCl. To modulate the film properties, the multilayers were subject to three post-treatment strategies: (i) immersion in an aqueous solution with pH = 2.4 for 1 min, followed by a 15 s immersion step in water and drying at 80 oC for 60 min; (ii) immersion for 30 min in water and (iii) immersion in an aqueous solution with pH = 2.4 for 5 min, followed by immersion for 1 min in water and thermal treatment at 120 oC for 60 min. The changes of the film morphology, thickness, and wetting state as a function of deposition conditions and post-treatment strategies used were followed by atomic force microscopy, spectroscopic ellipsometry and contact angle measurements. Keywords: polyelectrolyte multilayer; chitosan; poly(acrylic acid); post-treatments

The purpose of this study was to evaluate colour changes of aesthetic fixed prosthetic restoration materials, when these materials are exposed to a drink rich in colorants, in this case, cola, coffee and red wine. For the study were required 18 fixed partial dentures: 6 integral polymeric dentures, 6 metal-polymeric dentures and 6 metal-ceramic dentures. To verify the colour there were used: VITA EASYSHADE spectrophotometer and the VITA shade for ceramic restorations. Following the results obtained, it was concluded that prosthetic composite resin changes quickly their colour, compared to the ceramic. Also, the liquid that affect the most in changing the colour of this material is coffee. Keywords: composite resin, colour change, aesthetic restorative materials

Polysomnography is a new and innovative test used for the diagnosis of sleep disorders. It offers the possibility to identify and to early treat important diseases which can lead sudden to death in children and adults too. The portable monitor simplifies the procedure and it permits to monitor the patients at home. Obesity is the most powerful and the only reversible risk factor for obstructive sleep apnea. This condition is one of the most serious problem of the 21st century. It can appear like common obesity caused by an increased food intake and it is also part of some rare genetic syndromes. Prader Willi Syndrome is a genetic disorder caused by an abnormality on the 15th chromosome. It is the most common known genetic cause of life-threatening obesity in children. The study aims to describe sleep disorders in patients diagnosticated with this genetical syndrome. The evaluated patients associated a characteristically phenotype for Prader Willi Syndrome with unrest sleep and they had no treatment before. A high number of obstructive sleep apneas and rapid eye movement sleep alteration was registered. Breath and cardio-vascular pathological changes were also identified. Large fluctuations in heart rate and relatively long duration of low oxygen saturation was threatening patients life and nasal continuous airway pressure was needed in order to reverse respiratory and cardiovascular symptoms. Keywords: polysomnography, obstructive sleep apnea, sleep disorders, Prader Willi Syndrome

Dental composite resins already have a history and a vast use in dentistry. In vivo and in vitro research gave precise directions and indications but the tests are not completely relevant. Different clinical parameters cannot be reproduced by in vivo and in vitro research. The evolution of dental materials leads to the use of nano materials. For the present study, were used human extracted teeth on which were prepared class I cavities. For half of the samples had been used normal adhesive and composite resin and for the second group was used nanomaterials- a ferric nanoparticles modified dental adhesive was used and then filled with the same resin composite material. The interfaces generated by hard dental tissue and classical adhesive and adhesive made from nano-particles were investigated through micro-CT imagistic investigation method. With the software VGStudio MAX the 3D reconstruction of the constituents were made. Micro-CT using the synchrotron technology and 3D reconstruction offers important details and of high quality of investigated area. All the samples were imagistic investigated through, X-ray, SEM and EDAX technologies. Each investigation method spotted the defects of the investigated area according to its limitation. Keywords: composite resin, dental adhesive, feeric nanoparticles, micro-CT, X-ray, SEM, EDAX

This article presents a benchmark between Dissipative Particle Dynamics (DPD) thermostat and Standard Molecular Dynamics (MD) simulations for three different systems: a water cube, a small dipalmitoylphosphatidylcholine (DPPC) bilayer in water, and a large DPPC bilayer in water. The DPPC phospholipids’ molecule consists of a hydrophilic head and two hydrophobic tails. The molecular dynamics simulations results for the three above systems as function of number of cores are shown. Keywords: molecular dynamics, thermostats, friction

The paper describes the components of an artificial intelligence based system intended to control the manufacturing processes of composite materials with polymeric matrix. Based on previous results in which neural networks were trained initially with simulated data and then continued to acquire experimental values over Internet for refining their knowledge, the system includes updated state-of-the-art data acquisition components, improved statistical data processing capabilities and the ability of real-time controlling the manufacturing equipment. Keywords: composite materials, polymeric matrix, artificial intelligence