• Journal of the Korean Institute of Gas
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• v.8 no.2 s.23
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• pp.15-27
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• 2004

The purpose of this paper is to improve the performance of Polymer electrolyte fuel cell(PEMFC) by studying the channel dimension of bipolar plates using commercial CFD program 'Fluent'. Simulations are done ranging from 0.5 to 3.0mm for different size in order to find the channel size which shoves the highst hydrogen consumption. The results showed that the smaller channel width, land width, channel depth, the higher hydrogen consumption in anode. When channel width is increased, the pressure drop in channel is decreased because total channel length Is decreased, and when land width is increased, the net hydrogen consumption is decreased because hydrogen is diffused under the land width. It is also found that the influence of hydrogen consumption is larger at different channel width than it at different land width. The change of hydrogen consumption with different channel depth isn't as large as it with different channel width, but channel depth has to be small as can as it does because it has influence on the volume of bipolar plates. however the hydrogen utilization among the channel sizes more than 1.0mm which can be machined in reality is the most at channel width 1.0, land width 1.0, channel depth 0.5mm and considered as optimum channel size. The fuel cell combined with 2cm${\times}$2cm diagonal or serpentine type flow field and MEA(Membrane Electrode Assembly) is tested using 100W PEMFC test station to confirm that the channel size studied in simulation. The results showed that diagonal and serpentine flow field have similarly high OCV and current density of diagonal (low field is higher($2-40mA/m^2$) than that of serpentine flow field under 0.6 voltage, but the current density of serpentine type has higher performance($5-10mA/m^2$) than that of diagonal flow field under 0.7-0.8 voltage.

• Korean Journal of Heritage: History & Science
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• v.44 no.1
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• pp.4-29
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• 2011

Paleoenvironments of the shell deposit-bearing sequence in the Hasandong Formation at Daesong-ri area, Hadong-gun, Korea, are interpreted on the basis of sedimentary facies and taphonomy of the shell deposits, with a discussion of their stratigraphic implications. A shell deposit-bearing sequence without reddish beds is mostly grayish, and the bedding is laterally extensive. These deposits are interpreted to have been formed in sandflats, mudflats, and shallow lakes generated by flooding on an alluvial plain. The shell deposits are classified into three types according to the occurrence, and the concentration of a single species of Brotiopsis wakinoensis in the shell deposits is deemed to have been attributed to the exclusive inhabitation of the genus Brotiopsis. Type 1 and 2 shell deposits are interpreted to have been fossilized in sandflats and mudflats after death in their habitat of shallow lakes and subsequent transformation by sheetflooding and lake flooding. Type 3 shell deposits are interpreted to have been fossilized in their habitat of shallow lakes during a stabilized period of lake development. The development of the shell deposit-bearing lacustrine sequence in a few tens of meters in thickness in the Hasandong Formation of fluvial deposits is compared to the shift of depositional environments from the Hasandong Formation (fluvial deposits) through the Jinju Formation (lacustrine deposits) to the Chilgok Formation (alluvial plain deposits), which suggests that additional lithostratigraphic classification is needed in the Hasandong Formation. The shell deposits at the study area can provide valuable data to understanding the paleoenvironments during the Early Cretaceous Period of Korea, and should give basic data to evaluate the value of the Cretaceous mollusc deposits in Korea as a geological heritage.

• Journal of Life Science
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• v.29 no.9
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• pp.1002-1009
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• 2019

Early life stress (ELS) increases the risk of depression. ELS may be involved in the susceptibility to subsequent stress exposure during adulthood. We investigated whether epigenetic mechanisms of p11 promoter affect the vulnerability to chronic unpredictable stress (CUS) induced by the maternal separation (MS). Mice pups were separated from their dams (3 hr/day from P1-P21). When the pups reached adulthood, we applied CUS (daily for 3 weeks). The levels of hippocampal p11 expression were analyzed by quantitative real-time PCR. The levels of acetylated and methylated histone H3 at p11 promoter were measured by chromatin immunoprecipitation. Depression-like behavior was measured by the forced swimming test (FST). The MS and CUS group exhibited significant decreases in p11 mRNA level and the MS plus CUS group had a greater reduction in this level than the CUS group. The MS plus CUS group also resulted in greater reduction in H3 acetylation than the CUS group. This reduction was associated with an upregulation of histone deacetylase 5. Additionally, the MS plus CUS group showed a greater decrease in H3K4met3 level and a greater increase in H3K27 met3 level than the CUS group. Consistent with the reduction of p11 expression, the MS plus CUS group displayed longer immobility times in the FST compared to the control group. Mice exposed to MS followed by CUS had much greater epigenetic alterations in the hippocampus compared to adult mice that only experienced CUS. ELS can exacerbate the effect of stress exposure during adulthood through histone modification of p11 gene.

