• Advances in concrete construction
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• v.7 no.2
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• pp.97-105
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• 2019

In this paper, the workability and static stability were evaluated using a proposed test method. Workability and static stability represent a key property of self-compacting concrete (SCC) in fresh state. A number of standardized test methods were developed to assess these properties. However, no accelerated test method reliably predicts both workability and static stability of SCC. In the present work, a modified K-slump test method was developed to evaluate workability and static stability of SCC. In order to take implicit mixture variations of SCC constituents that can affect fresh SCC properties, a central composite design was adopted to highlight the effect of gravel to sand ratio (G/S), gravel 3/8 to gravel 8/15 ratio (G1/G2), water to cement ratio (W/C), marble powder to cement ratio (MP/C) and superplasticizer content (SP) on workability measured with slump and flow time (T50) tests and static stability measured with sieve stability test (Pi), segregation test index (SSI), Penetration test (Pd) and the proposed K-slump test (Km). The obtained results show that G/S ratio close to 1 and G1/G2 ratio close to 60% can be considered as optimal values to achieve a good workability while ensuring a sufficient static stability of SCC. Acceptable relationships were obtained between Slump flow, Pi, Pd and Km. Results show that the proposed K-slump test allow to assess both workability and static stability of fresh SCC mixtures.

• Journal of the Korean Chemical Society
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• v.52 no.2
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• pp.140-147
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• 2008

.A new approach for a cloud point extraction-electrothermal atomic absorption spectrometric method was used for determining bismuth. The aqueous analyte was acidified with sulfuric acid (pH 3.0-3.5). Triton X-114 was added as a surfactant and natriumdiethyldithiocarbaminat (Na-DDTC) was used as a complexing agent. After phase separation at 50oC based on the cloud point separation of the mixture, the surfactant-rich phasen was diluted using tetrahydrofuran (THF). Twenty microliters (20 L) of the enriched solution and 10 l of 0.1% (w/v) Pd(NO3)2 as chemical modifier were dispersed into the graphite tube and the analyte determined by electrothermal atomic absorption spectrometry. After optimizing extraction conditions and instrumental parameters, a preconcentration factor of 195 was obtained for a sample of only 10 mL. The detection limit was 0.04 ng ml-1 and the analytical curve was linear for the concentration range of 0.04-0.70 ng mL-1. Relative standard deviations were <5%. The method was successfully applied for the extraction and determination of bismuth in water samples.

• BMB Reports
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• v.36 no.5
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• pp.468-474
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• 2003

The molecular mechanism of hypoxia-induced apoptosis has not been clearly elucidated. In this study, we investigated the involvement of extracellular signal-regulated protein kinase (ERK 1/2) in hypoxia-induced apoptosis using cobalt chloride in HeLa human cervical cancer cells. The cobalt chloride was used for the induction of hypoxia, and its $IC_{50}$ was $471.4\;{\mu}M$. We demonstrated the DNA fragmentation after incubation with concentrations more than $50\;{\mu}M$ cobalt chloride for 24 h, and also evidenced the morphological changes of the cells undergoing apoptosis with electron microscopy. Next, we examined the signaling pathway of cobalt chloride-induced apoptosis in HeLa cells. ERK1/2 activation occurred 6 and 9 h after treatment with $600\;{\mu}M$ cobalt chloride. Meanwhile, the pretreatment of the MEK 1 inhibitor (PD98059) completely blocked the cobalt chloride-induced ERK 1/2 activation. At the same time, the activated ERK 1/2 translocated into the nucleus and phosphorylated its transcriptional factor, c-Jun. In addition, the pretreatment of PD98059 inhibited the cobalt chloride-induced DNA fragmentation and apoptotic cell death. These results suggest that cobalt chloride is able to induce apoptotic activity in HeLa cells, and its apoptotic mechanism may be associated with signal transduction via ERK 1/2.

• Analytical Science and Technology
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• v.5 no.1
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• pp.63-71
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• 1992

Liquid chromatographic behavior of Pd(II), Ni(II) and Co(III) in N-Alkylisonitrosoacetylacetone imine(HIAA-NR) chelates was investigated by reversed phase high perfomance liquid chromatography. The optimum conditions for the separation of IAA-NR-metal chelates were examined respect to the flow rate and mobile phase strength. The metal-N-Alkylisonitrosoacetylacetone imine chelates in solution were successfully separated on Novapak $C_{18}$ column using acetonitrile/water mixture as mobile phase. The elution order of chelates is methyl>ethyl>propyl>butyl as N-alkyl group for ligand is varied. It was found that all IAA-NR-metal chelates were eluted in an acceptable range of capacity factor value($0{\leq}log\;k^{\prime}{\leq}1$). The dependence of log k' on the volume fraction of water in the binary mobile phase was examined. Also, the dependence of k' on the liquid-liquid extraction distribution ratio(Dc) in acetonitrile-water-alkane extraction system was investigated for IAA-NR-metal chelate. Both kinds of dependence are linear, which suggests that the retention of the electroneutral metal chelates on Novapak $C_{18}$ column is largely due to the hydrophobic effect.

