bluuebunny/crossref_metadata_2025 huggingface dataset:
New Model for Low-Frequency Noise in Poly-Si Resistors
Authors: Lee Jung Il , Han Il Ki , Chang Soo Kyung , Kim Eunkyu , Lee Myoung Bok
Published: March 2009

This paper presents a simple and novel model for low-frequency noise generation in
polycrystalline-Si resistors within the number fluctuation model. The grain boundary in
polycrystalline-Si thin films is the major source of noise and is modeled as independent symmetric Schottky barriers in series, face-to-face. It has been found that trapping and detrapping of the carriers at the traps in the space charge region of the grain boundary via thermal activation modulate the barrier height and generate the low-frequency noise. The model successfully explains the experimental data and gives useful information about the defects in the space charge region of the grain boundary. As a result, the Hooge parameter is interpreted in terms of defect density, among other parameters.
The Roles of Specific Residues on ERK2 for Nuclear Translocation in Response to Nerve Growth Factors in PC12 Cells
Authors: Yoon Seung Hee , Seger Rony , Choi Eui Jung , Yoo Young Sook
Published: March 2009

Extracellular signal-regulated kinases (ERKs) are phosphorylated on threonine and tyrosine residues at 183 and 185, respectively, and then translocated from cytosol to nucleus. ERK2 is retained in the nucleus for several hours by nerve growth factor (NGF), and this sustained retention of ERK2 in the nucleus has effect on the fate of biological response toward differentiation by neurite outgrowth in PC12 cells. The overexpression of Green Fluorescent Protein (GFP)-ERK2
and mutated GFP-ERK2 constructs without anchoring protein MEK1 were distributed throughout the resting and the activated cells. When GFP-ERK2 coexpressed along with MEK1, cytosolic localization of GFP-ERK2 is retained by MEK1 in the resting PC12 cells. This cytosolic retention was due to the binding of ERK2 to the MEK1. Upon stimulation by growth factors, the association between GFP-ERK2 and MEK1 was detached from each other, and then GFP-ERK2 was
translocated into the nucleus. However, inactive form of the MKP-3 cytosolic phosphatase forced ERK cytosolic retention in PC12 cells were either left untreated or stimulated by NGF. When the transfected PC12 cells were treated for 72hrs with NGF, GFP-ERK2 was distributed the cytosol. Regarding its subcellular localization, the roles of residues 179-185 located in the activation loop of ERK2 were examined. The substitution of residues in the activation loop to alanine showed different localization on the nuclear translocation of ERK2 in PC12 cells.
Development of High-Performance Ultra-Small Size RF Chip Inductors for Wireless Communication System Application
Authors: Jung Myung Hee , Yun Eui Jung
Published: March 2009

This work investigates ultra-small size, high-performance, solenoid-type RF chip inductors for wireless communication system application. The materials (96wt% Al2O3) and shape (I-type) of the core, the diameter (40 µm) of the coil, and the length (0.35 mm) of solenoid were determined by a Maxwell three-dimensional (3D) field simulator to maximize the performance of the inductors. The dimensions of the RF chip inductors fabricated were 1.0 mm×0.5 mm×0.5 mm and copper (Cu) coils were used. The high-frequency characteristics of the inductance (L) and quality factor (Q) of the developed inductors were measured using a RF impedance/material analyzer (E4991A with an E16197A test fixture). The developed inductors with 6 coil turns exhibit an inductance of 11 to 11.3 nH, have a quality factor of 22.3 to 65.7 over the frequency ranges of 250 MHz to 1.7 GHz, and show results comparable to those measured for the inductors prepared recently by CoilcraftTm. The simulated data predicted the high-frequency data of the L and Q of the inductors developed well. It was suggested from the equivalent circuit model of the developed inductors that the developed inductors with 6 turns have a self-resonant frequency of 8 GHz.
Optimization of Vibrio harveyi Luminometry Assay for Detecting Quorum Sensing Inhibitors
Authors: Kim Yeon Hee , Kim Y. , Park Sung Hoon , Kim Jung Sun
Published: March 2009

The luminometry assay using the wild-type Vibrio harveyi BB120 was evaluated as a
possible detection method for quorum sensing inhibitors. The effects of the concentration of the quorum sensing signal molecule (AHL) as well as the cell density of the reporter strain and the different AHL analogues on luminescence expressed as relative light units (RLU) were examined. Inhibition of V. harveyi luminescence was observed in a dose dependent manner for all five AHL analogues. The RLU values exhibited linearity within the range of 2.9 x 102 ~ 3.2 x 105. Detection up to 102nM was possible for dodecanoyl-homoserine lactone and AHLs with alkyl chain lengths of C-8~C-14 were more active than the shorter chain-lengthed hexanoyl-homoserine lactones. Lipophilicity of the AHL seems to affect the sensitivity of the assay.
Modeling and Simulation of Baroreflex Regulation of Heart Rate in Response to Respiratory Fluctuations in Arterial Pressure
Authors: Choi Youn Hee , Sun Ying
Published: March 2009

