• International Journal of Oral Biology
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• v.34 no.3
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• pp.151-155
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• 2009

The role of $Cl^-$ channels in regulatory volume decrease (RVD) in human salivary gland acinar cells was examined using a whole-cell patch clamp technique. Human tissues were obtained from healthy volunteers or from patients with oromaxillofacial tumors. During the measurements, $K^+$-free solutions were employed to eliminate contamination of whole-cell conductance by $K^+$ currents. When the cells were exposed to a 70% hypotonic solution, outward-rectifying currents, which were not observed in the resting state, were found to have significantly increased both in human labial and parotid gland acinar cells. The amplitudes of the currents were reduced in a low $Cl^-$ bath solution. Furthermore, the addition of $100{\mu}M$ 5-Nitro-2- (3-phenyl propylamino) benzoic acid (NPPB) or $100{\mu}M$ 4,4'-diisothio cyanatostilbene-2,2'-disulphonic acid (DIDS), known to partially block $Cl^-$ channels, significantly inhibited these currents. Its outward-rectifying current profile, shift in reversal potential in a low $Cl^-$ bath solution and pharmacological properties suggest that this is a $Ca^{2+}$-independent, volume activated $Cl^-$ current. We conclude therefore that volume activated $Cl^-$ channels play a putative role in RVD in human salivary gland acinar cells.

• The Journal of Engineering Geology
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• v.20 no.1
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• pp.13-23
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• 2010

Toppling failure of a slope is defined as failure behavior accompanying the rotation of rock block which is different from other failure such as sliding along with discontinuities and so on. It generally occurs in the region that discontinuities were developed with inverse dip direction to a slope and it could play a critical role in judging stability of slope. In this study, the stability evaluation was performed about toppling failure on a jointed road cut-slope. To check the deformation behavior, numerical analysis is widely used. However common analysis programs are based on continuum model. Recently, many methods that discontinuity properties can be considered in continuum analysis are suggested. In this study, numerical analysis based on FEM(Finite Element Method) was performed using interface element applied in heterogeneous boundary to simulate effects of discontinuities.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1933-1954
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• 2013

Multiple wireless devices are being widely deployed in Intelligent Transportation System (ITS) services on the road to establish end-to-end connection between vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) networks. Vehicular ad hoc networks (VANETs) play an important role in supporting V2V and V2I communications (also called V2X communications) in a variety of urban environments with distinct topological characteristics. In fact, obstacles such as big buildings, moving vehicles, trees, advertisement boards, traffic lights, etc. may block the radio signals in V2X communications. Their impact has been neglected in VANET research. In this paper, we present a realistic and efficient radio propagation model to handle different sizes of static and moving obstacles for V2X communications. In the proposed model, buildings and large moving vehicles are modeled as static and moving obstacles, and taken into account their impact on the packet reception rate, Line-of-sight (LOS) obstruction, and received signal power. We use unsymmetrical city map which has many dead-end roads and open faces. Each dead-end road and open faces are joined to the nearest edge making a polygon to model realistic obstacles. The simulation results of proposed model demonstrates better performance compared to some existing models, that shows proposed model can reflect more realistic simulation environments.

• Journal of the Korean Home Economics Association
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• v.37 no.3
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• pp.175-191
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• 1999

The purpose of this study was to investigate the eating behavior and life habits of kindergarten children 5 to 7 years old in Chuncheon area. This study was conducted in December, 1996. Anthropometric indices(height, weight, skinfold thickness, mid-arm circumference) were measured and body mass index(BMI), Rohrer index, arm fat area were calculated to estimate children’s body fatness. Also the eating behavior and life habits were determined tv using questionnaire method. The results were as follows: Body fat rate of the children was almost normal according to Rohrer index and BMI. There was significant difference in birth weight between male and female. The problems of the eating behavior were frequent skipping breakfast and eating-out. The rate of the children who took snacks 2 times a day was 46.9％. Most children tended to take sweet snacks such as ice-cream, chocolates, cookies, and they tended to prefer meats and fishes to vegetables. The rate of breast feeding was 28.3％ and the rate of weaning foods prepared at home was 61.1%. Many children preferred indoor activities such as watching TV, toy furniture play, building block to outdoor activities such as roller-skating, cycling, jogging in their spare time. The rate of the children who took exercise regularly was 15％. Children tended to eat kimbap, fried chicken, ramyeon more frequently in various instant foods. The intake rates of fruit juice and barly tea were relatively high and children's favorite fruits were watermelon and mandarin orange. From this results, skipping breakfast, frequent eating-out and the monotony of food preference appears to cause imbalance in nutrient intakes of the children and to have bad influence on children’s health. Accodgingiy, the comprehensive nutrition education and proper modification program should be needed for the children and their parents to correct the eating behavior and life habits. The reasonable exercise programs are needed to motivate outdoor activities of the children, and the importance of breast feeding and weaning foods should be emphasized to lactating women and pregnant women.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.42-42
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• 2003

