• Journal of Pharmacopuncture
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• v.24 no.1
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• pp.24-31
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• 2021

Objectives: Accumulation of cellular reactive oxygen species (ROS) leads to oxidative stress. Increased production of ROS, such as superoxide anion, or a deficiency in their clearance by antioxidant defences, mediates cellular pathology. Grewia Spp fruits are a source of bioactive compounds and have notable antioxidant activity. Although the antioxidant capacity of Grewia Spp has been studied, there is very limited evidence that links the antioxidant activities of Grewia bicolor and Grewia flava to the inhibition of free radical formation associated with damage in biological systems. Methods: This study evaluated the protective effects of Grewia bicolor and Grewia flava extracts against free radical-induced oxidative stress and the resulting cytotoxicity effect using HeLa cells. Antioxidant properties determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and total phenolic content (TPC) assays showed significantly higher (p < 0.05) antioxidant activity in Grewia flava (ethanol extract) than Grewia flava (water extract) and Grewia bicolor (ethanol and water extracts). Results: Using 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide or MTT assay, cytotoxicity results showed that extracts of Grewia bicolor and Grewia flava were less toxic to HeLa cells at tested concentrations compared to the untreated control. This confirmed the low toxicity of these edible fruits at the tested concentrations in HeLa cells. Furthermore, hydrogen peroxide (H2O2)-induced cell loss was effectively reduced by pre-incubating HeLa cells with Grewia bicolor and Grewia flava extracts, with Grewia flava (ethanol extract) revealing better protection. Conclusion: The effect was speculated to be associated with the higher antioxidant activity of Grewia flava (ethanol extract). Additional studies will warrant confirmation of the mechanism of action of such effects.

• Journal of Applied Biological Chemistry
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• v.44 no.4
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• pp.159-162
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• 2001

Plant stress incurred by flooding was studied in terms of oxidative stress, using greened rice seedlings subjected to a complete submergence followed by re-exposure to air under illumination ($30W/m^2$). It appeared that shoot tissues of the seedlings suffered oxygen deficiency during the flooding treatment, pertinent to the general concept. Interestingly enough, however, membrane peroxidation in shoots was enhanced by the submergence, as assessed by the content of 2-thiobarbituric acid-reactive substances (TBARS), and the re-aeration resulted in a rapid reduction of TBARS content. Such pattern of response was also seen in the change in the steady state level of $H_2O_2$. In contrast, superoxide dismutase and glutathione reductase that are involved in the detoxifying processes of superoxide in plant cells were significantly activated only during the re-aeration. These results allowed us to suggest the followings as a working hypothesis. Photorespiration-linked production of $H_2O_2$ may largely contribute to the increase in $H_2O_2$ level as well as TBARS production in shoots during the submergence. An abrupt re-supply of $CO_2$ by the re-aeration brings the photosynthetic apparatus back to full operation, suppressing photorespiration and probably causing a momentary, excess formation of superoxide and its dismutation product through side reaction, which gives rise to activating substrate-inducible antioxidative enzymes.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.3
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• pp.151-154
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• 2001

$TiO_2$ thin film has wide application because of its high capacitanca, reflection, and good transmissivity in visible range. $TiO_2$ thin film can be made by thermal deposition method, reactive evaporation method, activated reactive evaporation(ARE) method. In the case of thermal deposition, the oxygen deficiency can occur because the melting point of Ti is very high. While in the case of reactive evaporation, high density $TiO_2$ can not be made, because reactive gas($O_2$) and evaporated material(Ti) are not fully combined, activated reactive evaporation, $TiO_2$ is easily deposited at lower gas pressure compared with reactive evaporation because the ionized reactive gas is made by plasma. Therefore, activated reactive evaporation is very useful to deposit the material having the high melting point. In this work, we formed $TiO_2$ thin film by activated reactive evaporation method. The surface of $TiO_2$ thin film was analyzed by X-ray photoelectron spectroscopy. The surface morphology which was analyzed by atomic force microscopy(AFM) shows that feature of the film surface is uniform. The dielectric capacitance, withstanding voltage were $600{\mu}F/cm^2$, 0.4V respectively. In further work, we can increase the withstanding voltage by improving the deposition parameter of substrates.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.1
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• pp.13-17
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• 2014

The direct-patternable $SnO_2$ thin film was successfully fabricated by photochemical metal-organic deposition. The composition and chemical bonding state of $SnO_2$ thin film were analyzed by using X-ray photoelectron spectroscopy (XPS) from the surface to the interface with Si substrate. XPS depth profiling analysis allowed the determination of the atomic composition in $SnO_2$ film as a function of depth through the evolution of four elements of C 1s, Si 2p, Sn 3d, and O 1s core level peaks. At the top surface, nearly stoichiometric $SnO_2$ composition (O/Sn ratio is 1.92.) was observed due to surface oxidation but deficiency of oxygen was increased to the interface of patterned $SnO_2/Si$ substrate where the O/Sn ratio was about 1.73~1.75 at the films. This O deficient state of the film may act as an n-type semiconductor and allow $SnO_2$ to be applied as a transparent electrode in optoelectronic applications.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.6
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• pp.109-114
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• 2016

This study executes Importance-Performance Analysis (IPA) on existing firefighter helmet attributes and gathers ideas for improvements from fire-fighting officers to develop a convergence firefighter helmet. The results of empirical analysis were as follows: First, the weight, head fitness, ease of wearing and removal, and ease of managing the existing helmet's attributes need urgent improvement. In addition, fire-fighting officers want to add innovative functions such as oxygen deficiency alarms, poison gas sensors, temperature sensors, and network communication systems to the convergence firefighter helmet under development.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.536-540
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• 2011

