Romanian neurosurgery at European standards: The 45th Congress of the “Romanian Society of Neurosurgery”

Sibiu, 201

Dielectric silicone elastomers with mixed ceramic nanoparticles

A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles

Interpenetrating poly(urethane-urea)–polydimethylsiloxane networks designed as active elements in electromechanical transducers

A poly(urethane-urea-siloxane) was prepared in a two-step procedure involving the synthesis of a bis-isocyanate prepolymer on the basis of 4,4′-diphenylmethane diisocyanate, a polyether glycol and dimethylol propionic acid, and its extension by reacting with 1,3-bis(3-aminopropyl)tetramethyldisiloxane. The resulted polymer was used in different percentages to prepare three series of interpenetrating networks (IPNs) with polydimethylsiloxane-α,ω-diols with molecular masses, Mn, of 70000, 230000 and 370000 g mol−1. A polydimethylsiloxane–polyethyleneoxide graft copolymer was added as a compatibilizing agent. The IPN precursors were mixed in solution and processed as films. During solvent evaporation, the chemical crosslinking of the polydimethylsiloxane-α,ω-diols occurs with tetraethyl orthosilicate in the presence of dibutyltin dilaurate, while in the case of poly(urethane-urea-siloxane) only physical crosslinking by hydrogen bonds is expected to occur. The morphology and thermal transitions of the resulted networks were examined by scanning electron microscopy, differential scanning calorimetry with dynamic mechanical analysis. The mechanical and dielectric characteristics (dielectric permittivity, loss, strength) of the aged films were studied. Their responsiveness to an external stimulus in the form of an increasing electric field was assessed by electromechanical measurements and expressed as lateral strain. The results were critically analyzed with respect to each other as a correlation with their composition and compared with those obtained for three common commercially available dielectric elastomers

The Development and Study of Some Composite Membranes Based on Polyurethanes and Iron Oxide Nanoparticles

To improve the performance of composite membranes, their morphology can be tailored by precise control of the fabrication methods and processing conditions. To this end, the aim of this study was to develop novel high-performance composite membranes based on polyurethane matrix and magnetic nanoparticles with the desired morphology and stability, by selecting the proper method and fabrication systems. These well-prepared composite membranes were investigated from the point of view of their morphological, physico-chemical, mechanical, dielectric, and magnetic properties. In addition, their in vitro cytocompatibility was also verified by the MTT assay and their cell morphology. The results of this study can provide valuable information regarding the preparation of magnetic polyurethane-based composite membranes that could be used to design some suitable devices with tailored properties, in order to improve the image quality in magnetic resonance imaging investigations and to suppress local image artifacts and blurring

Improving Path Accuracy of Mobile Robots in Uncertain Environments by Adapted Bézier Curves

An algorithm that presents the best possible approximation for the theoretical Bézier curve and the real path on which a mobile robot moves in a dynamic environment with mobile obstacles and boundaries is introduced in this paper. The algorithm is tested on a set of scenarios that comprehensively cover critical situations of obstacle avoidance. The selection of scenarios is made by deploying robot navigation performances into constraints and further into descriptive characteristics of the scenarios. Computer-simulated environments are created with dedicated tools (i.e., Gazebo) and modeling and programming technologies (i.e., Robot Operating System (ROS) and Python). It is shown that the proposed algorithm improves the performance of the path for robot navigation in a highly dynamic environment, with dense mobile obstacles

Improving Path Accuracy of Mobile Robots in Uncertain Environments by Adapted Bézier Curves

An algorithm that presents the best possible approximation for the theoretical Bézier curve and the real path on which a mobile robot moves in a dynamic environment with mobile obstacles and boundaries is introduced in this paper. The algorithm is tested on a set of scenarios that comprehensively cover critical situations of obstacle avoidance. The selection of scenarios is made by deploying robot navigation performances into constraints and further into descriptive characteristics of the scenarios. Computer-simulated environments are created with dedicated tools (i.e., Gazebo) and modeling and programming technologies (i.e., Robot Operating System (ROS) and Python). It is shown that the proposed algorithm improves the performance of the path for robot navigation in a highly dynamic environment, with dense mobile obstacles

Bimodal silicone interpenetrating networks sequentially built as electroactive dielectric elastomers

Two polysiloxanes, a polydimethylsiloxane-α,ω-diol (PDMS) with Mn = 370000 g mol−1, and α,ω-bis(vinyl)polydimethylsiloxane (Vi2PDMS) with Mn = 34500 g mol−1, and appropriate crosslinking systems for each of them (tetraethyl orthosilicate–dibutyltindilaurate and α,ω-bis(trimethylsiloxy)poly(dimethylmethyl-H-siloxane)–Speier's catalyst, respectively), were mixed together in various weight ratios (1:0.1, 1:0.2, 1:0.3, 1:0.5) and cast into films. These were sequentially crosslinked by different mechanisms. A determined pre-stretch was applied to the first network after its formation followed by thermal treatment for curing the second network. Non-prestreched networks were also prepared in parallel for comparison. The aged films were characterized from the point of view of the soluble fraction content, and analysed by differential scanning calorimetry, water vapour sorption in dynamic regime, dielectric spectroscopy and tensile tests. Dielectric strength and actuation strain were measured to estimate the suitability of the samples for electromechanical applications. The results revealed that through this approach one can relatively easily obtain very simple and homogeneous materials suitable for use as dielectric elastomer transducers

Low Cost Mobile Embedded System for Air Quality Monitoring

This paper reports on a case study using a mobile platform for air-quality monitoring. This case study was done in Sibiu, Romania, and includes a description of related work, a survey, a summary of existing results regarding air quality, a description of the mobile air quality monitoring platform, and the results of trials done in February 2017. The aim of the case study is to pave the road for further studies of using mobile low-cost units for air quality monitoring

Preparation and Characterization of Electrospun Collagen Based Composites for Biomedical Applications

Electrospinning is a widely used technology for obtaining nanofibers from synthetic and natural polymers. In this study, electrospun mats from collagen (C), polyethylene terephthalate (PET) and a blend of the two (C-PET) were prepared and stabilized through a cross-linking process. The aim of this research was to prepare and characterize the nanofiber structure by Fourier-transform infrared with attenuated total reflectance spectroscopy (FTIR-ATR) in close correlation with dynamic vapor sorption (DVS). The studies indicated that C-PET nanofibrous mats shows improved mechanical properties compared to collagen samples. A correlation between morphological, structural and cytotoxic proprieties of the studied samples were emphasized and the results suggest that the prepared nanofiber mats could be a promising candidate for tissue-engineering applications, especially dermal applications