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The polymer foils, obtained from pure and coloured (with cycloimmonium ylids) poly (vinyl) alcohol (PVA) gel, are studied from the optical anisotropy point of view. The dried foils were stretched under heating and their optical birefringence was measured for different degrees of stretching. The changes in the birefringence were correlated with the stretching degree of the polymer foils. The influence of the cycloimmonium ylid structural peculiarities on the coloured foils’ anisotropy is also discussed. Keywords: cycloimmonium benzoyl anilido-benzoyl methylids, optical birefringence, stretched coloured and pure PVA foils

Within this paper an experimental analysis of an advanced composite U-beam pultruded profile based on isophtalic polyester resin reinforced with unidirectional glass fibres and overlay veil has been carried out to determine its most important mechanical properties. Tensile tests have been accomplished on specimens cut from the pultruded profile along and transverse to the fibers direction. Over thirty mechanical properties including Young’s moduli, stiffness, load-extension as well as stress-strain distributions determined at maximum load, maximum extension and at break have been determined on a Lloyd Instruments LS-100KPlus materials testing machine. Typical failure mechanisms such as fibres pull-out and delaminations have been noticed. The tests show that this kind of unidirectional glass fibers-reinforced isophtalic polyester resin with overlay veil obtained in the putrusion process is suitable for a large range of applications from the automotive and aerospace industry and put into evidence its strong anisotropy. Keywords: Pultrusion, Isophtalic polyester resin, Mechanical anisotropy, Tensile tests, Stiffness

The article presents the importance of using polymer additives in the hydraulic fluid flow, to reduce the friction, to reduce the linear pressure losses, to increase the flowing velocity, to reduce the pumping energy, to increase the efficiency of the hydraulic machines. The article highlights the Toms effect in hydraulic industrial applications. Its also shows experimental results on single stage centrifugal pump operating with additives in water in different poly acryl amide concentration, highlighting the significant increase of the pump efficiency when the concentration does not affect the fluid viscosity. The pump efficiency increased with 8-10% when the polymer additives concentration was 0,04%. Experiments were performed in Hydraulic Laboratory of University Politehnica of Bucharest. Enhancing theoretical and experimental research in this area, based on the viscosity and elasticity anisotropic properties of the polymer additives solutions, can be created new premises for hydrodynamics and hydro power applications. Keywords: polymer additives, hydraulic performances, centrifugal pumps

The goal of this paper is to study the creep behaviour of multi-walls carbon nanotubes (1, 3, 5 wt.% MWCNTs) filled polypropylene (PP) through the instrumented indentation technique. Two types of the 3-step indentation test were considered to analyse viscoelastic behaviour through sharp indentation at room temperature. Under the loading conditions, the PP/MWCNTs samples present a time-independent plastic behaviour which must be considered not to under/overestimate the viscoelastic properties. The ratio of residual indentation depth to the maximum indentation depth at peak load calculated from the initial portion of the unloading curve was over 0.7 and demonstrated the plastic character of tested materials. The indentation hardness and modulus calculated from the slope at the unloading curve were changed due to the presence of plastic deformation from the loading phase, to the load intensity and hold time. The local distribution of carbon nanotubes lead to the variation in creep response and also, in the mechanical properties of material. Calculating the creep rate, a better creep response was offered by the higher concentration of carbon nanotubes during the indentation test at peak load of 1 N. A 3-step standard indentation test (Oliver and Pharr method) was considered to avoid the influence of the duration from the holding phase on the mechanical parameters. We found that a holding phase of 40 seconds was enough to have a negligible influence of creep on the indentation modulus for 5 wt.% of MWCNTs sample. Keywords: indentation, creep, carbon nanotubes, indentation hardness, indentation modulus

In order to perform standardized diagnostic and operative techniques the knowledge of the anatomical setup is essential. The main goal of our study was to determine the position of the lumbar dorsal rami of the spinal nerve at the level of the articular process, as well as the position of the surrounding structures. Plastinated slices with 1.5 mm thickness are produced out of five non-pathologic vertebral columns. Subsequently the slices were digitalized and processed anatomically and topographically. The gained data of digitalization offered in the next step the possibility to determine the localization of the spinal nerve and its medial branch as well as to build an anatomical three-dimensional computer model of the region. The plastinated slices produced by E12-technique showed intact and unimpaired anatomical structures and highly transparent tissue. This base was used for the analysis and measurement of structural episodes and for the three-dimensional reconstruction of a lumbar moving segment. The constructed 3D-model displays the morphology of the region in the same quality as the cadaver specimen. Based on our anatomic data, the dorsal ramus of the spinal nerve passes very closely to the neck of the superior articular process at the level of the cranial border of the transverse process. Anatomic characteristics should be kept in mind when denervation techniques of the zygapophyseal joints are performed, thereby reducing the risk of injury to the dorsal ramus. Keywords: plastination, ramus medialis nervus spinalis, E12 technique, radiofrequency facet denervation