• Journal of the Korea Institute of Building Construction
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• v.20 no.6
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• pp.489-495
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• 2020

Whereas the control of the hydration heat in mass concrete has been important as the concrete structures enlarge, many conventional strategies show some limitations in their effectiveness and practicality. Therefore, In this study, as a solution of controling the heat of hydration of mass concrete, a method to reduce the heat of hydration by controlling the hardening of cement was examined. The reduction of the hydration heat by the developed Phosphate Inorganic Salt was basically verified in the insulated boxes filled with binder paste or concrete mixture. That is, the effects of the Phosphate Inorganic Salt on the hydration heat, flow or slump, and compressive strength were analyzed in binary and ternary blended cement which is generally used for low heat. As a result, the internal maximum temperature rise induced by the hydration heat was decreased by 9.5~10.6% and 10.1~11.7% for binder paste and concrete mixed with the Phosphate Inorganic Salt, respectively. Besides, the delay of the time corresponding to the peak temperature was apparently observed, which is beneficial to the emission of the internal hydration heat in real structures. The Phosphate Inorganic Salt that was developed and verified by a series of the aforementioned experiments showed better performance than the existing ones in terms of the control of the hydration heat and other performance. It can be used for the purpose of hydration heat of mass concrete in the future.

• Microbiology and Biotechnology Letters
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• v.49 no.1
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• pp.111-119
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• 2021

A bacterial strain isolated from a Malva verticillata leaf was identified as Bacillus velezensis MV2 based on the 16S rRNA sequencing results. Complete genome sequencing revealed that B. velezensis MV2 possessed a single 4,191,702-bp contig with 45.57% GC content. Generally, Bacillus spp. are known to produce diverse antimicrobial compounds including bacteriocins, polyketides, and non-ribosomal peptides. Antimicrobial compounds in the B. velezensis MV2 were extracted from culture supernatants using hydrophobic interaction chromatography. The crude extracts showed antimicrobial activity against both gram-positive bacteria and gram-negative bacteria; however, they were more effective against gram-positive bacteria. The extracts also showed antifungal activity against phytopathogenic fungi such as Fusarium fujikuroi and F. graminearum. In time-kill assays, these antimicrobial compounds showed bactericidal activity against Bacillus cereus, used as indicator strain. To predict the type of antimicrobial compounds produced by this strain, we used the antiSMASH algorithm. Forty-seven secondary metabolites were predicted to be synthesized in MV2, and among them, fourteen were identified with a similarity of 80% or more with those previously identified. Based on the antimicrobial properties, the antimicrobial compounds may be nonribosomal peptides or polyketides. These compounds possess the potential to be used as biopesticides in the food and agricultural industry as an alternative to antibiotics.

• Journal of Food Hygiene and Safety
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• v.36 no.3
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• pp.271-279
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• 2021

