• Journal of the Korean Electrochemical Society
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• v.22 no.1
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• pp.36-42
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• 2019

A macroporous Sn thick film as a high capacity negative electrode for a lithium ion secondary battery was prepared by using a chemical etching method using nitric acid for a Sn film having a thickness of $52{\mu}m$. The porous Sn thick film greatly reduced the over-voltage for the alloying reaction with lithium by the increased reaction area. At the same time. The porous structure of active Sn film plays a part in the buffer and reduces the damage by the volume change during cycles. Since the porous Sn thick film electrode does not require the use of the binder and the conductive carbon black, it has substantially larger energy density. As the concentration of nitric acid in etching solution increased, the degree of the etching increased. The etching of the Sn film effectively proceeded with nitric acid of 3 M concentration or more. The porous Sn film could not be recovered because the most of Sn was eluted within 60 seconds by the rapid etching rate in the 5 M nitric acid. In the case of etching with 4 M nitric acid for 60 seconds, the appropriate porous Sn film was formed with 48.9% of weight loss and 40.3% of thickness change during chemical acid etching process. As the degree of etching of Sn film increased, the electrochemical activity and the reversible capacity for the lithium storage of the Sn film electrode were increased. The highest reversible specific capacity of 650 mAh/g was achieved at the etching condition with 4 M nitric acid. The porous Sn film electrode showed better cycle performance than the conventional electrode using a Sn powder.

• Journal of Plant Biotechnology
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• v.30 no.4
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• pp.405-410
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• 2003

Environmental stress is the major limiting factor in plant productivity. In order to evaluate the stress tolerance of potato plants, leaf discs of two potato cultivars, Atlantic and Superior, were subjected to various stress conditions of high temperature, methyl viologen, H2O2, or $H_2O$$_2$. When potato leaf discs were exposed to high temperature at 37$^{\circ}C$ for 84 hr, Atlantic plants, a cultivar with high sensitivity to heat stress, showed about 20％ higher membrane damage than Superior plants. When exposed to 2$\mu$M methyl violgen (MV), a superoxide generating non-selective herbicide, for 36 hr, Atlantic plants also showed about 38％ higher membrane damage than Superior plants, and were more susceptible up to 10$\mu$M MV concentration tested. On treatment with 0.75M NaCl, Atlantic plants also had about 45％ less chlorophyll contents in leaf discs than Superior plants. There was, however, no difference in chlorophyll content of two cultivars at higher NaCl concentrations. The effect of $H_2O$$_2$ on the two cultivars was mixed. At low $H_2O$$_2$ concentration (25 mM) , Superior plants were more susceptible to $H_2O$$_2$stress after 36 hr. However, at high $H_2O$$_2$ concentration (100 mM), Atlantic plants exhibited higher susceptibility after 36 hr. The results indicate that in vitro leaf discs reflecting the whole plants in this study will be useful for selection and characterization of elite transgenic potato plants with enhanced tolerance to environmental stress.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.41 no.4
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• pp.341-350
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• 2015

Skin carrys out protective role against harmful outer environment assaults including ultraviolet radiation, heavy metals and oxides. Especially, ultraviolet-B (UVB) light causes inflammatory reactions in skin such as sun burn and erythma and stimulates melanin pigmentation. Furthermore, the influx of UVB into skin cells causes DNA damage in keratinocytes and dermal fibroblasts, inhibition of extracellular matrix (ECM) synthesis which leads to a decrease in elasticity of skin and wrinkle formation. It also damages dermal connective tissue and disrupts the skin barrier function. Prolonged exposure of human skin to UVB light is well known to trigger severe skin lesions such as cell death and carcinogenesis. Haloarcula vallismortis is a halophilic microorganism isolated from the Dead Sea, Its growth characteristics have not been studied in detail yet. It generally grows at salinity more than 10%, but the actual growth salinity usually ranges between 20 to 25%. Because H. vallismortis is found mainly in saltern or salt lakes, there could exist defense mechanisms against strong sunlight. One of them is generation of additional ATP using halorhodopsin which absorbs photons and produces energy by potential difference formed by opening the chloride ion channel. It often shows a color of pink or red because of their high content of carotenoid pigments and it is considered to act as a defense mechanism against intense UV irradiation. In this study, the anti-inflammatory effect of the halophilic microorganism, H. vallismortis, extract was investigated. It was found that H. vallismortis extract had protective effect on DNA damage induced by UV irradiation. These results suggest that the extract of halophilic bacterium, H. vallismortis could be used as a bio-sunscreen or natural sunscreen which ameliorate the harmful effects of UV light with its anti-inflammatory and DNA protective properties.

