• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.39 no.5
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• pp.224-230
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• 2013

Objectives: Papilloma frequently develops as a benign tumor of the head and neck area, but its potential for malignant transformation has yet to be studied. This study aims to provide basic information for papillomas using the immunohistochemical staining of matrix metalloproteinase 2 (MMP-2) and human papilloma virus (HPV) 16 and 18. Materials and Methods: To evaluate the malignant transformation of papillomas, the selected tissue samples were serially diagnosed with pre-cancerous papilloma (with epithelial dysplasia, pseudo-epitheliomatous hyperplasia) or malignant lesion (squamous cell carcinoma, SCC) after the first diagnosis (squamous papilloma, inverted papilloma). The selected tissues were stained with an antibody to MMP-2 and HPV 16-E7, HPV 18-L1. A statistical analysis was performed according to each transformation step. Results: The epithelial layer of papilloma and pre-cancerous papilloma lesions had a similar MMP-2 expression, but that of the malignant lesion had a significantly increased MMP-2 expression. HPV 16 and 18 infection rates were 28.6%, 33.3% and 63.6% in papillomas, pre-cancerous papilloma lesions, and SCC. Conclusions: A relatively high MMP-2 expression and HPV 16 or 18 infection of papillomas may be associated with early events in the multistep processes of malignant transformation of papillomas.

• Proceedings of the CALSEC Conference
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• 2005.03a
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• pp.130-134
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• 2005

This research describes the comparison broker's role and its effectiveness measurement using a developed logical framework of comparison shopping service. And verifies that seller-led comparison challenge method provide comparison information of products to buyers more efficiently. In electronic commerce, buyer's satisfaction of purchase (S) can be defined as an interactive function between seller's competitiveness vector (P) of products that supplied to the market, and buyer's informed level vector (B) of products that is known from a lot of sources. Then the buyer's informed level can be changed through the information analysis among products by transformation process using comparison matrix (C). So the role of comparison shopping is to construct a comparison matrix and to serve it to the buyers, and to change the buyer's informed level. The changed informed level influences a buyer's satisfaction, that improved satisfaction of purchase is defined as the effectiveness of comparison shopping. As a perfect provision and usage of comparison matrix is impossible cause of cognitive limit, the most efficient method for improving the comparison effectiveness is the comparison challenge that detects the comparison elements of the largest buyer's information efficiency, and then to be compared between elementary products selectively. This research verifies the substantial superiority of comparison challenge through television market data experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.7
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• pp.555-561
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• 2003

An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported Euler-Bernoulli beams with the moving masses. The influences of the velocities of moving masses, the distance between the moving masses and a crack have been studied on the dynamic behavior of a simply supported beam system by numerical method. The Presence of crack results In large deflection of beam. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. This flexibility matrix defines the relationship between the displacements and forces across the crack section and is derived by applying fundamental fracture mechanics theory. Totally, as the velocity of the moving masses and the distance between the moving masses are increased, the mid-span deflection of simply supported beam with the crack is decreased.

• Advances in materials Research
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• v.5 no.3
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• pp.131-140
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• 2016

Copper/silicon nitride ($Cu/Si_3N_4$) composites are fabricated by powder technology process. Copper is used as metal matrix and very fine $Si_3N_4$ particles (less than 1 micron) as reinforcement material. The investigated powder were used to prepare homogenous ($Cu/Si_3N_4$) composite mixtures with different $Si_3N_4$ weight percentage (2, 4, 6, 8 and10). The produced mixtures were cold pressed and sintered at different temperatures (850, 950, 1000, $1050^{\circ}C$). The microstructure and the chemical composition of the produced $Cu/Si_3N_4$ composites were investigated by (SEM) and XRD. It was observed that the $Si_3N_4$ particles were homogeneously distributed in the Cu matrix. The density, electrical conductivity and coefficient of thermal expansion of the produced $Cu/Si_3N_4$ composites were measured. The relative green density, sintered density, electrical conductivity as well as coefficient of thermal expansion were decreased by increasing the reinforcement phase ($Si_3N_4$) content in the copper matrix. It is also founded that the sintered density and electrical conductivity of the $Cu/Si_3N_4$ composites were increased by increase the sintering temperature.

• International Journal of Oral Biology
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• v.41 no.2
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• pp.63-68
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• 2016

The aim of this study was to investigate the effect of n-3 polyunsaturated fatty acids (PUFAs) on eruptive movement during tooth development. Sprague-Dawley (SD) rat pups were randomly divided into two groups; control group and experimental group. The experimental group was administered daily with n-3 PUFA by intraperitoneal (IP) injection. After 10 days postpartum, rat pups were sacrificed to evaluate the effect of n-3 PUFA on eruptive tooth movement. Histological analyses were by hematoxylin-eosin (H&E) staining. Tartrate-resistant acid phosphatase (TRAP) assay was performed to compare the osteoclast distribution in the bone matrix above the developing molar teeth. Incisor teeth eruptions were noticeably observed in IP group, as compared to control group. Rat pups in IP group showed faster tooth eruption on day 8 after birth. Through histological analyses, IP group showed thinner bone matrix and more osteoclasts above the $1^{st}$ molar teeth, as compared to control group. TRAP assay showed significantly stronger stained pattern that the osteoclast above the $1^{st}$ molar teeth in IP group, as compared to control group. The results suggested that n-3 PUFA could affect osteoclastic activity involved in bony remodeling during eruptive tooth movement.

