• Journal of Life Science
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• v.34 no.1
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• pp.9-17
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• 2024

Diabetes mellitus (DM) is one of the main global health problems. Chronic exposure to hyperglycemia can lead to cellular dysfunction that may become irreversible over time, a process that is termed glucose toxicity. Our perspective about glucose toxicity as it pertains to the pancreatic β-cell is that the characteristic decreases in insulin secretion are caused by regulated apoptotic gene expression. In this study, we examined whether ferulic acid protects INS-1 pancreatic cells against high glucose-induced apoptosis. High glucose concentration (30 mM) induced glucotoxicity and death of INS-1 pancreatic β cells. However, treatment with 1, 5, 10, or 20 μM ferulic acid increased the cell viability in a concentration-dependent manner. Treatment with ferulic acid dose-dependently decreased the intracellular levels of reactive oxygen species, thiobarbituric acid reactive substances, and nitric oxide in INS-1 pancreatic β cells pretreated with high glucose. These effects influence the apoptotic pathway, increasing the expression of the anti-apoptotic protein Bcl-2 and reducing the levels of pro-apoptotic proteins, including Bax, cytochrome C, and caspase 9. Annexin V/propidium iodide staining indicated that ferulic acid significantly reduced high glucose-induced apoptosis. These results demonstrate that ferulic acid is a potential therapeutic agent to protect INS-1 pancreatic β cells against high glucose-induced apoptosis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.72-72
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• 2009

본 연구에서는 Photoconductor materials 기반의 평판형 X-ray Detector film 제작에 관한 연구를 수행하였다. 기존의 광도전성 물질로 사용되어 오던 비정질 셀레늄(Amorphous seleinum; a-Se) 기반의 디지털 방사선 검출기 보다 높은 신호 및 동작 특성을 가지는 Mercury Iodide(HgI2)와 열적, 전기적 특성이 안정적이며, 소자의 동작특성이 우수한 Lead Oxide(PbO) 기반의 X-ray Detector film의 개발에 있어서 각각 HgI2 및 PbO 두 물질 층을 적정비율에 맞추어 제작함으로써 최적의 X-ray Detector를 구현하고자 하였다. 이는 빠른 영상획득을 통해 기존의 방식이 가지는 문제점을 해결하고 의료기기 디지털화를 구현할 수 있는 차세대 시스템을 개발하고자 하는 것이다. 본 연구에서는 기존의 진공증착법의 두꺼운 대면적 필름의 제조가 어려운 문제점을 해결하고자 Particle In Binder method(PIB) 방법을 이용하여 $3"{\times}3"$사이즈의 두께 $200{\mu}m$의 다결정의 Photoconductor 필름을 제조하여 전기적 특성을 평가하였다. 제작된 필름의 전기적 특성을 dark current, X-선 sensitivity와 SNR(Signal to -Noise Rate) 등을 측정하여 정량적으로 평가 하였다. 기준 실험으로 진행한 DG 2.1 바인더를 사용한 single-HgI2 층에서 보다 높은 sensitivity 값을 보였지만 높은 dark current로 인해 SNR이 떨어지는 결과를 볼 수 있었다. 본 연구에서 제시하는 두 Photoconductor material의 Soaking method를 이용한 실험에서는 single-HgI2에 해당하는 높은 sensitivity 및 저감된 dark current로 인해 높은 SNR 값을 획득하였다. 하지만 습도와 같은 주변 환경에 의한 재현성 문제로 인한 신호값의 불안정성에 대한 문제점도 남아 있으므로, 차후 최적화된 material 제작 공정을 위한 연구가 꾸준히 진행 되어져야 할 것이다.

• Archives of Pharmacal Research
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• v.27 no.3
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• pp.305-313
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• 2004

The effect of diazoxide, a $K^{+}$channel opener, on apoptotic cell death was investigated in HepG2 human hepatoblastoma cells. Diazoxide induced apoptosis in a dose-dependent manner and this was evaluated by flow cytometric assays of annexin-V binding and hypodiploid nuclei stained with propidium iodide. Diazoxide did not alter intracellular $K^{+}$concentration, and various inhibitors of $K^{+}$channels had no influence on the diazoxide-induced apoptosis; this implies that $K^{+}$channels activated by diazoxide may be absent in the HepG2 cells. However, diazoxide induced a rapid and sustained increase in intracellular $Ca^{2+}$ concentration, and this was completely inhibited by the extracellular $Ca^{2+}$ chelation with EGTA, but not by blockers of intracellular $Ca^{2+}$ release (dantrolene and TMB-8). This result indicated that the diazoxide-induced increase of intracellular $Ca^{2+}$ might be due to the activation of a Ca2+ influx pathway. Diazoxide-induced $Ca^{2+}$ influx was not significantly inhibited by either voltage-operative $Ca^{2+}$ channel blockers (nifedipinen or verapamil), or by inhibitors of $Na^{+}$, $Ca^{2+}$-exchanger (bepridil and benzamil), but it was inhibited by flufenamic acid (FA), a $Ca^{2+}$-permeable nonselective cation channel blocker. A quantitative analysis of apoptosis by flow cytometry revealed that a treatment with either FA or BAPTA, an intracellular $Ca^{2+}$ chelator, significantly inhibited the diazoxide-induced apoptosis. Taken together, these results suggest that the observed diazoxide-induced apoptosis in the HepG2 cells may result from a $Ca^{2+}$ influx through the activation of $Ca^{2+}$-permeable non-selective cation channels. These results are very significant, and they lead us to further suggest that diazoxide may be valuable for the therapeutic intervention of human hepatomas.

