• Restorative Dentistry and Endodontics
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• v.43 no.2
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• pp.26.1-26.12
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• 2018

Objective: The purpose of this study was to investigate the degree of conversion (DC) and mechanical properties of a microhybrid Filtek Z250 (3M ESPE) resin composite after aging. Method: The specimens were fabricated using circular molds to investigate Vickers microhardness (Vickers hardness number [VHN]) and DC, and were prepared according to ISO 4049 for flexural strength testing. The initial DC (%) of discs was recorded using attenuated total reflectance-Fourier transforming infrared spectroscopy. The initial VHN of the specimens was measured using a microhardness tester under a load of 300 g for 15 seconds and the flexural strength test was carried out with a universal testing machine (crosshead speed, 0.5 mm/min). The specimens were then subjected to thermocycling in $5^{\circ}C$ and $55^{\circ}C$ water baths. Properties were assessed after 1,000-10,000 cycles of thermocycling. The surfaces were evaluated using scanning electron microscopy (SEM). Data were analyzed using 1-way analysis of variance followed by the Tukey honest significant difference post hoc test. Results: Statistical analysis showed that DC tended to increase up to 4,000 cycles, with no significant changes. VHN and flexural strength values significantly decreased upon thermal cycling when compared to baseline (p < 0.05). However, there was no significant difference between initial and post-thermocycling VHN results at 1,000 cycles. SEM images after aging showed deteriorative changes in the resin composite surfaces. Conclusions: The Z250 microhybrid resin composite showed reduced surface microhardness and flexural strength and increased DC after thermocycling.

• Clinical and Experimental Pediatrics
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• v.48 no.5
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• pp.500-505
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• 2005

Purpose : This study was designed to estimate the prevalence of Mycoplasma pneumoniae infection during an epidemic period by means of examining the antibody conversion rate and to investigate the association of the antibody conversion with age, initial antibody titer, and atopy. Methods : We chose 191 children whose antibody titer to M. pneumoniae was negative, 1 : 40, or 1 : 80 during the first half of 2003. After the second half of 2003 when the M. pneumoniae epidemic occurred, follow-up collection of sera was performed during the first half of 2004. M. pneumoniae antibody titer was measured by Serodia-Myco II particle agglutination test. Results : Of 191 children, antibody conversion was detected in 83 children(43.5 percent). No significant difference was found between the conversion and non-conversion group with respect to age, sex and atopy. Dividing the subjects into four groups by age, results on the antibody conversion rate revealed no significant differences between the groups. Assessed by initial antibody titer, a diminished trend of conversion rate was observed in children with 1 : 80 titer but the difference was not significant. There was no significant difference in the antibody conversion rate between atopic and non-atopic children. Conclusion : Based on the antibody conversion rate in this study, the prevalence of M. pneumoniae infection during an epidemic period was estimated to be 43.5 percent. This high infection rate suggests that during an epidemic, we should bear in mind M. pneumoniae as an important etiologic agent for respiratory infection in children.

• Journal of Hydrogen and New Energy
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• v.17 no.3
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• pp.293-300
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• 2006

KIER has been developing a Ru-based preferential oxidation catalysts and a novel fuel processing system to provide hydrogen rich gas to residential PEMFCs system. The catalytic activity of Ru-based catalysts was investigated at different Ru loading amount and different support structure. The obtained result indicated that 2 wt% loaded Ru-based catalyst supported on ${\alpha}-Al_2O_3$ showed high activity in low temperature range and suppressed the methanation reaction. The developed prototype fuel processor showed thermal efficiency of 78% as a HHV basis with methane conversion of 92%. CO concentration below 10 ppm in the produced gas is achieved with separate preferential oxidation unit under the condition of $[O_2]/[CO]=2.0$. The partial load operation have been carried out to test the performance of fuel processor from 40% to 80% load, showing stable methane conversion and CO concentration below 10 ppm. The durability test for the daily start-stop and 8 h operation procedure is under investigation and shows no deterioration of its performance after 50 start-stop cycles. In addition to the system design and development.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.1
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• pp.1-9
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• 2010

In this study, the selective catalytic reduction of $NO_x$ with ammonia was carried out in a filter bag support reactor. The experiments were performed by powder type $MnO_x$ and $V_2O_5$/$TiO_2$ catalyst at low temperature between 130 and $250^{\circ}C$. Also, the effect of $SO_2$ and $H_2O$ on the NO conversion was investigated under our test conditions. The powder type catalysts were analyzed by X-ray photoelectron spectrum (XPS), X-ray diffraction(XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). It was observed that NO removal efficiency of the powder type $V_2O_5$/$TiO_2$ catalyst was 85% at low temperature($200^{\circ}C$) under presence of oxygen and that of $MnO_x$ was 50% at the same condition. The powder type $V_2O_5$/$TiO_2$ catalyst, in conclusion, was found to be available for SCR reaction in a filter bag support system.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.400-404
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• 2011

