On evaluation of wear resistance of tooth enamel and dental materials

A survey of the literature shows that in many studies on the wear resistance of tooth enamel or dental materials a large scatter of experimental data has been obtained when wear tests were performed at a fixed load. Despite the steady loading, wear conditions vary during sliding, since tooth enamel as well as dental materials have inhomogeneous structure. This leads to changes in contact interactions between sliding surfaces, and as a result, we get changes in the friction and wear behaviour of tested materials. This is why at the same loading the wear can be different. In this study, more reliable approach to evaluation of the wear resistance of human enamel and dental materials is proposed. The procedure is based on the correlation between the volumetric wear and the friction energy dissipated during sliding. The model can be useful to compare the wear resistance of different dental materials tested in different ambient conditions.     

Investigation of structural,optical and electrical properties of (Ti,Nb)Ox thin films deposited by high energy reactive magnetron sputtering

In this work the results of investigations of the titanium-niobium oxides thin films have been reported. The thin films were manufactured with the aid of a modified reactive magnetron sputtering process. The aim of the research was the analysis of structural, optical and electrical properties of the deposited thin films. Additionally, the influence of post-process annealing on the properties of studied coatings has been presented. The as-deposited coatings were amorphous, while annealing at 873 K caused a structural change to the mixture of TiO₂ anatase-rutile phases. The prepared thin films exhibited good transparency with transmission level of ca. 50 % and low resistivity varying from 2 Ωcm to 5×10^?2 Ωcm, depending on the time and temperature of annealing. What is worth to emphasize, the sign of Seebeck coefficient changed after the annealing process from the electron to hole type electrical conduction.     

Structural and surface properties of TiO2 thin films doped with neodymium deposited by reactive magnetron sputtering

Thin films were deposited using modified, high energy magnetron sputtering method from Ti-Nd mosaic targets. The amount of neodymium dopant incorporated into two sets of thin films was estimated to be 0.8 and 8.5 at.%, by means of energy dispersive spectroscopy. On the basis of x-ray diffraction method, the type of crystalline structure and crystallites size were evaluated directly after the deposition process and after additional post-process annealing at 800 °C temperature. The influence of annealing on the surface properties was evaluated with the aid of atomic force microscopy. Uniformity of the dopant distribution in titanium dioxide matrix was examined with the aid of secondary ion mass spectroscopy. Additionally, using atomic force microscope, diversification and roughness of the surface was determined. Chemical bonds energy at the surface of TiO₂:Nd thin films was investigated by x-ray photoelectron spectroscopy method. Wettability measurements were performed to determine contact angles, critical surface tensions and surface free energy of prepared coatings. On the basis of performed investigations it was found, that both factors, the amount of neodymium dopant and the post-process annealing, fundamentally influenced the physicochemical properties of prepared thin films.     

On the modeling of electrochemical systems with simultaneous gas evolution. Case study: The zinc deposition mechanism

Electrodeposition of zinc with simultaneous hydrogen evolution in an aqueous acidic sulphate solution is investigated in an Inverted Rotating Disk Electrode (IRDE) reactor. A simulation tool, based on the MITReM (Multi-Ion Transport and Reaction Model) model is used to describe the electrochemical behavior. This model can account for mass transport by convection, diffusion and migration and for the presence of homogeneous reactions. The electron transfer at the electrode is described by a Butler-Volmer relation. A reaction mechanism is proposed from surface analysis of the deposited zinc layer. Field Emission Auger Electron Spectroscopy (FE-AES) in combination with Factor Analysis (FA) is used to determine the compositional structure of the formed zinc layer. The model parameters such as diffusion coefficients, rate constants and transfer coefficients are determined by comparison of experimental and simulated polarization curves and current efficiency profiles for different rotation speeds of the IRDE and concentrations of supporting electrolyte. The importance of the homogeneous reactions is shown. The influence of gas bubble evolution (induced micro-stirring effects, reduced electrolyte conductivity and surface blockage) on the electrodeposition process is elucidated.     

Assessment of femtosecond temporal gating for imaging in biological medium by Monte Carlo simulations

The authors demonstrate the potential of femtosecond laser pulsed illumination and picosecond detection in biomedical imaging via an efficient and simple Monte Carlo laser pulse diffusion simulation, based on realistic biological parameters. The evolution of the contrast of a sinusoidal grid in a diffuse medium as a function of the width of a temporal gate is shown.     

Catalytic reaction performed in the liquid–liquid system at batch and semibatch operating mode

Hydrolysis of the propionic anhydrite catalysed with sulphuric acid at batch and semibatch operating conditions has been investigated using the reaction calorimeter RC1 Mettler Toledo. Due to a limited solubility of the anhydrite in the aqueous phase where the reaction takes place, mass transfer with simultaneous chemical reaction has to be considered. Contributions of both phases to the reaction mixture change during the reaction progress, so that a complex, strongly non-linear behaviour of the reactor has been noticed. Influence of the concentration of the catalyst, the reaction temperature as well as the initial volume fraction of the organic phase in the reaction mixture and the stirrer speed on the overall conversion rate have been determined directly from calorimetric measurements. Some indications related to the safe and efficient performance of the investigated process as well as to a simplified experimental kinetic model have been formulated.     

Dimensioning of survivable WDM networks

In this paper routing, planning of working capacity, rerouting, and planning of spare capacity in wavelength division multiplexing (WDM) networks are investigated. Integer linear programming (ILP) and simulated annealing (SA) are used as solution techniques. A complex cost model is presented. The spare capacity assignment is optimized with respect to three restoration strategies. The benefit of wavelength conversion, the choice of the fiber line system, and the influence of cost parameter values are discussed, with respect to the different restoration strategies and solution techniques. Wavelength conversion is found to be of limited importance, whereas tunability at the end points of the connections has substantial benefits