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Bucharest, Romania

Matei E.,Polytechnic University of Bucharest | Predescu A.M.,Polytechnic University of Bucharest | Predescu A.,Polytechnic University of Bucharest | Vasile E.,METAV CD | Predescu C.,Polytechnic University of Bucharest
Optoelectronics and Advanced Materials, Rapid Communications | Year: 2011

The paper refers at synthesis preparation of some iron oxides useful in different industrial applications, with high capacities of adsorption for different metal ions from wastewaters. The synthesis method was partial reduction coprecipitation for Fe3O4 nanoparticles, followed by aeration of acidified magnetite nanoparticles for obtaining the γ-Fe2O3 nanoparticles, and also a mechanical alloying in order to obtain a nanoscale compound, copper ferrite (CuFe2O4). In order to validate the obtained compounds the investigation methods were scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDX) and X-ray diffraction (XRD) techniques. The stability of the nanomaterials, after 24 hours, was tested and measured with atomic absorption spectrometry (AAS). Source

Sima M.,National Institute of Materials Physics Bucharest | Vasile E.,METAV CD | Sima A.,Romanian National Institute for Lasers, Plasma and Radiation Physics
Digest Journal of Nanomaterials and Biostructures | Year: 2013

Electrophoretic deposition (EPD) method is employed to obtain a thick ZnO layer on a ZnO nanorod array prepared in a hydrothermal-electrochemical process. ZnO nanorods have the role to improve the mechanical stability and adherence of ZnO layer deposited by electrophoretic technique. D149 dye is used as sensitizer for ZnO semiconductor. The thus prepared ZnO layer is used for the photoanode of dye-sensitized solar cell (DSC). Performance parameters were extracted from standard current-voltage characteristic (I-V) and charge transfer phenomena occurring at ZnO/dye/electrolyte was evaluated by electrochemical impedance spectroscopy (EIS). Source

Galateanu B.,University of Bucharest | Dimonie D.,Romanian National Institute for Research and Development in Chemistry and Petrochemistry | Vasile E.,METAV CD | Nae S.,Emergency Hospital of Plastic Surgery and Burns | And 2 more authors.
BMC Biotechnology | Year: 2012

Background: The reconstruction of adipose tissue defects is often challenged by the complications that may occur following plastic and reconstructive surgery, including donor-site morbidity, implant migration and foreign body reaction. To overcome these problems, adipose tissue engineering (ATE) using stem cell-based regeneration strategies has been widely explored in the last years. Mounting evidence has shown that adipose-derived stem cells (ADSCs) represent a promising cell source for ATE. In the context of a small number of reports concerning adipose tissue regeneration using three-dimensional (3-D) systems, the present study was designed to evaluate the biological performance of a novel alginate matrix that incorporates human ADSCs (hADSCs).Results: Culture-expanded cells isolated from the stromal vascular fraction (SVF), corresponding to the third passage which showed the expression of mesenchymal stem cell (MSC) markers, were used in the 3-D culture systems. The latter represented a calcium alginate hydrogel, obtained by the diffusion of calcium gluconate (CGH matrix), and shaped as discoid-thin layer. For comparative purposes, a similar hADSC-laden alginate hydrogel cross-linked with calcium chloride was considered as reference hydrogel (RH matrix). Both hydrogels showed a porous structure under scanning electron microscopy (SEM) and the hADSCs embedded displayed normal spherical morphologies, some of them showing signs of mitosis. More than 85% of the entrapped cells survived throughout the incubation period of 7 days. The percentage of viable cells was significantly higher within CGH matrix at 2 days post-seeding, and approximately similar within both hydrogels after 7 days of culture. Moreover, both alginate-based hydrogels stimulated cell proliferation. The number of hADSC within hydrogels has increased during the incubation period of 7 days and was higher in the case of CGH matrix. Cells grown under adipogenic conditions for 21 days showed that both analyzed 3-D culture systems support adipogenic differentiation in terms of neutral lipid accumulation and perillipin expression. Furthermore, the cells encapsulated in CGH matrix displayed a more differentiated phenotype.Conclusions: The results of this study suggest that both CGH and RH matrices successfully support the survival and adipogenesis of hADSC. An enhancement of biological performance was detected in the case of CGH matrix, suggesting its promising application in ATE. © 2012 Galateanu et al;licensee BioMed Central Ltd. Source

Ionita M.,Polytechnic University of Bucharest | Ciupina V.,Ovidius University | Vasile E.,METAV CD
Journal of Optoelectronics and Advanced Materials | Year: 2011

In this work we present a computational routine based on molecular mechanics, dynamics and dissipative particle dynamics to predict mechanical properties and morphology of polyaniline (PANI), PANI-single walled carbon nanotubes octadecylamine (SWCNTs-ODA) functionalized and PANI-SWCNTs carboxylic acid (SWCNTs-CA) functionalized composite systems. Computational models of PANI-SWCNTs-ODA and PANI-SWCNTs-CA were implemented at atomistic and meso-scale. Computational results clearly confirmed that SWCNTs-ODA and SWCNTs-CA are properly dispersed and have beneficial effect on PANI mechanical properties. The Young's moduli generally increased with increasing SWCNTs content and values range from 2.77 GPa in the case of pure PANI to 7.39-9.31 GPa in the case of PANI-SWCNTs-PABS composite system. Source

Matei E.,Polytechnic University of Bucharest | Predescu A.,Polytechnic University of Bucharest | Vasile E.,METAV CD
Journal of Physics: Conference Series | Year: 2011

The paper describes the properties of some nanopowders obtained by coprecipitation and used as adsorbent for wastewater treatment. The Fe 3O4 and γ-Fe2O3 nanopowders were obtained using iron salts and NaOH as precipitation agents. D-sorbitol was used to prevent the agglomeration between the nanoparticles. The particle size and distribution were detected using a transmission electron microscopy (TEM) and a scanning electron microscope (SEM) equipped with dispersive analyze system in X radiation energy (EDS). The structure of the iron oxide nanoparticles was characterized by X-ray powder diffraction. Thus, the nanoparticles were characterized and compare in terms of particle size and chemical composition and used for adsorption studies in order to removal hexavalent chromium from waste waters. Source

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