Search results for "GLASS"
showing 10 items of 1153 documents
Effects of ions-releasing restorative materials on the dentine bonding longevity of modern universal adhesives after load-cycle and prolonged artific…
2019
This study aimed at evaluating the microtensile bond strength (MTBS) and fractographic features of dentine-bonded specimens created using universal adhesives applied in etch-and-rinse (ER) or self-etching (SE) mode in combination with modern ion-releasing resin-modified glass-ionomer cement (RMGIC)-based materials after load cycling and artificial saliva aging. Two universal adhesives (FTB: Futurabond M+, VOCO, Germany
Aging in a free-energy landscape model for glassy relaxation
2005
The aging properties of a simple free-energy landscape model for the primary relaxation in supercooled liquids are investigated. The intermediate scattering function and the rotational correlation functions are calculated for the generic situation of a quench from a high temperature to below the glass transition temperature. It is found that the re-equilibration of molecular orientations takes longer than for translational degrees of freedom. The time scale for re-equilibration is determined by that of the primary relaxation as an intrinsic property of the model.
Dynamic anomalies at the glass transition of organic van der Waals liquids
1993
Abstract The paper discusses the question of whether there is a characteristic temperature T c above the calorimetric glass transition temperature T g . Mode-coupling theory (MCT) predicts a crossover from liquid- to solid-like dynamics at T c . Neutron scattering and gradient NMR experiments have been carried out to test MCT using the molecular van der Waals liquid ortho -terphenyl as a model system. A significant anomaly of the Debye—Waller factor and a “decoupling” of self-diffusion from viscosity support the MCT predictions. A critical discussion of the relevance of such tests and of the limitations of neutron scattering is presented.
Heterogeneity at the Glass Transition: Translational and Rotational Self-Diffusion
1997
Self-diffusion coefficients, D, have been measured in the glass forming liquids salol, glycerol, phenolphthaleine dimethyl ether (PDE), cresolphthaleine dimethyl ether (CDE), and ααβ-trinaphthylbenzene (TNB) in the supercooled regime. The NMR static magnetic field gradient technique was applied where D >10-14 m2 s-1 can be attained. The results are similar to previous diffusion experiments where an enhancement of translational diffusion was found in comparison with rotational diffusion and shear viscosity. Various models of spatial heterogeneity are related to a phenomenological environmental fluctuation model in view of recent diffusion and relaxation data close to the glass transition.
Computer simulation of the glass transition of polymer melts
2007
Bond fluctuation models on square and simple cubic lattices at melt densities are simulated, using potentials depending on the length of the (effective) bond (and also on the bond angle, in d=3 dimensions). Various relaxation functions have the Kohlrausch-Williams-Watts (KWW) form; the associated relaxation time diverges as exp (const/T 2) in d=2 and as exp [const/T−T 0)] in d=3. For d=3 the self-diffusion constant also follows the Vogel-Fulcher law, with T 0=250 K for chain lengths N=20 and potentials adapted to bisphenol-A-polycarbonate [BPA-PC].
Micro-variazioni audiovisive e forma-processo. Analisi semiotica di Koyaanisqatsi di Reggio, Glass e Fricke
2014
Uno degli esiti più importanti del minimalismo storico è l'apertura alle altre arti. Il motivo di questo “contatto”, tra musica minimalista e arti audiovisive (cinema) e performative (teatro, danza, opera) è da ricercare nella struttura stessa della musica minimalista: i suoi specifici stilemi linguistici la rendono particolarmente adatta non solo a supportare immagini e situazioni narrative, ma a divenire vero principio organizzatore di essi, dettando ritmo, continuità, coerenza semantica. Ciò accade ad esempio nel film Koyaanisqatsi, creato a sei mani da Godfrey Reggio (regia), Philip Glass (musiche) e Ron Fricke (fotografia e riprese). Uscito nel 1982, Koyaanisqatsi suscitò l'attenzione …
Tecnologie e valori dello sguardo. Occhiali e discorsività
2021
What is that very special object in our daily lives that is a pair of spectacles all about? It accompanies us faithfully through every moment of the day, it crouches beside us when we do without, or it is stowed away in a bag, momentarily resting on a shelf. But it is always ready to come back and ride our noses and ears in order to perform its inalienable function to the best of its ability. Function? A notion as pernicious as it is indispensable when dealing with a sure design product such as spectacles. An unfortunate, polysemic, inflated term, problematised in a thousand ways; an intrusive and unwelcome guest, with whom one never ends up coming to terms. One sends him away and finds him…
BSA Aggregation in Trehalose-Water Systems
2010
Introduction Recent studies [1] on ternary protein-trehalose-water samples have shown that the protein thermal denaturation temperature is linearly correlated with the glass transition temperature of the system, despite the quite large temperature difference between the two processes. In such studies it is stated that the collective, long range properties of the matrix that regulate the glass transition are strictly correlated with local features on which the denaturation of the protein depends. In order to ascertain whether an analogous correlation exists between the effects of trehalose on the protein’s aggregation process and the glass transition temperature of the system, we performed L…
Bioactive glass ions induce efficient osteogenic differentiation of human adipose stem cells encapsulated in gellan gum and collagen type I hydrogels
2019
Abstract Background Due to unmet need for bone augmentation, our aim was to promote osteogenic differentiation of human adipose stem cells (hASCs) encapsulated in gellan gum (GG) or collagen type I (COL) hydrogels with bioactive glass (experimental glass 2-06 of composition [wt-%]: Na2O 12.1, K2O 14.0, CaO 19.8, P2O5 2.5, B2O3 1.6, SiO2 50.0) extract based osteogenic medium (BaG OM) for bone construct development. GG hydrogels were crosslinked with spermidine (GG-SPD) or BaG extract (GG-BaG). Methods Mechanical properties of cell-free GG-SPD, GG-BaG, and COL hydrogels were tested in osteogenic medium (OM) or BaG OM at 0, 14, and 21 d. Hydrogel embedded hASCs were cultured in OM or BaG OM fo…
Oxidized graphene in ionic liquids for assembling chemically modified electrodes: a structural and electrochemical characterization study
2012
Dispersions of graphene oxide (GO) nanoribbons in ionic liquids, ILs (either 1-butyl-3-methylimidazolium chloride (BMIM-Cl-) or 1-butylpyridinium chloride (-Bupy-Cl-)) have been used to assemble modified screen printed electrodes (SPEs). The graphene oxide/ionic liquid dispersions have been morphologically and structurally characterized by the use of several techniques: X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared (FT-IR) spectroscopy, high-resolution-transmission electron microscopy (HR-TEM). The assembled modified SPEs have then been challenged with various compounds and compared to several electro-active targets. In all cases high peak currents were detected, as wel…