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Search Results: 1 - 10 of 45538 matches for " Hak-Jin Kim "
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Regulation of cerebrospinal fluid production by caffeine consumption
Myoung-Eun Han, Hak-Jin Kim, Young-Suk Lee, Dong-Hyun Kim, Joo-Taek Choi, Chul-Sik Pan, Sik Yoon, Sun-Yong Baek, Bong-Seon Kim, Jae-Bong Kim, Sae-Ock Oh
BMC Neuroscience , 2009, DOI: 10.1186/1471-2202-10-110
Abstract: In the present study we found that the long-term consumption of caffeine can induce ventriculomegaly; this was observed in 40% of the study rats. In the caffeine-treated rats with ventriculomegaly, there was increased production of CSF, associated with the increased expression of Na+, K+-ATPase and increased cerebral blood flow (CBF). In contrast to the chronic effects, acute treatment with caffeine decreased the production of CSF, suggesting 'effect inversion' associated with caffeine, which was mediated by increased expression of the A1 adenosine receptor, in the choroid plexus of rats chronically treated with caffeine. The involvement of the A1 adenosine receptor in the effect inversion of caffeine was further supported by the induction of ventriculomegaly and Na+, K+-ATPase, in A1 agonist-treated rats.The results of this study show that long-term consumption of caffeine can induce ventriculomegaly, which is mediated in part by increased production of CSF. Moreover, we also showed that adenosine receptor signaling can regulate the production of CSF by controlling the expression of Na+, K+-ATPase and CBF.Methylxanthine caffeine is present in many common beverages, and is widely consumed worldwide [1,4]. Caffeine consumption has been estimated to be 76 mg per person per day worldwide, as high as 238 mg per person per day in the United States and Canada, and more than 400 mg per person per day in Sweden and Finland [5,6]. Caffeine is absorbed rapidly after oral administration and distributed to various organs and tissues. In the liver, caffeine is metabolized to dimethyl- and monomethylxanthines, dimethyl and monomethyl uric acids, trimethyl- and dimethylallantoin, and uracil derivatives. Some metabolites of caffeine including 1,3-dimethylxanthine (theophylline) and 1,7-dimethylxanthine (paraxanthine) have pharmacological activity similar to caffeine [4]. The half-life of caffeine is ~5 hours in humans and ~1 hour in rats [4,7].The main mechanism of action of caffei
Jump exercise during hindlimb unloading protect against the deterioration of trabecular bone microarchitecture in growing young rats
Yong-In Ju, Teruki Sone, Kazuhiro Ohnaru, Hak-Jin Choi, Kyung-A Choi and Masao Fukunaga
SpringerPlus , 2013, DOI: 10.1186/2193-1801-2-35
Abstract: Three-dimensional femoral trabecular architecture was investigated in tail-suspended young growing rats and the effects of jump exercise during the period of tail-suspension were also examined. Eight-week-old male Wistar rats (n = 24) were randomly assigned to three body weight-matched groups: a tail suspended group (SUS, n = 8); a sedentary control group (CON, n = 8) and rats primed with jump exercise during the period of tail suspension (JUM, n = 8). The jump exercise protocol consisted of 30 jumps/day, five days/week with a 40 cm jump height. After 3 weeks of jump exercise, bone mineral density (BMD) of the entire right femur was measured using dual energy X-ray absorptiometry. Three-dimensional trabecular bone architecture at the distal femoral metaphysis was evaluated using microcomputed tomography (micro-CT). Tail suspension caused a decrease in femoral BMD ( 5%, p < 0.001) and trabecular bone architectural deterioration. Deterioration in the trabecular network during hindlimb unloading was mostly attributed to the reduction of trabecular number ( 32%, p < 0.001) in the distal femoral metaphysis. Jump exercise during the tail suspension period increased trabecular thickness (14%, p < 0.001) and the reduction of trabecular number was suppressed. The present data indicate that jump exercise applied during hindlimb unloading could be able to inhibit bone loss and trabecular bone architectural deterioration caused by tail suspension.