• Korean Journal of Materials Research
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• v.33 no.8
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• pp.344-351
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• 2023

Cesium lead iodide (CsPbI₃) with a bandgap of ~1.7 eV is an attractive material for use as a wide-gap perovskite in tandem perovskite solar cells due to its single halide component, which is capable of inhibiting halide segregation. However, phase transition into a photo inactive δ-CsPbI₃ at room temperature significantly hinders performance and stability. Thus, maintaining the photo-active phase is a key challenge because it determines the reliability of the tandem device. The dimethylammonium (DMA)-facilitated CsPbI₃, widely used to fabricate CsPbI₃, exhibits different phase transition behaviors than pure CsPbI₃. Here, we experimentally investigated the phase behavior of DMA-facilitated CsPbI₃ when exposed to external factors, such as heat and moisture. In DMA-facilitated CsPbI₃ films, the phase transition involving degradation was observed to begin at a temperature of 150 ℃ and a relative humidity of 65 %, which is presumed to be related to the sublimation of DMA. Forming a closed system to inhibit the sublimation of DMA significantly improved the phase transition under the same conditions. These results indicate that management of DMA is a crucial factor in maintaining the photo-active phase and implies that when employing DMA designs are necessary to ensure phase stability in DMA-facilitated CsPbI₃ devices.

• Current Photovoltaic Research
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• v.10 no.1
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• pp.16-22
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• 2022

The long-term stability of PSCs against visual and UV light, moisture, electrical bias and high temperature is an important issue for commercialization. In particular, since the operation temperature of solar cell can rise above 85℃, a study on thermal stability is required. In this study, the cause of thermal-induced degradation of PSCs was investigated using the SCAPS-1D simulation tool. First, PSCs of TiO₂/CH₃NH₃PbI₃/Spiro-OMeTAD/Au structure were exposed to a constant temperature of 85℃ to observe changes in conversion efficiency and quantum efficiency. Because the EQE reduction above 500 nm was remarkable, we simulated PSCs performance as a function of lifetime, doping density of perovskite and spiro-OMeTAD. Consequently, the main cause of thermal-induced degradation is considered to be the change in the perovskite doping concentration and lifetime due to ion migration of perovskite.

• Animal cells and systems
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• v.15 no.4
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• pp.287-294
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• 2011

The accelerated cooling rate associated with vitrification reduces injuries attributed to cryopreservation and improves the post-freezing developmental competence of vitrified embryos. In this study, embryos were vitrified and warmed and morphologically evaluated for their development to blastocysts. Survival rates between the fresh ($96.7%{\pm}3.8%$) and vitrified embryos ($90.7%{\pm}5.1%$) did not differ significantly (P>0.05). The mitochondrial membrane potential of fresh control cells measured by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl carbocyanide iodide staining was similar to that of cryoprotected and vitrified embryos. Mitochondrial staining with rhodamine 123 did not differ among the fresh, cryoprotected, and vitrified embryos. Moreover, the distribution of $H_2O_2$, assessed by 2',7'-dichlorodihydrofluorescein diacetate staining, did not differ among the groups. The results showed that the developmental rate did not differ significantly among the fresh ($87.8%{\pm}11.3%$), cryoprotected ($83.2%{\pm}7.6%$), and vitrified 2-cell embryos ($75.8%{\pm}14.2%$). The mean number of the inner cell mass (ICM), trophectoderm (TE), and apoptotic cells was counted and statistically compared, and although the number of ICM and TE was decreased in the cryoprotected and vitrified embryos, there were no significant differences among the groups (P>0.05). During the cultivation period, randomly selected blastocysts from each group were stained using either 4',6-diamidino-2-phenylindole and bisbenzimide or the terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling technique. The incidence of apoptosis appeared to be almost identical in all the groups. Droplet vitrification could subsequently lead to high survival and developmental rates of cryopreserved mouse embryos.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.517-522
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• 2020

