• Restorative Dentistry and Endodontics
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• v.35 no.4
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• pp.257-266
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• 2010

The purpose of this study was to determine the effect of post types and sizes on fracture resistance in immature tooth model with various restorative techniques. Bovine incisors were sectioned 8 mm above and 12 mm below the cementoenamel junction to simulate immature tooth model. To compare various post-and-core restorations, canals were restored with gutta-percha and resin core, or reinforced dentin wall with dual-cured resin composite, followed by placement of D.T. LIGHT-POST, ParaPost XT, and various sizes of EverStick Post individually. All of specimens were stored in the distilled water for 72 hours and underwent 6,000 thermal cycles. After simulation of periodontal ligament structure with polyether impression material, compressive load was applied at 45 degrees to the long axis of the specimen until fracture was occurred. Experimental groups reinforced with post and composite resin were shown significantly higher fracture strength than gutta-percha group without post placement (p < 0.05). Most specimens fractured limited to cervical third of roots. Post types did not influence on fracture resistance and fracture level significantly when cement space was filled with dual-cured resin composite. In addition, no statistically significant differences were seen between customized and standardized glass fiber posts, which cement spaces were filled with resin cement or composite resin individually. Therefore, root reinforcement procedures as above in immature teeth improved fracture resistance regardless of post types and sizes.

• Analytical Science and Technology
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• v.25 no.1
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• pp.25-32
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• 2012

Isotope dilution mass spectrometry (ID-MS) based on liquid chromatography tandem mass spectrometry (LC/MS/MS) was developed for the accurate determination of sorbic acid in tea-drink. An isotope analogue of sorbic acid, $^{13}C_2$-sorbic acid, was obtained by custom synthesis. MS was operated in the negative mode with selected reaction monitoring (SRM) mode of $[M-H]^-$ ${\rightarrow}$ $[M-CO_2H]^-$ channel at m/z 111 ${\rightarrow}$ 67 for sorbic acid and at m/z 113 ${\rightarrow}$ 68 for its isotope analogue. Chromatographic separation was accomplished with a C18 column and an isocratic mobile phase of 55% of 50 mM ammonium acetate (pH 4.5) and 45% of methanol. Homogeneous reference materials were prepared for validation of this method, including repeatability and reproducibility tests, by fortifying tea-drink with sorbic acid in our laboratory. Repeatability and reproducibility studies showed that the ID-LC/MS method is a reliable and reproducible method which provides less than 3.8% of relative standard deviation (RSD) for the analysis of sorbic acid.

• Research in Plant Disease
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• v.15 no.3
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• pp.170-174
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• 2009

In this paper, we report a characterization of Prunus necrotic ringspot virus (PNRSV) isolate. The virus was identified from 'Yumyeong' peach showing mild mosaic on leaves in commercial orchard of 'Umsung', Chungbuk province in Korea. The virus isolate produced ringspot symptom on the inoculated cotyledons and systemic mosaic and malformation on the upper leaves of Cucumis sativus. Systemic mottles were appeared in Chenopodium quinoa. When the buds of the virus infected stem were grafted on the healthy young Prunus persica GF305 seedlings, line pattern with mosaic appeared within 3 months. Isometric virus-like particles were found in parenchyma cells and plasmodesmata of C. sativus leaves inoculated mechanically with the virus. The cDNA fragments of PNRSV coat protein (CP) region, approximately 675bp, were synthesized from genomic RNA extracted from virus-infected leaves by RT-PCR using specific primer pairs. Partial nucleotide sequences of the CP regions were determined and analyzed with the known PNRSV. The CP gene of PNRSVKorea isolates showed 93.9~94.7% similarity to the 4 known PNRSV isolates.

