• Journal of Ocean Engineering and Technology
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• v.7 no.2
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• pp.57-67
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• 1993

The fracture behavior of plain woven glass/epoxy composite plates with a crack is investigated under static tensile loading. It is shown in this paper that the characteristic length associated with the point stress criterion depends on the crack length. To predict the not ched tensile strength, the point stress criterion proposed by Whitney and Nuismer are modified. An excellent agreement is found between the experimental results and the analytical prediction of the modified point stress criterion. The condition of unstable crack growth in the presence of a per-existing flaw(machined notch) is examined by means of the maximum stress intensity factor $K_max$ using maximumload P$_max$. The values of $K_max$ evaluated from energy release rate G$_max$(the compliance me thod) indicate a wide difference. Therefore in regard to anisotropy and heterogeneity of the composite materials studied, the modified shape correction factor f(a/W) is obtained. $K_max$evaluated by the compliance method a little or insignificantly depends on the initial crack length a, the specimen thickness B, the crack angle .theta. and the specimen geometry.

• Journal of Korean Dental Science
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• v.17 no.3
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• pp.105-111
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• 2024

Purpose: Research comparing and evaluating the properties of various dental materials is an important topic in the field of dentistry. This study aims to evaluate the fluoride release and microhardness properties of various fluoride-containing restorative materials used in dental treatments. Materials and Methods: Thirty specimens of four restorative materials were prepared (5 mm × 2 mm, cylindrical): alkasite-based material (Cention N, CN), Self-cure glass Ionomer (Riva self cure, RS), Resin-modified glass ionomer cement (Fuji LC II, FL) and composite resin (Filtek Z350XT, FZ). Fluoride release measurements were conducted on 25 specimens at intervals of 1, 2, 6, 13, 20, and 27 days with a fluoride electrode connected to the pH/ISE Meter (Orion Star A214, Thermo Scientific, USA) and cumulative fluoride release was calculated. Vickers microhardness measurements were performed on five specimens from each material with microhardness tester (DM2D, AFFRI, Italy). Results: As a result of measuring the amount of fluoride release over 27 days, the amount of fluoride release in CN showed a gradual increase, while the amount of fluoride release in RS, FL, and FZ gradually decreased. The cumulative fluoride release amount for 28 days was significantly higher in CN and FL than in RS (P < 0.05). FZ and RS demonstrated significantly higher microhardness compared to CN and FL (P < 0.05). FZ and RS showed similar microhardness, and FL showed the lowest microhardness. Conclusion: Cention N (CN) exhibited superior fluoride release compared to Glass Ionomer Cement (RS), making it a promising option for preventing secondary caries. However, it displayed a lower microhardness than the composite resin (FZ), indicating potential limitations in terms of mechanical strength. Therefore, if an anti-caries action is required, Cention N may be considered first; however, it appears to be difficult to use in posterior permanent teeth.

• Korean Journal of Agricultural Science
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• v.43 no.2
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• pp.215-220
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• 2016

The global cultivation area of genetically modified crops (GM crops) has been increasing every year. Cultivation of GM crops is not only beneficial to the economy but also has positive effects on the environment in decreasing the use of agrochemicals, chemical fertilizers, and agricultural machinery. However, there have been controversies about the admixture of GM crops and non-GM crops and the unintentional release of GM crops to the environment. Especially in Korea, where consumption of agricultural products is import-dependent, the economic importance of GM crops has been a significant issue. The Act on import and distribution of GM crops was established in 2001 to start the management of GM crops in Korea. Recently, the imported amount of GM crops to Korea has reached over 10 million tons and is increasing very rapidly; consequently, the potential environmental impact of GM crops is becoming a big issue in Korea. In Japan, the discovery of imported GM canola plants around ports in 2005 raised awareness of the unintentional release of GM crops. In Korea, GM maize plants were also found in port and feed factory surroundings from 2005 to 2007. It is now necessary to monitor imported GM crops by tracing distribution, transport process for practical environmental risk assessment. Possible gene transfer from GM crops to non-GM crops should also be investigated in the cultivation area and the surroundings as well.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.493-502
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• 2021