The activity and stability of the metal filter material Pt coated on NOx and soot oxidation were examined. The catalytic reaction test for NOx and soot were also performed independently and simultaneously. As a result, it showed the NO to $NO_2$ shift reaction with 20% conversion, NOx decomposition (about 10%) and perfect soot oxidation on the material Pt coated proceeded. Onset temperature of soot oxidation shift to lower temperature (about $30^{\circ}C$) by generated $NO_2$. The material also was less affected by thermal shock than $Pt/Al_2O_3$ or $Pt/TiO_3$ catalysts due to its stability of surface structure.

• Archives of Plastic Surgery
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• v.45 no.2
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• pp.158-164
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• 2018

Background During breast augmentation, the transaxillary approach provides the advantage of allowing the mammary prosthesis to be placed through incisions that are remote from the breast itself, thereby reducing the visibility of postoperative scars. For patients experiencing capsular contracture who do not want additional scars, the previous transaxillary scar can be used for site change and implant exchange. Methods This study analyzed 17 patients (34 breasts) with submuscular breast implants with grade III-IV capsular contracture who received treatment from 2010 to 2015. The mean age of the patients was 29 years (range, 20-38 years). The inclusion criterion was a pinch test of more than 3 cm at the upper pole of the breast. Previous axillary scars were used to expose the pectoralis fascia, and submuscular breast implants were removed carefully. The dissection underneath the pectoralis fascia was performed with endoscopic assistance, using electrocautery under direct visualization. Results The mean follow-up period was 14 months (range, 6-24 months). The entire dissection plane was changed from the submuscular plane to the subfascial plane. Round textured gel implants were used, with a mean implant size of 220 mL (range, 160-300 mL). Two patients developed grade II capsular contracture. There were no cases of malposition or asymmetry. Three patients complained of minor implant palpability. None of the patients required additional surgery. Conclusions Endoscopic subfascial conversion may be an effective technique for treating capsular contracture and avoiding scarring of the breast in selected patients.

• Restorative Dentistry and Endodontics
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• v.37 no.2
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• pp.96-103
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• 2012

Objectives: This study evaluated the effect of camphorquinone (CQ)-amine ratio on the C=C double bond conversion of resins with binary and ternary photoinitiation systems. Materials and Methods: Two monomer mixtures (37.5 Bis-GMA/37.5 Bis- EMA/25 TEGDMA) with binary systems (CQ/DMAEMA in weight ratio, group A [0.5/1.0] and B [1.0/0.5]) and four mixtures with ternary system (CQ/OPPI/DMAEMA, group C [0.1/1.0/0.1], D [0.1/1.0/ 0.2], E [0.2/1.0/0.1] and F [0.2/1.0/0.2]) were tested: 1 : 2 or 2 : 1 CQ-amine ratio in binary system, while 1 : 1 ratio was added in ternary system. The monomer mixture was cured for 5, 20, 40, and 300 sec with a Demetron 400 curing unit (Demetron). After each exposure time, degree of conversion (DC) was estimated using Fourier transform infrared (FTIR) spectrophotometer (Nicolet 520, Nicolet Instrument Corp.). The results were analyzed by ANOVA followed by Scheffe test, with p = 0.05 as the level of significance. Results: DC (%) was expressed in the order of curing time (5, 20, 40, and 300 sec). Group A ($14.63{\pm}10.42$, $25.23{\pm}6.32$, $51.62{\pm}2.69$, $68.52{\pm}2.77$); Group B ($4.04{\pm}6.23$, $16.56{\pm}3.38$, $37.95{\pm}2.79$, $64.48{\pm}1.21$); Group C ($16.87{\pm}5.72$, $55.47{\pm}2.75$, $60.83{\pm}2.07$, $68.32{\pm}3.31$); Group D ($23.77{\pm}1.64$, $61.05{\pm}1.82$, $65.13{\pm}2.09$, $71.87{\pm}1.17$); Group E ($28.66{\pm}2.92$, $56.68{\pm}1.33$, $60.66{\pm}1.17$, $68.78{\pm}1.30$); Group F ($39.74{\pm}6.31$, $61.07{\pm}2.58$, $64.22{\pm}2.29$, $69.94{\pm}2.15$). Conclusion: All the monomers with ternary photoinitiation system showed higher DC than the ones with binary system, until 40 sec. Concerning about the effect of CQ-amine ratio on the DC, group A converted into polymer more than group B in binary system. However, there was no significant difference among groups with ternary system, except group C when cured for 5 sec only.