Sweet pumpkin is rich in minerals such as calcium, phosphorus and fiber, and also contains a large amount of β-carotene, which has antioxidant effects. In this study, Makgeolli containing steaming sweet pumpkin (SP) was manufactured to enhance the antioxidant activity. To prepare the Makgeolli, SP was added in amounts of 5, 10, 20, and 30% (w/w), and the chemical (pH, total acidity, alcohol), microbiological (lactic acid bacteria, yeast) properties, and antioxidant activities (DPPH, ABTS) were examined during fermentation and storage for 9 days. The pH of SP Makgeolli was 4.00-4.23 at day 1 of fermentation, and then the pH gradually decreased as fermentation progressed, showing the lowest results at day 9 (3.28-3.52). At day 1, the total acidity was significantly increased (P<0.05) as the amount of SP (0-30%; 0.09-0.55%) and the total acidity in SP Makgeolli (1.01-1.20) was also rapidly increased by 5 days of fermentation. Alcohol content was significantly increased (P<0.05) as the amount of SP (0-30%; 4.59-5.77%) increased at day 9. The counts of lactic acid bacteria and yeast in SP Makgeolli were 8.0-8.1 and 7.9-7.8.0 CFU/mL, respectively, which was higher than SP 0% at day 9. DPPH and ABTS radical scavenging activities were significantly increased (P<0.05) as the amount of SP (0-30%; 48.29-78.97% for DPPH, 62.12-86.68% for ABTS) increased at day 9. This study suggests that Makgeolli added with SP could be potentially and commercially developed due to its superior microbiological and chemical properties, including high antioxidant activities.

• Korean Journal of Heritage: History & Science
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• v.55 no.1
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• pp.305-321
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• 2022

The stone chamber tomb in Eungpyeong-ri, Buyeo, is a joint tomb that contains the bodies of two individuals. This paper investigates the relationship between the buried persons and the characteristics of the stone chamber tomb. Based on the geographical location, relics, and the excavated human bones, it was determined that the tomb was built during the Sabi Period of the Baekje Dynasty and that the buried individuals were most probably residents of high stature or government officials. To study the excavated bones, the remains were carefully collected and conservation was carried out. Before collecting samples from the human bones for the analytical research, the results of near-infrared analysis were used to collect the samples for the isotope analysis and DNA analysis. The most important issue when handling the excavation site was the reinforcing agent and the concentration of the agent used. In situations like this, Paraloid B-72 is the most suitable agent. When the shape of human bones was difficult to distinguish from the soil, conservation was performed using X-ray and CT imaging data. The same chemical used for the reinforcement of the site was used to complete a minimum level of conservation to the surface areas where the conservation treatment of removing foreign substances, the reinforcement areas, and bonded areas were carried out. The collagen yield from the sample obtained at selected position was 3.8% to 6.1%. The results of analyzing the stable isotopes of carbon and nitrogen found in the extracted collagen showed that the stable isotope ratios came out to δ¹³C -18.3‰±0.1‰, -19.0‰±0.1‰ for EBW and δ¹⁵N 10.7‰±0.5‰, 10.6‰±0.1‰ for EBE. It is believed the two individuals consumed small amounts of minor cereals, mainly from C₃ plants, and protein was obtained from eating terrestrial animals. What's more, the deviations in data obtained from the two individuals were so small that it could be inferred that the individuals ate similar foods. Considering the preservation state of the sample, amplifying DNA for the DNA analysis would have been very difficult since the amount of surviving DNA was so deficient. For DNA analysis, it is anticipated that the results could be derived by applying improved extraction methods that will be developed in the future. In this research, any association between scientific analysis(DNA and stable isotope ratio) and near-infrared spectroscopy was difficult to establish. Further research is needed on the utilization of near-infrared analysis for gathering samples from human bones.

• Journal of Radiation Protection and Research
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• v.32 no.4
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• pp.140-156
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• 2007