Development of IEC61850 Based Substation Engineering Tools with IEC61850 Schema Library  [PDF]
Yong Hak Kim, Jeon Yeol Han, You Jin Lee, Yong Ho An, In Jun Song
Smart Grid and Renewable Energy (SGRE) , 2011, DOI: 10.4236/sgre.2011.23030
Abstract: IEC 61850 allows the replacement of conventional wire based systems to communication based system with local area network. Since new engineering processes are introduced in substation, the specifications and tools are required combined with new skills across the substation engineering. In order to construct the IEC 61850 based substation automation system, the IED engineering tools as an engineering means are necessary to cope with the substation automation by full digital devices in the real power systems. Compared the configuration tools provided IEDs vendors which are able to support the operation and communication analysis between IEDs, the XML based IED integration engineering tools as substation engineering tools which are developed can build, edit and save the ICD, SCL and CID files. Particularly, the substation engineering tools are possible to apply the IEC 61850 based IEDs for the engineering process of systems and also provide the reliability and efficiency of system for the utilities and manufacturers. The developed tools are applied to test and create the SCL files for domestic-made IEDs, and then compared with the conventional tools. The reliability including accuracy of results was proved.
Association between polymorphisms of arachidonate 12-lipoxygenase (ALOX12) and schizophrenia in a Korean population
Tae Kim, Hak-Jae Kim, Jin Park, Jong Kim, Joo-Ho Chung
Behavioral and Brain Functions , 2010, DOI: 10.1186/1744-9081-6-44
Abstract: Essential polyunsaturated fatty acids (EPUFAs) are major components of neural membranes. These membranes show an altered composition in schizophrenia patients [1]. Arachidonic acid (AA) and docosahexaenoic acid (DHA) constitute 80-90% of EPUFAs in neuronal tissue, but there is reduced AA in schizophrenia [2]. The enzyme ALOX12 oxygenates the C-12 of arachidonic acid, producing 12-hydroperoxy-5, 8, 10, 14- eicosatetraenoic acid (12-HPETE) [3], which, research has shown, inhibits protein kinase II [4]. Protein kinase II phosphorylates tyrosine hydroxylase, which is the rate-limiting enzyme in catecholamine synthesis [5]. Accordingly, 12-HPETE might affect dopamine synthesis. In addition, 12- HPETE inhibits neurotransmitter release per se [6]. However, no research has yet shown the association between ALOX12 and schizophrenia. Therefore, we hypothesized genetic variances of the ALOX12 gene might be associated with schizophrenia. To test this hypothesis, we investigated the single nucleotide polymorphisms (SNPs) of the ALOX12 gene in schizophrenia patients.We recruited patients meeting the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria for schizophrenia [7], resulting in a study population consisting of 289 Korean patients with schizophrenia [189 men and 100 women; age 42.85 ± 10.84 (mean ± S.D., in years)]. We also recruited 306 Korean control subjects (148 men and 158 women; age 36.06 ± 6.79). We reviewed the medical records of each patient and assessed the schizophrenia patients using the Brief Psychiatric Rating Scale (BPRS), the Scale for the Assessment of Negative Symptoms (SANS), and the operational criteria (OPCRIT) checklist [8]. All studies were carried out according to the guidelines of the Declaration of Helsinki [9]. Written informed consent was obtained from each subject, and the study was approved by the Institutional Review Board of Kyung Hee University Hospital, Seoul, Republic of Korea. We selected three coding