Large-conductance $Ca^{2+}$-activated potassium channels ($BK_{Ca}$ are a widely distributed and play key roles in various cell functions. In nerve cells, $BK_{Ca}$ channels shorten the duration of action potentials and block $Ca^{2+}$ entry thereby repolarizing excitable cells after excitation. $BK_{Ca}$ channel opening has been postulated to confer neuroprotection during stroke, and has attracted attention as a means for therapeutic intervention in asthma, hypertension, convulsions, and traumatic brain injury. Several natural and synthetic compounds including a steroid hormone, $\beta$-estradiol, have been identified as the activators of $BK_{Ca}$ channels. Based on the structural features of the previously reported activators of $BK_{Ca}$ channels, we designed several lead compounds, synthesized chemically, and tested their functional activity on cloned $BK_{Ca}$ channels. The $\alpha$ subunit of rat $BK_{Ca}$ channel was expressed alone or with different $\beta$ subunits in Xenopus oocytes and the effects of the compounds were tested electrophysiological means. One of the lead compounds affected the activity of the $\alpha$ subunit of $BK_{Ca}$ channel in a $\beta$ subunit-specific manner. While the activity of B $K_{ca}$ channel $\alpha$ subunit was Potentiated, the channel composed of $\alpha$ and $\beta$1 subunits were inhibited by this compound. We are currently investigating the mechanism of the $\beta$ subunit-dependent effects and planning to localize the receptor site of the lead compound.f the lead compound.

• Journal of Forest and Environmental Science
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• v.33 no.4
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• pp.330-341
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• 2017

Tropical forests play a key role for functioning of the planet and maintenance of life. These forests support more than half of the world's species, serve as regulators of global and regional climate, act as carbon sinks and provide valuable ecosystem services. Forest floor biomass and litterfall dynamics was measured in different sites influenced by fire in a seasonally dry tropical forest of Bhoramdeo wildlife sanctuary of Chhattisgarh, India. The forest floor biomass was collected randomly placed quadrats while the litterfall measured by placing stone-block lined denuded quadrat technique. The seasonal mean total forest floor biomass across the fire regimes varied from $2.00-3.65t\;ha^{-1}$. The total litterfall of the study sites varied from $4.75-7.56t\;ha^{-1}\;yr^{-1}$. Annual turnover of litter varied from 70-74% and the turnover time between 1.35-1.43 years. Monthly pattern of forest floor biomass indicated that partially decayed litter, wood litter and total forest floor were differed significantly. The seasonal variation showed that leaf fall differed significantly in winter season only among the fire regimes while the wood litter was found non significant in all the season. This study shows that significant variation among the site due to the forest fire. Decomposition is one of the ecological processes critical to the functioning of forest ecosystems. The decomposing wood serves as a saving account of nutrients and organic materials in the forest floor. Across the site, high fire zone was facing much of the deleterious effects on forest floor biomass and litter production. Control on such type of wildfire and anthropogenic ignition could allow the natural recovery processes to enhance biological diversity. Chronic disturbances do not provide time for ecosystem recovery; it needs to be reduced for ecosystem health and maintaining of the high floral and faunal biodiversity.

