• Journal of Advanced Marine Engineering and Technology
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• v.23 no.3
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• pp.300-310
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• 1999

A constant-volume combustion chamber is developed to measure the burnt gas temperature over the wide ranges of equivalence ratio from 1.5 to 2.7 and pressure from 0.1 to 2.7 and pressure from 0.1 to 6 MPa by two-color method. The combustion temperature is also calculated by the conventional two-region model. The premixed fuel rich propane-oxygen-inert gas mixtures under high pressures are simultaneously ignited by eight spark plugs located on the circumference of combustion chamber with 45 degree intervals. The eight converging flames compress the end gases to high pressures. The transmissiv-ity in the chamber center during the final stage of combustion at the highest pressure is measured by in situ laser extinction method. Comparisons are made with the combustion temperatures between two-color method and two-region model. It is found that the burnt gas temperature mea-sured by two-color method is higher than that calculated by two-region model because of being the negative temperature gradient on the calculation and the temperature distribution of light path-length on the measurement and the burnt gas temperature for the turbulent combustion is higher than that of the laminar combustion under the same conditions because the heat loss for turbulent combustion is lower due to the shorter combustion period.

• Advances in Traditional Medicine
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• v.9 no.3
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• pp.225-231
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• 2009

The present study deals with the amelioration by Lagerstroemia speciosa Linn. leaf extract against hepatotoxicity induced by carbon tetrachloride ($CCl_4$), which was evaluated in terms of serum marker enzymes like serum glutamate pyruvate transaminase, serum glutamate oxaloacetate transaminase, alkaline phosphatase, serum total bilirubin, total protein levels along with concomitant hepatic and antioxidants like superoxide dismutase, catalase, glutathione, glutathione peroxidase and lipid peroxidation enzymes were monitored. These biochemical parameters altered by the single dose level of $CCl_4$ (0.75 ml/kg body weight, i.p). Pre treatment with L. speciosa prior to the administration of $CCl_4$, at the doses of 50 and 250 mg/kg. body weight/day, p.o. for 7 days, significantly restored all the serum and liver tissue parameters near to the normal levels, respectively. Silymarin was used as a reference standard, prior to the administration of $CCl_4$ to rats. These findings indicate the protective potential of L. speciosa against hepato toxicity which possibly involve mechanism related to its ability of selective inhibitors of (reactive oxygen species like antioxidants brought about significant inhibition of TBARS suggesting possible involvement of $O_2{\cdot}-$, $HO_2{\cdot}$, and ${\cdot}OH$. In conclusion, the amelioration may be attributed to the synergistic effects of its constituents rather than to any single factor as the leaves are rich in tannins, sterols, flavonoids, saponins etc.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.231-236
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• 2003

HCCI(Homogeneous Charge Compression Ignition) combustion is an advanced combustion process explained as a homogeneously premixed charge of a fuel where air is admitted into the cylinder and compression ignited. It has possibility to reduce NOx by spontaneous auto-ignition at multiple points that allows very lean combustion resulting in low combustion temperatures. Particulate matters (PM) could be also reduced by the homogeneous combustion and no fuel-rich zones. Injection timing is extremely advanced to achieve homogeneous charge where a diesel fuel could not be vaporized sufficiently due to low pressure and low temperature condition. Also the over-penetration could be a severe problem. The small injection angle and multi-hole injectors were applied to solve these problems. Dimethyl ether (DME) as an altenative fuel was also applied to relive the bad vaporization problem associated with early injection of diesel fuel. Neat DME has a very high cetane rating and high vapor pressure. Contained oxygen reduces soot during the combustion. Experimental result shows DME can be easily operated in an HCCI engine. PM shows almost zero value and NOx is reduced more than 90% compared to direct-injection diesel engine operating mode but problem of early ignition needs more investigation.

• Journal of Genetic Medicine
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• v.13 no.1
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• pp.1-13
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• 2016

Although some mutations are beneficial and are the driving force behind evolution, it is important to maintain DNA integrity and stability because it contains genetic information. However, in the oxygen-rich environment we live in, the DNA molecule is under constant threat from endogenous or exogenous insults. DNA damage could trigger the DNA damage response (DDR), which involves DNA repair, the regulation of cell cycle checkpoints, and the induction of programmed cell death or senescence. Dysregulation of these physiological responses to DNA damage causes developmental defects, neurological defects, premature aging, infertility, immune system defects, and tumors in humans. Some human syndromes are characterized by unique neurological phenotypes including microcephaly, mental retardation, ataxia, neurodegeneration, and neuropathy, suggesting a direct link between genomic instability resulting from defective DDR and neuropathology. In this review, rare human genetic disorders related to abnormal DDR and damage repair with neural defects will be discussed.

• Korean Journal of Materials Research
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• v.25 no.11
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• pp.612-615
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• 2015

In this work, on-site corrosion behavior of heat resistant tubes of T91, used as components of a superheater in a power plant for up to 25,762 h, has been investigated using scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy (EDS), and electron backscattered diffraction(EBSD), with the objectives of studying the composition, phase distribution, and evolution during service. A multi-layer structure of oxide scale was found on both the steamside and the fireside of the tube surface; the phase distribution was in the order of hematite/magnetite/spinel from the outer to the inner matrix on the steamside, and in the order of slag/magnetite/spinel from the outer to the inner matrix on the fireside. The magnetite layer was found to be rich in pores and cracks. The absence of a hematite layer on the fireside was considered to be due to the low oxygen partial pressure in the corrosion environment. The thicknesses of the hematite and of the slag-deposit layer were found to exhibit no significant change with the increase of the service time.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.43-54
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• 1999