We prepared and investigated a biosynthesized nanoparticulate system with high adsorption and release capacity of letrozole. Silver nanoparticles (AgNPs) were biosynthesized using olive leaf extract. Cysteine was capped AgNPs to increase the adsorption capacity and suitable interaction between nanoparticles and drug. Morphology and size of nanoparticles were confirmed using transmission electron microscopy (TEM). Nanoparticles were spherical with an average diameter of less than 100 nm. Cysteine capping was successfully confirmed by Fourier transform infrared resonance (FTIR) spectroscopy and elemental analysis (CHN). Also, the factors of letrozole adsorption were optimized and the linear and non-linear forms of isotherms and kinetics were studied. Confirmation of the adsorption data of letrozole by cysteine capped nanoparticles in the Langmuir isotherm model indicated the homogeneous binding site of modified nanoparticles surface. Furthermore, the adsorption rate was kinetically adjusted to the pseudo-second-order model, and a high adsorption rate was observed, indicating that cysteine coated nanoparticles are a promising adsorbent for letrozole delivery. Finally, the kinetic release profile of letrozole loaded modified nanoparticles in simulated gastric and intestinal buffers was studied. Nearly 40% of letrozole was released in simulated gastric fluid with pH 1.2, in 30 min and the rest of it (60%) was released in simulated intestinal fluid with pH 7.4 in 10 h. These results indicate the efficiency of the cysteine capped AgNPs for adsorption and release of drug letrozole for breast cancer therapy.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.2
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• pp.81-89
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• 2019

Purpose: This study aimed to investigate the correlation between the solubility and the amount of fluoride release when a resin surface coating agent is applied to RMGIC. Materials and Methods: To measure the fluoride release and solubility, Fuji II $LC^{(R)}$and $Filtek^{TM}$ Z350XT without a surface coating, Fuji II $LC^{(R)}$ with G coat $plus^{TM}$ and Fuji II $LC^{(R)}$ with $Permaseal^{(R)}$ were prepared. And the amount of fluoride release and solubility were measured. Results: There was no significant difference in the daily fluoride release between the surface coating agents. The cumulative fluoride release was significantly different between the groups using RMGIC at 56 days (P < 0.05). In the solubility measurement, RMGIC without surface coating was significantly different only on the 7th day compared to the other three groups (P < 0.05). Conclusion: Surface coating agents can prevent the degradation of properties by the initial solvent in RMGIC. Therefore, fluoride is preserved inside the restorative material and the effect of surface coating after the addition is reduced, so that the effect on fluoride release and storage is also reduced.

• Journal of the korean academy of Pediatric Dentistry
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• v.51 no.2
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• pp.149-164
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• 2024

This study compared the solubility, water absorption, dimensional stability, release of various ions (hydroxyl, calcium, sulfur, strontium, and silicon), and cytotoxicity of light-cured resin-modified pulp-capping materials. Resin-modified calcium hydroxide (Ultra-blend^TM plus, UBP), light-cured resin-modified calcium silicate (TheraCal LC^TM, TLC), and dual-cure resin-modified calcium silicate (TheraCal PT^TM, TPT) were used. Each material was polymerized; solubility, 24-hour water absorption, and 30- day dimensional stability experiments were conducted to test its physical properties. Solubility was assessed according to the ISO 6876 standard, and 24 hours of water absorption, 30 days of dimensional stability were assessed by referring to the previous protocol respectively. Eluates at 3 and 24 hours and on 7, 14, and 28 days were analyzed according to the ISO 10993-12 standard. And the pH, Ion-releasing ability, cell proliferation rate, and cell viability were assessed using the eluates to evaluate biochemical characteristics. pH was measured with a pH meter and Ion-releasing ability was assessed using inductively coupled plasma atomic emission spectrometry (ICP-AES). Cell proliferation rate and cell viability were assessed using human dental pulp cells (hDPCs). The former was assessed by an absorbance assay using the CCK-8 solution, and the latter was assessed by Live and Dead staining. TPT exhibited lower solubility and water absorption than TLC. UBP and TPT demonstrated higher stability than TLC. The release of sulfur, strontium, calcium, and hydroxyl ions was higher for TLC and TPT than for UBP. The 28-day release of hydroxyl and silicon ions was similar for TLC and TPT. TLC alone exhibited a lower cell proliferation rate compared to the control group at a dilution ratio of 1 : 2 in cell proliferation and dead cells from Live and Dead assay evaluation. Thus, when using light-cure resin-modified pulp-capping materials, calcium silicate-based materials can be considered alternatives to calcium hydroxide-based materials. Moreover, when comparing physical and biochemical properties, TPT could be prioritized over TLC as the first choice.

