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At least 145 records · Page 8Linked to original sources
PubMed1980

[Use of the effect of impaired complete internal reflection for studying the adhesion of animal cells to glass. III. Measurement of the refractive index of hyaloplasm and determination of the distance between cell membrane surface and glass].

The kinetics of form change (flattening) of Chinese hamster fibroblast cell surface facing the glass has been studied during attachment of fibroblasts to the glass using the effect of frustrated total reflection. Two stages of the process were shown to exist. The first one is characterized by a rapid (5 min) partial flattening and requires no serum in the medium. The second stage occurs only in the presence of serum in the medium, it lasts no longer than one hour and ends in a complete flattening. After the second stage is completed, spreaded cells appear.

Animals↗
PubMed1976

Platelet retention in glass bead columns: adhesion to glass and subsequent platelet-platelet interactions.

In normal heparinized blood, the retention of platelets in glass bead columns was low in the first 1 or 2 ml, increasing to more than 80% by the 4th or 5th ml. Prior flushing of the columns with platelet-poor plasma or saline lowered retention in all 5 ml. Additional studies were carried out with a two-stage procedure in which a sample of blood (A) was pumped through a column, immediately flushed out with saline or plasma, and followed by a second blood sample (B). When as little as 1 ml of blood A preceded the flushing solution, retention was very high in all 5 ml of the subsequent blood B. This enhancement of retention in B occurred, providing blood A contained platelets (other than thrombasthenic), fibrinogen, and adequate divalent cations. Enhancement did not require von Willebrand factor (vWF) in A, nor was ADP necessary, since enhancement occurred even when heparinized blood as A contained prostaglendin E1 (PGE1) or creatine phosphokinase with creatine phosphate (CPK-CP). However, the presence of PGE1 or CPK-CP in the plasma used to flush the columns prevented the enhancement of retention in the first milliliter of B. Retention in the first milliliter of B (following normal blood as A and saline or normal plasma for flushing) was high when B was afibrinogenemic, moderately high when B contained PGE1 or CPK-CP, and low in thrombasthenic, EDTA, or vWF-deficient blood. Retention declined in subsequent milliliters of PGE1 or CPK-CP blood and remained low in thrombasthenic, vWF-deficient, or EDTA blood. Our findings suggest that (1) the platelets in A adhere to glass; this adhesion requires fibrinogen but not vWF or ADP; (2) the adherent platelets release ADP and become sticky; (3) adhesion of platelets in the first milliliter of B to the sticky platelets from A requires vWF and divalent cations but not ADP; (4) retention is maintained thereafter by repetitive platelet-platelet interactions involving ADP release, alteration of adherent platelets by released ADP, and adhesion of further platelets to these ADP-altered platelets which requires vWF.

Adenosine Diphosphate↗
PubMed2000

Analytical control of silica glass production. Voltammetric determination of titanium and iron in raw materials and silica glass samples.

Adsorptive stripping voltammetric (AdSV) methods are presented for the determination of titanium and iron in quartz and silica glass samples obtained after pressure decomposition. Mandelic acid and catechol were used as complexing agents for titanium and iron, respectively. The method for titanium determination is based on the catalytic effect of chlorate ions. An insoluble residue remaining after decomposition of quartz and silica glass samples in HF+H2SO4 mixture was checked by energy-dispersive X-ray analyses. ET-AAS was applied as a reference method to AdSV measurements.

Journal Article↗
PubMed2003

The distribution of glass-transition temperatures in nanoscopically confined glass formers.

Despite the decade-long study of the effect of nanoconfinement on the glass-transition temperature (T(g)) of amorphous materials, the quest to probe the distribution of T(g)s in nanoconfined glass formers has remained unfulfilled. Here the distribution of T(g)s across polystyrene films has been obtained by a fluorescence/multilayer method, revealing that the enhancement of dynamics at a surface affects T(g) several tens of nanometres into the film. The extent to which dynamics smoothly transition from enhanced to bulk states depends strongly on nanoconfinement. When polymer films are sufficiently thin that a reduction in thickness leads to a reduction in overall T(g), the surface-layer T(g) actually increases with a reduction in overall thickness, whereas the substrate-layer T(g) decreases. These results indicate that the gradient in T(g) dynamics is not abrupt, and that the size of a cooperatively rearranging region is much smaller than the distance over which interfacial effects propagate.

