National Institute Of Materials Physics - Romania

The laser-phase-transition analogy is considered for a system of identical emitters interacting with a cavity mode. As in the case of equilibrium phase transitions, the thermodynamic limit is shown to be an essential condition for the appearance of an abrupt transition, with a well-defined threshold. The proof is discussed first in the simpler formalism of the rate equation and then at the higher level of the master equation for probabilities. The latter is derived from the von Neumann-Lindblad evolution of the density operator. In the thermodynamic limit and for two-level emitters the master equation becomes a two-dimensional dynamic flow with two possible fixed points, related to the normal and the lasing regimes, respectively. The master equation analysis confirms the threshold value deduced from the rate equation, but also provides further evidence of lasing by showing that all photonic autocorrelation functions converge to unity.

We report a study on the biocompatibility vs. thickness in the case of titanium nitride (TiN) films synthesized on 410 medical grade stainless steel substrates by pulsed laser deposition. The films were grown in a nitrogen atmosphere, and their in vitro cytotoxicity was assessed according to ISO 10993-5 [1]. Extensive physical-chemical analyses have been carried out on the deposited structures with various thicknesses in order to explain the differences in biological behavior: profilometry, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction and surface energy measurements. XPS revealed the presence of titanium oxynitride beside TiN in amounts that vary with the film thickness. The cytocompatibility of films seems to be influenced by their TiN surface content. The thinner films seem to be more suitable for medical applications, due to the combined high values of bonding strength and superior cytocompatibility.

The storage and catabolism of Ultrasmall SuperParamagnetic Iron Oxide (USPIO) nanoparticles were analyzed through a multiscale approach combining Two Photon Laser Scanning Microscopy (TPLSM) and High-Resolution Transmission Electron Microscopy (HRTEM) at different times after intravenous injection in an atherosclerotic ApoE(-/-) mouse model. The atherosclerotic plaque features and the USPIO heterogeneous biodistribution were revealed down from organ's scale to subcellular level. The biotransformation of the nanoparticle iron oxide (maghemite) core into ferritin, the non-toxic form of iron storage, was demonstrated for the first time ex vivo in atherosclerotic plaques as well as in spleen, the iron storage organ. These results rely on an innovative spatial and structural investigation of USPIO's catabolism in cellular phagolysosomes. This study showed that these nanoparticles were stored as non-toxic iron compounds: maghemite oxide or ferritin, which is promising for MRI detection of atherosclerotic plaques in clinics using these USPIOs. From the Clinical Editor: Advance in nanotechnology has brought new contrast agents for clinical imaging. In this article, the authors investigated the use and biotransformation of Ultrasmall Super-paramagnetic Iron Oxide (USPIO) nanoparticles for analysis of atherosclerotic plagues in Two Photon Laser Scanning Microscopy (TPLSM) and High-Resolution Transmission Electron Microscopy (HRTEM). The biophysical data generated from this study could enable the possible use of these nanoparticles for the benefits of clinical patients. (C) 2015 Elsevier Inc. All rights reserved.

BaxSr1-xFe12O19 (x=0.05, 0.15, 0.25, 0.35) ferrites were prepared by both the sol gel and conventional solid state reaction techniques. The structural characteristics and dielectric properties of these ferrites were investigated and compared. BaxSr1-xFe12O19 ceramics obtained by the sol gel method show homogeneous morphology and single crystalline phase while those prepared by solid state reaction route exhibit less homogeneous morphology, being accompanied by a secondary crystalline phase (BaFe2O4). The size of the grains varies in the range 200-300 nm for x=0.05-0.35 when the powders are prepared by sol gel method and, 600-700 nm for the powders prepared by solid state reaction. For the same value of x, the BaxSr1-xFe12O19 ferrites obtained via sol-gel display higher permittivity and lower dielectric losses compared to those prepared by solid state reaction route. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Glassy nanocomposites containing Eu3+-doped LaOCl nanocrystals of about tens of nm size embedded in a silica matrix have been prepared by using sol-gel route followed by controlled crystallization of the xerogel. Crystallization behavior of LaOCl nanocristalline phase was discussed on the basis of thermal analysis, X-ray diffraction and photoluminescence measurements. LaOCl nanocrystalline phase precipitation is the result of lanthanum chloride hydrolytic and oxidative reactions. As the annealing temperature increases nanocrystallites size grows up to tens of nm; Eu3+-ions are gradually incorporated during the nanocrystals growth. Structural changes were studied using the Eu3+ as probe ion and the luminescence properties were analysed by using Judd-Ofelt theory. (C) 2015 Elsevier Ltd. All rights reserved.

