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Highly bioactive scaffolds for tissue engineering were synthesized using a glass belonging to the SiO2-CaO-K2O (SCK) system. The glass SCK was prepared by a traditional melting-quenching route and its bioactivity was assessed by in vitro tests in a simulated body fluid (SBF). The glass was ground and sieved to obtain powders of specific size that were subsequently mixed with polyethylene particles of two different dimensions. The powders were then uniaxially pressed to obtain a crack free green compact that was thermally treated to remove the organic component and to sinter the inorganic phase. The obtained biomaterial was characterised by means of X-ray Diffraction, SEM equipped with EDS, mercury intrusion porosimetry, density measurements, image analysis, mechanical tests and in vitro evaluations. A glass-ceramic macroporous scaffold with a homogenously distributed and highly interconnected porosity was obtained. The amount and size of the introduced porosity could be tailored using various amounts of polyethylene powders of different size.
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PMID:Macroporous bioactive glass-ceramic scaffolds for tissue engineering. 1712 21

Sol-gel derived bioactive glasses of the 70S30C (70mol% SiO2, 30mol% CaO) composition have been foamed to produce 3D bioactive scaffolds with hierarchical interconnected pore morphologies similar to trabecular bone. The aim of this study was to investigate primary human osteoblast response to porous bioactive glass scaffolds. The scaffolds supported osteoblast growth and induced differentiation, within the 3-week culture period, as depicted by enhanced ALPase enzymatic activity, without the addition of supplementary factors such as ascorbic acid, beta-glycerophosphate and dexamethasone. This is the first time this has been observed on a bioactive glass that does not contain phosphate. Deposition of extracellular matrix was also confirmed by enhanced production of the extracellular matrix protein collagen type I. SEM showed indications of mineralized bone nodule formation without the addition of growth factors. The 70S30C bioactive glass scaffolds therefore fulfil many of the criteria for an ideal scaffold for bone tissue engineering applications.
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PMID:Extracellular matrix formation and mineralization on a phosphate-free porous bioactive glass scaffold using primary human osteoblast (HOB) cells. 1717 22

Y0.9Eu0.1BO3 phosphor layers were deposited on monodisperse SiO2 particles of different sizes (300, 570, 900, and 1200 nm) via a sol-gel process, resulting in the formation of core-shell-structured SiO2@Y0.9Eu0.1BO3 particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence (CL) spectra as well as lifetimes were employed to characterize the resulting composite particles. The results of XRD, FE-SEM, and TEM indicate that the 800 degrees C annealed sample consists of crystalline YBO3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution. Under UV (240 nm) and VUV (172 nm) light or electron beam (1-6 kV) excitation, these particles show the characteristic 5D0-7F1-4 orange-red emission lines of Eu3+ with a quantum yield ranging from 36% (one-layer Y0.9Eu0.1BO3 on SiO2) to 54% (four-layer Y0.9Eu0.1BO3 on SiO2). The luminescence properties (emission intensity and color coordinates) of Eu3+ ions in the core-shell particles can be tuned by the coating number of Y0.9Eu0.1BO3 layers and SiO2 core particle size to some extent, pointing out the great potential for these particles applied in displaying and lightening fields.
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PMID:Monodisperse and core-shell-structured SiO2@YBO3:Eu3+ spherical particles: synthesis and characterization. 1733 18

