Papers by Keyword: Poly(methyl methacrylate) (PMMA)

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Authors: Chien Hua Lin, Ti Kuang Hou, Dong Cherng Wen
Abstract: Electromagnetic optical scanning mirrors for both horizontal and vertical scanning of a Laser Projection Display have been proposed. Electromagnetic actuation is selected because of the millimeter-sized mirror. For low cost reason, the glass and PMMA films are respectively used as the main structure of horizontal and vertical scanning mirrors. A mathematical model considering the operation frequency of the Laser Projection Display has been derived to fast design the geometry of the scanning mirror. In order to machine scanning mirrors with high quality geometry, the 193 nm excimer laser is used as the major machine tool. Different control circuits have been developed to control both horizontal and vertical scanning. The scanning frequencies, 4.15 kHz and 260 Hz respectively for horizontal and vertical scanning mirrors, have been measured by laser Doppler vibrometer. Comparing to other optical scanners, 193 nm excimer laser machined optical scanning mirrors have advantages in low cost and easy to fabricate. In this paper, a Laser Projection Display consisting of the horizontal and vertical scanning mirrors has also been built to show the application potential. A 2-D single color image with resolution of 46 × 32 pixels, 4.15 kHz of horizontal scanning frequency and 60Hz of regulated vertical scanning frequency has been demonstrated.
Authors: Sarla Sharma, Rishi Vyas, Y.K. Vijay
Abstract: Swift heavy ion induced modification in the optical properties of TiO2/Poly (Methyl methacrylate) nanocomposites is reported in this paper. The as prepared anatase TiO2 nanoparticles were uniformly dispersed in PMMA matrix using solution casting method. These nanocomposites were then irradiated with Ag+12 (120 MeV) ion beam and characterized by X-ray diffraction, scanning electron microscopy, UV-Vis spectroscopy, PL and Raman spectroscopy. The PL spectra exhibited an enhanced broad emission peak in visible region (400 nm - 750 nm) while UV-Vis spectroscopy revealed an increased absorption in visible region in irradiated specimen in comparison to unirradiated sample.
Authors: S. Shinzato, Takashi Nakamura, Tadashi Kokubo
Authors: Anton Valkov, Faina Nakonechny, Marina Nisnevitch
Abstract: Photosensitizers immobilized in polymers can serve as antibacterial surfaces or coatings and can be applied for disinfection of water or medical instruments. The antibacterial activity of the immobilized photosensitizers is based on their excitation by visible light followed by energy transfer from the photosensitizers to oxygen dissolved in an aqueous phase which produces reactive oxygen species that cause irreversible damage to bacterial cells. The photosensitizer Rose Bengal immobilized in polystyrene, polycarbonate and poly (methyl methacrylate) was shown to eradicate Gram-positive Staphylococcus aureus bacteria under moderate illumination.
Authors: S. Shinzato, Takashi Nakamura, Koji Goto, Tadashi Kokubo
Abstract: A new bioactive bone cement (cGBC) consisting of crystallized MgO-CaO-SiO2-P2O5 glass beads and high-molecular-weight polymethyl methacrylate (hPMMA) has been developed to overcome the degradation seen with a previously reported cement (GBC) consisting of MgO-CaO-SiO2-P2O5-CaF2 glass beads and hPMMA. The purpose of the present study was to evaluate the degradation of cGBC using an in vivo aging test, and to compare the degradation of cGBC with that of GBC. Hardened rectangular specimens (20x4x3mm) were prepared from both cements. Their initial bending strengths were measured using the three-point bending method. GBC and cGBC specimens were then implanted into the dorsal subcutaneous tissue of rats, removed after 6 or 12 months, and tested for bending strength. The initial bending strengths (MPa) of GBC and cGBC were 141.9±1.8 and 144.4±2.4, respectively, while at 6 months they were 109.1±2.6 and 114.1±4.9, and at 12 months they were 109.1±3.2 and 113.1±3.3, respectively. Although the difference in initial bending strengths was not significant, the bending strength of cGBC was significantly higher than that of GBC at 6 and 12 months, indicating that cGBC is more resistant to cement degradation. The bending strengths of both GBC and cGBC decreased significantly from 0 to 6 months but did not change significantly thereafter. Thus, degradation of cGBC and GBC does not appear to continue after 6 months. We believe that cGBC and GBC are strong enough for use under weight-bearing conditions and that their mechanical strength (especially that of cGBC) is retained in vivo.
Authors: Koji Goto, Masami Hashimoto, Hiroaki Takadama, Jiro Tamura, Shunsuke Fujibayashi, Shin Hasegawa, Keiichi Kawanabe, Tadashi Kokubo, Takashi Nakamura
Abstract: Three types of polymethylmethacrylate (PMMA)-based composite cements containing 40− 56 wt% micron-sized titania (titanium oxide) particles, designated ST2-40c, ST2-50c, and ST2-56c, were developed as bone substitutes for vertebroplasty, and evaluated for their mechanical, setting, and biological properties. In animal experiments, ST2-50c and ST2-56c were implanted into rat tibiae and solidified in situ. Their biological properties were evaluated at 6 and 12 weeks after implantation. Compressive strength, bending strength, and bending modulus increased with increasing titania content. Peak temperature during the setting reaction decreased as the filler content increased. ST2-56c had direct contact with bone over larger areas than ST2-50c at 6 and 12 weeks. Data from the present study indicated that ST2-56c is a good candidate as a bone substitute for vertebroplasty.
Authors: B.J.M. Leite Ferreira, M.G.G.M. Duarte, M. Helena Gil, Rui N. Correia, J. Román, Maria Vallet-Regí
Abstract: Two materials with potential application in bone tissue repair have been developed: 1) a non-biodegradable composite based in a new methacrylic-co-acrylic matrix; and 2) a biodegradable composite based in a chitosan (Ch) matrix. Both matrices were reinforced with glass-ceramic particles of composition (mol%) 70 SiO2 – 30 CaO. The in vitro bioactivity of composites was assessed by soaking in simulated body fluid (SBF) for periods of up to 7 days at 37º C. X-ray diffraction (XRD) and scanning electron microscopy coupled with X-ray energy dispersive spectroscopy (SEM-EDS) were used for deposit identification after different soaking periods. Calcium phosphate particulate deposits were detected after 3 days of immersion, followed by growth and maturation towards apatite.
Authors: Masami Hashimoto, Hiroaki Takadama, Mineo Mizuno, Tadashi Kokubo, Koji Goto, Takashi Nakamura
Abstract: Bioactive bone cement with mechanical properties higher than that of commercial polymethylmethacrylate (PMMA) bone cement are strongly desired to be developed. In the present study, PMMA-based cement incorporated with nano-sized rutile particles was prepared. The PMMA-based cement (rutile content was 50 wt%) shows the compressive strength (136 MPa) higher than that of commercial PMMA bone cement (88 MPa). The hardened cement formed apatite on the surface in a simulated body fluid within 3 days. Therefore, this PMMA-based cement incorporated with rutile particles might be useful as cement for fixation of prostheses as well as self-setting bone substitutes, because of its high apatite forming ability and mechanical strength.
Authors: L. Sharma, Giuseppe Pezzotti
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