• Korean Journal of Food Science and Technology
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• v.40 no.6
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• pp.669-673
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• 2008

For the development of a biological control method against B. cereus in cheonggukjang, 20 Bacillus spp. were isolated from the naturally fermented baektae and heuktae cheonggukjang, identified by using 16S rDNA sequences. Among the isolated strains, Bacillus sp. SC-8 was selected using the B. cereus lawn cell assay as an antagonistic microorganism against B. cereus. The culture medium of Bacillus sp. SC-8 after 24 hr of incubation at $37^{\circ}C$ also evidenced a high level of antagonistic activity. In cheonggukjang fermented with the mixed culture of Bacillus sp. SC-8 and B. cereus, antagonistic effect against B. cereus was maintained during the fermentation of cheonggukjang, while its effect was reduced during storage at $4^{\circ}C$ due to the decrement of cell population of Bacillus sp. SC-8. In Bacillus sp. SC-15, which was utilized a control, antagonistic activity against B. cereus was not demonstrated on the lawn cell plate assay and culture medium, but its effects were detected in cheonggukjang. Therefore, the production of antagonistic substances of Bacillus spp. depends on the fermentative environment.

• Korean Journal of Food Science and Technology
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• v.41 no.3
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• pp.339-344
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• 2009

Concentrations of polycyclic aromatic hydrocarbon (PAH) in processed chestnut products were determined by HPLC/FLD. The methodology involved procedures of sonication with water, extraction with hexane, and clean-up on a Sep-pak florisil cartridge. The PAH limits of detection (LOD) and limits of quantitation (LOQ) ranged from 0.012 to 0.382 ${mu}g/kg$ and from 0.042 to 1.273 ${mu}g/kg$, respectively. The coefficients of variation for intra- and inter-day assays were 0.02-4.48% and 0.37-9.83%, respectively, and the accuracies were 81.95-125.44% and 79.89-116.53%, respectively. The overall recoveries for eight PAHs spiked into the processed chestnut products ranged from 87.83 to 100.56%. As a result, PAH contents were not detected in the processed chestnut products.

• Korean Journal of Food Science and Technology
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• v.48 no.6
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• pp.565-568
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• 2016

This study was conducted to soften the tough texture of retorted beef in storage by increasing the water holding capacity (WHC) after pretreatment involving soaking and blanching in a phosphate solution. The yield of pretreated beef, based on weight as an indirect indicator of WHC, soaked in 0.35% (w/w) complex phosphates for 1 h, increased by 5-10%, in contrast to the untreated control in which the rib and shank was heated at $100^{\circ}C$ for 5-40 min. Additionally, strength of mechanical toughness in the fore rump and rib after phosphate curing at $115^{\circ}C$ for 30 min and blanching at $100^{\circ}C$ for 2 min were significantly decreased to 1.3 and $1.4kg_f$ (p<0.05) as compared to 2.0 and $1.8kg_f$ in the control, respectively. During storage of retorted beef for 30 days at $10^{\circ}C$, rib and shank pretreated with 0.35% complex phosphates exhibited a highly soft texture as compared to that of untreated beef. The softening of pretreated beef was based on the increased WHC due to complex phosphates.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.361-367
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• 2011

The uniaxial compressive strength (UCS) is an important factor in the design and construction of surface and underground structures. However, the method employed to measure UCS is time consuming and expensive to apply in the field. Therefore, we developed a model to estimate UCS based on a few properties using linear regression analysis, which is a statistical method. To develop the model, valid factors from the test results were selected from a correlation analysis using a statistical program, and the model was formulated by linear regression based on the relationships among factors. UCS estimates derived from the model were compared with the results of UCS tests, to assess the reliability of the model. The relationship between rock properties and UCS indicates that the factors with the greatest influence on UCS are point load strength and shape facto r. The UCS values obtained using the model are in good agreement with the results of the UCS test. Therefore, the developed model may be used to estimate the UCS of rocks in regions with similar conditions to those of the present study area.