Journal Article↗
PubMed2006

The role of temperature and density on the glass-transition dynamics of glass formers.

A correlation between the monomeric volume and the dynamic quantity E*(V)/H*, used to provide a quantitative measure of the role of temperature and density on the dynamics, is demonstrated for a series of polymers and glass-forming liquids. We show that monomeric volume and local packing play a key role in controlling the value of this ratio and thus the dynamics associated with the glass temperature.

Journal Article↗
PubMed2001

Dynamic light scattering study of the liquid <--> glass transition for the GdCl3-3AlCl3 glass-forming mixture.

The dynamics of density and orientation fluctuations for a member of a family of inorganic glass-forming molten salts based on rare-earth halide-aluminum halide mixtures, namely, the GdCl3-3AlCl3, has been investigated in the supercooled state by means of dynamic light scattering. The temperature dependence of the structural relaxation time near the glass transition temperature was found to be rather strong, indicating the "fragile" character of this liquid. The microscopic origin of the structural relaxation has been rationalized by employing structural information that has been independently extracted from other spectroscopic techniques.

Journal Article↗
PubMed2005

Configurational entropy and its crisis in metastable states: ideal glass transition in a dimer model as a paragidm of a molecular glass.

We discuss the need for discretization to evaluate the configurational entropy in a general model. We also discuss the prescription using restricted partition function formalism to study the stationary limit of metastable states where a more stable equilibrium state exists. We introduce a lattice model of dimers as a paradigm of molecular fluid and study stationary metastability in it to investigate the root cause of glassy behavior. We demonstrate the existence of entropy crisis in metastable states, from which it follows that the entropy crisis is the root cause underlying the ideal glass transition in systems with particles of all sizes. The orientational interactions in the model control the nature of the liquid-liquid transition observed in recent years in molecular glasses.

Journal Article↗
PubMed2004

Critical currents at the bragg glass to vortex glass transition.

We present simulations of the transport properties of superconductors at the transition from the Bragg glass (BG) to the vortex glass (VG) phase. We study the frustrated anisotropic 3D XY model with point disorder, which has been shown to have a first-order transition as a function of the intensity of disorder. We add an external current to the model, and we obtain current-voltage curves as a function of disorder at a low temperature. We find that the in-plane critical current has a steep increase at the BG-VG transition, while the c-axis critical current has a discontinuous jump down, this later result in agreement with the first-order character of the transition.

Journal Article↗
PubMed2004

Atomic fermi-bose mixtures in inhomogeneous and random lattices: from fermi glass to quantum spin glass and quantum percolation.

We investigate strongly interacting atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. We derive an effective Hamiltonian for the system and discuss its low temperature physics. We demonstrate the possibility of controlling the interactions at local level in inhomogeneous but regular lattices. Such a control leads to the achievement of Fermi glass, quantum Fermi spin-glass, and quantum percolation regimes involving bare and/or composite fermions in random lattices.

Journal Article↗
PubMed2003

The glass-to-glass transition and its end point in a copolymer micellar system.

We present experimental evidence, obtained from small-angle neutron scattering and photon correlation measurements, indicating the existence of two types of structurally arrested (glassy) states in a copolymer micellar system with a short-range interparticle attractive interaction. Within a certain range of micellar volume fractions, a sharp transition between these two types of glass is observed by varying the temperature. Furthermore, we found an end point of this transition line beyond which the two glasses become identical in their local structure and their long-time dynamics. These findings confirm the recent mode-coupling theory predictions regarding the phase behavior of the structurally arrested states for this type of system.

Journal Article↗
PubMed2004

Germania-glass-core silica-glass-cladding modified chemical-vapor deposition optical fibers: optical losses, photorefractivity, and Raman amplification.