Diamond like carbon (DLC) is an amorphous carbon material suitable for use in a variety of in vivo biomedical applications, which may constitute a step forward in biotechnology of dental or orthopedic implants. Previous in vitro studies focusing on DLC films demonstrate that cellular behavior on DLC is cell type specific. The aim of the present study was to evaluate the interaction between DLC substrates and keratinocyte stem cells isolated from oral epithelia. Oral keratinocyte stem cells were isolated using a magnetic technique. Various DLC films were synthesized using Thermoionic Vacuum Arc plasma (TVA) by adjusting the distance between substrate and anode. We assessed important cell characteristics such as proliferation rate, colony forming efficiency of oral keratinocyte stem cells placed on various DLC films. Our results demonstrate that DLC substrates are biocompatible with the analyzed cell type, and do not affect cell size or colony forming efficiency, in specific conditions being able to stimulate their proliferative potential. The data demonstrates for the first time that oral keratinocyte stem cells are biocompatible with DLC films. Moreover the proliferative potential of cells may be enhanced by adjusting the deposition parameters of DLC films.

Synthetic hydroxyapatite (HAp) is one of the most commonly used material for a large variety of biomedical applications. This paper presents structural, morphological and preliminary ultrasonic characterizations of the HAp nanopowder synthesized by an adapted co-precipitation method. To this end, the structural and morphological properties were evaluated by Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Biological investigation were also performed in order to evidence the influence of HAp tablets on the development and growth of endothelial cells. The ultrasonic measurements obtained for the HAp dispersion allowed us to calculate the ultrasonic velocity and the attenuation. The study of ultrasonic waves propagation through dispersions could be used as future standard quality test, thus improving the quality of biomedical devices based on hydroxyapatite.

Reducing the recombination rate of photo-generated electron-hole pairs in the surface of pristine TiO2 materials can be done, among others, via local spatial charge separation in the photocatalytically active surface region. A local electric field acting for this purpose can be ensured, for instance, in hetero-junction regions formed at the interface between a TiO2 film and a WO3 ultra-thin layer. The option for the WO3-TiO2 semiconductor pair is related to the suitable fit of their band structures. To model the interface, a more in-depth knowledge of local atomic environment is required. Here, we discuss the local atomic ordering and the related effects in the interface region of TiO2/WO3 and WO3/TiO2 structures grown on Si (100) substrates. Materials characterization was done by using XRD, XPS and XAS techniques. We demonstrate that tungsten atoms enter as W6+ or W4+ cations into the rutile-type TiO2 lattice, by substituting the Ti4+ cations. While W6+-Ti4+ substitution leaves the surrounding rutile matrix unchanged, the W4+-Ti4+ substitution induces a local rutile-to-anatase transition. The current results are relevant in designing new applications structures with enhanced photocatalytic performances.

The goal of this paper was to investigate the antifungal activity of Enamel layers deposited on titanium substrate (Ti-Enamel) and Enamel layers deposited on titanium substrate previously coated with a vinyl polydimethylsiloxane layer (Ti-PDMS-Enamel). The physicochemical properties were also investigated. The Candida albicans biofilm development on the obtained layers was examined after 24 h, 48 h, and 72 h by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) after ethidium bromide staining. A significant inhibition of the fungal adherence and biofilm development was observed on Ti-Enamel layers. The antifungal results demonstrated that the use of new Ti-Enamel composite layers could represent a promising perspective for the prevention of fungal biofilms associated implant infections.

In this contribution the design and fabrication of ceramic microsystems with integrated different microfluidic elements and sensors will be presented. Ceramic microsystems are based on unconventional application of low-temperature co-fired ceramic technology and materials. This unconventional application is related to three-dimensional ceramic structures, such as cantilevers, ledges, bridges, diaphragms, valleys, channels, holes and cavities, valves, mixers, diffusors, distributors, collectors, flow limiters, sensors, and actuators.