Publications

A series of MgB2 samples were irradiated with protons of 11.3 and 13.2 MeV. Magnetization data shows an insignificant reduction of the critical temperatures but a continuous decrease of the Meissner fraction with increasing fluence or energy. All samples show a consistent improvement of the critical current density compared to the virgin sample and an increase of the pinning energy at high fields as resulted from relaxation data. (C) 2016 Elsevier B.V. All rights reserved.

Chitosan/biomimetic apatite thin films were grown in mild conditions of temperature and pressure by Combinatorial Matrix-Assisted Pulsed Laser Evaporation on Ti, Si or glass substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. A KrF* excimer (lambda = 248 nm, tau(FWHM) = 25 ns) laser source was used in all experiments. The nature and surface composition of deposited materials and the spatial distribution of constituents were studied by SEM, EDS, AFM, GIXRD, FTIR, micro-Raman, and XPS. The antimicrobial efficiency of the chitosan/biomimetic apatite layers against Staphylococcus aureus and Escherichia coli strains was interrogated by viable cell count assay. The obtained thin films were XRD amorphous and exhibited a morphology characteristic to the laser deposited structures composed of nanometric round shaped grains. The surface roughness has progressively increased with chitosan concentration. FTIR, EDS and XPS analyses indicated that the composition of the BmAp-CHT C-MAPLE composite films gradually modified from pure apatite to chitosan. The bioevaluation tests indicated that S. aureus biofilm is more susceptible to the action of chitosanrich areas of the films, whilst the E. coli biofilm proved more sensible to areas containing less chitosan. The best compromise should therefore go, in our opinion, to zones with intermediate-to-high chitosan concentration which can assure a large spectrum of antimicrobial protection concomitantly with a significant enhancement of osseointegration, favored by the presence of biomimetic hydroxyapatite. (C) 2016 Elsevier B.V. All rights reserved.

Thin amorphous As2S3 films show a giant photoexpansion of similar to 5% upon femtosecond laser illumination and this expansion remains after switching off the laser beam. To understand the structural modifications which occur during the photoexpansion process we assumed a molecular cluster structure of the amorphous As2S3. The focused femtosecond laser beam induces electrical charge redistribution on the sulfur atoms of each cluster, which increases the electrical repulsion between sulfur atoms, and thus induces an expansion of the clusters, by network reconfiguration, without breaking the bonds. An increase of the van der Waals distance between molecular clusters also takes place. (C) 2016 Elsevier B.V. All rights reserved.

Thin films of amorphous and polycrystalline indium zinc oxide (IZO) having various In/(In + Zn) nominal compositions from 0.3 to 0.9 were grown by the pulsed laser deposition technique at room temperature or at 400 degrees C on oxidized Si and quartz substrates. After deposition, the films were gamma irradiated at doses of 10, 20 and 30 kGy under Ar atmosphere. Grazing incidence X-ray diffraction investigations could not find measurable changes of the structure after irradiation. Simulations of the X-ray reflectivity (XRR) and diffuse scattering curves acquired from the films showed a small density decrease after irradiation, accompanied by an increase of the thickness and surface roughness. Spectroscopic ellipsometry investigations confirmed the increase of the IZO films' thickness after irradiation, being in agreement with the XRR results. Small changes in the refractive index, most probably caused by changes in the film density were also observed. Four point probe measurements showed very small resistivity increases after irradiation, with the films containing higher In concentration presenting negligible changes. (C) 2016 Elsevier B.V. All rights reserved.

Dye-doped polymer thin films were obtained by spin-coating of 8% polyvinylpyrrolidone (PVP) solutions (in ethanol). Ni or ZnO nanowires were incorporated in Rhodamine 6G doped polymer films (10(-4) M dye concentration). Optical and morphological properties of simple dye-doped polymer films and films containing metallic or semiconducting nanostructures were investigated. Optical microscopy and scanning electron microscopy were used to image the nanowires. The presence of Ni nanowires induces a small shift (2-3 nm) to longer wavelengths on the emission band of Rh 6G doped PVP film. The ZnO nanowires' presence was confirmed by X-ray diffraction measurements. An enhancement of the emission of the dye doped polymer is induced by the semiconducting structures. (C) 2015 Elsevier B.V. All rights reserved.

