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Two-dimensional oxide films are potentially useful for future technological applications, but also important objects to study model catalyst systems on the more fundamental side. Here we study silica, germania, and mixed silica-germania films supported on a metal single crystal surface Ru(0001). Those mixed films are interesting objects to systematically modify the properties of silica films, which may be used as membranes or covers for model studies in confined space, due to the modification of the rather stiff silica layers by incorporating germanium atoms replacing silicon atoms. Here we report a combined experimental and theoretical study of such layers, where we show how X-ray photoelectron spectroscopy in combination with LEED and I/V LEEM measurements allow us to judge the formation of such mixed films.

Disordered oxides, such as vitreous silica (v-SiO2) and vitreous germania, (v-GeO2) and chalcogenide glasses, such as vitreous germanium diselenide (v-GeSe2) are currently key materials in many technological fields, ranging from Si-based microelectronic to optical fibers and information storage devices production. Thus an increasing interest is nowadays devoted to understanding the structural arrangements of atoms in these materials. Diffraction probes like x-ray and neutron diffraction applied to amorphous materials can only partially characterize their atomic structure, since these materials lack translational symmetry. A complementary class of experimental techniques is constituted by vibrational spectroscopies, since the latter are also sensitive to the underlying structure. Yet, extracting structural information from the associated experimental data is rather difficult and above all it requires an accurate theoretical modeling of the material under investigation. This thesis is dedicated to the first-principles investigation of vibrational spectra of the tetrahedrally bonded glasses v-SiO2, v-GeO2 and v-GeSe2. To this aim, we make use of methods based on density functional theory which allow us to calculate vibrational spectra for a set of selected model structures for each one of these materials. We take advantage of a recent development which consists in applying a finite electric field under the constraint of periodic boundary conditions to calculate coupling factors, and hence to derive the infrared and Raman spectra. Through a comparison with experimental data of several vibrational spectroscopies, and by taking into account the structural differences of our models, we interpret features of the considered vibrational spectra. The extracted structural information represents a refinement of our knowledge of the investigated materials.

This study presents experimental results and an analysis approach for polarized light effects associated with thermomechanical stress during cooling of glass promoting solutions, with applications to cryopreservation and tissue banking in a process known as vitrification. Polarized light means have been previously integrated into the cryomacroscope-a visualization device to detect physical effects associated with cryopreservation success, such as crystallization, fracture formation, and contamination. The experimental study concerns vitrification in a cuvette, which is a rectangular container. Polarized light modeling in the cuvette is based on subdividing the tridimensional (3D) domain into a series of planar (2D) problems, for which a mathematical solution is available in the literature. The current analysis is based on tracking the accumulated changes in light polarization and magnitude, as it passes through the sequence of planar problems. Results of this study show qualitative agreement in light intensity history and distribution between experimental data and simulated results. The simulated results help explaining differences between 2D and 3D effects in photoelasticity, most notably, the counterintuitive observation that high stress areas may correlate with low light intensity regions based on the particular experimental conditions. Finally, it is suggested that polarized-light analysis must always be accompanied by thermomechanical stress modeling in order to explain 3D effects.

A comparison of the cellular content of needle tip aspirates and entry sites after transconjunctival intravitreal injection (IVI) using different needle types was performed. White outbred rats and human cadaver eyes were used for IVI by hypodermic 27 gauge (G) and 30G needles, and spinal anesthesia Pencan 27G needles. Aspiration of vitreous for quantitative morphological and cell cultivation analysis, as well as cyto-histological analysis of aspirates and entry sites were carried out. The most common cells in the aspirates from all needle types were conjunctival epithelial-, ciliary body non-pigmented epithelial- and sclerocyte-like cells and granular proteins. Crystallized vitreous specimens were present in each aspirate. The entry sites of hypodermic needles showed marked trauma in all wall layers of rat and human eyes accompanied by cellular destruction and hemorrhages. Pencan 27G needle caused less tissue trauma with partial reposition of sclerocytes. Transconjunctival IVIs with hypodermic 27G and 30G, and Pencan 27G needles result in trauma of all layers of the eyeball. The possible consequences of cellular content being cut and injected into the eye, as well as the entry site wound shape deserve future consideration and improvements.

