• Journal of Life Science
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• v.18 no.11
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• pp.1485-1492
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• 2008

Prostaglandin $A_2$ ($PGA_2$), one of cyclopentenone PGs, induced both apoptosis and heme oxygenase (HO)-1 expression in U2OS cells. $PGA_2$-induced apoptosis was not perturbed by either over-expression or knock-down of HO-1, whereas $H_2O_2$-induced cell death was inversely modulated by the expression level of HO-1. In addition, N-acetyl-L-cysteine (NAC), a thiol antioxidant, blocked both apoptosis and HO-1 expression induced by $PGA_2$. But, non-thiol antioxidants like butylated hydorxyanisole (BHA) and ascorbic acid did not block either apoptosis or HO-1-induction. Taken together, these results suggest that $PGA_2$ induces both apoptosis and HO-1 expression, which are critically related to the thiol- reactivity of $PGA_2$, but not oxidative stress, and HO-1 expression may be independent or functionally located downstream of apoptosis by $PGA_2$ without contribution to apoptosis progression.

• Interdisciplinary Bio Central
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• v.1 no.2
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• pp.7.1-7.7
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• 2009

"To be, or not to be?" This question is not only Hamlet's agony but also the dilemma of mitochondria in a cancer cell. Cancer cells have a high glycolysis rate even in the presence of oxygen. This feature of cancer cells is known as the Warburg effect, named for the first scientist to observe it, Otto Warburg, who assumed that because of mitochondrial malfunction, cancer cells had to depend on anaerobic glycolysis to generate ATP. It was demonstrated, however, that cancer cells with intact mitochondria also showed evidence of the Warburg effect. Thus, an alternative explanation was proposed: the Warburg effect helps cancer cells harness additional ATP to meet the high energy demand required for their extraordinary growth while providing a basic building block of metabolites for their proliferation. A third view suggests that the Warburg effect is a defense mechanism, protecting cancer cells from the higher than usual oxidative environment in which they survive. Interestingly, the latter view does not conflict with the high-energy production view, as increased glucose metabolism enables cancer cells to produce larger amounts of both antioxidants to fight oxidative stress and ATP and metabolites for growth. The combination of these two different hypotheses may explain the Warburg effect, but critical questions at the mechanistic level remain to be explored. Cancer shows complex and multi-faceted behaviors. Previously, there has been no overall plan or systematic approach to integrate and interpret the complex signaling in cancer cells. A new paradigm of collaboration and a well-designed systemic approach will supply answers to fill the gaps in current cancer knowledge and will accelerate the discovery of the connections behind the Warburg mystery. An integrated understanding of cancer complexity and tumorigenesis is necessary to expand the frontiers of cancer cell biology.

• Journal of Life Science
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• v.15 no.4 s.71
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• pp.626-632
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• 2005

The polyamines are essential components of all eukaryotic cells and absolutely necessary for cell growth. In the present study, the cytoprotective role of polyamine was characterized. When $Ac_2F$ rat liver cells were treated with 1M 2,2'-azobis (2-amidinopropane) dehydrochloride (AAPH), a water soluble free radical initiator, viability of the cells was noticeably decreased due to the increase of reactive oxygen species (ROS). The cytotoxic effect of AAPH as well as ROS generation were significantly inhibited by the treatment of polyamines. Among polyamines, especially spermine at $20{\mu}M$ concentration exerted over $45\%$ inhibition of AAPH-induced ROS generation. Western blotting was performed to determine whether superoxide dismutase(SOD) or catalase (CAT) expression was involved in oxidative stress. The AAPH treatment blocked both SOD and CAT protein expressions. Spermine could recover those protein expressions to the untreated control levels. According to the result of cycline E measurement, AAPH might block the entry of the cells into S phase of the cell cycle. The reduced expression of cyclin E protein could be fully recovered by the addition of spermine. The antioxidative effects of spermine was also further proved by the apopotitic morphological analysis using ethidium bromide and acridine orange.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1267-1273
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• 2022

