Peri-implantitis is a chronic inflammatory process with advanced bone loss and impaired healing potential. For peri-implantitis treatment, tissue engineering can be applied to enhance bone regeneration of peri-implant defects. This study aimed to evaluate ex vivo bone morphogenetic protein 2 (BMP2) gene delivery using canine periodontal ligament stem cells (PDLSCs) for regeneration of peri-implantitis defects. Canine PDLSCs were transduced with adenoviral vectors containing BMP2 (BMP2/PDLSCs). After peri-implantitis was induced by ligature placement in six beagle dogs, regenerative procedures were performed; hydroxyapatite (HA) particles and collagen gel with autologous canine PDLSCs (PDLSC group) or BMP2/PDLSCs (BMP/PDLSC group) or without cells (control group) were grafted into the defects and covered by an absorbable membrane. Three months later, the animals were sacrificed. In vitro, BMP2/PDLSCs showed similar levels of stem cell properties to PDLSCs, such as colony-forming efficiency and expression of MSC markers STRO-1 and CD 146. BMP2/PDLSCs produced BMP-2 until day 21 at a concentration of 4-8 ng/mL. In vivo, the BMP2/PDLSC group showed significantly more new bone formation and re-osseointegration in peri-implantitis defects compared to the other groups. In conclusion, ex vivo BMP2 gene delivery using PDLSCs enhanced new bone formation and re-osseointegration in peri-implantitis defects.

The effect of substituting sodium for calcium on enhanced osteoconductivity of hydroxyapatite was newly investigated. Sodium-substituted hydroxyapatite was synthesized by reacting calcium hydroxide and phosphoric acid with sodium nitrate followed by sintering. As a control, pure hydroxyapatite was prepared under identical conditions, but without the addition of sodium nitrate. Substitution of calcium with sodium in hydroxyapatite produced the structural vacancies for carbonate ion from phosphate site and hydrogen ion from hydroxide site of hydroxyapatite after sintering. The total system energy of sodium-substituted hydroxyapatite with structural defects calculated by ab initio methods based on quantum mechanics was much higher than that of hydroxyapatite, suggesting that the sodium-substituted hydroxyapatite was energetically less stable compared with hydroxyapatite. Indeed, sodium-substituted hydroxyapatite exhibited higher dissolution behavior of constituent elements of hydroxyapatite in simulated body fluid (SBF) and Tris-buffered deionized water compared with hydroxyapatite, which directly affected low-crystalline hydroxyl-carbonate apatite forming capacity by increasing the degree of apatite supersaturation in SBF. Actually, sodium-substituted hydroxyapatite exhibited markedly improved low-crystalline hydroxyl-carbonate apatite forming capacity in SBF and noticeably higher osteoconductivity 4 weeks after implantation in calvarial defects of New Zealand white rabbits compared with hydroxyapatite. In addition, there were no statistically significant differences between hydroxyapatite and sodium-substituted hydroxyapatite on cytotoxicity as determined by BCA assay. Taken together, these results indicate that sodium-substituted hydroxyapatite with structural defects has promising potential for use as a bone grafting material due to its enhanced osteoconductivity compared with hydroxyapatite.

In the synthesis of hydroxyapatite powders by spray pyrolysis, control of the particle size was investigated by varying the initial concentration of the precursor solution and the pyrolysis temperature. Calcium phosphate solutions (Ca/P ratio of 1.67) with a range of concentrations from 0.1 to 2.0 mol/L were prepared by dissolving calcium nitrate tetrahydrate and diammonium hydrogen phosphate in deionized water and subsequently adding nitric acid. Hydroxyapatite powders were then synthesized by spray pyrolysis at 900°C and at 1500°C, using these calcium phosphate precursor solutions, under the fixed carrier gas flow rate of 10 L/min. The particle size decreased as the precursor concentration decreased and the spray pyrolysis temperature increased. Sinterability tests conducted at 1100°C for 1 h showed that the smaller and denser the particles were, the higher the relative densities were of sintered hydroxyapatite disks formed from these particles. The practical implication of these results is that highly sinterable small and dense hydroxyapatite particles can be synthesized by means of spray pyrolysis using a low-concentration precursor solution and a high pyrolysis temperature under a fixed carrier gas flow rate.

