• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.383-394
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• 2018

This study analyzed the latent profile for identifying the difference in the dependence on smartphone use among middle school students in the 1st grade using the Korean Children and Youth Panel Survey (KCYPS). From the result of this study, first the latent class was separated according to the type of dependence on smartphone use. Class 1 included the students (from fifth grade in elementary school) whose level of reliance on smartphone use was low. Class 2 was selected as the group whose level of reliance on smartphone was high. Secondly, in comparing class 2 to class 1, it was found that the students who have a high probability of being in class 1 were those whose fathers are high achievers, have high early self-esteem and less age attachment. Thirdly, the students in class 1 had a higher sense of neglect than those in class 2. Furthermore, the self-determination of the students in class 2 mediated the effect of neglect on the adolescents' dependence on smartphone use both directly and indirectly.

• Polymer(Korea)
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• v.30 no.3
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• pp.259-265
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• 2006

Small intestinal submucosa (SIS) consists of some growth factors which can stimulate cell activity, and PVA has been widely utilized in the area of wound dressing as hydrogel which is easy to be removed from wounds. In this study, native SIS sheets were coated with PVA by immersing them into 2, 4, and 10 wt% of PVA solution and then lyophilized on two type of molds to endow the prepared wound dressing with easy removal property from wounds. The mechanical properties were examined through tensile test. Moreover, enzymatic degradation, water uptake, and in vitro test were carried out to characterize the prepared SIS sheets. The tensile strength of the SIS sheets coated with PVA (PVA-SIS) were decreased, whereas the elongation were increased. Degradation ratio of the PVA-SIS sheets was decreased compare to native SIS. Water uptake ability was improved at 2 and 4 wt% of PVA. The degree of fibroblast attachment was lower than the native SIS sheets. In conclusion, this study suggests that the PVA coated SIS sheets have a potential for the applications of wound dressing and biodegradable injectable materials.

• Polymer(Korea)
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• v.36 no.3
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• pp.357-363
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• 2012

Surface-modified poly(L-lactic acid) (PLLA) films and scaffolds were treated with plasma discharge in oxygen gas and subsequently subjected to $in$ $situ$ grafting of acrylic acid (AA) in order to increase the cell compatibility. The surface of AA-grafted PLLA was converted to hydroxyapatite (HA)-deposited PLLA in stimulated body fluid (SBF). After the samples were immersed in phosphate-buffered saline (PBS), fetal bovine serum (FBS), normal saline, or cell medium, the water contact angles were significantly reduced on the surface of HA-deposited PLLA. Chondrocyte and osteoblast showed a higher attachment and cell proliferation on HA-deposited surfaces and in particular, it was confirmed that chondrocyte was considerably influenced by HA. However, osteoblast showed better cell proliferation on the surfaces immersed in FBS, cell medium or HA-deposited surface. In addition, the cell proliferation in 3D scaffolds was much higher than that on film type, irrespective of chondrocyte and osteoblast. Therefore, such surface-modified PLLAs are expected to be useful as organic-inorganic hybrid scaffolds in the regeneration of cartilage and bone.

• Journal of Periodontal and Implant Science
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• v.41 no.5
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• pp.227-233
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• 2011

Purpose: The aim of this study was to compare osteoblast behavior on zirconia and titanium under conditions cultured with bone morphogenetic protein-2. Methods: MC3T3-E1 cells were cultured on sandblasted zirconia and sandblasted/etched titanium discs. At 24 hours after seeding MC3T3-E1, the demineralized bone matrix (DBM) gel alone and the DBM gel with bone morphogenetic protein-2 (BMP-2) were added to the culture medium. The surface topography was examined by confocal laser scanning microscopy. Cellular proliferation was measured at 1, 4, and 7 days after gel loading. Alkaline phosphatase activity was measured at 7 days after gel loading. The mRNA expression of ALPase, bone sialoprotein, type I collagen, runt-related transcription factor 2 (Runx-2), osteocalcin, and osterix were evaluated by real-time polymerase chain reaction at 4 days and 7 days. Results: At 1, 4, and 7 days after loading the DBM gel alone and the DBM gel with BMP-2, cellular proliferation on the zirconia and titanium discs was similar and that of the groups cultured with the DBM gel alone and the DBM gel with BMP-2 was not significantly different, except for titanium with BMP-2 gel. ALPase activity was higher in the cells cultured with BMP-2 than in the other groups, but there was no difference between the zirconia and titanium. In ALPase, bone sialoprotein, osteocalcin, Runx-2 and osterix gene expression, that of cells on zirconia or titanium with BMP-2 gel was much more highly increased than titanium without gel at day 7. The gene expression level of cells cultured on zirconia with BMP-2 was higher than that on titanium with BMP-2 at day 7. Conclusions: The data in this study demonstrate that the osteoblastic cell attachment and proliferation of zirconia were comparable to those of titanium. With the stimulation of BMP-2, zirconia has a more pronounced effect on the proliferation and differentiation of the osteoblastic cells compared with titanium.