Autonomic derangement can be assessed by depressed baroreflex sensitivity in a
restrictive left ventricular diastolic filling pattern. However, it is unclear how reflex or other compensations affect the inspiratory fall of systolic arterial pressure (IFSAP) during acute airway obstruction. In an in-vivo situation, it is particularly difficult to isolate individual effects of heart rate, vascular tone, pleural pressure variation, and ventricular interdependence. For this reason, a computer model study was undertaken. A previously validated computer model of the cardiopulmonary system was adapted for this study, relating mechanisms such as baroreflex
regulation of heart rate to IFSAP. The model provided time-course simulations of hemodynamics by numerically integrating 28 nonlinear, time-varying differential equations. Two models for baroreflex gain were tested, including a simple 1st-order relationship between systolic arterial pressure (SAP) and R-R interval (RRI) and the autoregressive moving average (ARMA) model reported in literature. The ARMA model predicted the next RRI based on SAP from several previous cardiac cycles and previous RRI predictions. Experimental data were obtained retrospectively from 22 patients with chronic airway obstruction before and during breathing through an external resistance. The computer model provided good fits to arterial pressure waveforms: correlation coefficients (r) ranging from 0.71 to 0.96 (mean±SD: 0.87±0.06) with a simple 1st-order SAP-RRI model. The ARMA model did not improve the goodness of fit.
Sketch Analysis-Based Engineering Solution for Online Story Authoring and Animation
Authors: Nam Yang Hee
Published: March 2009

This paper introduces an easy way of authoring and presenting a user’s own story in the form of animation on the World Wide Web. Since visual authoring is difficult and time-consuming, most of the existing online story-making tools support text-based authoring, and a few others allow users the freedom of choosing characters from a given database. Comparatively, we suggest a way of incorporating a user’s own sketches of characters and scenes to build a story without demanding much intervention from the user. We also present an automatic view control method to transform simple sketches into animation on the web.
A Study on the Knowledge Community for Creating and Sharing Implicit Knowledge
Authors: Lee Joo Young , Hahn Sun Hwa , Yoon Jung Sun
Published: March 2009

The ultimate goal of a knowledge-based society is to encourage the individuals to share and disseminate their knowledge spontaneously, so that the circulation of knowledge is accomplished. The structure of knowledge circulation consists of the following loop: preparation of explicit knowledge from implicit knowledge (externalization), sharing of the explicit knowledge, reproduction of implicit knowledge from shared explicit knowledge (internalization) and externalization of reproduced implicit knowledge. In addition, for the purpose of sharing knowledge,
the market place should be established and offer a variety of incentives that induce people to willingly participate in the creation of knowledge. In this paper, we show a successful example of a knowledge community, the Global Network of Korean Scientists and Engineers (KOSEN, www.kosen21.org), focusing on its organization and operation. KOSEN was established in 1999 in order to share
knowledge and information resources of Korean scientists and engineers all over the world. Among 4 knowledge management processes--knowledge creation and acquisition, knowledge organization and storage, knowledge distribution and knowledge utilization--KOSEN supports 3 processes (aside from the utilization of knowledge). Moreover, KOSEN seeks knowledge utilization by encouraging the
formation of small groups within the community.
Microarray Expression Analysis Using Seed-Based Clustering Method
Authors: Shin Mi Young , Park Seon Hee
Published: March 2009

Clustering methods have been often used to find biologically relevant groups of genes or conditions based on their expression levels. Since many functionally related genes tend to be coexpressed, by identifying groups of genes with similar expression profiles, the functionalities of unknown genes can be inferred from those of known genes in the same group. In this paper we address a novel clustering approach, called seed-based clustering, where seed genes are first systematically chosen by computational analysis of their expression profiles, and then the clusters
are generated by using the seed genes as initial values for k-means clustering. The seed-based clustering method has strong mathematical foundations and requires only a few matrix computations for seed extraction. As a result, it provides stability of clustering results by eliminating randomness in the selection of initial values for cluster generation. Our empirical results reported here indicate that the entire clustering process can be systematically pursued using seedbased clustering, and that its performance is favorable compared to current approaches.
Web Image Classification Using an Optimized Feature Set
Authors: Cho Soo Sun , Han Dong Won , Hwang Chi Jung
Published: March 2009

Redundant images currently abundant in World Wide Web pages need to be removed in order to transform or simplify the Web pages for suitable display in small-screened devices. Classifying removable images on the Web pages according to their uniqueness of content will allow simpler representation of Web pages. For such classification, machine learning based methods can be used to categorize images into two groups; eliminable and non-eliminable. We use two representative learning methods, the Naïve Bayesian classifier and C4.5 decision trees. For our Web image classification, we propose new features that have expressive power for Web images to be classified. We apply image samples to the two classifiers and analyze the results. In addition, we propose an algorithm to construct an optimized subset from a whole feature set, which includes most influential features for the purposes of classification. By using the optimized feature set, the accuracy of classification is found to improve markedly.
A Study of Inductance Computations for Transverse Flux Linear Motor Considering Nonlinearity of Magnetic Material
Authors: Lee Ji Young , Hong Jung Pyo , Kang Do Hyun
Published: March 2009

Inductance is an important parameter to assess electric motor characteristics. In this paper, the methods of apparent and incremental inductance calculations are introduced for a transverse flux linear motor (TFLM), which has a peculiar coil shape. To consider the nonlinearity of magnetic material, nonlinear analysis is performed by 3-dimensional equivalent magnetic circuit network (3D EMCN). The calculation method is verified by test results.
Generalized Additive Model of Air Pollution to Daily Mortality
Authors: Kim Jae Hee , Yang Hee Eun
Published: March 2009

The association of air pollution with daily mortality due to cardiovascular disease,
respiratory disease, and old age (65 or older) in Seoul, Korea was investigated in 1999 using daily values of TSP, PM10, O3, SO2, NO2, and CO. Generalized additive Poisson models were applied to allow for the highly flexible fitting of daily trends in air pollution as well as nonlinear association with meteorological variables such as temperature, humidity, and wind speed. To estimate the effect of air pollution and weather on mortality, LOESS smoothing was used in generalized additive models. The findings suggest that air pollution levels affect significantly the daily mortality.
N-Acetylphytosphingosine Enhances the Radiosensitivity of Tumor Cells by Increasing Apoptosis
Authors: Han Young Soo , Kim Yun Hwa , Yun Yeon Sook , Jeon Soo Jin , Kim Ki Sung , Hong Sung Hee , Park Chang Soe , Song Jie Young
Published: March 2009