A self-humidifying membrane based on low-cost sulfonated poly (ether ether ketone) (SPEEK) hybrid with sulfated zirconia (SO4(2-)/ZrO2, SZ)-supported platinum catalyst (Pt-SZ catalyst) was investigated for fuel cell applications. The SZ particle, a solid-state superacid with hygroscopic and high proton conductivity properties, was employed as the catalyst support. The SPEEK/Pt-SZ self-humidifying membrane was characterized by TEM and SEM coupled with EDX. FT-IR was conducted to verify the effect of SPEEK/Pt-SZ membrane on catalytic combination of crossover hydrogen and oxygen. To display the advantages of Pt-SZ catalyst as the additive, the IEC, water uptake, proton conductivity, single-cell performance, and areal resistance measurements were compared between the plain SPEEK membrane, SPEEK/Pt-SiO2 membrane, and the SPEEK/Pt-SZ membrane. The SPEEK/Pt-SZ membrane exhibited the highest IEC value, proton conductivity, single-cell performance, and the lowest areal resistance relative to the plain SPEEK and SPEEK/Pt-SiO2 membranes. The SPEEK/Pt-SZ self-humidifying membrane exhibited peak power density of 1.0 W/cm2 under dry operation condition compared with 0.89 W/cm2 and 0.58 W/cm2 of SPEEK/Pt-SiO2 and plain SPEEK membranes, respectively. The incorporation of the catalytic, hygroscopic and proton conductive Pt-SZ catalyst in the SPEEK/Pt-SZ self-humidifying membrane facilitated water balance and proton conduction, and accordingly improved its single cell performance under dry operation. In addition, the enhanced OCV and the decreased areal ohmic resistance confirmed the promotion effect of Pt-SZ catalyst in the self-humidifying membrane on suppressing reactant crossover and the membrane self-humidification.
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PMID:Promotion of PEM self-humidifying effect by nanometer-sized sulfated zirconia-supported Pt catalyst hybrid with sulfonated poly(ether ether ketone). 1752 Nov 83

Wet spray pyrolysis of fine, well-dispersed a SiO2 sol was used for the deposition of thin films of silicon dioxide. The sol was obtained by hydrothermal precipitation of silicon acid from a solution at pH = 10. The morphology, roughness, phase composition, chemical homogeneity and the mechanism of the films were investigated by SEM, EDS and IR spectroscopy. The obtained results show a complete covering of the titanium substrate with SiO2 after 3 h of deposition. It was observed that the film thickness increased from 3 to 19 microm, the roughness of the film decreased from 12 to 3 microm, while the morphology of the deposit changed considerably. A hydroxyapatite film was prepared on the so-obtained SiO2 thin film by spray pyrolysis deposition and its morphology and phase composition were investigated.
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PMID:Thin films of SiO2 and hydroxyapatite on titanium deposited by spray pyrolysis. 1791 12

TiO2/SiO2/Fe3O4 composite was synthesized by sol-gel technique for silica and titania coatings on magnetite core to enable recovery after photocatalytic degradation. Carbon coating was also carried out by calcination of TiO2/SiO2/Fe3O4 under nitrogen atmosphere in presence of PVA as a source of carbon to enhance the adsorption of organic compounds on catalyst surface and to get better activity. All prepared samples were characterized using EDX, CN analyzer, XRD, BET and SEM. Degradation of methyl orange dye was used to assess the photocatalytic performance of the prepared samples. Calcination temperature was found to affect rate of reaction because of the formation of rutile phase at high calcination temperature. Carbon coated samples unexpectedly exhibited lower rate of reaction at almost all calcination temperatures.
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PMID:Preparation and characterization of magnetically separable photocatalyst (TiO2/SiO2/Fe3O4): effect of carbon coating and calcination temperature. 1808 53

Eu(DBM)3Phen/silica nanospheres with a uniform diameter of approximately 40 nm and the characteristic fluorescence of Eu3+ ions have been synthesized by a microemulsion method. SEM and TEM analysis indicate that the hybrid nanospheres are core/shell structures with fine spherical surfaces and that Eu(DBM)3Phen has been successfully enveloped in the SiO2 spheres as chromophore cores. IR absorption spectra and photoluminescence spectra suggest that the hybrid nanoparticles are promising materials for bioassay.
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PMID:Europium(III) complexes/silica hybrid nanospheres synthesized in microemulsion. 1846 27