• Journal of Periodontal and Implant Science
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• v.44 no.5
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• pp.242-250
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• 2014

Purpose: This study aimed to evaluate the effects of fibronectin and oxysterol immobilized on machined-surface dental implants for the enhancement of cell attachment and osteogenic differentiation, on peri-implant bone healing in the early healing phase using an experimental model in dogs. Methods: Five types of dental implants were installed at a healed alveolar ridge in five dogs: a machined-surface implant (MI), apatite-coated MI (AMI), fibronectin-loaded AMI (FAMI), oxysterol-loaded AMI (OAMI), and sand-blasted, large-grit, acid-etched surface implant (SLAI). A randomly selected unilateral ridge was observed for 2 weeks, and the contralateral ridge for a 4-week period. Histologic and histometric analyses were performed for the bone-to-implant contact proportion (BIC) and bone density around the dental implant surface. Results: Different bone healing patterns were observed according to the type of implant surface 2 weeks after installation; newly formed bone continuously lined the entire surfaces in specimens of the FAMI and SLAI groups, whereas bony trabecula from adjacent bone tissue appeared with minimal new bone lining onto the surface in the MI, AMI, and OAMI groups. Histometric results revealed a significant reduction in the BIC in MI, AMI, and OAMI compared to SLAI, but FAMI demonstrated a comparable BIC with SLAI. Although both the BIC and bone density increased from a 2- to 4-week healing period, bone density showed no significant difference among any of the experimental and control groups. Conclusions: A fibronectin-coated implant surface designed for cell adhesion could increase contact osteogenesis in the early bone healing phase, but an oxysterol-coated implant surface designed for osteoinductivity could not modify early bone healing around implants in normal bone physiology.

• The Korean Journal of Nuclear Medicine Technology
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• v.21 no.2
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• pp.13-27
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• 2017

Purpose In the procedure of domestic medical radioactive self-disposal, there are many requests of supplementation and difficulties on the screening process. In this regard, presentation of basic guideline will improve the work processing efficiency of medical institution radioactive waste. From 2015 to 2016, We reviewed and compared a supplementary requests of domestic fifteen medical institution radioactive self-disposal Plan & Procedure manual. In connection with this, we derive the details of the radioactive waste document based on the relative regulation of nuclear safety Act. The representative supplementary requests of Korea Institute of Nuclear Safety are disposal method of non-flammability radioactive waste, storage method of scheduled self-disposal waste, the legitimacy of self-disposal and pre-treatment of self-disposal, reference radioactivity of disused filter and output of storage period, attachment the evidential matter of measurement efficiency when using a gamma counter. Through establishing a medical radioactive waste guideline, we can clearly suggest a classification standard of radioactive nuclide and the type of occurrence. As a result, we can confirm the reduction of examination processing period while preparing a self-disposal document and there is no spending expenses for business agency. Also, the storage efficiency of facility will better and reduce the economic expenses. On the basis of this guideline, we will expect a contribution to the improvement of work efficiency for officials who has a working-level difficulty of radioactive waste self-disposal.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.5
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• pp.490-499
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• 2002

Recently, gamma radiographic equipments have been used about 1,000 sets manually and operated by about 2,500 persons in Korea. In order for a radiography to work effectively with avoiding any hazard of the high level radiation from the source, many field workers have expected developing a wireless automatic remote exposure controller. The KlTCO research team has developed an automatic remote exposure controller that can regulate the speed of $0.4{\sim}1.2m/s$ by BLDC motor of 24V 200W which has output of $54kgf{\cdot}cm$, suitable torque and safety factor for the work. And the developed automatic remote exposure controller can control rpm of motor, pigtail position by photo-sensor and exposure time by timer to RF sensor. Thus, the developed equipment is expected that the unit can be used in many practical applications with benefits in economical advantage to combine the use of both automatic and manual type because attachment is possible existent manual remote exposure controller, AC and DC combined use.