Germania-glass-core silica-glass-cladding single-mode fibers (deltan as great as 0.143) with a minimum loss of 20 dB/km at 1.85 microm were fabricated by modified chemical-vapor deposition. The fibers exhibit strong photorefractivity, with type IIa index modulation of 2 x 10(-3). A Raman gain of 300 dB/(kmW) was determined at 1.12 microm. Only 3 m of such fibers is sufficient for constructing the 10-W Raman laser at 1.12 microm with a 13-W pump at 1.07 microm.

Journal Article↗
PubMed1984

The effect of a proline-rich polypeptide (PRP) on the humoral immune response. I. Distinct effect of PRP on the T cell properties of mouse glass-nonadherent (NAT) and glass-adherent (GAT) thymocytes in thymectomized mice.

It has been shown, using thymectomized, irradiated and reconstituted mice and a proline-rich polypeptide (PRP) that glass-nonadherent thymocytes contain a precursor of helper cell, and glass-adherent thymocytes a precursor of suppressor cells in the humoral immune response to SRBC. Precursor cells differentiate into helper or suppressor cells upon in vitro contact with PRP. Moreover, it was demonstrated that NAT and GAT fractions are related to PNA+ and PNA- thymocytes respectively.

Animals↗
PubMed2005

The effect of bioactive glass content on synthesis and bioactivity of composite poly (lactic-co-glycolic acid)/bioactive glass substrate for tissue engineering.

Tissue engineering offers a promising new approach to bone tissue grafting. One material that has received attention in this regard is the polymer poly (lactic-co-glycolic acid) (PLGA). It has the advantage of controllable bioresorption and ease of processing. Another material of interest is bioactive glass (BG), which shows the ability to stimulate osteoblastic differentiation of osteoprogenitor cells. In this study, we reported on the optimal synthesis parameters and the kinetics of formation of calcium phosphate (Ca-P) phase at the surface of PLGA/BG composites. The formation of calcium phosphate layer was confirmed using scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDXA). PLGA-30%BG microspheres based porous scaffolds for bone tissue engineering were examined for their ability to promote osteogenesis of marrow stromal cells (MSC). This porous scaffold supported both MSC proliferation and promoted MSC differentiation into cells expressing the osteoblast phenotype. It therefore demonstrates significant potential as a bone replacement material.

Animals↗
PubMed2004

Microtensile bond strength to ground enamel by glass-ionomers, resin-modified glass-ionomers, and resin composites used as pit and fissure sealants.

OBJECTIVES: To measure the microtensile bond strength to ground enamel of different types of materials used as pit and fissure sealants in combination with different substrate conditioners. METHODS: From 40 sound extracted molars, eight groups of five teeth were randomly formed. The experimental groups were: (1) (C) 37% phosphoric acid/ClinPro Sealant (3M ESPE); (2) (G) 37% phosphoric acid/Guardian Seal (Kerr); (3) (E/TF) 37% phosphoric acid/Excite/Tetric Flow (Ivoclar-Vivadent) (4) (OS/UF) 37% phosphoric acid/One Step (Bisco)/UniFil Flow (GC); (5) (OS/AE) 37% phosphoric acid/One Step/AEliteflo (Bisco); (6) (UB/UF) UniFil Bond/UniFil Flow (GC); (7) (CC/FVII) GC Cavity Conditioner/Fuji VII (GC); (8) (CC/FII) GC Cavity Conditioner/Fuji II LC Improved (GC). On the buccal of each tooth, a 5mm high build-up was created by incrementally adding layers of the sealing material on the conditioned enamel. By serially cutting the built-up tooth, multiple beam-shaped specimens about 1mm x 1mm in cross section were obtained, and loaded in tensile (0.5 mm/min) until failure occurred. RESULTS: The bond strengths measured in MPa were: (C) 20.41+/-11.79; (G) 16.02+/-7.99; (E/TF) 24.06+/-9.67; OS/UF 15.63+/-9.00; (OS/AE) 9.31+/-6.05; (UB/UF) 4.96+/-3.46; (CC/FVII) 1.70+/-2.19; (CC/FII) 2.19+/-1.44. CONCLUSIONS: The conventional and the resin-modified glass ionomers measured bond strengths significantly lower than those of any resin-based materials. Failure frequently occurred cohesively within the cement. Flowable composites in combination with phosphoric acid and a total-etch adhesive performed similarly to resin-based materials specifically conceived for sealings, such as ClinPro Sealant and Guardian Seal. The bond achieved by resin composite when treating enamel with the self-etching primer used in this study (UniFil Bond) was significantly lower than that developed when the substrate was etched with 37% phosphoric acid.