Hepatocellular carcinoma (HCC) is the most common primary tumor of the liver, ranking as the second most common cause of death from cancer worldwide. Magnetic nanoparticles (MNPs) have been used so far in tumor diagnosis and treatment, demonstrating great potential and promising results. In principle, three different approaches can be used in the treatment of tumors with superparamagnetic iron oxide nanoparticles: magnetically induced hyperthermia, drug targeting and selective suppression of tumor growth. This review focuses on the use of iron oxide nanoparticles for the diagnosis and treatment of liver cancer and offers a walkthrough from the MNPs imaging applicability to further therapeutic options, including their potential flaws. The MNP unique physical and biochemical properties will be mentioned in close relationship to their subsequent effects on the human body, and, also, their toxic potential will be noted. A presentation of what barriers the MNPs should overcome to be more successful will conclude this review.

Our research was focused on the evaluation of the photocatalytic and antimicrobial properties, as well as biocompatibility of cotton fabrics coated with fresh and reused dispersions of nanoscaled TiO2-1% Fe-N particles prepared by the hydrothermal method and post-annealed at 400 degrees C. The powders were characterized by X-ray diffraction (XRD), Mossbauer spectroscopy and X-ray photoelectron spectroscopy. The textiles coated with doped TiO2 were characterized by scanning electron microscopy and energy dispersive X-ray analyses, and their photocatalytic effect by trichromatic coordinates of the materials stained with methylene blue and coffee and exposed to UV, visible and solar light. The resulting doped TiO2 consists of a mixture of prevailing anatase phase and a small amount (similar to 15%-20%) of brookite, containing Fe3+ and nitrogen. By reusing dispersions of TiO2-1% Fe-N, high amounts of photocatalysts were deposited on the fabrics, and the photocatalytic activity was improved, especially under visible light. The treated fabrics exhibited specific antimicrobial features, which were dependent on their composition, microbial strain and incubation time. The in vitro biocompatibility evaluation on CCD-1070Sk dermal fibroblasts confirmed the absence of cytotoxicity after short-term exposure. These results highlight the potential of TiO2-1% Fe-N nanoparticles for further use in the development of innovative self-cleaning and antimicrobial photocatalytic cotton textiles. However, further studies are required in order to assess the long-term skin exposure effects and the possible particle release due to wearing.

The vortex activation energy U-AC in the AC magnetic response of superconductors exhibits a logarithmic variation with the screening current density J (regardless of the pinning structure details), and takes surprisingly high values in the vicinity of the DC irreversibility line, especially at low external DC magnetic fields, as often reported. This is essentially different from the behaviour of the vortex-creep activation energy at long relaxation time scales in DC magnetic measurements, and is not completely understood. We investigated the DC relaxation and the AC response for YBa2Cu3O7 films containing nanorods and nanoparticles, with the DC and AC fields oriented perpendicular to the film surface. It is shown that the large U-AC values in the vicinity of the DC irreversibility line, where the critical-state-related AC signal occurs, are generated by a non-diffusive vortex motion during the AC cycle, with the mean vortex hopping length longer than the average distance between the pinning centres. In these conditions, the smearing of the vortex pinning potential by thermally induced vortex fluctuations is weak, and U-AC mainly results from the strong influence of the pinning-enhanced viscous drag on the vortex hopping process. The logarithmic U-AC(J) dependence is consistent with a high U-AC.

The phenomena occurring at the interface between the electrodes and a liquid with ionic conductivity is manifested specifically in the spectrum of the dielectric permittivity. The theoretical model of the electrode polarization (charge space polarization) is met in the dielectric spectroscopy measurements in which electrodes are conductors (allow transfer of electric charge) and the adsorption-desorption of ions occurs on their surface. A pair of ions with equal and opposite charge is considered. The ions are produced by the association dissociation of neutral molecules. We propope general boundary conditions (BCs) with charge transfer current which contains the adsorption-desorption parameters. The BCs and the basic equations of the Poisson-Nernst Planck model, i.e. transport equations of charge carriers and Poisson equation, are re-formulated through new variables. The mathematical problem is solved analytically. The results allow finding a criterion for choosing a general and simple admittance expression, thus using a unified approach for different cases. We show that the small" signal approximation is no longer needed, at least for modern dielectric spectroscopy equipment. The ions can be point-like or may have finite dimensions. For the last case a model of Stem compact layer with charge transfer is proposed, which allows to calculate the compact layer impedance. Finally we obtain the equivalent admittance of the physical system composed from metal electrodes and ionic liquid in the presence of the Stern layer and the space charge polarization. The limitations of the model are given by the hypothesis of "flat band" and the non-selective adsorption of ions. (C) 2016 Elsevier B.V. All rights reserved.