Hydrophilic silica (SiO2) nanoparticles were dispersed in solutions of poly(methyl methacrylate) (PMMA) and in solutions of a commercial poly(alkyl siloxane) (Rhodorsil 224), and the suspensions were sprayed on glass surfaces. The effect of the particle concentration on the hydrophobic character of PMMA-SiO2 and Rhodorsil-SiO2 films was investigated and showed the following: (i) Static contact angles (theta s), measured on surfaces that were prepared from dilute dispersions (particle concentration <1% w/v), increase rapidly with particle concentration and reach maximum values (154 and 164 degrees for PMMA-SiO2 and siloxane-SiO2, respectively). Further increases in particle concentration do not have any effect on theta s. (ii) The effect of particle concentration on the contact angle hysteresis (thetaAlpha - thetaR) is more complicated: as the particle concentration increases, we first notice an increase in hysteresis, which then decreases and finally becomes constant at elevated particle concentrations. The lowest thetaAlpha - thetaR values were 5 degrees for PMMA-SiO2 and 3 degrees for siloxane-SiO2, respectively. (iii) SEM and AFM images show that a two-length-scale hierarchical structure is formed on the surface of the superhydrophobic films. It is demonstrated that superhydrophobicity can be achieved using various hydrophilic nanoparticles (alumina and tin oxide nanoparticles were successfully tested) and that the substrate has almost no effect on the hydrophobic character of the applied coatings, which were produced on silicon, concrete, aluminum, silk, wood, marble, and of course glass. The results are discussed in light of Wenzel and Cassie-Baxter models.
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PMID:Superhydrophobic composite films produced on various substrates. 1872 Sep 65

A 45S5 bioactive glass (nominal composition: 46.1 mol.% SiO2, 2.6 mol.% P2O5, 26.9 mol.% CaO, 24.4 mol.% Na2O) was electrothermally poled by applying voltages up to 750 V for 45 min at 200 degrees C, and the thermally stimulated depolarization currents (TSDCs) were recorded. Changes in chemical composition and electrical properties after poling were investigated by TSDC measurements, impedance spectroscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX). The poling led to the formation of interfacial layers underneath the surface in contact with the electrodes. Under the positive electrode, the layer was characterized by Na+ ion depletion and by a negative charge density, and the layer was more resistive than the bulk. The influence of poling on the bioactivity was studied by immersion of samples in simulated body fluid (SBF) with subsequent cross-sectional SEM/EDX and X-ray diffraction analysis. It was found that poling leads to morphological changes in the silica-rich layer and to changes in the growth rate of amorphous calcium phosphate and bone-like apatite on the glass surface. The bone-like apatite layer under the positive electrode was slightly thicker than that under the negative electrode.
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PMID:Bioactivity of electro-thermally poled bioactive silicate glass. 1909 52

We have studied growth behavior of carbon nanotubes (CNTs) on iron (Fe) catalyzed substrate using newly developed atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD) system. To investigate the improved growth performance with simple equipment and process on large scale, a new AP-PECVD system containing different concept on downstream gas was designed and manufactured. As a catalyst, either sputtered or evaporated Fe thin film on SiO2/Si substrate was used and acetylene gas was used as a carbon source. We observed growth behavior of CNTs such as height, rate and density were strongly affected by plasma power. The maximum height of 427 microm and 267 microm was synthesized under RF plasma power of 30 W for 30 min and 40 W for 3 min, respectively. The growth rate dramatically increased to 6.27 times as plasma power increased from 30 to 40 W which opens the possibility the mass production of CNTs. By SEM and TEM observation, it was verified the grown CNTs was consists of mixture of single-wall and multi-wall CNTs. The graphitization ratio was measured to be 0.93, indicating that the graphitized CNTs forest was formed and relatively high purity of CNTs was synthesized, being useful for nano-composite materials to reinforce the strength. From our experiments, we can observe that the height and growth rate of CNTs is strong function of plasma power.
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PMID:Investigation on growth behavior of CNTs synthesized by atmospheric pressure plasma enhanced chemical vapor deposition system on Fe catalyzed substrate. 1919 78


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