• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.59-62
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• 2006

Formability is requested to successfully develop of a metal bipolar plate for mass production. From this point of view, wider channel and land width is more helpful to improve formability. But the performance of the fuel cell can be affected by its channel and land shape. So it is very important to select proper channel and land shape not to deteriorate the fuel cell performance. In this work, 3-dimensional, non-isothermal numerical simulation was performed to analyse the effects of channel and land width on the fuel cell performance. 3 types of straight channel were selected for the numerical simulation. The simulation results reveal that wide channel and land width lower fuel cell performance and decrease voltage at a high current density region. Water activity, temperature, oxygen concentration distributions were investigated to find the reasons of performance degradation. The results show that wide channel and land width give an bad effect on fuel cell performance because of low cool ins efficiency and lack of oxygen gas under the land.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.85-93
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• 2021

For accurate and reliable process design for phenol oxidation in a plug flow reactor with supercritical water, modeling can be very insightful. Here, the velocity and density distribution along the reactor have been predicted by a numerical model and variations of temperature and phenol mass fraction are calculated under various flow conditions. The numerical model shows that as we proceed along the length of the reactor the temperature falls from above 430 ℃ to approximately 380 ℃. This is because the generated heat from the exothermic reaction is less that the amount lost through the walls of the reactor. Also, along the length, the linear velocity falls to less than one-third of the initial value while the density more than doubles. This is due to the fall in temperature which results in higher density which in turn demands a lower velocity to satisfy the continuity equation. Having a higher oxygen concentration at the reactor inlet leads to much faster phenol destruction; this leads to lower capital costs (shorter reactor will be required); however, the operational expenditures will increase for supplying the needed oxygen. The phenol destruction depends heavily on the kinetic parameters and can be as high as 99.9%. Using different kinetic parameters is shown to significantly influence the predicted distributions inside the reactor and final phenol conversion. These results demonstrate the importance of selecting kinetic parameters carefully particularly when these predictions are used for reactor design.

• Biomolecules & Therapeutics
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• v.32 no.5
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• pp.568-576
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• 2024

Colorectal cancer (CRC) continues to demonstrate high incidence and mortality rates, emphasizing that implementing strategic measures for prevention and treatment is crucial. Recently, the dopamine receptor D2 (DRD2), a G protein-coupled receptor, has been reported to play multiple roles in growth of tumor cells. This study investigated the anticancer potential of domperidone, a dopamine receptor D2 antagonist, in HCT116 human CRC cells. Domperidone demonstrated concentration- and time-dependent reductions in cell viability, thereby inducing apoptosis. The molecular mechanism revealed that domperidone modulated the mitochondrial pathway, decreasing mitochondrial Bcl-2 levels, elevating cytosolic cytochrome C expression, and triggering caspase-3, -7, and -9 cleavage. Domperidone decreased in formation of β-arrestin2/MEK complex, which contributing to inhibition of ERK activation. Additionally, treatment with domperidone diminished JAK2 and STAT3 activation. Treatment of U0126, the MEK inhibitor, resulted in reduced phosphorylation of MEK, ERK, and STAT3 without alteration of JAK2 activation, indicating that domperidone targeted both MEK-ERK-STAT3 and JAK2-STAT3 signaling pathways. Immunoblot analysis revealed that domperidone also downregulated DRD2 expression. Domperidone-induced reactive oxygen species (ROS) generation and N-acetylcysteine treatment mitigated ROS levels and restored cell viability. An in vivo xenograft study verified the significant antitumor effects of domperidone. These results emphasize the multifaceted anticancer effects of domperidone, highlighting its potential as a promising therapeutic agent for human CRC.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.1
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• pp.65-74
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• 2020

The purpose of this study was to investigate the physical characteristics of marine environment, and to predict the probability of the occurrence of hypoxia in the Dangdong bay. We predicted hypoxia using the logistic regression model analysis by observing the water temperature, salinity, and dissolved oxygen concentration. The analysis showed that the Brunt-Väisälä frequency which was shallow than the deep bay entrance, was higher inside the bay due to a lesser amount of fresh water inflow from the inner side of the bay, and density stratification was formed. The Richardson number, and Brunt-Väisälä frequency were very high occasionally from June to September; however, after September 2, the stratification had a tendency to decrease. Analysis of dissolved oxygen, water temperature, and salinity data observed in Dangdong bay showed that the dissolved oxygen concentration in the bottom layer was mostly affected by the temperature difference (dt) between the surface layer and bottom layer. Meanwhile, when the depth difference (dz) was set as a fixed variable, the probability of the occurrence of hypoxia varied with respect to the difference in water temperature. The depth difference (dz) was calculated to be 5 m, 10 m, 15 m, 20 m, and the difference in water temperature (dt) was found to be greater than 70 % at 8℃, 7℃, 5℃, and 3℃. This indicated that the larger the difference in depth in the bay, the smaller is the temperature difference required for the generation of hypoxia. In particular, the place in the bay, where the water depth dif erence was approximately 20 m, was found to generate hypoxia.