This study reports the origin of the electrochemical improvement of $LiFePO_4$ when synthesized by wet milling using acetone without conventional carbon coating. The wet milled $LiFePO_4$ delivers 149 $mAhg^{-1}$ at 0.1 C, which is comparable to carbon coated $LiFePO_4$ and approximately 74% higher than that of dry milled $LiFePO_4$, suggesting that the wet milling process can increase the capacity in addition to conventional carbon coating methods. UV spectroscopy, elemental microanalysis, and evolved gas analysis are used to find the root cause of the capacity improvement during the mechanochemical reaction in acetone. The analytical results show that the improvement is attributed to the conductive residual carbon on the surface of the wet milled $LiFePO_4$ particles, which is produced by the reaction of $FeC_2O_4{\cdot}2H_2O$ with acetone during wet milling through oxygen deficiency in the precursor.

• Journal of Magnetics
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• v.14 no.4
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• pp.161-164
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• 2009

Iron-doped $Sn_{1-x}Fe_xO_2$ (x = 0.0, 0.05, 0.1, 0.2, 0.33) thin films on Si(100) substrates and powders were prepared by a chemical solution process. The x-ray diffraction (XRD) patterns of the $Sn_{1-x}Fe_xO_2$ thin films and powders showed a polycrystalline rutile tetragonal structure. Thermo gravimetric (TG) - differential thermal analysis (DTA) showed the final weight loss above $430{^{\circ}C}$ for all powder samples. According to XRD Rietveld refinement of the powders, the lattice parameters and unit cell volume decreased with increasing Fe content. The magnetic properties were characterized using a vibrating sample magnetometer (VSM) and M$\ddot{o}$ssbauer spectroscopy. The thin film samples with x = 0.1 and 0.2 showed paramagnetic properties but thin films with x = 0.33 exhibited ferromagnetic properties at room temperature. Mossbauer studies revealed the $Fe^{3+}$ valence state in the samples. The ferromagnetism in the samples can be interpreted in terms of the direct ferromagnetic coupling of ferric ions via an electron trapped in a bridging oxygen deficiency, which can be explained using the F-center exchange model.

• Sleep Medicine and Psychophysiology
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• v.5 no.2
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• pp.177-184
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• 1998

Objectives : Disturbance of sleep with or without sleep apnea may impair the memory function. Sleep deficiency, sleepiness, sleep apnea and emotional problem in sleep disorders can induce an impairment of memory function. Methods : In this study, the polysomnographies were administered to 58 sleep apnea patients and 38 sleep disorder patients without sleep apnea. Their clinical symptoms were quantitatively evaluated. Short term and long term memory were evaluated before and after polysom no graphy with Digit symbol test and Rey-Osterrieth complex figure test. And correlations among various sleep, repiratory and clinical variables were statistically studied in order to explore which variables may influence on memory function. Results and Conclusions : Results are as follows. Depth of sleep cis positively correlated with memory function. As sleep apnea increases and average saturation of blood oxygen decreases, memory function is more impaired. Emotional depression, high blood pressure, obesity or alcohol impaired memory function. However, daytime sleepiness was not significantly correlated with memory function. The possible mechanisms how above factors influence on the memory function were discussed.

• Journal of the Korean Applied Science and Technology
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• v.24 no.1
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• pp.1-9
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• 2007

It prepared the $TiO_2$ powder which has photo-catalytic activity in the visible-light by the wet process with titanium oxysulfate. The titanium $dioxide(TiO_2)$ by the wet process creates a new absorption band in the visible light region, and is expected to create photocatalytic activity in this region. Anatase $TiO_2$ powder which has photocatalytic activity in the visible light region, is treated using microwave and radio-frequency(RF) plasma. But, the $TiO_2$ powder for the visible light region, which also can be easily produced by wet process. The wet process $TiO_2$ absorbed visible light between 400nm and 600nm, and showed a high activity in this region, as measured by the oxidation removal of aceton from the gas phase. The AH-380 sample appears the yellow color to be strong, the catalytic activity in the visible ray was excellent in comparison with the plasma-treated $TiO_2$. The AH-380 $TiO_2$ powder, which can be easily produced on a large scale, is expected to have higher efficiency in utilizing solar energy than the plasma-treated $TiO_2$ powder.

• Proceedings of the Korea Environmental Mutagen Society Conference
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• 2002.05a
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• pp.48-64
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• 2002

The primary recognized health risk from common deficiencies in glucose-6-phosphate dehydrogenase (G6PD), a cytoprotective enzyme for oxidative stress, is red blood cell hemolysis. Here we show that litters from untreated pregnant mutant mice with a hereditary G6PD deficiency had increased prenatal (fetal resorptions) and postnatal death. When treated with the anticonvulsant drug phenytoin, a human teratogen that is commonly used in pregnant women and causes embryonic oxidative stress, G6PD-deficient dams had higher embryonic DNA oxidation and more fetal death and birth defects. The reported G6PD gene mutation was confirmed and used to genotype fetal resorptions, which were primarily G6PD deficient. This is the first evidence that G6PD is a developmentally critical cytoprotective enzyme for both endogenous and xenobiotic-initiated embryopathic oxidative stress and DNA damage. G6PD deficiencies accordingly may have a broader biological relevance as important determinants of infertility, in utero and postnatal death, and teratogenesis.-Nicol, C. J., Zielenski, J., Tsui, L.-C., Wells, P. G. An embryoprotective role for glucose-6-phosphate dehydrogenase in developmental oxidative stress and chemical teratogenesis.