• Health Policy and Management
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• v.26 no.4
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• pp.359-372
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• 2016

Background: The purpose of this study was to develop risk-adjustment models for acute stroke mortality that were based on data from Health Insurance Review and Assessment Service (HIRA) dataset and to evaluate the validity of these models for comparing hospital performance. Methods: We identified prognostic factors of acute stroke mortality through literature review. On the basis of the avaliable data, the following factors was included in risk adjustment models: age, sex, stroke subtype, stroke severity, and comorbid conditions. Survey data in 2014 was used for development and 2012 dataset was analysed for validation. Prediction models of acute stroke mortality by stroke type were developed using logistic regression. Model performance was evaluated using C-statistics, $R^2$ values, and Hosmer-Lemeshow goodness-of-fit statistics. Results: We excluded some of the clinical factors such as mental status, vital sign, and lab finding from risk adjustment model because there is no avaliable data. The ischemic stroke model with age, sex, and stroke severity (categorical) showed good performance (C-statistic=0.881, Hosmer-Lemeshow test p=0.371). The hemorrhagic stroke model with age, sex, stroke subtype, and stroke severity (categorical) also showed good performance (C-statistic=0.867, Hosmer-Lemeshow test p=0.850). Conclusion: Among risk adjustment models we recommend the model including age, sex, stroke severity, and stroke subtype for HIRA assessment. However, this model may be inappropriate for comparing hospital performance due to several methodological weaknesses such as lack of clinical information, variations across hospitals in the coding of comorbidities, inability to discriminate between comorbidity and complication, missing of stroke severity, and small case number of hospitals. Therefore, further studies are needed to enhance the validity of the risk adjustment model of acute stroke mortality.

• Journal of Food Hygiene and Safety
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• v.31 no.4
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• pp.278-285
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• 2016

This study used response surface methodology (RSM) in an effort to optimize the ultrasoundassisted extraction condition of Camellia sinensis L. and Artemisia argyi mixture in order to increase extraction yield in the extract. The effects of three independent variables, $X_1$ (Mixture ratio, 60-80%), $X_2$ (Ratio of water to raw material, 20~100 mL/g), and $X_3$ (Extraction time, 25-145 min), were investigated at three levels using Box-Behnken design (BBD) to obtain the highest extraction efficiency. Y (Extraction yield) was chosen as dependent variable. Our result showed that the coefficient of determination ($R^2$) of the model was 0.9747, with significant at the level of p < 0.002. Furthermore, the predicted values of each variable were similar to the actual values. The optimum extraction conditions were as follows: mixture ratio of 85.86%, ratio of water to raw material of 92.73 mL/g, and extraction time of 56.52 min. At these conditions, predicted extraction yield was 30.03%. The analysis of variance (ANOVA) indicated a high goodness of model fit and the success of the RSM method for optimizing extraction conditions of Camellia sinensis L. and Artemisia argyi mixture.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.729-734
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• 2002

In this study, the polyaniline films of emeraldine base(EB) and lucoemeraldine base(LEB) form chemically doping with poly(sodium-4 styrenesulfonate, PSS) were prepared by casting the mixed solution of chloroform and m-cresol on ITO(indium tin oxide) electrode. By analyzing UV-vis spectra of the mixed solutions, the effects of the secondary doping by m-cresol were obtained. And the conductivity of polyaniline film was increased with increasing m-cresol content. The results suggest that the improvement of conductivity obtained by secondary doping results primarily from interaction of polyaniline and m-cresol. As the results of analyzing cyclic voltammograms, it was known that the redox peak currents of polyaniline electrode prepared from LEB were larger and more reversible than those of polyaniline electrodes prepared from EB. The charge transfer resistances($R_{ct}$) of polyaniline electrodes were reduced with increasing m-cresol content, and LEB/PSS electrodes were smaller than EB/PSS electrodes. This result agrees to the analysis of the redox peak current of cyclic voltammograms. The solution resistance and the capacity of electrical double layer almost unchanged in all prepared polyaniline electrodes. It was confirmed that solution resistance was independent of frequency factor in AC impedance spectra. Also the polyaniline film doping with PSS was revealed pseudo n-type characteristics of conducting polymer.