DNMT (DNA methyltransferase) inhibitors radiosensitize human cancer cells by suppressing DNA repair activity
Hak Jae Kim, Jin Ho Kim, Eui Kyu Chie, Park Da Young, In Ah Kim, Il Han Kim
Radiation Oncology , 2012, DOI: 10.1186/1748-717x-7-39
Abstract: A549 (lung cancer) and U373MG (glioblastoma) cells were exposed to radiation with or without six DNMT inhibitors (5-azacytidine, 5-aza-2'-deoxycytidine, zebularine, hydralazine, epigallocatechin gallate, and psammaplin A) for 18 hours prior to radiation, after which cell survival was evaluated via clonogenic assays. Cell cycle and apoptosis were analyzed via flow cytometry. Expressions of DNMT1, 3A/3B, and cleaved caspase-3 were detected via Western blotting. Expression of γH2AX, a marker of radiation-induced DNA double-strand break, was examined by immunocytochemistry.Pretreatment with psammaplin A, 5-aza-2'-deoxycytidine, and zebularine radiosensitized both A549 and U373MG cells. Pretreatment with psammaplin A increased the sub-G1 fraction of A549 cells, as compared to cells exposed to radiation alone. Prolongation of γH2AX expression was observed in the cells treated with DNMT inhibitors prior to radiation as compared with those treated by radiation alone.Psammaplin A, 5-aza-2'-deoxycytidine, and zebularine induce radiosensitivity in both A549 and U373MG cell lines, and suggest that this effect might be associated with the inhibition of DNA repair.Epigenetic alteration is one of the most important gene regulatory mechanisms. Unlike genetic alterations, epigenetic events are not changes in gene function that occur in conjunction with DNA sequence changes. Recently, epigenetic studies have been conducted in many different aspects of biology, and particularly in the cancer field. DNA methylation and histone modifications are two principal factors in epigenetic phenomena. These two mechanisms perform a crucial function in carcinogenesis and tumor progression.DNA methylation is controlled by DNA methyltransferase (DNMT), an enzyme that catalyzes the transfer of a methyl moiety from S-adenosyl-l-methionine to the 5-postion of cytosines in the CpG dinucleotide [1]. DNMT overexpression has been detected in a variety of malignancies, including lung, prostate, and colorect
Designing an Energy Storage System Fuzzy PID Controller for Microgrid Islanded Operation
Jong-Yul Kim,Hak-Man Kim,Seul-Ki Kim,Jin-Hong Jeon,Heung-Kwan Choi
Energies , 2011, DOI: 10.3390/en4091443
Abstract: Recently, interest in microgrids, which are composed of distributed generation (DG), distributed storage (DS), and loads, has been growing as a potentially effective clean energy system to mitigate against climate change. The microgrid is operated in the grid-connected mode and the islanded mode according to the conditions of the upstream power grid. The role of the energy storage system (ESS) is especially important to maintain constant the frequency and voltage of an islanded microgrid. For this reason, various approaches for ESS control have been put forth. In this paper, a fuzzy PID controller is proposed to improve the frequency control performance of the ESS. This fuzzy PID controller consists of a fuzzy logic controller and a conventional PI controller, connected in series. The fuzzy logic controller has two input signals, and then the output signal of the fuzzy logic controller is the input signal of the conventional PI controller. For comparison of control performance, gains of each PI controller and fuzzy PID controller are tuned by the particle swam optimization (PSO) algorithm. In the simulation study, the control performance of the fuzzy PID was also tested under various operating conditions using the PSCAD/EMTDC simulation platform.
