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Hydrogels studied in this investigation, synthesized starting from agarose and Carbomer 974P, were chosen for their potential use in tissue engineering. The strong ability of hydrogels to mimic living tissues should be complemented with optimized degradation time profiles: a critical property for biomaterials but essential for the integration with target tissue. In this study, chosen hydrogels were characterized both from a rheological and a structural point of view before studying the chemistry of their degradation, which was performed by several analysis: infrared bond response [Fourier transform infrared (FT‐IR)], calorimetry [differential scanning Calorimetry (DSC)], and % mass loss. Degradation behaviors of Agar‐Carbomer hydrogels with different degrees of crosslinkers were evaluated monitoring peak shifts and thermal property changes. It was found that the amount of crosslinks heavily affect the time and the magnitude related to the process. The results indicate that the degradation rates of Agar‐Carbomer hydrogels can be controlled and tuned to adapt the hydrogel degradation kinetics for different cell housing and drug delivery applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   
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The photoluminescence lifetimes of Si quantum wires and dots have been previously calculated within a continuum model that takes into account the anisotropy of silicon band structure. Here, we present our calculations on the optical transitions in Si quantum wires modulated by a quantum dot. The geometrical parameters of the buldged wire are appropriate for porous Si and the ground state is localized. The photoluminescence lifetimes are calculated and compared with those of straight wires and dots. The magnitude of the lifetime is sensitive to the structural parameters of the nanostructures. Lifetimes varying from nanoseconds to milliseconds have been obtained. The results of the calculations provide insight to the optical properties of Si nanostructures.  相似文献   
4.
It is known that the thermoelectric efficiency of nanowires increases when their diameter decreases. Recently, we proposed that increase of the thermoelectric efficiency could be achieved by modulating the diameter of the nanowires. We showed that the electron thermoelectric properties depend strongly on the geometry of the diameter modulation. Moreover, it has been shown by another group that the phonon conductivity decreases in nanowires when they are modulated by dots. Here, the thermoelectric efficiency of diameter modulated nanowires is estimated, in the ballistic regime, by taking into account the electron and phonon transmission properties. It is demonstrated that quasi-localized states can be formed that are prosperous for efficient thermoelectric energy conversion.  相似文献   
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Ag-doped sol-gel derived bioactive glass-ceramic particles (Ag-BG) were used to fabricate highly porous scaffolds exhibiting advanced antibacterial properties and formation of an apatite-like layer. The applied heat treatment for the development of the 3D Ag-BG scaffolds was selected after the characterization of the thermal behavior of Ag-BG particles using differential thermal analysis (DTA), thermogravimetric analysis (TGA), and hot stage microscopy (HSM). The structural characteristics of the scaffolds were studied using optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), micro-computerized tomography (Micro-CT), X-ray diffraction (XRD), Fourier-transformed infrared (FTIR), magic angle spinning nuclear magnetic resonance (MAS-NMR), and transmission electron microscopy (TEM) to correlate how the characteristics in the hierarchal structure of the Ag-BG scaffolds affected their antibacterial performance and apatite forming ability. Methicillin-resistant Staphylococcus aureus (MRSA) was used to evaluate the antibacterial response of the Ag-BG scaffolds. The observed characteristics make these Ag-BG scaffolds attractive candidates for biomedical applications.  相似文献   
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The fabrication and characterization of sol–gel derived hydroxyapatite–calcium oxide (HAp–CaO) material is investigated focusing on the effect of the addition of a bioactive glass on the material bioactive behaviour through the fabrication of a novel HAp–CaO (70 wt.%)–bioactive glass (30 wt.%) composite material. The bioactive behaviour of the materials was assessed by immersion studies in Simulated Body Fluid (SBF) and the alterations of the materials surfaces after soaking periods in SBF were characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). A brittle and weakly crystalline carbonate hydroxyapatite (HCAp) layer was found to develop on the surface of all samples, few hours after immersion in SBF, confirming the high bioactivity of the material. Alterations of the morphology of the developed HCAp layer, which led to a more compact structure, were observed on the surface of composite samples after 7 days of immersion in SBF. The presence of the CaO phase seems to accelerate the formation of HCAp, while the bioactive glass affects both the morphology and cohesion of the developed layer.  相似文献   
7.
The aim of this study is the fabrication of dental glass-ceramics able to elicit bioactive behaviour around the margins of fixed restorations and to provide a bioactive surface which can lead to periodontal tissue attachment, providing complete sealing of the marginal gap between tooth and fixed prosthesis. Sol–gel technique is applied for the fabrication of a new glass-ceramic in the system SiO260%–P2O53%–Al2O314%–CaO6%–Na2O7%–K2O10% (wt.%) and a related composite material combining this phase with the bioactive glass 58S. This composite material aims to create a bioactive surface which could lead to periodontal tissue attachment, providing complete sealing of the marginal gap between tooth and fixed prosthesis. The microstructural and thermal properties and the bioactive behaviour of the new materials were determined and were observed to be similar in respect to a commercial leucite based fluorapatite dental glass-ceramic. The feasibility of the new composite material to be applied as coating on the base porcelain as well as the bioactive behaviour of the fabricated coated specimes were confirmed.  相似文献   
8.
The energy subband structure of nanowires with periodically modulated cross-section has been calculated within a continuum model and the effective mass approximation. A characteristic structure of minibands and resonances has been found. This leads to a remarkable enhancement of the Seebeck coefficient compared with that of nonmodulated nanowires of the same dimensions. The Seebeck coefficient enhancement depends on the interplay between the thermal broadening and the quantum confinement. It is pointed out here that the modulation geometry and material parameters can provide design tools for Seebeck coefficient enhancement in nanowires.  相似文献   
9.
The sintering process of 45S5 Bioglass® powder (mean particle size < 5 μm) was investigated by using different thermal analysis methods. Heating microscopy and conventional dilatometry techniques showed that bioactive glass sinters in two major steps: a short stage in the temperature range 500–600 °C and a longer stage in the range 850–1100 °C. The optimal sintering temperature and time were found to be 1050 °C and 140 min, respectively. Differential thermal analysis (DTA) showed that Bioglass® crystallises at temperatures between 600 and 750 °C. The characteristic crystalline phases were identified by Fourier Transformed Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). The crystallisation kinetics was studied by DTA, using a non-isothermal method. The Kissinger plot for Bioglass® powder heated at different heating rates between 5 and 30 °C/min yielded an activation energy of 316 kJ/mol. The average value of Avrami parameter determined using the Augis–Bennett method was 0.95 ± 0.10, confirming a surface crystallisation mechanism. After sintering at 1050 °C for 140 min, the main crystalline phase was found to be Na2Ca2Si3O9. The results of this work are useful for the design of the sintering/crystallisation heat treatment of Bioglass® powder which is used for fabricating tissue engineering scaffolds with varying degree of bioactivity.  相似文献   
10.
The modification of a widely used dental ceramic by a bioactive glass via sol–gel method resulted in the fabrication of novel dental ceramic composites with bioactive behavior. The presence of leucite (Lt), apatite (Ap), various calcium silicate phases (CS) and a glassy aluminosilicate matrix were detected, while after sintering the predominance of wollastonite (W) among the other calcium silicate phases was observed, along with further crystallization of apatite. Concerning the bioactivity, the onset of the apatite formation was directly dependent on the bioactive glass amount, while a delay of the sintered specimens compared to the raw powders was also observed.  相似文献   
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