Although the Korea shipbuilding industry has recently been receiving most of the orders for ships in the world, production processes are being disrupted due to a shortage of manpower at the production site. This is because the workers quit the shipyard as both work and wages were reduced due to the long slump in the shipbuilding industry. The main reason for the increase in orders was the large-scale orders for Qatar LNG carriers, and the situation in which the technical specifications required for ships are becoming more complex is also working to an advantage. Because the contract delivery time is of utmost importance for ships, the dock launch plan is the most important management item among the shipyard's major processes. The structure to be built in the dock may be a hull that has left the design work or a finished vessel, and in some cases, it is often at the level of some blocks of the hull. When launching, the hull is affected by the hogging or sagging moment due to the fluid force, and securing the safety of the structural strength of the block connection is of utmost importance. In a normal process, the connecting member launches after welding has been completed, but in actual shipbuilders, quick decision-making is needed on the conditions for securing structural safety to comply with the docking schedule. In this study, a detailed analysis method and applicability using a bending stress evaluation method and finite element analysis modelling were analyzed to rationally judge the above-mentioned problems from an engineering point of view. The main contents mentioned in the thesis can be used as good examples when conducting similar structural strength evaluations in the future.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.541-548
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• 2012

The hollow slab has advantages that its self-weight does not greatly increase notwithstanding the increase of its thickness and its flexural performance does not significantly degrade in comparison with general reinforced concrete slab. However, the utilization of the hollow slab is currently being underestimated in spite of structural system that enables economic design of building and construction of eco-friendly structure. the significant reasons for this situation is that the method of structural analysis and design for hollow slab is not generalized. In this study, to consider practical compressive zone of hollow slab, the equation for its flexural strength is proposed by the volume of compressive stress block according to neutral axis location in hollow section assumed. Existing estimation method of flexural strength of hollow slab considering only compressive zone above hollow part is evaluated as the most conservative method and the method estimating flexural strength by two alternative cross-section of hollow slab is evaluated as more practical method.

• Horticultural Science & Technology
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• v.33 no.3
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• pp.309-316
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• 2015

In this experiment, five commercial cultivars and one wild species of loquat were used to investigate frost tolerance and enzymatic activities in leaves and young fruits under cold stress at $-3^{\circ}C$. The frost injury, malondialdehyde (MDA) content, and oxygen-scavenging enzyme activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were studied. This results showed that the wild species 'Wild Oak-leaf' loquat was the most frost tolerant among accessions tested, followed by the cultivar 'Golden Block'. Other cultivars, 'Wu Gong Bai', 'Taicheng 4', 'Xiangzhong 11' and 'Zaozhong 6', were relatively weak in frost tolerance. The enzymatic activities of SOD, POD and CAT increased initially and then decreased as the exposure time increased. However, the enzymatic peak occurred later in the frost-tolerant accession than in the frost-sensitive accession. The correlation coefficients of MDA contents between leaves and immature fruits were from 0.93 to 0.99 in the five commercial loquat cultivars. For the 'Wild Oak-leaf' loquat, the correlation coefficients of MDA and POD were 0.98 and 0.95, respectively, but the coefficients for SOD, CAT and APX were relatively low. In general, there were good correlations between loquat leaves and immature fruits in MDA content and enzyme activities. These results indicate that analysis of these physiological and biochemical activities in loquat leaves could potentially be used to predict the cold tolerance in loquat at immature fruit stage and to accelerate breeding programs for cold tolerance in loquat.

• Horticultural Science & Technology
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• v.33 no.3
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• pp.340-348
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• 2015