This research was performed to investigate the morphological changes of folliculus ovary according to the radiation dose. The whole body radiation of 200 cGy, 400 cGy, and 600 cGy was given to the each groups of 5 months-aged female mouse. Various staining methods used in this research are: Hematosylin-Eosin method, and immunohistochemistrical methods using BrdU, TUNEL, p53, p21, PCNA and inhibin. The minute structural changes of folliculus ovary were observed through an electron microscope with high magnification. The morphological changes of growing folliculus ovary became distinct as the dose of X-rays increased. Especially, the nuclei of granular cells showed manifest condensation and the changes of the transparent zone were distinct. As a result of histochemical reaction according to Masson's trichrome method and reticular fiber method, the changed granular cells, the deformed basilar membrane of folliculus ovary and the abnormal arrangement of the reticular fiber were observed. In the reaction of BrdU, the granular cells of normal folliculus ovary with positive reaction rapidly decreased according to the increase of the dose of X-rays. In TUNEL study, granular cells showing positive reaction in retarded folliculus ovary were expanded to growing folliculus ovary and primordial folliculus ovary according to the increase of the dose of X-rays. In case of 600 cGy of X-rays, oocyte underwent apoptosis. In p53 immunohistochemistry, p53 manifested to be stronger as the dose of X-rays increased. p53 reactivity was manifested distinctively in all cells comprising folliculus ovary following irradiation of 600 cGy. p21 was manifested in granular cells of folliculus ovary and showed very positive reaction around follicular antrum according to the increase of the dose of X-rays. In PCNA, positive reaction was manifested in growing folliculus ovary, mature folliculus ovary and primordial folliculus ovary, but the extent of the reaction decreased as the dose of the X-rays decreased. The finding that the reaction of granular cells around folliculus ovary was stronger than that near follicular membrane indicates that what was damaged first by X-ray was the cells near folliculus ovary and follicular antrum. The reactivity of $inhibin-{\alpha}$ showed difference according to the growing stage of folliculus ovary: $inhibin-{\alpha}$ showed the most strong reaction in mature folliculus ovary with follicular antrum. There was strong reaction in granular cells around follicular membrane but $inhibin-{\alpha}$ did not occur at all in theca cells comprising follicular membrane. $Inhibin-{\alpha}$ in ovary tissue exposed to 400 cGy of X-rays was manifested more strongly than in ovary tissue exposed to 600 cGy of X-rays, which was related to the phenomenon that granular cells of mature folliculus ovary underwent necrosis or apoptosis increasingly due to X-rays. In an electron microscope with high magnification, nuclei and protoplasm of granular cells in growing folliculus ovary abruptly underwent minute structural changes according to the increase of dose of X-rays. Cell residue, by-product of cell decease, neutrophil and macrophage around follicular antrum were observed. The minute structural changes in granular cells showed typical characteristics of apoptosis: the increase of electronic density due to nuclear condensation, fragmentation of nuclei and atrophy of protoplasm. Necrosis of cells was identified but it was not so remarkable. Macrophage with apoptotic bodies was scattered. Proportional to the radiation dose, we found that the generation of heterogeneous substance of normal ovary texture's follicular fluid, the emergence of dyeing characteristic in the basilar membrane of folicle, the generation of apoptosis, and the transformation of macrophages, etc. From this results, we can infer the possible radiation hazard on the ovary of cervix cancer patient with radiation therapy.

• Journal of Periodontal and Implant Science
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• v.24 no.3
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• pp.581-596
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• 1994

This in vitro study was undertaken to obtain optimal tetracycline concentration that aids proliferation and spreading of human periodontal ligament cells, for clinical application in root surfaces of periodontally diseased teeth. Periodontal ligament cells used in this study were obtained from explants of periodontal ligament of 1st premolar teeth which were extracted for the purpose of orthodontic treatment. The cells were cultured in Dulbecco's Modified Eagle Medium(DMEM) supplemented with 100 U/ml penicillin, $100\;{\mu}g/ml$ streptomycin and 10% FBS at $37^{\circ}C$, 100% humidity, 5% $CO_2-95%$ air. Cells were used between the third to 4th passage. After root planing of periodontally extracted teeth, the root slabs were cut with carborundum disk. In the cell proliferation experiment, experimental groups were root planing only group, immersed groups in 25, 50, 75, 100, 150mg/ml aqueous solution of Tetracycline HCl followed by a vigorous rinse in PBS. Human PDL cells at concentration of $1{\times}10^5\;cells/ml$ were seeded in each culture well which contained root slabs and incubated for 6 hours. Then, all of the root slabs were moved into new 24 culture well and incubated 24, 48 and 72 hours. The cell counting was done by inverted phase contrast microscope after trypsinization. The following results were obtained. The cell number was increased in order root planing only group, 25, 150, 50, 75, 100mg/ml of Tetracycline HCl treated group in 24, 48 and 72 hours. The maximal cell number was obtained when the root slabs were immersed in solution with 100mg/ml of Tetracycline HCl. There were statistically significant between the root planing only group and 75, 100 mg/ml of Tetracycline HCl treated group in 24 hours, between the root planing only group and 100mg/ml of Tetracycline HCl treated group in 48 hours, between the root planing only group and 50, 75, 100mg/ml of Tetracycline HCl treated group, between 25 and 100mg/ml of Tetracycline HCl treated group in 72 hours(p<0.05). In the cell spreading experiment, after 30 minutes of incubated, in the root planing only group, the cells were generally round in shape. The cell surface was mostly covered with blebs. The cells started to attach to root surface by cytoplasmic extension in 50, 100mg/ml of Tetracycline HCl treated groups, more numerous cells attached to root surface than root planing only group. Many orifices of dentinal tubule were exposed, cells showed radially spreaded cytoplasm and unspreaded central region of the cell was covered with blebs. After 6 hours of incubation, in the root planing only group, cells showed radially spreaded cytoplasm and were attached flat appearance. In 50, 100mg/ml of Tetracycline HCl treated groups, cellular margin was concaved and cytoplasm showed elongated appearance with polarity. After 24 hours of incubation, in the root planing group, cells showed characteristic polarity. In 50, 100mg/ml of Tetracycline HCl treated groups, cells showed more elongated and spindle - like appearance.