• Journal of Plant Biotechnology
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• v.49 no.3
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• pp.163-170
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• 2022

There is a continuous rise in the commercialization of living modified (LM) organisms worldwide. While LM plants have not yet been cultivated in South Korea, research, development, import of products, and registration of related research facilities are progressing. LM plants should be tested in greenhouses and fields during development. Furthermore, environmental risk assessment and safety management should be performed before their release into the environment. Research on LM plant development is conducted in laboratories as well as confined greenhouses and fields. Safety management regulations are provided as combination standards for the LMO Act in each research district. The accidental release of the LM petunia in Japan was a significant incident related to LM plant research. It implies that normal plants within the distance of crossing should be regarded as LM plants. In the United States, LM creeping bentgrass was released into the environment, thus necessitating the establishment of stringent measures to prevent the scattering of LM plant seeds by wind or other mediums. In South Korea, LM Zoysia and LM cotton were released through rainwater. Therefore, safety measures that prevent LM seed mixing and plant vegetative propagules escaping into the environment via rainwater must be established. Preventing the dispersal of unapproved LM plants requires significant time, expenditure, and effort. Researchers should first identify the impact of LM plants on the ecosystem, and steps to avert their environmental release must be implemented.

• Journal of Pharmaceutical Investigation
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• v.41 no.2
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• pp.67-73
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• 2011

Ion exchange resins can be one of the good carriers for sustained drug release. However, the sustained release may not be enough only with themselves and hence film coating with rate controlling polymers can be applied to have a further effect on the drug release. Due to the environmental and economic issues of organic solvent for the polymer coating, aqueous polymeric systems were selected to develop dosage forms. Among the many aqueous polymeric dispersions for the film coating, EC (ethylcellulose) based polymers such as Aquacoat$^{(R)}$ ECD and Surelease$^{(R)}$ were evaluated.A fluid-bed coating was applied as a processing method. The drug release rate was quite dependent on the coating level so the release rate could be modified easily by changing different levels of the coating. The drug release rate in the Aquacoat$^{(R)}$ coated resin particles was strongly dependent on curing, which is a thermal treatment to make homogeneous films and circumvent drug release changes during storage. After dissolution test using the compressed tablets in which the coated resin particles are contained, inhomogeneous coating and even pores could be observed showing that the mechanical properties of EC were not resistant to granulation and compaction process. However, when tablets were prepared in different batches, the release profiles were almost identical showing the feasibility of the coated resin particle as incorporated into the tablet formulation.

• Journal of Korean Neurosurgical Society
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• v.60 no.1
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• pp.82-88
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• 2017

Objective : We assessed the surgical results of bipolar release in 31 adult patients with uncorrected congenital muscular torticollis (CMT) and more than 12 months of follow-up. Methods : Thirty-one patients underwent a bipolar release of the sternocleidomastoid muscle (SCM) and were retrospectively analyzed. The mean follow-up period was 14.9 months (range, 12-30). The mean age at time of surgery was 30.3 years (range, 20-54). Patients were evaluated with a modified Lee's scoring system, cervicomandibular angle (CMA) measurement, and a global satisfaction rating scale using patient self-reporting. Results : The modified Lee's scoring system indicated excellent results in 4 (12.9%) patients, good in 18 (58.1%), and fair in 9 (29.0%) at the last follow-up after surgery. The improvements in neck movement and head tilt were statistically significant (p<0.05). The preoperative mean CMA was $15.4^{\circ}$ (range, 5.4-29.0), which was reduced to a mean of CMA of $6.3^{\circ}$ (range, 0-25) after surgery (p<0.05). The global satisfaction rating scale was 93.7% (range, 90-100). A transient sensory deficit on the ipsilateral lower ear lobe was noted in three cases. No significant permanent complications occurred. Conclusion : Bipolar release of the SCM is a safe and reliable technique for the treatment of CMT in adults.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.3
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• pp.145-157
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• 2020

Purpose: This study was to determine the possible effects of trichloroacetic acid (TCA) and epidermal growth factor (EGF) through cell survival genes of the PI3K-AKT signaling pathway when applying an hydrophobically modified glycol chitosan (HGC)-based nanocontrolled release system to human gingival fibroblasts in oral soft tissue regeneration. Materials and Methods: An HGC-based nano-controlled release system was produced, followed by the loading of TCA and EGF. The group was divided into control (CON), TCA-loaded nano-controlled release system (EXP1), and the TCA- and EGF- individually loaded nano-controlled release system (EXP2). A total for 29 genes related to the PI3K-AKT signaling pathway were analyzed after 48h of culture in human gingival fibroblasts. Real-time PCR, 1- way ANOVA and multiple regression analysis were performed. Results: Cell survival genes were significantly upregulated in EXP1 and EXP2. From multiple regression analysis, ITGB1 was determined to be the most influential factor for AKT1 expression. Conclusion: The application of TCA and EGF through the HGC-based nano-controlled release system can up-regulate the cell survival pathway.