• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3529-3550
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• 2016

In heterogeneous networks (HetNets), energy saving is vital for a sustainable network development. Many techniques, such as spectrum allocation, network planning, etc., are used to improve the network energy efficiency (EE). In this paper, micro BSs utilizing cell range expansion (CRE) and spectrum allocation are considered in multi-channel heterogeneous networks to improve EE. Hotspot region is assumed to be covered by micro BSs which can ensure that the hotspot capacity is greater than the average demand of hotspot users. The expressions of network energy efficiency are derived under shared, orthogonal and hybrid subchannel allocation schemes, respectively. Particle swarm optimization (PSO) algorithm is used to solve the optimal ratio of subchannel allocation in orthogonal and hybrid schemes. Based on the results of the optimal analysis, we propose three service control strategies on the basis of large-scale user behaviors, i.e., adjust micro cell rang expansion (AmCRE), adjust micro BSs density (AmBD) and adjust micro BSs transmit power (AmBTP). Both theoretical and simulation results show that using shared subchannel allocation scheme in AmBD strategies can obtain maximal EE with a very small area ratio. Using orthogonal subchannel allocation scheme in AmCRE strategies can obtain maximal EE when area ratio is larger. Using hybrid subchannel allocation scheme in AmCRE strategies can obtain maximal EE when area ratio is large enough. No matter which service control strategy is used, orthogonal spectrum scheme can obtain the maximal hotspot user rates.

• Biomolecules & Therapeutics
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• v.25 no.5
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• pp.504-510
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• 2017

Inhibitor of nuclear factor kappa-B kinase beta ($IKK{\beta}$) plays a critical role in cell proliferation and inflammation in various cells by activating $NF-{\kappa}B$ signaling. However, the interrelationship between peroxisome proliferator-activated receptor ${\alpha}$ ($PPAR{\alpha}$) and $IKK{\beta}$ in cell proliferation is not clear. In this study, we investigated the possible role of $PPAR{\alpha}$ in the hepatic cell death in the absence of $IKK{\beta}$ gene using liver-specific Ikkb-null ($Ikkb^{F/F-AlbCre}$) mice. To examine the function of $PPAR{\alpha}$ activation in hepatic cell death, wild-type ($Ikkb^{F/F}$) and $Ikkb^{F/F-AlbCre}$ mice were treated with $PPAR{\alpha}$ agonist Wy-14,643 (0.1% w/w chow diet) for two weeks. As a result of Wy-14,643 treatment, apoptotic markers including caspase-3 cleavage, poly (ADP-ribose) polymerase (PARP) cleavage and TUNEL-positive staining were significantly decreased in the $Ikkb^{F/F-AlbCre}$ mice. Surprisingly, Wy-14,643 increased the phosphorylation of p65 and STAT3 in both Ikkb and $Ikkb^{F/F-AlbCre}$ mice. Furthermore, BrdU-positive cells were significantly increased in both groups after treatment with Wy-14,643. Our results suggested that $IKK{\beta}-derived$ hepatic apoptosis could be altered by $PPAR{\alpha}$ activation in conjunction with activation of $NF-{\kappa}B$ and STAT3 signaling.

• Journal of Astronomy and Space Sciences
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• v.13 no.2
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• pp.149-162
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• 1996

The results of space radiation experiments carried out on board the first two Korean technology demonstration microsatellites are presented in this paper. The first satellite, KITSAT-1, launched in August 1992, carries a radiation monitoring payload called cosmic ray experiment(CRE) for characterizing the low-earth orbit(LEO) radiation environment. The CRE consists of two sub-systems: the cosmic particle experiment (CPE) and the total dose experiment(TDE). In addition, single event upset(SEU)rates of the program memory and the RAM disk are also monitored. The second satellite, KITSAT-2, launched in September 1993, carries a newly developed 32-bit on-board computer(OBC), KASCOM(KAIST satellite computer in addition to OBC186. SEUs ocurred in the KASCOM, as well as in the program memory and RAM disk memory, have been monitored since the beginning of the satellite operation. These two satellites, which are very similar in structures but different in orbits, provide a unique opportunity to study the effects of the radiation environment characterized by the orbit.

