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Gel Samples (gel + sample)
Selected AbstractsA fluorescence study on swelling of hydrogels (PAAm) at various cross-linker contentsADVANCES IN POLYMER TECHNOLOGY, Issue 4 2009Demet Kaya Akta Abstract Disk-shaped acrylamide (AAm) gels were prepared from AAm with various N,N,-methylenebisacrylamide (Bis) contents as cross-linker in the presence of ammonium persulfate as an initiator by free-radical cross-linking copolymerization in water. Polyacrylamide (PAAm) gels were dried before using for swelling experiments. Steady-state fluorescence spectrometer was employed during the swelling of PAAm hydrogels in water. Pyranine was introduced as a fluorescence probe. Fluorescence intensity of pyranine from various Bis content gel samples was measured during in situ swelling process. It was observed that fluorescence intensity decreased as swelling has proceeded. Gravimetric and volumetric experiments were also performed. The Li,Tanaka equation was used to determine the swelling time constants, ,c, and cooperative diffusion coefficients, Dc, from intensity, weight, and volume variations during the swelling processes. It was observed that swelling time constants, ,c, increased and diffusion coefficients, Dc, decreased as the cross-linker content was increased. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 28:215,223, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20163 [source] Temperature Profiles in a Cylindrical Model Food During Pulsed Microwave HeatingJOURNAL OF FOOD SCIENCE, Issue 7 2001H.W. Yang ABSTRACT: Cylindrical 2%-agar gel samples were heated by pulsed and continuous microwave applications. The total microwave application time of 3 min was maintained for all experiments. Sample temperature was measured at various depths along the radial dimension to experimentally determine the internal temperature profile as a function of heating time. A local hot spot was observed at the center portion of the sample during the continuous microwave application. This hot spot was less significant during pulsed microwave applications, especially when longer intermittent power-off times were employed. An implicit finite-difference model was used to estimate temperature profiles within the sample during microwave heating. The estimated temperature profiles matched the experimental values well. [source] Effect of gluten content on recrystallisation kinetics and water mobility in wheat starch gelsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2004Xin Wang Abstract The effect of gluten on starch retrogradation at 5 °C was studied using 1H NMR relaxometry. Gels were made from gluten and starch at 27.8 and 38.5% total solids and with gluten comprising either 10, 15 or 20% of the solids. Changes in the transverse relaxation time constant (T2) were related to water mobility. Mono-exponential analysis of relaxation curves showed that, in general, gluten retarded starch retrogradation. T2 values in gluten gels also decreased during storage, but to a much lesser extent. Distributed exponential analysis showed that two distinct regions of T2 were observed in all samples. During aging, the peak values of both regions shifted to lower values for all gels. Starch gel samples showed the most significant shift, and gluten gels showed the least. The three levels of gluten addition in starch/gluten gels produced similar shifts. For all samples the signal intensity of the less mobile region decreased more dramatically than that of the more mobile region during storage. It was suggested that gluten retards water loss in the granule remnants. Copyright © 2004 Society of Chemical Industry [source] Removal of dyes from water by poly(vinyl pyrrolidone) hydrogel,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2006Bahire Filiz Senkal Abstract The interaction between polymer and dye leading to polymer-dye complex formation exhibits many interesting and important practical features. For this purpose, a hydrogel was prepared by crosslinking copolymerization of vinyl pyrrolidone with tetraallyl ammonium bromide in aqueous solution, using K2S2O8 as a radical initiator. Dye extraction experiments were carried out simply by contacting wetted gel samples with aqueous dye solutions at room temperature. Capacities were determined by colorimetric analysis of the residual dye contents. The hydrogel swelled in water showing that reasonable high dye sorption capacity (0.71,1.13,g per gram of gel) was achieved. This material is also able to remove the anionic dyes completely even from highly diluted aqueous dye solutions. No trace absorbance was detected in the visible range, after processing. Copyright © 2006 John Wiley & Sons, Ltd. [source] Pyroelectric investigations of a hydrogen bonded ferroelectric liquid crystal gel by LIMMPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2005Jianjun Li Abstract The laser intensity modulation method (LIMM) is employed to determine spatially resolved polarization distributions in sandwich cells containing a hydrogen-bonded ferroelectric liquid crystal (FLC) gel. At no external electric fields, contributions to the distributions at the surface of the FLC layer are dominating in all the samples with different concentration of gel former. These are attributed to non-vanishing polarization due to surface interaction. In this case, the effect of hydrogen-bonded network on the polarization distribution is not visible. In external electric fields, additional contribution to the resulting distribution caused by the induced polarization due to unwinding the FLC helix has been observed. Furthermore, the influence of hydrogen-bonded network on the polarization distribution is also detected when the gel former content is increased up to 5.0,wt%. Therein the shape of the measured pyrospectra is completely different to other FLC gel samples with lower gel former concentration, where their maximum distributions still locate at the surface of FLC layer which is comparable to the initial field-free state. These result indicate that the helical structure and orientation director of FLC are able to be stabilized effectively by the gel network even under strong external electric field. Copyright © 2004 John Wiley & Sons, Ltd. [source] Effects of Cyclic Hydrostatic Pressure on the Metabolism of Human Osteoarthritic Chondrocytes Cultivated in a Collagen GelARTIFICIAL ORGANS, Issue 2 2007Karsten Gavénis Abstract:, Among other parameters, the application of mechanical force may provide an important stimulus in modulating the structure and function of tissue-engineered articular cartilage. We developed a cultivation chamber in which six collagen type-I gel samples, seeded with human osteoarthritic chondrocytes, can be cultivated simultaneously. A cyclic hydrostatic pressure of up to 40 kPa with a frequency of 0.0125 Hz was applied, and cultivation was performed for 1, 4, 7, or 14 days. Histological examinations revealed a spheroidal cell morphology in the treatment group. In contrast, control samples of the same patients represented a more fibroblastic appearance. Collagen type-II (col-II) protein was found in the very pericellular region of all investigated samples; the col-II content did not obviously vary between the control and treatment groups. In the treatment group, col-II and aggrecan gene expression were elevated. A spectrophotometric quantification of proteoglycan concentrations in media supernatants revealed a statistically significant enhancement in the treatment group. [source] Flow cytometric and morphological characterization of platelet-rich plasma gelCLINICAL ORAL IMPLANTS RESEARCH, Issue 6 2006Juan Emilio Fernández-Barbero Abstract Background of problems: Platelet-rich plasma (PRP) gel is derived from an autogenous preparation of concentrated platelets and is widely used in implant dentistry as a vector for cell growth factors. However, limited data are available on its structure and composition. The present study was aimed at providing a flow cytometric and ultrastructural characterization of PRP gel. Materials and methods: Twenty PRP gel samples were obtained from healthy volunteers. These PRP gel specimens were prepared for transmission (TEM) and scanning electron microscopy (SEM) examination of their morphological ultrastructure. Flow cytometry with CD41-PE monoclonal antibody was used to detect platelet cells, as this antibody recognizes human-platelet-specific antigen CD41. Results: Both SEM and TEM showed that PRP gel contains two components: a fibrillar material with striated band similar to fibrin filaments, and a cellular component that contains human platelet cells. Both techniques indicated that no morphological elements were bound between the cellular component and the fibrillar material. The cells were confirmed as platelet cells by flow cytometric study after incubation with specific monoclonal antibody CD41-PE. Conclusion: PRP gel contains a fibrillar and a cellular (largely human platelet cell) component. This unique structure may be capable of acting as a vehicle for carrying of cells that are essential for soft/hard tissue regeneration. [source] | |||||||||||||