Ceramides are well-known second messengers which mediate apoptosis, proliferation, differentiation in mammalian cells, but the physiological roles of phytosphingosines are poorly understood. We hypothesized that one of the phytosphingosine derivatives, N-acetylphytosphingosine (NAPS) can induce apoptosis in human leukemia Jurkat cell line and increase apoptosis in irradiated
MDA-MB-231 cells. We first examined the effect of NAPS on apoptosis of Jurkat cells. NAPS had a more rapid and stronger apoptotic effect than C2-ceramide in Jurkat cells and significant increase of apoptosis was observed at 3 h after treatment. In contrast, the apoptosis induced by C2-ceramide was observed only after 16 h of treatment. NAPS induced apoptosis was mediated by caspase 3 and 8
activation and inhibited by z-VAD-fmk. Ceramide plays a pivotal role in radiation induced apoptosis. We postulated that exogenous treatment of NAPS sensitizes tumor cells to ionizing radiation, since NAPS might be used as a more effective alternative to C2-ceramide. As expected, NAPS decreased clonogenic survival of
irradiated MDA-MB-231 cells dose dependently, and apoptosis of irradiated cells in the presence of NAPS was increased through the caspase activation. Taken together, NAPS is an effective apoptosis-inducing agent, which can be readily synthesized from yeast sources, and is a potent alternative to ceramide for the further study of ceramide associated signaling and the development of radiosensitizing agent.
Silicon Oxide Thin Film Deposition on Alumina in a Circulating Fluidized Bed Reactor
Authors: Park Sang Min , Jung Soon Hwa , Park Soung Hee , Kim Sang Done
Published: March 2009

Silicon oxide deposition on fine alumina powders by plasma-enhanced chemical vapor deposition (PECVD) at atmospheric pressure was carried out in a circulating fluidized bed reactor. To deposit silicon oxide on alumina powders, the organo-silicon source precursors (tetraethoxysilane (TEOS) and hexamethyldisiloxane (HMDSO)) and oxygen were used as the reactant gases while helium and argon were used as the dilute gases. The surface property of
plasma-treated alumina powder varies from hydrophobic to hydrophilic in the surface composition with variation of the discharge power. In oxygen-containing atmospheres, chemical composition of the deposited film is more inorganic with increasing the discharge power and the flow ratio of O2/precursor for both organo-silicon precursors.
Gravitational Lensing for Measuring Astrophysical Quantities
Authors: Chang K.
Published: March 2009

Gravitational lensing (GL) provides the sudden changes in flux densities, when a
compact source crosses a critical curve. Due to lensing, the image of the lensed object is split into at least two images, and merged together upon the source crossing the critical curve. Light paths of the images differ from one another’s, so results time delay to the observer. Asymmetric light curves and the time delay in lensing contain astrophysical information on the GL system: e.g. source structure,
density distribution, and cosmological distance scale. The disalignment of GL system, b, is an important parameter in the GL analysis. We derive b as a function of density parameter of gravitational lens mass. We present an analytical formulation
to determine cosmological distance scales, hence the Hubble parameter, and other properties of GL system. We also discuss degeneracies in the GL mapping.
Preparation and Charaterization of the Electrode Catalyst Supported on Mesoporous Carbons for the Dmfc Application
Authors: Kim Hee Soo , Kim Pil , Park Young Geun , Lee Jae Ho , Choi Kyung Hee , Yi Jong Heop
Published: March 2009

Mesoporous carbon (MCs) was synthesized using mesoporous silica as a template. Prepared mesoporous carbon materials were found to have high surface area and large pore volume with uniform pore size. Resulting materials showed a different pore arrangement from mesoporous silica templates. Pt catalysts supported on mesoporous carbon prepared were applied to an anode catalyst for Direct Methanol Fuel Cell (DMFC). Results indicate that a mesoporous carbon having
3-dimensional pore system (3D-MC) had higher catalytic activity than 2-dimensional one (2D-MC) due to a favorable pore structure in methanol electro-oxidation.
Design and Characterization of Microfluidic Analysis System for RNA-Aminoglycoside Interactions
Authors: Lee Ji Hye , Jang June Moon , Cho Han Sang , Han Ki Cheol , Kim Tae Song , Kang Ji Yoon , Yang Eun Gyeong
Published: March 2009

Microfluidic devices are of considerable interest, since such technology offers great
promise for the development of powerful and versatile miniaturized analyzers. Accordingly, the present work describes a microfluidic screening system that is composed of a microchip, hydrodynamic pumping unit and fluorescence detectors. To develop an assay for RNA-aminoglycoside interactions, microchips are designed and fabricated on a glass substrate, then flow simulations are performed in the microchannels. After optimizing the flow control and buffer composition for fluorescence-based biochemical assays, a fluorescently labeled aminoglycoside
probe and RNA are allowed to flow continuously to the main micro-channel based on hydrodynamic pumping and their interactions monitored by fluorescence quenching, which is reversed upon competition with other aminoglycosides. Consequently, the proposed device can serve as an integrated microfluidic platform for the high-throughput screening of high affinity antibiotics for RNA targets.
Site-Defined Micropatterning Using Atomic Force Microscopic Lithography
Authors: Choi In Hee , Kim Young Hun , Kim Chang Mook , Kim Jin Soo , Choi Kyung Hee , Yi Jong Heop
Published: March 2009