The paper aims to evaluate the optical and dielectric properties of the nanocomposites based on polystyrene containing various amounts of barium titanate. The characteristics of the thermoplastic polymer are determined using the connectivity indices formalism, while those corresponding to the nanocomposites are evaluated using the parallel and series models. The variation of the optical and dielectric properties with the volume fraction of the nanofiller is discussed. Keywords: polystyrene, nanocomposites, optical properties, dielectric constant

The present context of the international studies identifies the electrospinning process as one of the key technologies for obtaing nanofibers. The dynamics of the studies connected to the implementation of this technology is given by the great diversity of the applications of the obtained nanofibers which start from filtering mediums and separating membranes to sensors and actuators, implants, structures for the controlled release of drugs up to the molecular photonics. This paper aims to present a new equipment for obtaining the nanofibers from polymer solutions by means of the electrospinning technology. The suggested equipment accomplishes the computerized control of the electrospinning technological parameters on starting from the idea of modularity and automatic control of the electrospinning process. The equipment allows the real time control for the electrospinning process based on determination of both jet characteristics and the obtained nanofibers properties. Keywords: nanofibers, equipment, technology, modular conception, electrospinning

relied on conventional mechanical, anti-infective modalities, followed by a range of regenerative procedures. An innovative medical device, using thermoforming ethylene acetate base, with an electromagnetic applicator, homologated with CE mark in class 2a, was used in the treatment of second degree teeth mobility. The affected areas were exposed to a precise, totally atraumatic and noninvasive electromagnetic field. The preliminary study on 10 subjects was performed with this medical device, using a standard protocol of 30 exposures of 2 h each, on the affected area. Subjects were both male and female, aged between 20-70 years, in healthy state and having a good oral hygiene status. After 2 months, the results were recorded by testing the mobility of the affected teeth, by measuring the periodontal pockets depth and by comparing the radiographs effectuated before and after the treatment. The results were assessed and proved the appreciable reduction of teeth mobility, the reduction of periodontal pockets depth and bone regeneration in the regions exposed to the electromagnetic applicator. The conclusions of this preliminary study recommend this innovative medical device for the use in the healing of periodontal lesions as noninvasive and atraumatic therapy. Keywords: periodontal lesions, innovative medical device, healing

Alternative research techniques are essential in order to prove the efficacy of graphene dental materials and their viability, especially if we associate them with other materials studied so far. It is important to determine the effects of these techniques because they can demonstrate the viability and credibility of the research on its properties. The purpose of this study was to measure and analyze the mechanical properties of several composite materials with/without graphene and commercial composite Herculite, designed for dental composites restorations. The materials were composed of a visible light-curing monomer mixture (Bis-GMA+TEGDMA) as a matrix and hydroxyapatite with graphene, bioglasses, colloidal silica as a reinforcing filler. Ten specimens of different composites were prepared for each mechanical test: flexural strength, Young’s modulus, diametral tensile strength, and compressive strength test (Lloyd Instruments- LR5k Plus). Mean values and standard deviations were calculated and ANOVA and Student Newman Keuls multiple comparison tests were applied (P[ 0.05). The addition of 5-10 wt% of hydroxyapatite with graphene nanoparticles to the unfilled monomer mixtures led to the increase of both Young’s modulus, surface hardness of the material, and the flexural strength. Hydroxyapatite with graphene has been used as reinforcing nanofiller in polymeric materials, having potential applications for restorative composites. Keywords: graphene, hydroxyapatite, dental composites restoration, mechanical properties

Rubber is widely used in railway infrastructure and in rolling stock. Rubber pads are used in fastening systems of rail to sleepers and rubber elements are used in the primary suspension of Romanian (and foreign) electric locomotives, in freight and passengers railway cars, metro trains and trams; the trams wheels are built with rubber insertion in order to reduce the vehicle unsprung mass. Also, rubber elastic elements are used in railway vehicles buffers. From these examples it can be seen that the rubber elements are used in the construction of parts which are directly contributing to traffic safety. Keywords: rubber, railway car, suspension, railway safety