• Tuberculosis and Respiratory Diseases
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• v.52 no.3
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• pp.230-240
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• 2002

Background : The majority of chemotherapy-treated small cell lung cancers(SCLC) patients eventually recur. Although many patients are in excellent physical condition at the time of recurrence, few drugs or drug combinations are capable of effecting a tumor regression in this setting. Topotecan, a topoisomerase I inhibitor, is one of the more widely studied single afents in SCLC. The aim of this study was to determine the response rate, survival and toxicity of topotecan as a second line traeatment SCLC. Materials and Methods : 19 patients with measurable SCLC, progressive during the first line chemotherapy (9 cases) or recurrent after the first line chemotherpy(10 cases), were enrolled in this study. Topotecan was administered as a 30-minute daily infusion at a dose of 1.5mg/$m^2$ for 5 consecutive days, every 3 weeks. Results : The overall response rate was 26.3%(5/19, CR 2, PR 3, SD 3, PD 11). The median survival was 24 weeks. The response rate and survival were poor in the nonresponders during first chemotherapy, those who were refractory to the first chemotherapy(recurrent within 3 months after completion of first chemotherapy) and extensive disease, but the results were not statistically significant. The toxicities were mainly hematologic and anemia grade III 1/90, leukopenia grade III 6/90 IV 4/90, thrombocytopenia grade III 1/90 IV 1/90, vomiting grade III 1/90 of cycles were occurred. There was no treatment-related deaths due to severe myelosuppression. Conclusion : Topotecan can be an active second line chemotherapeutic agent for treating SCLC.

• BMB Reports
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• v.50 no.5
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• pp.237-246
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• 2017

Synapse is the basic structural and functional component for neural communication in the brain. The presynaptic terminal is the structural and functionally essential area that initiates communication and maintains the continuous functional neural information flow. It contains synaptic vesicles (SV) filled with neurotransmitters, an active zone for release, and numerous proteins for SV fusion and retrieval. The structural and functional synaptic plasticity is a representative characteristic; however, it is highly vulnerable to various pathological conditions. In fact, synaptic alteration is thought to be central to neural disease processes. In particular, the alteration of the structural and functional phenotype of the presynaptic terminal is a highly significant evidence for neural diseases. In this review, we specifically describe structural and functional alteration of nerve terminals in several neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD).

• Journal of the Korean Wood Science and Technology
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• v.45 no.1
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• pp.85-95
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• 2017

This study aimed at more precisely estimating the age of big old trees using dendrochronological method. Gesan-gun in Chungbuk (CBGS), Gurye-gun in Jeonnam (JNGR) and Uljin-gun in Gyeongbuk (GBUJ) were study areas and Zelkova serrata (ZS) and Pinus densiflora (PD) selected as protected trees therein were used as experimental tree species. The increment cores were extracted from 12, 8, and 6 ZSs and 10, 3, and 9 PDs in CBGS, JNGR, and GBUJ, respectively, using an increment borer (${\phi}5.2mm$). In order to clearly distinguish tree-ring boundary, the surface in the transverse section was cut for ZS using a sliding microtome and sanded for PD using a sand paper. Ring widths were measured in the resolution of 0.01 mm. Based on the measurement values, 203-year long (1813-2015) ZS local master tree-ring chronologies were successfully established and 175-year long (1841-2015) ZS local master tree-ring chronology for JNGR was also successfully established. In the case of PD, 154-, 175-, and 250-year long local master tree-ring chronologies for CBGS, JNGR, and GBUJ were successfully established, respectively. In the comparisons between local master tree-ring chronologies, they showed low t-values and Glks. According to the comparisons of the local master tree-ring chronologies with 50-year (1950~2000) average temperature and precipitation distribution maps, the annual variations of local master tree-ring chronologies seem to be determined by not temperature but precipitation. For such cross-dating therefore more local master tree-ring chronologies have to be established at the least based on the distribution map for precipitation.