Site-defined metal microstructure was fabricated on the pre-designed organic template via a surface modification of Si(100) wafer. Site-defined substrate with octadecyltrichlorosilane (OTS) was oxidized by AFM (Atomic Force Microscopy) at threshold voltage (Vo). Terminal group (-CH3) of OTS was changed into carboxyl group (-COOH). Then, locally modified monolayer surface was used to induce the site-selective self-assembly of different materials (organic, metal, and semiconductor), according to the predefined patterns. The target metal selected is copper ions for the feasibility examination of conductive metal line fabrication
Nano Pattern Mold Technology Using Nano Stamper Based on Quartz
Authors: Choi Doo Sun , Je Tae Jin , Seo Young Ho , Whang Kyung Hyun
Published: March 2009

In this paper, we present a reusable quartz master fabricated by electron-beam lithography and the results of the preliminary test of injection molding using the reusable quartz master. Since patterned structures of photoresist can be easily damaged by demolding process of nickel stamper and master, a master with photoresist cannot be reused in stamper fabrication process. In this work, we have made it possible of the repeated use of master by directly patterning on quartz in nickel stamper fabrication process. We have developed a 100nm-pit sized reusable quartz master with intaglio carving patterns of finer sizes than those of DVD (400nm) and blue-ray disc (200nm). In the preliminary test of the injection molding, we have found optimum injection molding conditions using polypropylene.
Sonochemical Synthesis of Silicon Nanocrystals
Authors: Lee Soo Jin , Cho Woon Jo , Chin Chong Shik , Han Il Ki
Published: March 2009

Silicon nanocrystals in a range from 2 nm to 5 nm were prepared from Zintl salt, soldium silicide (NaSi) by sonochemical method. This synthesis permits that the reaction be completed in only a few hours and the easy alkyl-modification of nanocrystals surface at room temperature and ambient pressure. The average size of nanocrystals measured by the dynamic light scattering analysis was 2.7 nm. The high-resolution transmission electron micrograph confirmed the material identity of nanocrystals as crystalline silicon. FT-IR spectra are consistent with the surface states of nanocrystals that are chlorine-or butyl-capped. The emission peak center moved to a longer wavelength (up to 430 nm) with the reaction time, under a 325 nm excitation.
Raman Spectra Study on Multilayered Compositional Graded (Ba0.8Sr0.2)(Ti1-xZrx)O3 Thin Films
Authors: Wang Can , Cheng Bo Lin , Wang S.Y. , Dai S.Y. , Chen Zhao Hui
Published: March 2009

Compositional graded thin films of (Ba0.8Sr0.2)(Ti1-xZrx)O3 (BSTZ) are grown on MgO by pulsed laser deposition technique with four BSTZ ceramic targets. Gradients of composition are achieved by artificially tailoring composition in multilayered thin films to form compositional graded layers (CGL). In each CGL four individual layers of BSTZ with x = 0.36, 0.18, 0.08 and 0 are grown^in series with equal thickness. Three kinds of CGL samples comprising one, two or four CGLs have been elaborated with the same total thickness by varying the thickness of each CGL. Raman spectra show existence of tetragonal structure in all the multilayered BSTZ thin films. Raman peak at 535 cm-1 shifts to high frequency with increasing of compositional gradient, and the peak at 750 cm-1 also shows a small shift to high frequency. Moreover, other Raman peak is observed at about 830 cm-1,
which is associated with phonon mode of cubic phase, and such peak shifts towards lower frequency with increasing of compositional gradient. The shift of Raman peak is related to variation of internal stress in BSTZ thin film due to increasing compositional gradient.
Study of Graphite/Bakelite/BaTiO3-Based PTC Ceramics Composite
Authors: Qu Yuan Fang , Yang Guang Jun , Li Xiao Lei , Ma Wei Bing
Published: March 2009

The influence of grahtite and bakelite content of Graphite/Bakelite/BaTiO3-based PTC ceramic composite on their properties was studied. It was found that the composite's room- temperature resistivity was decreased and the PTC intensity was assured. This method offered a new way to solving the problem of high room-temperature resistivity of the BaTiO3-based PTC ceramic.
Study on Si Dependence of RB-SiC Thermoelectric Properties
Authors: Qiao Guan Jun , Shi Y.W. , Gao Ji Qiang , Wang Hong Jie , Yang Jian Feng , Jin Zhi Hao
Published: March 2009

The effects of free silicon on thermoelectric properties of reaction-bounded silicon carbide (RB-SiC) were studied. RB-SiC ceramic consists of some free silicon after reaction sintering. Some RB-SiC samples were reheated at high temperature in vacuum to adjust silicon content. The results showed that free silicon affects thermoelectric properties remarkably, especially for the thermoelectric power. A surprising phenomenon was found in SiC/Si composite consisting ~20wt% free-Si,
i.e., thermoelectric power, figure of merit Z and ZT are all sharply increased above 400oC. The peak value (4.2X10-4) of ZT appears in original SiC/Si composite at about 500oC, which is increased more than 1000 times than that at room temperature.
Hydroxyapatite-Coated Femoral Stem Survivorship at 10 Years
Authors: Lee Gregory Y. , Srivastava Ajay , D'Lima Darryl D. , Pulido Pam , Colwell Clifford W.
Published: March 2009