The degeneration of Müller cells has been recognized to involve in the pathogenesis of diabetic retinopathy. However, the mechanism is not yet clear. This study is to explore the potential role of Cyr61, a secreted signaling protein in extracellular matrix, in inducing human Müller cell degeneration in diabetic retinopathy (DR). Twenty patients with proliferative diabetic retinopathy (PDR) and twelve non-diabetic patients were recruited for this study. Vitreous fluid was collected during vitrectomy surgery for Cyr61 ELISA. Human Müller cell line MIO-M1 were cultured to be subconfluent, and then treated with glucose (0-20 mM) or Cyr61 (0-300 ng/ml). Cyr61 expression induced by increasing concentrations of glucose was evaluated by RT-qPCR and Western blot. Effects of Cyr61 on Müller cells viability, migration and apoptosis were observed by MTT assay, Transwell assay, and TUNEL assay. Vitreous Cyr61 levels were observed to be 8-fold higher in patients with PDR (3576.92 ± 1574.58 pg/mL), compared with non-diabetic controls (436.14 ± 130.69 pg/mL). Interestingly, the active PDR group was significantly higher than the quiescent PDR group (P

We have used high-energy x-ray scattering to map the strain fields around crack tips in fracture specimens of a bulk metallic glass under load at room temperature and below. From the measured strain fields we can calculate the components of the stress tensor as a function of position and determine the size and shape of the plastic process zone around the crack tip. Specimens tested at room temperature develop substantial plastic zones and achieve high stress intensities ((K(If) = 76 MPa m(1/2)) prior to fracture. Specimens tested at cryogenic temperatures fail at reduced but still substantial stress intensities (K(If) = 39 MPa m(1/2)) and show only limited evidence of crack-tip plasticity. We propose that the difference in behavior is associated with changes in the flow stress and elastic constants, which influence the number density of shear bands in the plastic zone and thus the strain required to initiate fracture on an individual band. A secondary effect is a change in the triaxial state of stress around the crack tip due to the temperature dependence of Poisson's ratio. It is likely that this ability to map elastic strains on the microscale will be useful in other contexts, although interpreting shifts in the position of the scattering peaks in amorphous materials in terms of elastic strains must be done with caution.

Purpose To analyze the level of human inflammatory immune mediators in the intraocular fluid aspirated from foldable capsular vitreous body (FCVB) filled-eyes during FCVB removal surgery, 3 months after implantation. Methods 8 samples of intra-FCVB fluids (n = 8) were collected from 8 FCVB filled patients in our previous FCVB exploratory clinical trial. The intra-FCVB fluids were aspirated from the FCVB filled-eyes during the FCVB removal surgeries at the third month. For the control groups, the vitreous fluids were collected from patients with idiopathic macular hole (n = 9) or rhegmatogenous retinal detachment (n = 6) during pars plana vitrectomy. A multiplex immunoassay was used to determine levels of 9 cytokines (IL-1β, IL-2, IL-6, IL-8, IL-10, IL-17, TNF-α, IFN-γ and VEGF) in these samples. The VEGF level of some intra-FCVB fluids (n = 6) were re-tested using enzyme-linked immunosorbent assay (ELISA). Results In the intra-FCVB fluids, 9 cytokines concentrations of most samples (n = 5) measured by Multiplex immunoassay showed low values, except for Patient 02, 06, and 09. The VEGF concentrations of some intra-FCVB fluids (n = 6) tested by ELISA were in accordance with Multiplex immunoassay results. For all eight patients (n = 8), the concentrations of IL-1β, IL-2, IL-6, TNF-α, IFN-γ and VEGF were slightly higher as compared to the idiopathic macular hole control group. While, the concentrations of IL-8, IL-10, and IL-17 were not statistically significant different compared with the idiopathic macular hole control samples. Most cytokines concentrations (IL-2, IL-6, IL-8, IL-10, IL-17, TNF-α, IFN-γ, VEGF) were not statistically significant different compared to the rhegmatogenous retinal detachment control group except IL-1β. Conclusions The FCVB had sufficient porosity to allow cytokines to pass through. This study first discovered that the FCVB possesses favorable permeability of proteins in the human eye.

This is an open-access article.-- et al., This paper reports the effect of soda-lime-glass-nAg coating on the viability of an in vitro biofilm of Streptococcus oralis. Three strains (ATCC 35037 and two clinical isolates from periodontitis patients) were grown on coated with glass, glass containing silver nanoparticles, and uncoated titanium alloy disks. Two different methods were used to quantify biofilm formation abilities: crystal violet staining and determination of viable counts. The influence of the surface morphology on the cell attachment was studied. The surface morphology was characterized by scanning electron microscopy (SEM) and using a profilometer. SEM was also used to study the formation and the development of biofilm on the coated and uncoated disks. At least a >99.7% inocula reduction of biofilm respect to titanium disks and also to glass coated disks was observed in the glass-nAg coated disks for all the studied strains. A quantitative evaluation of the release of silver was conducted in vitro to test whether and to what extend the biocidal agent (silver) could leach from the coating. These findings suggest that the biofilm formation of S. oralis strains is highly inhibited by the glass-nAg and may be useful for materials which require durable antibacterial effect on their surfaces, as it is the case of dental implants. © 2012 Cabal et al., This work was supported by the Spanish Ministry of Science and Innovation under the project MAT2009-14542-C02-01.