• 한국해양학회지
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• v.3 no.1
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• pp.16-25
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• 1968

This study was undertaken to assess the annual cycle of primary production and plant pigments in a downstream of the Han River. Measurements were carried out at three week intervals during April 1966 and March 1967, and ancillary data include water temperature, transparency, pH, dissolved oxygen and phytoplankton cell number. The seasonal cycle in water temperature profile shows the hihgest in the end of August with 27$^{\circ}C$, lowest in the middle of February with 0.2$^{\circ}C$. The transparency with Secchi disk reading varied from a maximum 4.0m in fall and a minimum 0.5m or less in early spring and flood season of summer. The pH of the river water varied from 6.5 to 7.3, averaged 6.91 in the surface water and 6.98 in the bottom water, showed little seasonalvariability. The dissolved oxygen in the surface water ranged from 5.93-9.64ml/L, while in the bottom water it ranged from 5.54-9.72 ml/L, and the oxygen saturation never fall below 94%. None thermal, the distribution of pH and content of oxygen, stratifications occurred. An apparent seasonal cycle of primary productivity was observed with remarkably high levels in the spring and fall, the lowest level in the winter. The range of net carbon assimilations showed 3.1-112.6 mgC/㎥/day or 15-427 mgC/㎡/day in spring, 37.0-271.2 mgC/㎥/day or 115-329 mgC/㎡/day in summer, 27.2-168.0 mgC/㎥ /day or 139-415 mgC/㎡/day in fall and 0.5-10.9 mgC/㎥/day or 5-19 mg/㎡/day in winter, respectively. Amount of chlorophyll ${\alpha}$ ranged from a minimum concentration of 0.2-0.3 mg/㎥ in the middle of February and a maximum 4.1-6.7 mg/㎥ in the middle of June. A general increase trend in chlorophyll ${\alpha}$ concentration was noted with increase of the river water temperature.

• Journal of Aquaculture
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• v.13 no.1
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• pp.87-99
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• 2000

Field survey on the variational characteristics of water quality and chlorophyll a concentraion were carried out at the 25 stations for four seasons in Kogum-sudo(Straits) southern coast of Korean Peninsula from Feburuary to October in 1993. We made an analysis on biological factor as chlorophyll a concentraion as well as physicio-chemical factors such as water temperature salinity sigma-t transparency dissolved oxygen(DO) chemical oxygen demand(COD) nutrients (ammonia, nitrite, nitrate, phosphate, and silicate) N/P ratio and suspended solid(SS). The waters in the Kogum-sudo were not stratified due to the tidal mixing. And the high productivity in photic layer were supported by high nutrients concentration from bottom waters. The high concen-trations of suspended solid in straits had a bad influence upon marine biology of nature and cultivations. In Kogum-sudo had a sufficient nutrients for primary productivity during a year. Especially phosphate and inorganic nitrogen were high the other side silicate was very low. The source of nutrients supply depend on rather mineralization of organic matters and input of seawater from outside than input of freshwaters from lands. Phytoplankton biomass as measured by chlorphyll a concentratiion was very high all the year round and it was controlled by the combination o f several environmental factors especially of phosphate in summer and dissolved nitrogen in other seasons.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.4
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• pp.55-63
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• 1997

Constructed wetland system which can be applied to the rural wastewater treatment system was examined by pilot plant in Kon-Kuk University. Hydraulic loading rate of wastewater was about 0.16m$^3$/m$^2$. day and theoretical detention time in the system was 1.38 days. The effluent of the septic tank for the school building was applied as inflow to the system. The influent concentration of DO was zero but effluent was up to 4.37mg/${\ell}$ which implies that oxygen was supplied enough from atmosphere by reaeration to support biological activity of the system. Average influent concentration of BOD was 104mg/${\ell}$ and effluent was 24mg/${\ell}$ with average removal rate of 76%. Average influent concentration of COD was 215mg/${\ell}$ and effluent was 63mg/${\ell}$ with average removal rate of 70 % . Average influent concentration of SS was 78mg/${\ell}$ and effluent was 10mg/${\ell}$ with average removal rate of 87%. Two components, BOD and SS, are regulated by law to keep maximum water quality standard of 80mg/${\ell}$ when daily outflow rate is less than 100$m^3$/day which is the case of most rural communities. Therefore, the results from the experiment showed that constructed wetland system can meet the water quality standard easily. Average influent concentration of total nitrogen was 165mg/lwhich is relatively higher than normal wastewater, and effluent was about 156mg/${\ell}$ with average removal rate of only 6%. Average influent concentration of total phosphorus was 41 mg/${\ell}$ and effluent was 6mg/${\ell}$ with average removal rate of 87%. Overall, constructed wetland system was thought to be effective to treat wastewater if nitrogen removal mechanism is improved. Considering low cost, less maintenance, and high treatability, this system can be a practical alternative for the wastewater treatment in rural area The experiment was performed during the summer and fall season, and treatment efficiency of the system is expected to decrease in low temperature. therefore, further study including temperature is required to evaluate feasibility of the system more in detail.