The Omnifit-HA femoral stem component has shown excellent results in early clinical
studies. This is an independent prospective study of the outcome of a ydroxyapatite-coated femoral component implanted by one surgeon with an intermediate-term follow up. The senior author performed 103 consecutive uncemented total hip arthroplasties in 96 patients from July 1991 to December 1996. The components implanted were the Omnifit-HA femoral stem and the Omnifit PSL porous-coated acetabular shell. The mean age at the time of the index procedure was 52 years old
(range, 27–78) and male:female ratio was 54:42. Three patients were deceased and four patients were lost to follow-up. The mean follow up was 10.3 years (range, 7.3–12.7 years). Clinical and radiographic evaluations were performed by an independent observer. The average preoperative and postoperative Harris Hip Scores were 55 and 92, respectively. The overall survivorship of the
Omnifit-HA stem was 100% with no femoral revisions. The survivorship of the Omnifit PSL cup was 89.7% with 4 acetabular revisions for aseptic loosening and 6 polyethelene liner exchanges for osteolysis or late instability. The mean polyethylene wear rate was 0.24 mm per year. This long-term follow up shows that the use of circumferentially coated hydroxyapatite stems can protect against the
migration of wear debris along the femoral stem.
Stearate Salts as Brushite Bone Cement Setting Retardants
Authors: Hofmann M.P. , Gbureck Uwe , Grover Liam M. , Barralet J.E.
Published: March 2009

This study sought to examine the efficiency of coating cement powder reactants in order to reduce the solubility rate of reactants and thereby increase setting times of cement systems. In this investigation magnesium and sodium stearate salts were used to coat the highly soluble monocalcium phosphate monohydrate (MCPM) powder component of a hydraulic brushite forming calcium phosphate cement system with b-tricalcium phosphate (b-TCP) as other component. The results showed that stearate coating of the MCPM reactant could lead to a 100%
increase in setting and working times without affecting compressive strength of the set cement when applied with the appropriate P/L-ratio.
Novel Hydroxyapatite Coating on Alumina by Electrospraying
Authors: Huang Jie , Best Serena , Jayasinghe S.N. , Edirisinghe Mohan J. , Bonfield William
Published: March 2009

Electrospraying of nano-sized hydroxyapatite (HA) has been used as a technique to modify the surface of alumina in order to achieve the goal of improving bone integration. A porous HA coating on alumina was produced by heat treating electrsprayed HA. Preliminary in vitro studies shown that this porous HA coating provided a favourable surface for attachment and growth of HOB cells. The results indicate that electrospraying is a very promising technique to create thin HA coatings on a range of biomedical implants to improve interfacial bonding with the host tissue.
Biphasic and Preferentially Oriented Microcrystalline Calcium Phosphate Coatings: In Vitro and In Vivo Studies
Authors: Kim Hyun Bin , Vohra Yogesh K. , Louis Patrick J. , Lacefield William R. , Lemons Jack E. , Camata Renato P.
Published: March 2009

We report results of in-vitro and in-vivo studies on biphasic thin film coatings of
hydroxyapatite/tetracalcium phosphate produced by pulsed laser deposition using ablation targets of crystalline hydroxyapatite. Changes in coating phase composition during in-vitro dissolution experiments were monitored by x-ray diffraction. Scanning electron microscopy was used to assess variations in surface morphology. In-vivo experiments involving the insertion of coated metallic implants in the proximal tibia and distal femur of New Zealand White Rabbits were carried out. Histomorphometric studies on implant samples after surgical extraction show that biphasic coatings
produced may lead to enhanced osteointegration compared to pure hydroxyapatite coatings.
Enhancing Effect of Autoclaving on Bioactivity of ß-Titanium Alloy Coated with Calcium Phosphate Glass-Ceramic
Authors: Kasuga Toshihiro , Nogami Masayuki , Niinomi Mitsuo , Hattori Tomokazu , Hench Larry L.
Published: March 2009

60CaO-30P2O5-7Na2O-3TiO2 (mol%) glass-ceramic can be strongly joined with a new β-type Ti-29Nb-13Ta-4.6Zr alloy. In the present work apatite-forming ability in simulated body fluid of the glass-ceramic-coated titanium alloy was enhanced by autoclaving in water at 120°C for 1 h; surface of the autoclaved coating was completely covered with apatite after 10 days of soaking. In vivo tests showed that the glass-ceramic-coated titanium alloy after autoclaving in water makes a strong bond to natural bone.
Fabrication of Hydroxyapatite Ceramics with Interconnected Macro Porosity
Authors: Müller Lenka , Müller Frank A. , Zeschky Jürgen , Fey Tobias , Greil Peter
Published: March 2009

Calcium phosphate bioceramics with an interconnective pore structure were produced by foaming of hydroxyapatite and methyl phenyl poly(silsequioxane) melts in the temperature range between 250 °C and 310 °C. The cellular structure of the resulting porous bodies were controlled by foaming parameters and filler load. A porosity of up to 92 % was achieved by decreasing the HAfiller amount and increasing the foaming temperature. Subsequent pyrolysis in air at temperatures of
900 °C and 1100 °C resulted in macroporous foams composed of HA and HA/b-TCP, respectively. The porous bodies with tailorable structure and composition are of interest for bone tissue engineering scaffolds and orthopedic implants.
Biocompatibility Evaluation of Three Different Titanium-Hydroxyapatite Composites
Authors: Sampaio B.V. , Göller G. , Oktar Faik Nuzhet , Valério Patricia , Goes Alfredo , Leite M. Fatima
Published: March 2009

Titanium reinforced with hydroxyapatite (TiHA) prepared using 15% of titanium and 3 different sinterizing temperatures 1100, 1200 and 1300 oC showed a significant increase in cell proliferation, when compared to the control.
Hydroxyapatite-Chitosan Hybrid Nano-Materials
Authors: Kumar R. Roop , Prakash K.H. , Lim K.G. , Kiat N.H. , Yennie K. , Cheang P. , Khor Khiam Aik
Published: March 2009