• Journal of Korean Academy of Nursing
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• v.50 no.4
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• pp.621-630
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• 2020

Purpose: This study was aimed to evaluate the external validity of a carbapenem-resistant Enterobacteriaceae (CRE) acquisition risk prediction model (the CREP-model) in a medium-sized hospital. Methods: This retrospective cohort study included 613 patients (CRE group: 69, no-CRE group: 544) admitted to the intensive care units of a 453-beds secondary referral general hospital from March 1, 2017 to September 30, 2019 in South Korea. The performance of the CREP-model was analyzed with calibration, discrimination, and clinical usefulness. Results: The results showed that those higher in age had lower presence of multidrug resistant organisms (MDROs), cephalosporin use ≥ 15 days, Acute Physiology and Chronic Health Evaluation II (APACHE II) score ≥ 21 points, and lower CRE acquisition rates than those of CREP-model development subjects. The calibration-in-the-large was 0.12 (95% CI: - 0.16~0.39), while the calibration slope was 0.87 (95% CI: 0.63~1.12), and the concordance statistic was .71 (95% CI: .63~.78). At the predicted risk of .10, the sensitivity, specificity, and correct classification rates were 43.5%, 84.2%, and 79.6%, respectively. The net true positive according to the CREP-model were 3 per 100 subjects. After adjusting the predictors' cutting points, the concordance statistic increased to .84 (95% CI: .79~.89), and the sensitivity and net true positive was improved to 75.4%. and 6 per 100 subjects, respectively. Conclusion: The CREP-model's discrimination and clinical usefulness are low in a medium sized general hospital but are improved after adjusting for the predictors. Therefore, we suggest that institutions should only use the CREP-model after assessing the distribution of the predictors and adjusting their cutting points.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.1-8
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• 2012

Numerical analysis has been carried out to investigate the fully developed flow and heat transfer characteristics of a plate heat exchanger. Multi-cell models with an inlet part and outlet part are used to perform the numerical simulation. The plate heat exchanger is characterized by a chevron angle of $20^{\circ}$ and a P/H ratio of 2.0~4.0. The working fluid is water and the Reynolds numbers range from 300 to 1,500. The correlation is given in the form of $f=CRe^m$ for the friction factor and $j=CRe^m$ for the Colburn factor. It is found that the fully developed flow starts from the third cell and the Nusselt number increases with decreasing P/H ratios.

• The Korean Journal of Physiology and Pharmacology
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• v.25 no.6
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• pp.585-592
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• 2021

Cisplatin has been reported to cause side effects such as muscle wasting in humans and rodents. The physiological mechanisms involved in preventing muscle wasting, such as the regulation of AKT, PGC1-α, and autophagy-related factor FOXO3a by MuRF 1 and Atrogin-1, remain unclear following different types of exercise and in various skeletal muscle types. Eight-week-old male Wistar rats (n = 34) were assigned to one of four groups: control (CON, n = 6), cisplatin injection (1 mg/kg) without exercise (CC, n = 8), cisplatin (1 mg/kg) + resistance exercise (CRE, n = 9) group, and cisplatin (1 mg/kg) + aerobic exercise (CAE, n = 11). The CRE group performed progressive ladder exercise (starting with 10% of body weight on a 1-m ladder with 2-cm-interval grids, at 85°) for 8 weeks. The CAE group exercised by treadmill running (20 m/min for 60 min daily, 4 times/week) for 8 weeks. Compared with the CC group, the levels of the autophagy-related factors BNIP3, Beclin 1, LC3-II/I ratio, p62, and FOXO3a in the gastrocnemius and soleus muscles were significantly decreased in the CRE and CAE groups. The CRE and CAE groups further showed significantly decreased MuRF 1 and Atrogin-1 levels and increased phosphorylation of AKT, FOXO3a, and PGC1-α. These results suggest that both ladder and aerobic exercise directly affected muscle wasting by modulating the AKT/PGC1-α/FOXO3a signaling pathways regardless of the skeletal muscle type.

• Clinical and Experimental Reproductive Medicine
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• v.50 no.3
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• pp.170-176
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• 2023

Objective: Autophagy is highly active in ovariectomized mice experiencing hormone deprivation, especially in the uterine mesenchyme. Autophagy is responsible for the turnover of vasoactive factors in the uterus, which was demonstrated in anti-Müllerian hormone receptor type 2 receptor (Amhr2)-Cre-driven autophagy-related gene 7 (Atg7) knockout (Amhr-Cre/Atg7^f/f mice). In that study, we uncovered a striking difference in the amount of sequestosome 1 (SQSTM1) accumulation between virgin mice and breeder mice with the same genotype. Herein, we aimed to determine whether repeated breeding changed the composition of mesenchymal cell populations in the uterine stroma. Methods: All female mice used in this study were of the same genotype. Atg7 was deleted by Amhr2 promoter-driven Cre recombinase in the uterine stroma and myometrium, except for a triangular stromal region on the mesometrial side. Amhr-Cre/Atg7^f/f female mice were divided into two groups: virgin mice with no mating history and aged between 11 and 12 months, and breeder mice with at least 6-month breeding cycles with multiple pregnancies and aged around 12 months. The uteri were used for Western blotting and immunofluorescence staining. Results: SQSTM1 accumulation, representing Atg7 deletion and halted autophagy, was much higher in virgin mice than in breeders. Breeders showed reduced accumulation of several vasoconstrictive factors, which are potential autophagy targets, in the uterus, suggesting that the uterine stroma was repopulated with autophagy-intact cells during repeated pregnancies. Conclusion: Multiple pregnancies seem to have improved the uterine environment by replacing autophagy-deficient cells with autophagy-intact cells, providing evidence of cell mixing.