• Investigative Magnetic Resonance Imaging
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• v.8 no.1
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• pp.32-41
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• 2004

Purpose : To measure the NMR relaxation properties of MnPC, to observe the characteristics of liver enhancement patterns on MR images in experimentally implanted rabbit VX2 tumor model, and to estimate the possibility of tissue specific contrast agent for MnPC in comparison with the hepatobiliary agent. Materials and Methods : Phthalocyanine (PC) was chelated with paramagnetic ions, manganese (Mn). 2.01 g (5.2 mmol) of phthalocyanine was mixed with 0.37 g (1.4 nlmol) of Mn chloride at $310^{\circ}C$ for 36 hours and then purified by chromatography ($CHCl_3:\;CH_3OH=98:2$, volume ratio) to obtain 1.04 g $(46\%)$ of MnPC (molecular weight = 2000 daltons). The T1/T2 relaxivity (R1/R2) for MnPC were determined at a 1.5 T (64 MHz) MR spectrometer. VX2 tumor model was experimentally implanted in the liver parenchyma of rabbits. All MR studies were performed on 1.5 T. The human extremity radio frequency coil of a bird cage type was employed. MR images were acquired at 17 to 24 days after VX2 carcinoma implantation.4 mmol/kg MnPC and 0.01 mmol/kg Mn-DPDP were injected via the ear vein of rabbits. T1-weighted images were obtained with spin-echo (TR/TE=516/14 msec) and fast multiplanar spoiled gradient recalled (TR/TE : 80/4 msec, $60^{\circ}$ flip angle) pulse sequence. Fast spin-echo (TR/TE=1200/85 msec) was used to obtain the T2-weighted images. Results : The value of T1/T2 relaxivity (R1/R2) of MnPC was $7.28\;mM^{-1}S^{-1}$ and $55.56\;mM^{-1}S^{-1}$ respectively at 1.5 T (64 MHz). Because the T2 relaxivity of MnPC that bonded strongly, covalently manganese with phthalocyanine was very high, the signal intensity of liver parenchyma was decreased on postcontrast T2-weighted images and we could easily distinguish the VX2 carcinoma within the liver parenchyma. When MnPC was administrated intravenously, the tumor margin delineation was more remarkable than Mn-DPDP-enhanced images. The enhancement of liver parenchyma with MnPC persisted at relatively high levels over at least one hour after injection of the contrast agents. Conclusion : The hepatic uptake and biliary excretion of MnPC, which are similar to Mn-DPDP, suggest that this agent is a new liver-specific agent. Also, MnPC seems to be used as a dual contrast agent (T1 and T2) with high T2 relaxivity. However, it is warranted that MnPC needs further investigation as a potential contrast agent for MR imaging of the liver. That is, further characterizations of MnPC are needed in vivo and in vitro before clinical trials. The diagnostic potential of MnPC will also have to be examined more in the animal models of additional types.