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Records of pulpal blood flow obtained from human teeth with a laser Doppler flowmeter include a very large component derived from the periodontal tissue and other tissues outside the pulp. This contamination can be reduced by isolating the tooth from the surrounding tissues. The purpose of the present study was to show that polymers and resins make possible an optimal pulp vitality testing when used for fixing the laser probe, as well as for reducing the signals originating from the periodontium. Recordings were taken from 10 healthy, intact frontal upper teeth, in 8 individuals, ages between 20 - 40 years. Signals were recorded with the laser Doppler MoorLab and a straight optical probe, MP3b. Two consecutive determinations of the pulpal blood flow at a 5 minute interval where taken for each tooth using the following methods: 1 – a silicone impression combined with light curing periodontal liquid dam, and 2 – without periodontal isolation system. The data were processed using the statistical analysis software SPSS v16.0.1. The combination of the silicon impression with the Light curing periodontal resin isolation decreased significantly statistic the flux values (68.01% decrease) and was more effective in individualizing the pulpal blood flow than simple silicone impression. The presented technique is a viable method for determining pulp vitality, reproducible, easily applicable and shows a significant reduction in the intake of nonpulpar origin signals. Key words: condensation silicones, light curing periodontal liquid dam, laser Doppler flowmetry, pulp vitality

The formation of the oxygen inhibition layer is examined on some commercial methacrylate resin based composite restorative materials: nano-filled Filtek Ultimate Universal Restorative and Filtek Supreme XT Universal Restorative and for comparison the microfilled Filtek Z250 Universal Restorative. Each material type is analyzed using scanning electron microscopy for microstructure and energy-dispersive X-ray spectroscopy for the chemical composition. Two polymerization lamps were used for various exposure times. It results an excellent chemical stability for Filtek Ultimate, while the percent of oxygen is increasing with the photo-polymerization time for the other two composites. From element mapping, the filler particles were identified and their volume percents and cluster particle size distributions were calculated. No correlation of these parameters with oxygen inhibition layer was found. Keywords: oxygen inhibition layer, chemical composition, dental restorative composites

With increasing of electromagnetic pollution and wide use of commercial and military products, there is an increasing interest in electromagnetic interference (EMI) shielding. For EMI shielding materials, typical metals have been used. Electroless copper plating of polyester fabrics was demonstrated in the present investigation and compared to sample coated by Cu-Ni-P plated after five times washing and rubbing fastness test . In order to evaluate the residual copper after applying rubbing the surface of samples, SEM images and WDX analysis have been used. The evaluation of electrical conductivity after washing and rubbing tests shows high stability in spite of detaching of some part of coating which remarkably confirms the high stability in EMI shielding effectiveness. Keywords: electroless, copper-coating, polyester fabric, washing and rubbing tests, surface resistance

Two curing protocols were used to polymerize a difunctional benzoxazine monomer based on 4,4`-diamino diphenyl methane. The thermal degradation behaviour of both resulted materials (named PBZ_190 and PBZ_250) was investigated by thermogravimetric analysis coupled with mass spectrometry (TGA/MS), Fourier transform infrared spectroscopy (FT-IR) and X-Ray photoelectron spectroscopy (XPS). The dependence of activation energy on conversion was established using Kissinger-Akahira-Sunose isocoversional method. Degradation of PBZ_250 starts at lower temperatures compared with PBZ_190 but its residual char is higher than for PBZ_190. The degradation of PBZ_250 exhibits a lower activation energy at conversion a < 0.3, and higher values than PBZ_190 for a > 0.3. Keywords: polybenzoxazine, degradation kinetics, thermogravimetric analysis (TGA)

This paper refers to the electromechanical strain response of PDMS/TiO2/SiO2 composites as an electroactive polymer actuator. Lightweight electro-active polymers (EAPs) are ideal for control surface since they offer high strain rate, fast response, high elastic energy density and ease of manufacture [1,2]. We investigate the frequency response and vibrational modes of rectangular films with aluminum electrodes using Scanning Laser Doppler Vibrometry (SLDV) technique described elsewhere [3,4]. The results showed a similar behaviour with those of acrylic and silicone films coated with carbon-based compliant electrodes from literature. Field-induced vibrational strains decrease with frequency due to the increase in stiffness of sample and change of dielectric permittivity. These materials are possible candidates in polymer actuators for micro-pump and micro-valve applications in MEMS. Keywords: electroactive polymers, dielectric elastomers, non-destructive technique, frequency response, vibrational modes

This paper presents the maleinization study of linear styrene-butadiene block-copolymers carried out in solution by radical mechanism. The vinyl microstructure effect of the polybutadiene block on the kinetics reaction was established and the physical and mechanical properties were correlated with the maleinization degree of the elastomers. Keywords: styrene-butadiene block-copolymers, maleic anhydride, functionalized block-copolymers

The paper presents an algorithm to assess damages in composite structures, based on how natural frequencies of weak-axes bending vibration modes change due to damage. The authors have contrived a correlation between the strain energy stored in a segment of a beam-like structure and the frequency change for that mode if damage occurs on that segment. Finding that the dynamic behavior of composite structures can be best modeled using the share model, which consider the bending moment together with lateral displacement and share deformation, we worked out a relation which gives the frequency shift of all bending modes, involving one coefficient depending on the support type. To evaluate damages, we determine analytically the relative frequency shift as ratio between the frequency change and the natural frequency of the undamaged beam, for the more vibration modes, considering a large number of damage scenarios. Comparing these results with that obtained by measurements on the real structure, it is possible to detect and locate damages with high precision. The method was validated by numerous experiments. Keywords: composite materials, fiber reinforcement, damage detection, natural frequency

The paper presents results on friction and wear, obtained from testing polybutylene terephthalate (PBT) against steel in a block-on-ring tribotester, for dry sliding. There were identified particular processes characterizing the friction couple and the test conditions. Tests were done for three sliding speeds: 0.25 m/s, 0.50 m/s and 0.75 m/s and for five normally applied loads: 1.0 N, 2.5 N, 5.0 N, 10.0 N and 20.0 N. The sliding distance was 7500 m. For comparing reason, there were also done tests for blocks made of PTFE. For PBT-steel couple, the friction coefficient remains in an acceptable range for forces above 2.5 N but it has higher value at the lowest tested values of the force (F=1.0...2.5 N). For evaluating the wear of PBT blocks, there was plotted a wear map using as wear parameter the linear wear intensity as a function of sliding speed and normal force. On this map, there were identified two zones with low values. There were indentified particular processes taking place on the PBT blocks and the steel rings that explain the good tribological behavior of this friction couple. The results of these tests recommend PBT for tribological applications that would function under similar dry regimes. Keywords: friction coefficient, wear, PBT, dry sliding, block-on-ring

The main objective of this paper is to develop a complex experimental investigation and, by this way, to describe and analyze the influence of pulsed Nd: YAG laser cutting main parameters on the process energy consumption. The tested material was a Glass fiber/epoxy composite. The experimental program was performed by two approaches, factorial and classic. The design of experiments allowed the research results presentation as regression polynomial equation, Pareto effects diagram, response surfaces diagrams and single-factorial classic diagrams. A pertinent final discussion gave a global image and proved the validity of developed research. Keywords: design of experiments, pulsed Nd: YAG laser cutting, Glass fiber/epoxy composite, energy consumption ratio