Self-assembled nano-materials are currently an area of research with high throughput due to the opportunities it provides to fields ranging from semiconductor engineering to gene delivery. There is also considerable interest in nano-particulate systems that attain a lower energy state by self-assembly through favorable and repeated surface interactions as they mimic those commonly found in natural biological systems. This work presents a simple route to first synthesise a highly
stable suspension of nano-hydroxyapatite (~40nm) with chitosan and subsequently self-assemble the suspended nano-hydroxyapatite particulates onto a substrate.
Preparation of a Bioactive Functionally Graded Ceramic-Polymer Hybrid
Authors: Lee Y.H. , Kim Hyun Min , Lee Kwon Yong , Lee Jae Hoon , Ahn S.H. , Koh M.-Y.
Published: March 2009

A ceramic-polymer nano-hybrid, in which the bioactive silicate surface is nano-hybridized with flexible silicone bulk, was synthesized in the tetraethoxysilane (TEOS)-polydimethylsiloxane (PDMS) sol-gel system. Different solutions for surface silicate and bulk silicone, whose component ratio of SiO2: PDMS were respectively 100: 0 and 50: 50, were subjected to lamination and delayed
polymerization and condensation process, producing a large transparent crack-free monolithic bulk. Characterizations at near-surface cross-section of the hybrid bulk revealed typical bioactive silicate structure with no distinct interface with the interior, indicating possibility of a novel bioactive nano-composite with enhanced physical and biological functions.
Comparison of Recombinant Growth/Differentiation Factor-5 (rGDF-5) and Bone Morphogenetic Protein-2 (rBMP-2) in the In Vivo Bone Formation in Porous Hydroxyapatite Ceramic
Authors: Shimaoka H. , Dohi Y. , Narikawa K. , Ohgushi Hajime , Ikeuchi M. , Okamoto M. , Kirita T. , Yonemasu K.
Published: March 2009

Various recombinant growth factors have been used for promoting osteoblastic differentiation cascade. To compare the growth/differentiation factor-5 (GDF-5) and bone morphogenetic protein-2 (BMP-2) in the in vivo osteogenic potential of bone marrow mesenchymal stem cells (MSCs), the bone formation was assessed by rat subcutaneous implantation of 5 kinds of hydroxyapatite (HA) implants; namely GDF/HA composites, BMP/HA composites, MSCs/HA
composites and the MSCs/HA composites supplemented with recombinant mouse GDF-5 (GDF/MSCs/HA) or recombinant human BMP-2 (BMP/MSCs/HA). Neither the GDF/HA nor the BMP/HA composites exhibited any bone formation at any time after implantation. At both 2 and 4 weeks after implantation, obvious de novo bone formation together with active osteoblasts was seen histologically in many pores of the GDF/MSCs/HA and BMP/MSCs/HA composites.
The GDF/MSCs/HA and BMP/MSCs/HA composites also showed high alkaline phosphatase (ALP) and osteocalcin expression determined at both the protein and gene levels. Compared with GDF/MSCs/HA, the BMP/MSCs/HA composites exhibited excellent osteogenesis with relatively early osteoblastic phenotype expression. These findings indicate that the two growth factors synergistically enhance de novo bone formation capability of MSCs/HA composites and the importance of ceramic surface to retain and to deliver the molecules of growth factors for the cell differentiation and maturation.
Phase Stability of Zirconia and Alumina/Zirconia Composite Heads against UHMWPE Liners in a Temperature-Controlled Hip Simulation Study
Authors: Liao Yen Shuo , Hanes Mark , Fryman J.Craig , DiSilvestro Mark
Published: March 2009

This study evaluated the wear performance of cobalt-chromium, zirconia and
alumina/zirconia composite heads against moderately crosslinked ultra-high-molecular-weight polyethylene liners under different temperature conditions. A temperature control unit was utilized to allow direct cooling/heating the head components at 4, 20, 37 and 45 °C in addition to the conventional no temperature control method. Results showed that the polyethylene wear was affected by the coolant temperature. The CoCrMo and the alumina/zirconia groups had similar wear
rate without temperature control, however, the CoCrMo group generated 50% more wear than the alumina/zirconia group did when the coolant temperatures were above 20 °C. The zirconia group had the lowest wear rate of the three groups in all temperature conditions. The monoclinic phase content of the zirconia heads were about 0.2 M% before the test and 6.0 M% after the test, while the X-ray diffraction remained similar before and after the test in alumina/zirconia composite heads.
The current study was able to reproduce the phase transformation of zirconia ceramics as reported in some clinical retrieval reports. A temperature control feature is recommended in a wear study in order to better simulate implant wear performance under the physiological condition in human body.
The Preparation of Pore-Size Controlled Mesoporous Silicas by Biodegradable Diblock Copolymers
Authors: Chang Jeong Ho , Kim Kyung Ja , Shin Young Kook
Published: March 2009