Acrylic Resins↗
PubMed1992

The clinical performance of a glass polyalkenoate (glass ionomer) cement used in a 'sandwich' technique with a composite resin to restore Class II cavities.

The use of glass polyalkenoate (GPA) cement in conjunction with composite resin using an acid etch technique is now well known and a 'sandwich' of tooth/GPA cement/composite resin has been recommended to form the cervical seal at the base of approximal boxes in Class II cavities. This paper reports on the 2-year results of a controlled clinical trial using a commercial GPA lining cement. The trial was designed to evaluate the efficacy of this 'sandwich' technique. Sixty-four restorations in the mouths of 22 patients were evaluated during the 2.5 year period of the trial. The composite resin component of the restorations performed well. Five restorations failed, all in the region of the approximal box. Four failures were related to the exposed GPA cement component of the 'sandwich'. Failure was probably related to placement difficulties of the technique. The use of GPA cement laminated with composite resin when the GPA cement was enclosed within the final restoration appeared to be a successful technique.

Adult↗
PubMed2003

Resin-modified glass ionomer, modified composite or conventional glass ionomer for band cementation?--an in vitro evaluation.

The aims of this study were to compare the mean shear-peel bond strength and predominant site of bond failure of micro-etched orthodontic bands cemented with resin-modified glass ionomer cement (RMGIC; Fuji Ortho LC or 3M Multi-Cure), a modified composite or a conventional GIC. The survival time of bands was also assessed following simulated mechanical stress in a ball mill. One hundred and twenty molar bands were cemented to extracted human third molars. Eighty bands (20 cemented with each cement) were used to assess the debonding force and 40 bands (10 cemented with each cement) were used to determine survival time. The specimens were prepared in accordance with the manufacturers' instructions for each cement. After storage in a humidor at 37 degrees C for 24 hours, the shear debonding force was assessed for each specimen using a Nene M3000 testing machine with a crosshead speed of 1 mm/minute. The predominant site of band failure was recorded visually for all specimens as either at the band/cement or cement/enamel interface. Survival time was assessed following application of mechanical stress in a ball mill. There was no significant difference in mean shear-peel bond strength between the cement groups (P = 0.816). The proportion of specimens failing at each interface differed significantly between cement groups (P < 0.001). The predominant site of bond failure for bands cemented with the RMGIC (Fuji Ortho LC) or the modified composite was at the enamel/cement interface, whereas bands cemented with 3M Multi-Cure failed predominantly at the cement/band interface. Conventional GIC specimens failed mostly at the enamel/cement interface. The mean survival time of bands cemented with either of the RMGICs or with the modified composite was significantly longer than for those cemented with the conventional GIC. The findings indicate that although there appears to be equivalence in the mean shear-peel bond strength of the band cements assessed, the fatigue properties of the conventional GIC when subjected to simulated mechanical stress seem inferior to those of the other cements for band cementation.

Acid Etching, Dental↗
PubMed1992

Anti-IgG immobilized controlled-pore glass. Thionyl chloride-activated succinamidopropyl-glass as a covalent immobilization matrix.

Rabbit anti-bovine IgG was covalently immobilized on thionyl chloride-activated succinamidopropyl controlled-pore glass (CPG) beads (3000 A pore diam; 120/200 mesh). Thionyl chloride-activated beads remained stable for over 1 y retaining full capability of immobilizing protein upon recirculation of protein solution. The immobilized anti-bovine IgG is capable of binding IgG with a dissociation constant (Kd) of 9.45 x 10(-7) M and a capacity of 0.85 g/L of matrix. A column of immobilized anti-IgG is able to remove all detectable contaminating IgG from partially purified enzyme preparations of sulfhydryl oxidase and gamma-glutamyltransferase as determined by ELISA and Western blot. The column matrix could be regenerated by washing with 0.1M acetic acid, pH 2.8.

Animals↗