Although the immediate peri-implantitis model is challenging for regeneration, it may be able to replace the conventional model to study regenerative peri-implantitis treatment due to its short experimental time and similar defect configuration.

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Sensor networks are composed of a great number of sensor nodes with constrained battery. Disjoint multipath scheme based flooding method has a merit that efficiently construct multipath in irregular networks, but causes lots of energy consumption in networks. Flooding method is not a suitable technology in wireless sensor networks with constrained battery. We introduce energy-efficient geographic routing scheme considered as an efficient, simple, and scalable routing protocol for wireless sensor networks. The geographic routing scheme on multipath generates a problem with a congestion. So we introduce the concept of multipath pipeline as a congestion avoidance strategy. But multipath pipelines have a big problem on the boundary of holes under irregular networks. We propose a novel disjoint multipath scheme as combined method with geographic routing scheme and hole detouring algorithm on multipath. A novel disjoint multipath scheme constructs disjoint multipath pipelines efficiently for reliability without a collision in irregular wireless sensor networks. Simulation results are provided to validate the claims.

Mobile TV" is recently emerging across the world. In Korean and Japanese markets, a next generation digital broadcasting service, S-DMB system, has been developed for automotive and handheld terminals. Because S-DMB service is mobile and personalized, the market demand is expected to be higher and broader than existing household-based broadcasting services. S-DMB service offers high-quality streaming videos and CD quality music at low cost [1]. S-DMB adopts the code-division multiplexing (CDM) technology and supports the ITU-R BO/1130-4 Digital System E standard. S-DMB service provides extended coverage using a satellite in most areas and gap fillers in shadow areas such as inside buildings and subways. To maximize the coverage with a satellite, a diversity architecture is strongly recommended for the S-DMB tuner by service providers.Main challenges of an S-DMB tuner are small size, low power consumption, low noise and wide dynamic range. At diversity operating mode, small gain difference and high path isolation between diversity paths are also important constraints over the wide dynamic range. In this paper, a fully monolithic diversity 2.6GHz S-DMB tuner IC is presented. The proposed solution has a die size of 2.3×2.3mm 2 , an NF of less than 1.8dB, a path isolation of more than 25dB, and a DR of over 100dB while it has a less than 4dB path-gain mismatch and a power consumption of 112mW.To reduce size and power consumption for use in battery-operated mobile-TV terminals, two signal path units for diversity architecture are integrated into a single chip with a shared common LO unit, as shown in Fig. 33.6.1. For both signal path units, direct conversion architecture is used to further reduce the size and power consumption. Over 100dB DR, to receive signals from both a satellite and gap fillers, is achieved by the mixed gain-control scheme: wide continuous gain control for the VGA and step gain control for the RF front-end. This step-gain-control scheme is used to achieve lower noise, smaller size, and lower power RF front-end design by eliminating requirements for RF VGA and associated control blocks.The RF front-end of both signal path units consists of a low-noise step-gain amplifier (LNSGA), a low-noise step-gain down-conversion I/Q mixer (LNSGDCM), and a quadrature LO generator as shown in Fig. 33.6.2. The LNSGA has two gain modes: a highgain mode and a low-gain mode. For the high-gain mode, an inductively degenerated cascode structure is used to achieve 17dB gain and 1.2dB NF while drawing only 4mA. For the lowgain mode, a digitally adjusted resistor (R1) and a MOS switch (Q3) are used for -13dB loss and over +25dBm IIP3. Coupling between two LNSGA via bonding wires and ground paddle of the package are main causes of degrading path isolation. The path isolation of over 25dB is achieved by reducing the bonding wire coupling factor by careful pin placements, reducing coupling through ground paddle by controlling degeneration amount, and reducing coupling through substrate by careful layout using trench hole. T...

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