• Journal of Environmental Science International
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• v.8 no.1
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• pp.107-113
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• 1999

A new biological nutrient removal system combining $A^2/O$ process with fixed film was developed in this work and the characteristics of denitrification were especially investigated in the combined fixed film reactor(CFFR). Media was added in the anaerobic, anoxic and aerobic reactors, respectively. Tests were made to establish the effluent level of $NO_x-N$, COD, DO and nitrite effects on $NO_x-N$ removal in the CFFR by decreasing hydraulic retention time (HRT) from 10.0 to 3.5 hours and by increasing internal recycle ratio form 0% to 200%. The influent was synthesized to levels similar to the average influent of municipal wastewater treatment plants in Korea. SARAN media with a porosity of 96.3% was packed 40% / 130% / 25% based on its reactor volume, respectively. It was found that COD rarely limited dentrification in the anoxic reactor because of high $C/NO_x/-N$ ratio in the anoxic reactor, while DO concentration in the anoxic reactor and $NO_2-N/NO_x/-N$ from the aerobic effluent inhibited denitrification in the anoxic reactor. It was proved that the critical points of DO concentration in the anoxic reactor and $NO_2-N/NO_x/-N$ from the aerobic effluent were 0.15mg/L and 10%, respectively. As the internal recycle ratio increased, DO concentration in the anoxic reactor and $NO_2-N/NO_x/-N$ from the aerobic effluent increased. Especially, at the condition of internal recycle ratio, 200%, DO concentration in the anoxic reactor and $NO_2-N/NO_x/-N$ from the aerobic effluent exceeded the critical points of 0.15mg/L and 10%, respectively. Then, denitrification efficiency considerably decreased. Consequently, it was represented that the control of DO concentration in the anoxic reactor and $NO_2-N/NO_x/-N$ from the aerobic effluent can assure effective denitrification.

• Biomolecules & Therapeutics
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• v.32 no.1
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• pp.77-83
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• 2024

Alzheimer's disease (AD) is a neurodegenerative disease characterized by neuronal cell death and memory impairment. Corticosterone (CORT) is a glucocorticoid hormone produced by the hypothalamic-pituitary-adrenal axis in response to a stressful condition. Excessive stress and high CORT levels are known to cause neurotoxicity and aggravate various diseases, whereas mild stress and low CORT levels exert beneficial actions under pathophysiological conditions. However, the effects of mild stress on AD have not been clearly elucidated yet. In this study, the effects of low (3 and 30 nM) CORT concentration on Aβ_25-35-induced neurotoxicity in SH-SY5Y cells and underlying molecular mechanisms have been investigated. Cytotoxicity caused by Aβ_25-35 was significantly inhibited by the low concentration of CORT treatment in the cells. Furthermore, CORT pretreatment significantly reduced Aβ_25-35-mediated pro-apoptotic signals, such as increased Bim/Bcl-2 ratio and caspase-3 cleavage. Moreover, low concentration of CORT treatment inhibited the Aβ_25-35-induced cyclooxygenase-2 and pro-inflammatory cytokine expressions, including tumor necrosis factor-α and interleukin-1β. Aβ_25-35 resulted in intracellular accumulation of reactive oxygen species and lipid peroxidation, which were effectively reduced by the low CORT concentration. As a molecular mechanism, low CORT concentration activated the nuclear factor-erythroid 2-related factor 2, a redox-sensitive transcription factor mediating cellular defense and upregulating the expression of antioxidant enzymes, such as NAD(P)H:quinone oxidoreductase, glutamylcysteine synthetase, and manganese superoxide dismutase. These findings suggest that low CORT concentration exerts protective actions against Aβ_25-35-induced neurotoxicity and might be used to treat and/or prevent AD.

• Journal of Environmental Health Sciences
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• v.38 no.3
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• pp.251-260
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• 2012

Objectives: The purpose of this study was evaluating the applicability of the circulation dielectric barrier plasma process (DBD) for efficiently treating non-biodegradable wastewater, such as phenol. Methods: The DBD plasma reactor system in this study consisted of a plasma reactor (discharge, ground electrode and quartz dielectric tube, external tube), high voltage source, air supply and reservoir. Effects of the operating parameters on the degradation of phenol and $UV_{254}$ absorbance such as first voltage (60-180 V), oxygen supply rate (0.5-3 l/min), liquid circulation rate (1.5-7 l/min), pH (3.02-11.06) and initial phenol concentration (12.5-100 mg/l) were investigated. Results: Experimental results showed that optimum first voltage, oxygen supply rate, and liquid circulation rate on phenol degradation were 160 V, 1 l/min, and 4.5 l/min, respectively. The removal efficiency of phenol increased with the increase in the initial pH of the phenol solution. To obtain a removal efficiency of phenol and COD of phenol of over 97% (initial phenol concentration, 50.0 mg/l), 15 min and 180 minutes was needed, respectively. Conclusions: It was considered that the absorbance of $UV_{254}$ for phenol degradation can be used as an indirect indicator of change in non-biodegradable organic compounds. Mineralization of the phenol solution may take a relatively longer time than that required for phenol degradation.