• Journal of Embryo Transfer
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• v.29 no.2
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• pp.195-200
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• 2014

Endothelin 2 (EDN2) induces follicular rupture by constricting periovulatory follicles. In this study, it was investigated the mechanisms of EDN2 action on follicular rupture with respect of receptor using the conditionally granulosa cell specific EDN2 receptor type A (ETa) KO mice (gcETaKO; $ETa^{flox/-}{\cdot}Amhr2^{Cre}$). It was generated the gcETaKO mice by breeding with $ETa^{flox/-}$ mice after mono-alleic ETa knockout by $ZP3^{Cre}$ and $Amhr2^{Cre}$ mice. Fertility, ovulation and maturation rates of ovulated oocytes after super ovulation were investigated in the gcETaKO mice compared with wild-type mice ($ETa^{flox/flox}$ and $ETa^{flox/-}$) as a control group. In the gcETaKO mice, normal fertility after breeding with male mice was shown compared with wild-type mice. And, there was no significant differences in ovulation rates after super ovulation, however its maturation rates was lower than that of wild type mice. These findings show that EDN2 in follicular rupture for ovulation is related with an other ETa not in granulosa cells. Further studies are needed to investigate how EDN2 is acted in ovarian follicular rupture for ovulation.

• Journal of Microbiology and Biotechnology
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• v.8 no.1
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• pp.14-20
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• 1998

Syntheses of the B. stearothermophilus xylanolytic enzymes such as xylanases, ${\beta}$-xylosidases, ${\alpha}$-arabinofurano-sidases, and esterases, were observed to be regulated by the carbon source present in the culture media. Xylan induced synthesis of ${\beta}$-xylosidase at the highest level while xylose gave about 30% of the ${\beta}$-xylosidase activity induced by xylan. The lowest syntheses of the xylanolytic enzymes above mentioned were detected in the basal medium containing glucose as a sole carbon source. When a mixture of xylan and glucose was used as a carbon source, we could observe glucose repression of xylanase (about 70-fold) and ${\beta}$-xylosidase (about 40-fold) syntheses. Whereas, the level of the glucose repression of the expression of the xylA gene encoding the major ${\beta}$-xylosidase of B. stearothermophilus was assessed to be about l0-fold when the relative amounts of the xylA transcript were determined. From the sequence of the xylA gene, we could find two CRE-like sequences (CRE-l: nucleotides ＋124 to ＋136 and CRE-2:＋247 to ＋259) within the reading frame of the xylA gene, either or both of which were suspected to be involved in catabolite repression of the xylA gene.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.389-398
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• 2020

The prevalence of carbapenem-resistant Enterobacteriaceae (CRE) is increasing globally, resulting in high mortality rates. Although CRE is a relatively recent problem in Korea (the first case was not diagnosed until 2010), it is responsible for serious morbidities at an alarming rate. In this study, we carried out a molecular genetic analysis to determine the incidence of CRE and carbapenemase-producing Enterobacteriaceae (CPE) at a general hospital in Korea between August 2017 and August 2019. Forty strains of CPE were isolated from various clinical specimens and analyzed via antimicrobial susceptibility testing, polymerase chain reaction to detect β-lactamase genes, deoxyribonucleic acid sequencing, multilocus sequence typing, curing testing, and conjugal transfer of plasmids. The results demonstrated that all 40 isolates were multidrug-resistant. The fluoroquinolone susceptibility test showed that 75% of the Enterobacteriaceae isolates were resistant to ciprofloxacin, whereas 72.5% were resistant to trimethoprim-sulfamethoxazole. Further, conjugation accounted for 57.5% of all resistant plasmid transfer events, which is 4.3-fold higher than that observed in 2010 by Frost et al. Finally, the high detection rate of transposon Tn4401 was associated with the rapid diffusion and evolution of CPE. Our results highlight the rapid emergence of extensively drugresistant strains in Korea and emphasize the need for employing urgent control measures and protocols at the national level.