• Tuberculosis and Respiratory Diseases
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• v.56 no.5
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• pp.485-494
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• 2004

Background : To assess the effects of mDOT implementation on sputum smear conversion for AFB (Acid fast bacilli) positive pulmonary tuberculosis patients, modified Directly Observed Treatment (mDOT) was started on October $8^{th}$ 2001 at a health center in Seoul. mDOT was defined through weekly interviewing and supervising of a patient by a supervisor (doctor, nurse, or lay health worker). The sputum smear conversion of a mDOT group was compared with that of a self-medication (self) group. Methods : This study included 52 AFB positive pulmonary tuberculosis patients registered at a health center in Seoul between October $8^{th}$ 2001 and April $23^{rd}$ 2002. 24 and 28 patients were enrolled in the mDOT and self medication groups, respectively. Paired (1:1) individual matching, by gender, extent of disease, relapse and age-matching variables, was performed between the two groups, resulting in 20 paired matches. This prospective study was planned as an unblinded, non-randomized quasiexperimental pilot project. Outcomes were identified from results of sputum smear examinations for AFB in both groups at 2 weeks, and 1 and 2 months. The paired matching data were analyzed using the SAS program version 8.1 by McNemar test. Results : At the end of 2 weeks of treatment, the sputum smear conversion of the mDOT group was somewhat higher than that of the self medication group (78.57 vs. 50%, p-value=0.289), and after 1 month of treatment no statistically significant difference was shown between the two groups (83.33 vs. 50, p-value=0.125). At the end of 2 months of treatment (initial intensive phase), the sputum smear conversions of the mDOT and self groups were 95 and 75%, respectively (p-value=0.219). Conclusions : The implementation of mDOT did not result in clinically significant increases in the sputum smear conversion at 2 weeks, and 1 and 2 months compared with that of the self medication group. However, the increases experienced might contribute to diminishing the infectious period of AFB positive patients, and this approach may act as a guide for a specific group of patients. In this study, mDOT was performed for one hundred percent of the intensive treatment phase. It can also be an effective treatment for pulmonary tuberculosis patients, and may be useful for some high risk tuberculosis patients.

• Restorative Dentistry and Endodontics
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• v.41 no.4
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• pp.271-277
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• 2016

Objectives: In this study, we evaluated the influence of different radiant exposures provided by single-peak and polywave light-curing units (LCUs) on the degree of conversion (DC) and the mechanical properties of resin cements. Materials and Methods: Six experimental groups were established for each cement (RelyX ARC, 3M ESPE; LuxaCore Dual, Ivoclar Vivadent; Variolink, DMG), according to the different radiant exposures (5, 10, and $20J/cm^2$) and two LCUs (single-peak and polywave). The specimens were made (7 mm in length ${\times}$ 2 mm in width ${\times}$ 1 mm in height) using silicone molds. After 24 hours of preparation, DC measurement was performed using Fourier transform infrared spectrometry. The same specimens were used for the evaluation of mechanical properties (flexural strength, FS; elastic modulus, E) by a three-point bending test. Data were assessed for normality, after which two-way analysis of variance (ANOVA) and post hoc Tukey's test were performed. Results: No properties of the Variolink cement were influenced by any of the considered experimental conditions. In the case of the RelyX ARC cement, DC was higher when polywave LCU was used; FS and E were not influenced by the conditions evaluated. The LuxaCore cement showed greater sensitivity to the different protocols. Conclusions: On the basis of these results, both the spectrum of light emitted and the radiant exposure used could affect the properties of resin cements. However, the influence was material-dependent.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.1 s.49
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• pp.111-114
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• 2005

This study is about the cosmeceutical products using enzyme induced bio-conversion system. In general, ascorbic acid (AA) has the higher reducing activity and can be used for various purpose in the cosmetics. But it is very unstable in the aqueous system and difficult to maintain its stability in the cosmetics product. 2-O-$\alpha$-D-Glucopyranosyl-L-ascorbic acid (AA2G) is the stabilized form of AA and showed the less whitening activity than AA. In this study, we developed bio-conversion system improving the stability and efficacy of AA2G and AA, respectively. In this system, AA2G (over $80\%$) can be converted to AA and glucose within 30 min. The converted product showed higher anti-tyrosinase activity like AA (AA2G showed no anti tyrosinase activity) and depigmenting activity in the artificial tanning test. From these results, we could conclude this system is a brand new method to increase the activity of AA and maintain its stability.