The effects of equivalence ratio and pressure on burnt gas temperature in premixed fuel rich propane-oxygen-inert gas combustion are investigated over the wide ranges of equivalence ration from 1.5 to 2.7 and pressure from 0.1 to 7 MPa by using a specially designed disk -type constant-voume combustion chamber, The premixtures are simultaneously ignited by eight spark plugs located on the circumference of combustion chamber with 45 degree interals. The eight converging flames compress the end gases to high pressures. The burnt gas temperature is meausured by the nmodifie dtow-colr pyrometry method. The transmissivity in the chamber center during the final stage of combustion at the hightest pressure is meausred by in situ laser extinction method. It is found that a temperature difference between the burnt gas temperature measured by mofidied and conventrational two-color method is 10 to 20 K, but the accuracy of the modified two-color methdo is higher if the local transmissivity in observed region is uniform , and the combustion at higher pressures results gas density conditions and the burnt gas temperature increases as the volume fraction of argon is increased because the specific heat of argon is lower compared to that of nitrogen with a constant equivalence ratio.

• CELLMED
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• v.5 no.2
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• pp.14.1-14.6
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• 2015

Antioxidative and free radical scavenging properties of different stem extracts of Euphorbia trigona were evaluated and correlated with its total phenolic content. Aqueous, acetone and methanolic extracts of shade dried stem were obtained and were concentrated in vacuo. The antioxidant and free radical scavenging activities of stem extracts was determined by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging assay, reducing power assay, deoxyribose degradation assay and $Fe^{2+}$ chelating assay. Total phenolic contents (TPC) were evaluated using Folin-Ciocalteu reagent. The results confirmed that the plant is a rich source of polyphenolic compounds which are invariably higher compared to other herbs. All extracts showed TPC in the range of 146.6 - 168.6 mg/g gallic acid equivalents at $300{\mu}g/ml$ of extract. Among the three extracts ME showed highest scavenging activity as evidenced by maximum scavenging of DPPH (83.2%), $OH{\bullet}$ radicals (94.81%), $Fe^{2+}$ chelating activity (88.59%) and a high reducing power 0.623 at $300{\mu}g/ml$. Our results demonstrate that Euphorbia trigona, an unexplored xerophytic plant could be potential source of natural antioxidants and phytotherapeutic agents. The plant possess invariably high amount of polyphenolic compounds with a broad spectrum of antioxidant properties and could be further used for food, feed and pharmaceutical applications.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.26-33
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• 2014

The gas-centerd swirl injectors are widely used on the main combustor of large liquid propellant rocket engines. Since the gas-liquid propellants, such as kerosene and oxygen-rich gas combination, are mixed and burned in the high pressure condition over the critical pressure point, the cold-flow spray test in the atmospheric condition can not represent the actual spray pattern. To observe the near actual spray patterns of gas-centered swirl injector, the high pressure spray chamber and the control system were constructed. The operating sequence was controlled precisely to obtain clear visualization images.

• Korean Journal of Medicinal Crop Science
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• v.23 no.1
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• pp.49-56
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• 2015

Edible berries are rich in anthocyanins and phenolic acids, compounds that possess antioxidant, anti-inflammatory, and other biological activities. Antioxidant and anti-inflammatory activities of five berries including acaiberry (Euterpe oleracea Mart.), Aronia/black chokeberry (Aronia melanocarpa), blueberry (Vaccinium angustifolium), black currant (Ribes nigrum L.), and cranberry (Vaccinium macrocarpon) were assessed. The Aronia G (prepared by GreenField s.c.) exhibited the highest antioxidant activities as shown in total phenolic (138.81 mg CAE/g), flavonoid (3.68 mg QE/g), and anthocyanin (20.31 mg/g) contents compared to the other berries. It also showed the strongest scavenging activities such as DPPH (69.69 mg vitamin C/g) and ABTS radical scavenging activity ($757.79{\mu}mol$ trolox/g). Aronia G exhibited strong ferric reducing antioxidant power ($553.98{\mu}mol$ vitamin C/g), and oxygen radical absorbance capacity ($820.92{\mu}mol$ trolox/g). In addition, black currant and Aronia showed stronger inhibition of nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 cell than the other berries. According to the above results, the Aronia and other edible berries have notably high level of antioxidant activities and they could be used as a potential source of natural antioxidants.

• Journal of Microbiology and Biotechnology
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• v.27 no.2
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• pp.365-371
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• 2017

Hydrogen has potential for preventive and therapeutic applications as an antioxidant. However, micro- and macroparticles of hydrogen in water disappear easily over time. In order to eliminate reactive oxygen species (ROS) related with the aging process, we used functional water containing nanoparticle hydrogen. Nanoparticle hydrogen does not disappear easily and collapse under water after long periods of time. We used murine embryonic fibroblasts that were isolated from 12.5-day embryos of C57BL/6 mice. We investigated the ability of nanoparticle hydrogen in water to suppress hydroxyurea-induced ROS production, cytotoxicity, and the accumulation of ${\beta}-galactosidase$ (an indicator of aging), and promote cell proliferation. The accumulation of ${\beta}-galactosidase$ in the cytoplasm and the appearance of abnormal nuclei were inhibited by daily treatment of cells with hydrogen water. When the aging process was accelerated by hydroxyurea-induced oxidative stress, the effect of hydrogen water was even more remarkable. Thus, this study showed the antioxidant and anti-senescence effects of hydrogen water. Nanoparticle hydrogen water is potentially a potent anti-aging agent.