Mowing turfgrasses, especially fast growing species like perennial ryegrass, is one of the most time and money consuming tasks of their management. Trinexapac-ethyl (TE) is a popular plant growth regulator used to reduce mowing requirements, improve stress tolerance, and enhance turf quality. This study was conducted to investigate the effect of TE rate and frequency of applications on growth response and traffic tolerance of perennial ryegrass. The experiment was a split-plot laid out in a randomized complete block (RCB) design with three replications. TE was applied to main plots at 0.00, 0.25, and $0.50kg\;a.i.\;ha^{-1}$. Application pattern included an initial application, followed by two sequential applications at 6-wk intervals. Traffic treatment was applied to subplots with a cleated roller. Results demonstrated that TE consistently reduced vertical shoot growth, clippings dry weight, with maximum growth reduction of 59% and 65%, for 0.25 and $0.50kg\;a.i.\;ha^{-1}$, respectively, occurring at 2 weeks after initial TE treatment (WAT). Traffic also dramatically reduced vertical shoot growth and clippings dry weight. Overall, quality of perennial ryegrass was enhanced by sequential TE applications, however, turf quality and surface coverage reduced greatly under traffic, regardless of TE treatment. Total chlorophyll, chlorophyll a and chlorophyll b and total carbohydrates (TC) contents were also positively influenced following sequential TE application. Our results indicated that TE reduces mowing frequency and enhances turf quality rather than influencing traffic resistance.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.539-550
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• 2006

New Songdo city is currently developing on the reclaimed land on a marine deposit and among the development the four sixty-four(64) stories high rise buildings are under construction at block 125. The ground condition of the site is comprised of a deep seated weathered rock staratum under a soft marine deposit layer. As a foundation system, a bored pile was planned to transmit the applied load to the stable layer. In this study, the behavior of the weathered rock especially locating at a upper part having a weak strength(HWR, MWR) has been evaluated through series of hi-directional pile load test(BD PLT) carried out on the 3 drilled shafts socketed in a weathered rock layer in a design stage. It has been planned to increase the effect of the tests that the length of test piles was prepared short enough to perform the test under a high stress. The summary of the design reflecting the test results has been made up. In addition, the 4 hi-directional pile tests excuted on the working piles during the construction stage for the purpose of confirmation and the evaluation of the adequacy of the pile behaviors have been included in this study.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.4
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• pp.333-342
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• 2002

World widely, the occurrences of earthquakes have been increased recently. Speculating from cases of earthquakes in the world, it is reported that damages have been made underground structures like cut-and-cover tunnels, especially on the upper of tunnel with a shallow depth and the backfilled area adjacently by earthquakes. Earthquakes have a tendency to increase recently in Korea but it is deficient in seismic design criteria. In this study, Shaking table test on both soil and EPS blocks was performed to analyze the efficiency of the seismic performance of the cut-and-cover tunnels according to characteristic of backfill materials and embanking material. It turned out to be effective in improving the seismic performance according to analysis of strain and bending stress of tunnel by earthquakes.

• Membrane and Water Treatment
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• v.9 no.1
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• pp.43-51
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• 2018

Hollow fiber (HF) membranes are gaining wide interest over flat membranes due to their compaction and high area to surface volume ratio. This work addresses the fabrication of HF from polysulfone (PS) and polyethersulfone (PES) using N-methylpyrrolidone (NMP) as solvent in addition to other additives to achieve desired characteristics. The semi-pilot spinning system includes jacketed vessel, four spinneret block, coagulation and washing baths in addition to dryer and winder. Different parameters affecting dry-wet spinning phase inversion process were investigated. Dope compositions of PES, NMP and polyvinyl pyrrolidone (PVP) of varying molecular weights as additive were addressed. Some critical parameters of importance were also investigated. Those include dope flow rate, air gap, coagulation & washing baths and drying temperatures. The measured dope viscosity was in the range from 1.7 to 36.5 Pa.s. Air gap distance was adjusted from 20 to 45 cm and coagulation bath temperature from 20 to $46^{\circ}C$. The HF membranes were characterized by scanning electron microscope (SEM), atomic force microscope (AFM) and mechanical properties. Results indicated prevalence of finger like structure and average surface roughness from about 29 to 78.3 nm. Profile of stress strain characteristics revealed suitability of the fibers for downstream interventions for fabrication of thin film composite membrane. Different empirical correlations were formulated which enable deeper understanding of the interaction of the above mentioned variables. Data of pure water permeability (PWP) confirmed that the fabricated samples fall within the microfiltration (MF)-ultrafiltration (UF) range of membrane separation.