Selected MPEG-b-PDLLA block copolymers have been synthesized by ring-opening
polymerization with systematic variation of the chain lengths of the resident hydrophilic and hydrophobic blocks. The size and shape of the micelles that spontaneously form in solution are then controlled by the characteristics of the block copolymer template. All the materials prepared in this study showed the tunable pore size of 20-80Å with the increase of hydrophobic chain lengths and up
to 660m2/g of specific surface area. The formation mechanism of these nanoporous structures obtained by controlling the micelle size has been confirmed using both liquid and solid state 13C and 29Si NMR techniques. This work verifies the formation mechanism of nanoporous structures in which the pore size and wall thickness are closely dependent on the size of hydrophobic cores and
hydrophilic shells of the block copolymer templates.
Fabrication of Silicon Nitride Nano-Ceramics by High-Energy Mechanical Milling and Spark Plasma Sintering
Authors: Xu Xin , Nishimura Toshiyuki , Hirosaki Naoto , Xie Rong Jun , Yamamoto Yoshinobu
Published: March 2009

The fabrication of dense Si3N4 nano-ceramics via a high-energy mechanical milling
process and subsequent spark plasma sintering (SPS) was reported in this paper. A thermodynamically stable β-Si3N4 powder mixed with 5-mol% Y2O3 and 2-mol% Al2O3 was used as starting powders for high-energy mechanical milling. Milling resulted in the significant decrease of crystalline size and the amorphization of the starting powders. Based on XRD measurements, the amount of the amorphous phase and the grain sizes of the remaining crystalline silicon nitride
depended on the charge ratio. Milled powders could be SPSed at relatively low temperature. A homogenous dense silicon nitride ceramics with grain diameter of about 70 nm could be fabricated through SPS at a low temperature of 1600oC for 5 min. The significant decrease of grain size greatly increased the hardness of obtained ceramics.
Characterization of the SiCf/SiC Composite Fabricated by the Whisker Growing Assisted CVI Process
Authors: Park Ji Yeon , Kang S.M. , Kim Weon Ju , Ryu Woo Seog
Published: March 2009

To obtain a dense SiCf/SiC composite by the chemical vapor infiltration (CVI) process, whisker growing before matrix filling was applied, which is called the whisker growing assisted CVI process. The whisker growing and matrix filling processes were carried out using MTS (CH3SiCl3) and H2 as source and diluent gases, respectively. Tyranno-SATM was used as a reinforced substrate.
Characterizations of SiC whisker grown during the in situ whisker growing process have been investigated. The weight gain rates with the matrix filling time and the density of composites was measured. The flexural strength with the thickness of the pyrolytic carbon (PyC) interlayers has been evaluated. b-SiC whiskers with many stacking faults were grown well in the Tyranno SATM fabrics. Tyranno-SA/SiC composite with a PyC interlayer thickness of 150 nm had a flexural strength of 610 MPa and the density of 2.71 g/cm3.
Macro- to Atomic-Scale Tailoring of Si3N4 Ceramics to Enhance Properties
Authors: Becher Paul F. , Painter Gayle S. , Shibata Naoya , Lin Hua Tay , Ferber Mattison K.
Published: March 2009

Silicon nitride ceramics are finding uses in numerous engineering applications because of their tendency to form whisker-like microstructures that can overcome the inherent brittle nature of ceramics. Studies now establish the underlying microscopic and atomic-scale principles for engineering a tough, strong ceramic. The theoretical predictions are confirmed by macroscopic observations and atomic level characterization of preferential segregation at the interfaces between the grains and the continuous nanometer thick amorphous intergranular film (IGF). Two interrelated factors must be controlled for this to occur including the generation of the elongated reinforcing grains during sintering and debonding of the interfaces between the reinforcing grains and the matrix. The reinforcing grains can be controlled by (1) seeding with beta particles and (2) the chemistry of the additives, which also can influence the interfacial debonding conditions. In addition to modifying the morphology of the reinforcing grains, it now appears that the combination of preferential segregation and strong bonding of the additives (e.g., the rare earths, RE) to the prism planes can also result in sufficiently weakens the bond of the interface with the IGF to promote debonding. Thus atomic-scale engineering may allow us to gain further enhancements in fracture properties. This new knowledge will enable true atomic-level engineering to be joined with microscale tailoring to develop the advanced ceramics that will be required for more efficient engines, new electronic device architectures and composites.
Fabrication and Properties of Porous RBSN
Authors: Park Dong Soo , Lee Myoung Won , Kim Hai Doo , Park Young Jo , Jung Yeon Gil
Published: March 2009

Porous silicon nitride was prepared by extrusion of silicon followed by nitridation at 1723 K. PMMA spheres with 20 µm in diameter were employed as the pore-forming precursors. b-silicon nitride whiskers were added to the dough for extrusion and their effect on the properties of porous RBSN were examined. The nitridation rate that was obtained from the weight change of the sample due to the nitridation process was between 75% and 80%. However, XRD patterns of the samples after nitridation had no Si peak. That means the actual nitridation rate of the sample was higher than that obtained from the weight change. Porosity of the sample was between 45% and 55%. The XRD patterns from the surfaces of the samples with the silicon nitride whiskers parallel and perpendicular to the extrusion direction showed a slight anisotropy. The pore size distributions of the samples showed a highly populated pores smaller than 3 micrometer, especially for the
samples with the whiskers. The room temperature flexural strengths of the samples were between 25 MPa and 35 MPa, the sample with 5 wt% whiskers showing the highest value. The microstructures of the samples contained pores with about 100 micrometer in diameter as well as fine pores with a few micrometer in diameter. Closer observation of the fracture surface of the samples revealed that fine whiskers were inside the pores. A small honeycomb was fabricated by
reaction bonding of silicon.
Application of Powder Blasting Techniques to Micro-Pattern Making Process for Si3N4-hBN Composites
Authors: Cho Myeong Woo , Cho Won Seung , Park Dong Sam , Lee Jae Hyung , Lee Eun Sang , Seo Tae Il , Kim D.W.
Published: March 2009