• Journal of Biomedical Engineering Research
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• v.17 no.2
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• pp.255-262
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• 1996

Antithrombogenic surFace is one of the most important things to the artificial vascular prostheses. This problem will be solved if the surface of prosthesis is covered with endothelial cells. The attachment and the growth of endothelial cells onto vascular prosthesis are very difficult. So many studies have been concentrated on the attachement of endothelial cell. But no good performance of the in uiwo experiments has been shown until now. In this study, we used the whole extracellular matrix (ECM) excreted from fibroblasts as an underlying matrix, and the endothelial cells were seeded to obtain the long term patency of vascular graft(i.e., for the patent 8 week implanted wafts in the animal model of rat). In order to study the antithrombogenic functions of cultured endothelial cells, prostaglandin(PGF 1 a) synthesis and platelet adhesion were assayed. The concentration of PGF a of stimulated group was sisnificantly higher than that of control group(21.97 $\pm$ 3.45 vs 4.93 $\pm$0.71 pg/1000 cells). The platelet adhesion of the polyurethane sheet covered with endothelial cells was lower than that of polyurethane sheet or sheet covered with ECM(1.04$\pm$0.28, 2.87$\pm$0.77, 2.89$\pm$0.70, % radioactivities, respectively). Endothelial cells grew well on polyurethane coated with ECM, synthesized the prostacyclin and functioned well as antithrombogenic. Therefore the endothelialization onto the ECM excreted from fibroblasts may be a good method for the vfudig prosthesis.

• The Korean Journal of Physiology and Pharmacology
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• v.20 no.1
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• pp.1-8
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• 2016

Damage in the periphery or spinal cord induces maladaptive plastic changes along the somatosensory nervous system from the periphery to the cortex, often leading to chronic pain. Although the role of neural circuit remodeling and structural synaptic plasticity in the 'pain matrix' cortices in chronic pain has been thought as a secondary epiphenomenon to altered nociceptive signaling in the spinal cord, progress in whole brain imaging studies on human patients and animal models has suggested a possibility that plastic changes in cortical neural circuits may actively contribute to chronic pain symptoms. Furthermore, recent development in two-photon microscopy and fluorescence labeling techniques have enabled us to longitudinally trace the structural and functional changes in local circuits, single neurons and even individual synapses in the brain of living animals. These technical advances has started to reveal that cortical structural remodeling following tissue or nerve damage could rapidly occur within days, which are temporally correlated with functional plasticity of cortical circuits as well as the development and maintenance of chronic pain behavior, thereby modifying the previous concept that it takes much longer periods (e.g. months or years). In this review, we discuss the relation of neural circuit plasticity in the 'pain matrix' cortices, such as the anterior cingulate cortex, prefrontal cortex and primary somatosensory cortex, with chronic pain. We also introduce how to apply long-term in vivo two-photon imaging approaches for the study of pathophysiological mechanisms of chronic pain.

• Journal of Powder Materials
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• v.1 no.2
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• pp.159-166
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• 1994

The variation of the microstructures and the mechanical properties with varying vacuum hot pressing temperature and pressure was investigated in PyM processed 20 vol%) SiCw/ 2124Al composites. As increasing the vacuum hot pressing temperature, the aspect ratio of whiskers and density of composites increased due to the softening of 2124Al matrix with the increased amount of liquid phase. The tensile strength of composite increased with increasing vacuum hot pressing temperature up to $570^{\circ}C$ and became saturated above $570^{\circ}C$, To attain the high densification of composites above 99%, the vacuum hot pressing pressure was needed to be above 70 MPa. However, the higher vacuum hot pressing pressure above 70 MPa was not effective to increase the tensile strength due to the reduced aspect ratio of SiC whiskers from damage of whiskers during vacuum hot pressing. A phenomenological equation to predict the tensile strength of $SiC_w$/2124AI composite was proposed as a function including two microstructural parameters, i.e. density of composites and aspect ratio of whiskers. The tensile strength of $SiC_w$/2124AI were found more sensitive to the porosity than other P/M materials due to the higher stress concentration and reduced load transfer efficiency by the pores locating at whisker/matrix interfaces.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.4
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• pp.189-197
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• 2003

The problem of designing a parallel feedforward compensator (PFC) is considered for a class of non-square linear systems such that the closed-loop system is strictly passive. If a given square system has (vector) relative degree one and is weakly minimum phase, the system can be rendered passive by a state feedback. However, when the system states are not always measurable and the given output is considered, passivation (i.e. rendering passive) of a non-minimum phase system or a system with high relative degree cannot be achieved by any other methodologies except by using a PFC. To passivate a non-square system we first determine a squaring gain matrix and design a PFC such that the composite system has relative degree one and is minimum phase. Then the system is rendered strictly passvie by a static output feedback law. Necessary and sufficient conditions for the existence of the PFC and the squaring gain matrix are given by the static output feedback formulation, which enables to utilize linear matrix inequality (LMI). As an application of the scheme, an alternative way of replacing the role of velocity measurements is provided for the PD-control law of a convey-crane system.

• Journal of the Korean Ceramic Society
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• v.34 no.8
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• pp.886-896
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• 1997

To investigate an effect of phase separation on precipitation characteristics of CuCl nanocrystals in CuCl doped nonlinear optical glasses, borosilicate glass systems with 9 different compositions with ~2wt% of CuCl were selected and CuCl doped glasses were prepared by melting and precipitation method. Microstructural properties of the CuCl doped glasses were analyzed by optical absorption spectroscopy, acid elution test, TEM, and EDXS. While phase separation did not occur in Glass A~D, interconnected and droplet microstructures due to phase separation were found in Glass E, F and Glass G~I, respectively. In the particular composition of the matrix glasses in this study, the precipitation of the CuCl particles was observed in the phase separable glasses, not in phase non-separable glasses. The CuCl particles were precipitated in both silica-rich phase region and boronrich phase region of the glass matrix. In the case of 7.7Na2O-36.6B2O3-52.7SiO2(mole%) glass, the larger CuCl particles than those in the silica-rich phase region were observed in the boron-rich phase region.