• Applied Chemistry for Engineering
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• v.32 no.5
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• pp.547-555
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• 2021

A catalyst-plasma reactor was applied to the storage of agricultural products, e.g., apple and kiwi, to remove the ethylene generated during the storage. Two 1-m³ unit containers were prepared, and the long-term storage stability of the control group at room temperature was compared with that of the experimental group of which the produced ethylene was treated by the catalyst-plasma reactor. In case of the experimental group, a small amount of ozone was injected to the unit container to suppress the growth of microorganisms such as mold. The apples and kiwis were stored at room temperature for 50 and 57 days, respectively, and the changes in ethylene concentration, hardness, sugar content, acidity, and loss rate were compared. The ethylene concentration during the storage for the control group was higher than that for the experimental group, indicating that the ethylene was effectively removed. Hardness, sugar content, and sugar acid ratio after the storage were better than before the storage, and in particular, the storage stability of kiwifruit was improved significantly. In addition, after the storage, the loss rates of apples and kiwis in the control group were 10 and 54.1%, respectively, but the loss rates in the experimental group were 6 and 34.8%, respectively. Therefore, the storage stability of the experimental group was a lot better than that of the control group.

• Journal of Periodontal and Implant Science
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• v.47 no.5
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• pp.264-272
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• 2017

Purpose: This study evaluated trends in tooth extraction due to acute and chronic periodontal disease (PD) using data from the National Health Insurance Service-National Sample Cohort for 2002-2013. Methods: A random sample of 1,025,340 individuals was selected as a representative sample of the population, and a database (DB) of diagnostic and prescription codes was followed up for 12 years. We used multivariate logistic regression analysis to assess the incidence of total extraction (TE), extraction due to periodontal disease (EPD), and immediate extraction due to periodontal disease (IEPD) according to sociodemographic factors (sex, age, household income, health status, and area of residence). Results: The incidence of tooth extraction was found to be increasing, and at a higher rate for TE in PD patients. In 2002, 50.6% of cases of TE were caused by PD, and this increased to 70.8% in 2013, while the number of cases of IEPD increased from 42.8% to 54.9% over the same period. The incidence rates of extraction due to acute and chronic PD increased monotonically. We found that the incidence rates of TE, EPD, and IEPD were all 2-fold higher among patients with high income levels and those who were not beneficiaries of health insurance. Conclusions: The rates of TE, EPD, and IEPD have been steadily increasing despite dental healthcare policies to expand public health insurance coverage, increasing the accessibility of dental clinics. Moreover, the effects of these policies were found to vary with both income and education levels. Consistent patient follow-up is required to observe changes in trends regarding tooth extraction according to changes in dental healthcare policies, and meticulous studies of such changes will ensure optimal policy reviews and revisions.

• Journal of Periodontal and Implant Science
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• v.50 no.5
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• pp.340-354
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• 2020

Purpose: This pilot study was conducted to evaluate the cleaning efficacy of an angled implant brush for home oral hygiene of full-arch fixed-implant prostheses. Methods: Forty-one patients treated with a full-arch implant rehabilitation in the maxilla or mandible (164 implants) for at least 4 months were enrolled. The screw-retained fixed prostheses were removed and baseline (T0) parameters were recorded, including plaque index (PI), probing depth (PD), and bleeding on probing (BOP). All patients completed a 5-item questionnaire on hygiene maintenance and received an implant brush for home hygiene. After 1 month (T1) PI, PD, and BOP were recorded again and patients completed a 7-item questionnaire to evaluate their satisfaction with the implant brush. One-way repeated-measures analysis of variance was conducted to evaluate the significance of changes in PI, PD, and BOP. A P value <0.05 was considered to indicate statistical significance. Results: A statistically significant reduction of BOP (0.62±0.6 at T0 vs. 0.5±0.5 at T1; P=0.032) was found, while no statistically significant changes in PD (1.74±0.5 mm at T0 vs. 1.77±0.5 mm at T1; P=0.050) or PI (1.9±0.7 at T0 vs. 1.7±0.7 at T1; P=0.280) occurred. According to the 7-item questionnaire, patients reported no difficulty in using the angled brush (63.4%) and deemed it highly (46.3%) or very highly (4.8%) effective in improving their home oral hygiene. Conclusions: Within the limits of the present pilot study, the patients experienced a reduction of BOP 1 month after being instructed to use the angled implant brush. The angled implant brush appeared to be a well-accepted device for home-care hygiene of full-arch fixed-implant rehabilitations.