• Parasites, Hosts and Diseases
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• v.29 no.2
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• pp.121-128
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• 1991

The degree of attraction of Toxoplasma gondii to vertebrate cells varies with cell type and cell phase. Human promyelocytic leukemia cells, HL-60, were synchronized by double thymidine block method and co-cultured with Toxoplasma for 1 hr at each cell stage to investigate the cell cycle specific susceptibility of parasites to host cells. For 30 hr the average number of Texoplasma that invaded was a little changed except at 3 hr from G1/S phase boundary which concurred with the peak point of DNA synthesis. At 3 hr which is a relatively short interval compared to whole S phase, modification of cells by parasitic invasion was most remarkable. The number of Toxoplasma that penetrated was increased to more than sin times. The shape of the cells became sludgy and almost indiscernible by strong accessibility of parasites only for an hour of mfd-S phase. The same auctuation was also observed at the second peak of S phase but weakly. This suggests that there be surface molecules concerning with the attachment of Texoplasma to the host cells, which is expressed at special point of S phase. further studies on the specific protein or similar molecules related could be carried out using synchronized HL-60 cells.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.35 no.2
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• pp.112-119
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• 2009

Extracellular matrix(ECM) is known to function as a reservoir of endogenous growth factors, can be an effective delivery system of growth factor that easily lost bioactivity in solution. Fibrillar collagens like type I collagen, are the major constituent of the ECM and structural protein of bone. Also, it can be a scaffold for osteoblast migration. The purpose of this study was to compare the effects of absorbable Atelo-collagen Sponge($Teruplug^{(R)}$) insertion in tooth extraction sites on periodontal healing of the mandibular second molar after the extraction of the impacted third molar. The study population comprised 31 cases who had been scheduled for surgical removal of impacted mandibular third molars. All patients were in good general health and were not using any medication that would influence wound healing after surgery. In 15 cases control group, none was inserted into the tooth extraction site. In 16 cases experimental groups, $Teruplug^{(R)}$ was inserted into the tooth extraction site. We evaluated tooth mobility, pocket depth, gingival margin level preoperatively and 1 week, 2 weeks, 4 weeks, and 3 months postoperatively. The change was compared with two groups using Mann-Whitney test. The results were as follows. 1. There was no significant change of tooth mobility on both groups. 2. There was tendency of decreasing of previous pocket depth causing tooth extraction on both groups. 3. On gingival margin level, there was various change according to initial swelling and loss of attachment on both groups. 4. There was tendency of decreasing of gingival margin level on both groups because of removal of inflammation and decreasing of previous pocket depth. 5. There was large change of pocket depth on buccal middle, distal, lingual distal area because of tooth extraction and bone reduction. Compared with the control group and experimental group, we observed significant difference during some periods. The results of this study suggest that absorbable atelo-collagen sponge($Teruplug^{(R)}$) is relatively favorable bone void filler with prevention of tissue collapse, food packing and enhance periodontal healing.

• Journal of Labour Economics
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• v.24 no.1
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• pp.97-124
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• 2001

Co-residence is a type of intergenerational private transfers of resources: money, time and space. Adult daughters and their elderly parents decide to co-reside, depending on their utility levels before and after co-residence that mainly depend on the health status of the elderly. Therefore, co-residence implies positive net benefits to both parties in the sense that, when they co-reside, elderly parents share childcare and adult daughter provide elderly care. In other words, formal (paid) care can be substituted with informal (unpaid) one. Both marriage and giving births are considered as the major obstacles to labor market attachment of women who bear burdens of home production and childcare. Co-residence can be a solution for married women to avoid career interruption by sharing burdens with their elderly parents. However, most previous studies using the U.S. data on intergenerational private transfers focused on elderly care and have concluded that they reduce government expenditures associated with public subsidies to the elderly. This study focuses on adult daughters and it examines effects of co-residence on labor supply of married women in Korea, who face limited formal childcare programs in terms of both quantity and quality. It applies the Tobit model of married women's labor supply to the data from the Second Wave of the Korean Labor and Income Panel Survey( 1999), in order to investigate effects of co-residence and the work and health status of the co-residing elderly as well as their own health status. Four specifications of the empirical model are tested that each includes co-residence with elderly parents, their gender, or their work and health status. Estimation results show that co-residence, co-residence with female elderly, and co-residence with not-working female elderly have significant positive effects on labor supply of married women while poor health status of co-residing female elderly does not bring about any negative effects. However, co-residence with male elderly, regardless of their work and health status, has no significant effect The results indicate that co-residence is closely related to sharing of home production among female elderly and adult daughters who are married and, through intergenerational private transfers of resources in terms of time, it helps women avoid career interruption.