Ion beam analysis (IBA)- and X-ray fluorescence (XRF)-based techniques have been well adopted in cultural-heritage-related analytical studies covering a wide range of diagnostic role, i.e., from screening purposes up to full quantitative characterization. In this work, a systematic research was carried out towards the identification and evaluation of the advantages and the limitations of laboratory-based (IBA, electron probe microanalyzer) and portable (milli-XRF and micro-XRF) techniques. The study focused on the analysis of an Archaic glass bead collection recently excavated from the city of Thebes (mainland, Greece), in order to suggest an optimized and synergistic analytical methodology for similar studies and to assess the reliability of the quantification procedure of analyses conducted in particular by portable XRF spectrometers. All the employed analytical techniques and methodologies proved efficient to provide in a consistent way characterization of the glass bead composition, with analytical range and sensitivity depending on the particular technique. The obtained compositional data suggest a solid basis for the understanding of the main technological features related to the raw major and minor materials utilized for the manufacture of the Thebian ancient glass bead collection. Anal Bioanal Chem

Thèse de 3ème cycle, spécialité : Sciences des Matériaux.; On explicite d'abord les contraintes physiques (absorption,diffusion) et chimiques (conditions de vitrification) qui guident la recherche, puis on décrit la mise en évidence de deux nouvelles familles de verre, l'une de verre fluore a base d'indium et l'autre de verre oxyhalogene a base d'antimoine,avec leurs caractéristiques thermiques et mécaniques, les propriétés optiques et magnétiques et leur étude structurale par cristallisation et diffusion raman ...; Non disponible

La façon dont se manifeste la dévitrification thermique d'un matériau vitreux, phénomène mis en évidence par des techniques expérimentales appropriées (Analyse thermique, radiocristallographie spectrographie d'absorption IR, etc...) peut apporter des informations intéressantes concernant la structure du verre de départ. L'enregistrement d'une courbe d'ATD met en évidence un ou plusieurs pics de dévitrification. La connaissance, par analyse radiocristallographique, de la nature des phases qui cristallisent lors du traitement thermique, permet d'établir certaines corrélations entre la composition chimique et la stabilité thermique du matériau de départ. La mise en oeuvre de techniques expérimentales annexes (dilatométrie, microscopie électronique à balayage, ...) montre que dans certains cas le phénomène de dévitrification thermique est complexe et peut être associé à un frittage du matériau surtout lorsque celui-ci est initialement à l'état pulvérulent. On présente un certain nombre d'exemples caractéristiques tirés de recherches sur des verres de silico-aluminate et sur des laitiers vitreux, matériaux qui peuvent être utilisés pour l'élaboration de vitrocéramiques. On montre en particulier que la présence de certains cations modificateurs de réseau (Mg2+, Fe3+) abaisse la stabilité thermique du verre alors qu'un effet inverse se manifeste lorsque le verre contient des quantités importantes d'alumine.

L'étude porte sur deux catégories de solides : — des matériaux silicatés vitreux ou partiellement vitrifiés, utilisés dans l'industrie des liants hydrauliques (clinkers de ciment portland, cendres volantes de centrales thermiques, laitiers de hauts fourneaux) ; - des verres de cordiérite 2 MgO, 2 Al2O3, 5 SiO2 traités thermiquement à l'état pur ou en présence de quantités croissantes d'alumine, de zircone, d'oxyde de titane ou d'oxyde de chrome Cr2O3, substances ajoutées intentionnellement aux fins de contrôle des processus de recristallisation. La microscopie électronique à balayage (appareil MEB 07 de CAMECA) permet de différencier très nettement, en fonction de leur origine, la morphologie et la texture des premiers matériaux cités, ces facteurs jouant un rôle très important dans le comportement thermique ou la réactivité de ces solides vis-à-vis de l'eau (hydraulicité). Dans le cas des verres de cordiérite, la technique expérimentale permet de suivre les phénomènes de recristallisation thermique, lesquels sont très sensiblement influencés selon la nature ou la teneur de l'oxyde utilisé comme agent de germination, et d'obtenir des informations très intéressantes sur la texture interne des céramiques vitreuses.