In this study, micro powder blasting techniques are applied to micro-pattern making process using developed Si3N4-hBN composites. Material properties of the developed machinable ceramics according to the variation of h-BN contents, those are used to give good machinability to the ceramics, are evaluated. And, a series of required experimental works are performed to determine optimum powder blasting conditions for micro-pattern making. The experiments are performed for the prepared samples with no mask, and samples with three different mask patterns. As the results, it can be observed that the machinability of the developed Si3N4-hBN composites increases as the h-BN contents in the composites. Also, from the experimental results, it is possible to determine the optimum blasting conditions for micro-pattern making process with Si3N4-hBN composites.
Electrophoretic Deposition of Hydroxyapatite Nano Coating on Etched Titanium Surface
Authors: Chen F. , Lin L.W. , Lin Chang Jian , Lu W.W.
Published: March 2009

Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is biocompatible and bioactive, however, it is relatively brittle. The development of HAp coatings on medical metal surface is a good way to improve the mechanical properties of HAp. In the present study, a HAp coating with nano-structure on a roughened titanium surface was developed by electrophoretic deposition process. To decrease sintering temperature HAp nanoparticles synthesized by a wet chemical method was used. It was observed that the coating was uniform and showed no cracks. After sintering the HAp coating still remained nano structured. The surface treatment of Ti was applied to form a distribution of small pits and a TiO2 thin layer on the Ti surface that improves the adhesion of coating to the Ti substrate. It was shown that the bonding strength of coating was 18 ± 2.5MPa. The hardness and Young’s modulus were 40.6 and 0.42 GPa, respectively.
Nanostructure Properties of Hydroxyapatite Nanobelts Prepared by Oil-in-Water Emulsion
Authors: Wang Ying Jun , Wei Kun , Lai Chen , Ning Chen Yun , Wu Gang , Zhao Na Ru , Chen Xiao Feng , Ye Jian Dong
Published: March 2009

The HA nanobelts had been synthesized by using surfactants. It possesses a uniform one-dimensional nanofibers with width in 1.37nm and a BET specific surface area of 85.2m2g-1. The 31P NMR spectrum showed three –0.59ppm,-1.76ppm,-3.22ppm followed by a series of identical sidebands and one weak peak at –4.69ppm . The FTIR spectra of the nanobelts included two types of vibration; three PO4 3- stretching modes at 939.1,1030.4 and 1100.0cm-1 band were attributed to the ν1(PO4), ν3(PO4), ν3(PO4) modes respectively. Two PO4 3- bending modes at 569.6 and 608.7cm-1 bands were attributed to the ν4(PO4) modes .The bands observed around 473.9cm-1 were attributed toν2(PO4) modes. The nanobelts were novel drug carries.
In Vitro Behaviors of Copolymer of Poly (1,4-Phenylene Sulfide-2, 4-Phenylene Sulfide Acid) and Its Nano Hydroxyapatite Composites
Authors: Yan Yong Gang , Chen Yong Rong , Li Yu Bao , Wolke Joop G.C. , Jansen John A.
Published: March 2009

The copolymer of poly (1, 4-phenylene sulfide-2, 4-phenylene sulfide acid)[p-PPS-m-PPSA] and its nano HA composite [NHA/ p-PPS-m-PPSA] were recently developed as a new kind of inorganic-organic system for biomaterials. This kind of copolymer and its nano-HA composites may have a potential use in loaded bone substitutes, fixation or tissue engineering. In the present research the in vitro behavior of this kind of composites has been investigated in the SBF, and the surface changes were measured by XRD, XPS. SEM and EDS. The results showed that the copolymer and the NHA/ p-PPS-m-PPSA composites were very stable in SBF. The Ca, P content increased to 1.64wt% and 0.77wt% on the surface of p-PPS-m-PPSA, and the Ca/P was 1.63, near to that of the stoichiometric HA, 1.67
meanwhile the Ca, P content increased on NHA/ p-PPS-m-PPSA surface increased to 8.50wt% and 3.42wt% and the Ca/P ratio of surface of the NHA/ p-PPS-m-PPSA composites decreased slowly from 2.01to 1.83 during the incubation in SBF. Analysis demonstrated that the precipitate on copolymer of p-PPS-m-PPSA was HA and the precipitate on the NHA/ p-PPS-m-PPSA surface was HA, TCP and
carbonated-apatite. All results showed that both the copolymer of p-PPS-m-PPSA and NHA/ p-PPS-m-PPSA composite were stable and bioactive, and might have a promising potential use in implantation and tissue engineering.
Gene Expression of C2C12 Cells on Calcium Phosphate Ceramic In Vitro
Authors: Tan Yan Fei , Zhang Ling Li , He Xin Lai , Xiao Wei Qiang , Fan Hong Song , Zhang Xing Dong
Published: March 2009

The osteoinduction of Calcium Phosphate (CaP) had been proved and generally been investigated by in vivo implantation. However, the mechanism of the osteoinductivity was not clear and it was difficult to judge the osteoinductivity in vitro. In this study, Mouse C2C12 cell line, a kind of myoblast precursor cell, was employed to co-culture with CaP. The induction of cell differentiation by materials was tested by MTT method, fluorescence observation, especially the mRNA expression of Osteocalcin, Type I collagen and Fibronectin by RT-PCR. It was founded that C2C12 cells could be induced to expression osteocalcin when growth on the surface of the HA/TCP ceramics. At the same time, the ceramics with different composition and sintering temperature seemed to induce difference expression level of the related genes. The results proved that phase composition was one of the most important factors in the regulation of bone-related genes. This study provided a potential model to evaluate the osteoinductivity of CaP ceramics in vitro.