Electron beam have many factors that affect dose distribution, so even if identical settings are used, they should be identified and used for radiation treatment, and the effects on the structures in the body are sensitive, making it difficult to investigate uniform dose distribution on tumors. In this study, a dosimeter was produced using PbI₂ which is a photoelectric material, and electrical characteristics were analyzed for 6, 9, and 12 MeV electronics in linear accelerators. The reproducibility test results showed that RSD were 1.1215%, 1.0160%, and 0.05137% respectively at 6, 9, and 12 MeV energies, indicating that the output signals were stable. The linearity evaluation results showed that the R² values of the reliability indicator for straight line trend lines were 0.9999, 0.9999, and 0.9994, respectively, at 6, 9, and 12 MeV, to confirm that the output signal was proportional to PbI₂ as dose increased. The PbI₂ dosimeter in this study is judged to be highly applicable to electromagnet measurement and is thought to be able to be used as a basic study of electron detector through photoelectric material.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.7
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• pp.776-781
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• 2006

Perchlorate ion($ClO_4^-$), which is present in the solid propellant for rocket, herbicide and some fertilizers. Perchlorate inhibits iodide uptake by the human thyroid gland. Impairment of thyroid function in expectant mothers may impact the fetus and result in effects including cerebral palsy, give rise to thyroid gland cancer. The US EPA(Environmental Protection Agency) adopted a reference dose(RfD) for perchlorate 0.0007 mg/kg-day, and this guidance lead to a Drinking Water Equivalent Level(DWEL) of 24.5 ${\mu}g/L$. The studies about perchlorate are actively performed in foreign countries, especially in USA but there is no study which surveyed the perchlorate contamination in Korea. Therefore, this study was done to investigate perchlorate contamination in Nak-dong river and tap water. The perchlorate was detected in Nakdong river and ranged from ND to 278.4 ${\mu}g/L$. The highest concentration was observed in Kumichon. The perchlorate concentration was decreased with the down stream of Nakdong river. The perchlorate concentration in tap water was varied with the cities and the concentration levels were $ND{\sim}34.1$ ppb. The highest perchlorate concentration was observed in DalsuGoo in Daegu and the similar concentration($9{\sim}11$ ${\mu}g/L$) was detected in most of the districts in Busan. The result of this study suggests that there is a perchlorate source near the Nakdong river and the urgent policy is needed to control perchlorate for the cities which are supplied from Nakdong river as for their tap water.

• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.381-386
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• 2022

Non-Destruction Test (NDT) is a method to check internal defects without destroying the product. Among them, radiographic testing (RT) uses high-energy radiation, so it is very important to prevent radiation exposure of workers. Therefore, in this study, in this study, a radiation sensor structure that improves radiation detection performance compared to the existing PbI₂ and can immediately detect accidents in RT was presented. For evaluation, the conversion efficiency was analyzed in the gamma ray source through FLUKA simulation. PbI₂ with overlapping Gd₂O₂S:Tb presented in this study showed a higher radiation sensitivity from 1.22 to 3.22 times than that of non-overlapping PbI₂. This indicates that the presented sensor is suitable for use as a radiation sensor for source detection in RT.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.529-540
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• 2011

The purpose of this study was to analyze experiments for the rules of material change unit in 9th grade science textbooks and develop experiments applying small-scale chemistry (SSC). For this study, experimental methods for the precipitation experiment, water electrolysis experiment, decomposition of hydrogen peroxide experiment presented in the 9 science textbooks were analyzed. Problems and improvements that were needed were extracted by 13 science teachers performing the experiments. Experiments applying SSC were developed based on the improvements needed. Afterwards, 19 pre-service science teachers performed both the developed SSC experiments and the science textbooks' experiments. A questionnaire about merits and demerits of the experiments applying SSC was performed. According to the results of this study, most of the 9th grade science textbooks included the lead iodide precipitation experiment, water electrolysis experiment by Hoffman voltameter, and decomposition of hydrogen peroxide experiment using catalytic manganese dioxide. Improvements were needed on the quantity of reagents, time for performing experiments, and scale of experimental apparatus. Merits of the developed experiments applying SSC which used small amount of reagents were safety, easy waste material disposal, short reaction time, and reproducible experimental results. Demerits of the experiments applying SSC were difficulty in observing, decreased achievement, and lack of skill in handling small-scale apparatus. Therefore, if the experiments developed applying SSC were to be utilized in 9th grade science experiments, it will be possible to use less reagent and be able to teach and carry out reproducible experiments at the same time. Also, the reproducible experiments based on SSC will help students under stand the scientific concepts for the rules of material change unit.