• Journal of Power Electronics
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• v.18 no.1
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• pp.234-250
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• 2018

This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.113-118
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• 1998

By their rapid and periodic actions, the cilia of the human respiratory tract play an important role in clearing inhaled noxious particles. Based on the automated image-processing technique, we studied the method analyzing ciliary beat frequency (CBF) objectively and quantitatively. Microscopic ciliary images were transformed into digitized gray ones through an image-grabber, and from these we extracted signals for CBF. By means of a FFT, maximum peak frequencies were detected as CBFs in each partitioned block for the entire digitized field. With these CBFs, we composed distribution maps visually showing the spatial distribution of CBFs. Through distribution maps of CBF, the whole aspects of CBF changes for cells and the difference of CBF of neighboring cells can be easily measured and detected. Histogram statistics calculated from the user-defined polygonal window can show the local dominant frequency presumed to be the CBF of a cell or a crust the region includes.

• Clinical and Experimental Reproductive Medicine
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• v.50 no.3
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• pp.154-159
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• 2023

Monospermy occurs in the process of normal fertilization where a single sperm fuses with the egg, resulting in the formation of a diploid zygote. During the process of fertilization, the sperm must penetrate the zona pellucida (ZP), the outer layer of the egg, to reach the egg's plasma membrane. Once a sperm binds to the ZP, it undergoes an acrosomal reaction, which involves the release of enzymes from the sperm's acrosome that help it to penetrate the ZP. Ovastacin is one of the enzymes that is involved in breaking down the ZP. Studies have shown that ovastacin is necessary for the breakdown of the ZP and for successful fertilization to occur. However, the activity of ovastacin is tightly regulated to ensure that only one sperm can fertilize the egg. One way in which ovastacin helps to prevent polyspermy (the fertilization of an egg by more than one sperm) is by rapidly degrading the ZP after a sperm has penetrated it. This makes it difficult for additional sperm to penetrate the ZP and fertilize the egg. Ovastacin is also thought to play a role in the block to polyspermy, a mechanism that prevents additional sperm from fusing with the egg's plasma membrane after fertilization has occurred. In summary, the role of ovastacin in monospermic fertilization is to help ensure that only one sperm can fertilize the egg, while preventing polyspermy and ensuring successful fertilization.

• Journal of Embryo Transfer
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• v.19 no.2
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• pp.101-112
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• 2004

Chloride($Cl^-$) channels play critical roles in cell homeostasis and its specific functions such as volume regulation, differentiation, secretion, and membrane stabilization. The presence of these channels have been reported in all kinds of cells and even in frog oocytes. These essential role of $Cl^-$­ channels in cell homeostasis possibly play any role in egg homeostasis and in the early stage of development, however, there has been no report about the presence of $Cl^-$­ channel in the mammalian oocyte. This study was performed to elucidate the presence of $Cl^-$­ channels in hamster eggs. When allowing only $Cl^-$­ to pass through the channel of the egg membrane by using impermeant cation such as N-methyl-D-glucamine(NMDG), single channel currents were recorded. These channel currents showed typical long-lasted openings interrupted by rapid flickering. Mean open $time({\tau}o)$ was 43${\pm}$10.14 ms(n=9, at 50 mV). The open probability(Po) was decrease with depolarization. The current-voltage relation showed outward rectification. Outward slop conductance(32${\pm}$5.4 pS, n=22) was steeper than the inward slop conductance(10${\pm}$1.3 pS). Under the condition of symmetrical 140 mM NaCl, single channel currents were reversed at 0 mV(n=4). This reversal potential(Erev) was shifted from 0 mV at 140 mM concentration of internal NaCl(140 mM [Na+]i) to ­9.8${\pm}$0.5 mV(n=4) at 70 mM [Na+]i and 11.5${\pm}$1.9 mV at 280 mM [Na+]i(n=4) respectively, strongly suggesting that these are single $Cl^-$­ channel currents. To examine further whether this channel has pharmacological property of the $Cl^-$­ channel, specific Cl­ channel blockers, IAA-94(Indanyloxyacetic acid-94) and DIDS(4, 4'-diisothiocyan ostillben- 2-2'disulfonic acid) were applied. IAA-94 inhibited the channel current in a dose-dependent manner and revealed a rapid and flickering block. From these electrophysiological and pharmacological resluts, we found the novel $Cl^-$­ channel present in the hamster oocyte membrane. The first identification of $Cl^-$­ channel in the hamster oocyte may give a clue for the further study on the function of $Cl^-$­ channel in the fertilization and cell differentiation.