Field Implementation of Wireless Vibration Sensing System for Monitoring of Harbor Caisson Breakwaters
Han-Sam Yoon,So-Young Lee,Jeong-Tae Kim,Jin-Hak Yi
International Journal of Distributed Sensor Networks , 2012, DOI: 10.1155/2012/597546
Weekend and nighttime effect on the prognosis of peptic ulcer bleeding
Young Hoon Youn,Yong Jin Park,Jae Hak Kim,Tae Joo Jeon
World Journal of Gastroenterology , 2012, DOI: 10.3748/wjg.v18.i27.3578
Abstract: AIM: To evaluate whether weekend or nighttime admission affects prognosis of peptic ulcer bleeding despite early endoscopy. METHODS: Retrospective data collection from four referral centers, all of which had a formal out-of-hours emergency endoscopy service, even at weekends. A total of 388 patients with bleeding peptic ulcers who were admitted via the emergency room between January 2007 and December 2009 were enrolled. Analyzed parameters included time from patients’ arrival until endoscopy, mortality, rebleeding, need for surgery and length of hospital stay. RESULTS: The weekday and weekend admission groups comprised 326 and 62 patients, respectively. There were no significant differences in baseline characteristics between the two groups, except for younger age in the weekend group. Most patients (97%) had undergone early endoscopy, which resulted in a low mortality rate regardless of point of presentation (1.8% overall vs 1.6% on the weekend). The only outcome that was worse in the weekend group was a higher rate of rebleeding (12% vs 21%, P = 0.030). However, multivariate analysis revealed nighttime admission and a high Rockall score (≥ 6) as significant independent risk factors for rebleeding, rather than weekend admission. CONCLUSION: Early endoscopy for peptic ulcer bleeding can prevent the weekend effect, and nighttime admission was identified as a novel risk factor for rebleeding, namely the nighttime effect.
Field Implementation of Wireless Vibration Sensing System for Monitoring of Harbor Caisson Breakwaters
Han-Sam Yoon,So-Young Lee,Jeong-Tae Kim,Jin-Hak Yi
International Journal of Distributed Sensor Networks , 2012, DOI: 10.1155/2012/597546
Abstract: A wireless sensing system for structural health monitoring (SHM) of harbor caisson structures is presented. To achieve the objective, the following approaches were implemented. First, a wave-induced vibration sensing system was designed for global structural health monitoring. Second, global SHM methods which are suitable for damage monitoring of caisson structures were selected to alarm the occurrence of unwanted behaviors. Third, an SHM scheme was designed for the target structure by implementing the selected SHM methods. Operation logics of the SHM methods were programmed based on the concept of the wireless sensor network. Finally, the performance of the proposed system was globally evaluated for a field harbor caisson structure for which a series of tasks were experimentally performed by the wireless sensing system. 1. Introduction According to a report of the Intergovernmental Panel on Climate Change [1], global warming is unambiguous. As sea surface temperature increases, water vapor in the lower troposphere also increases, and so does the energy of typhoons. The relationship between global warming and increased typhoon activity and intensity has been verified, reported by studies based on analyses of historical records and simulation results [2–4]. It was also reported that typhoons in the western North Pacific (WNP), including Korea, have become more intense as measured by their frequency in hurricane categories 4 and 5 [5] or the power dissipation index [3]. A strong typhoon usually brings strong winds and heavy rains, causes severe surge and floods, and then results in significant loss of life and property. Accordingly, the increase of typhoon intensity and frequency makes severer damages over the Pacific Ocean from the Philippine Islands to Taiwan, Japan, Korea, and the southwestern coast of China. In general, coastlines, interfaces between ocean and land, are facing a severe state of typhoon than inland; thus, the safety of coastal structures becomes more significant under storm waves. The safety can be checked in a regular or irregular time scale, depending on the state of the target coastal structures and occurrence of extreme loading conditions such as typhoons. The safety is usually done by structural health monitoring (SHM) to identify existing damages in the target structures, gravity type or pile type, and finally to make an assessment of their healthy status. In the gravity-type coastal structures, the damages can be classified into settlement, overturning, or sliding. Local defects such as scouring and disturbance in foundation can
New discrete method for investigating the response properties in finite electric field
Myong-Chol Pak,Nam-Hyok Kim,Hak-Chol Pak,Song-Jin Im
Physics , 2013,
Abstract: In this paper we develop a new discrete method for calculating the dielectric tensor and Born effective charge tensor in finite electric field by using Berry's phase and the gauge invariance. We present a new method to overcome non-periodicity of the potential in finite electric field due to the gauge invariance, and construct the dielectric tensor and Born effective charge tensor that satisfy translational symmetry in finite electric field. In order to demonstrate the correctness of this method, we also perform calculations for the semiconductors AlAs and GaAs under the finite electric field to compare with the preceding method and the experiment.
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