• Korean Journal of Environmental Agriculture
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• v.38 no.1
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• pp.54-60
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• 2019

BACKGROUND: Hydrogen fluoride is one of the 97 accident preparedness substances regulated by the Ministry of Environment (Republic of Korea) and chemical accidents should be managed centrally due to continual occurrence. Especially, hydrogen fluoride has a characteristic of rapid diffusion and very toxic when leaking into the environment. Therefore, it is important to predict the impact range quickly and to evaluate the residual contamination immediately to minimize the human and environmental damages. METHODS AND RESULTS: In order to estimate the accident impact range, the off-site consequence analysis (OCA) was performed to the worst and alternative scenarios. Also, in order to evaluate the residual contamination of hydrogen fluoride in crop, the samples in accident site were collected from 15-divided regions (East direction from accident sites based on the main wind direction), and the concentration was measured by fluoride ($F^-$) ion-selective electrode potentiometer (ISE). As a result of the OCA, the affected distance by the worst scenario was estimated to be >10 km from the accident site and the range by the alternative scenario was estimated to be about 1.9 km. The residual contamination of hydrogen fluoride was highest in the samples near the site of the accident (E-1, 276.82 mg/kg) and tended to decrease as it moved eastward. Meanwhile, the concentrations from SE and NE (4.96~28.98 mg/kg) tended to be lower than the samples near the accident site. As a result, the concentration of hydrogen fluoride was reduced to a low concentration within 2 km from the accident site (<5 mg/kg), and the actual damage range was estimated to be around 2.2 km. Therefore, it is suggested that the results are similar to those of alternative accident scenarios calculated by OCA (about 1.9 km). CONCLUSION: It is difficult to estimate the chemical accident-affecting range/region by the OCA evaluation, because it is not possible to input all physicochemical parameters. However simultaneous measurement of the residual contamination in the environment will be very helpful in determining the diffusion range of actual chemical accident.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.411-418
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• 2013

Recently, in order to reduce a damage of chloride attack and hydration heat in marine concrete structures, blended cement in mixing the marine concrete is widely used. Long term strength development is distinct in concrete with blended cement and it also has excellent resistance to chloride attack and reduction of hydration heat. However, blended cement has a characteristic of relatively low compressive strength in early age of 28 days. On the other hand, a high level of compressive strength is required in the Standard Specification for marine concrete mix design. Such concrete mix design satisfying Standard Specification is effective to chloride attack but disadvantageous for hydration heat reduction due to large quantity of binder. In this study, the material properties of marine concrete considering water-binder ratio and binder type are experimentally investigated. Through the research results, compressive strength in blended cement at the age of 56 days is similar although it has smaller compressive strength at the age of 28 days compared with result of OPC (ordinary portland cement). Even though blended cement has a large water-binder ratio and small unit of binder content, chloride ion diffusion coefficient is still small and hydration heat is also found to be reduced. For meeting the required compressive strength in Standard Specification for marine concrete at 28 days, the increased unit content of binder is needed but the increased hydration heat is also expected.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.19-34
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• 1996

It has been demonstrated that intracoronal bleaching of pulpless teeth may result in cervical root resorption. Several authors postulated that bleaching agents such as hydrogen peroxide penetrated through the dentinal tubules to damage the surrounding tissues that cause cervical root resorption. The purpose of this study was to suggest on in vitro model for direct determination of hydrogen peroxide penetration through CEJ during nonvital bleaching. In addition, this model permit the quantification of the amount of hydrogen peroxide penetrated during the procedure. Freshly extracted intact premolars, removed for orthodontic reasons were used. Root canal treatment was performed in each tooth. And then the outer surface and crown portion of the teeth was sealed with wax leaving the CEJ. The prepared teeth mounted on the wax laminates were placed in plastic assay tubes containing 1.5ml bidistilled water with their entire root, including the CEJ, submerged in the solution. The teeth were dividied into four groups. Thermo group : thermocatalytic bleaching with superoxol Walk group: walking bleaching with sodium perborate & superoxol Combi group : combination of thermocatalytic & walking bleaching Dw group : walking bleaching with sodium perborate & water The bleaching procedure was performed three times. The bleaching intervals were at 3 days. The hydrogen peroxide present in the assay system was added to ferrous ammonium sulfate resulting in ferric ion release. Upon the addition of potassium thiocyanate a ferrithiocyanate complex results, which absorbs light at the wavelength of 467nm. The radicular penetration of hydrogen peroxide in the four groups was assessed directly using spectrophotometer. The amount of hydrogen peroxide in the samples tested is determined by comparing them with a standard curve generated by known amounts of hydrogen peroxide. The results were obtained as follows : 1. In all experimental groups except the Dw group showed lower penetration amount in day 4 than day 1, there was statistical importance in the difference (P<0.05). 2. After 3rd treatment, Thermo group showed slightly increased value and narrow distribution. Walk group showed much more penetration amount and widely dispersed value. Value of Combi group showed wide distribution without regard to treatment time, but value of Dw group evenly distributed. 3. Thermo group, Walk group and Dw group showed a tendency of increasing penetration amount with increasing treatment times(P<0.01), but Combi group revealed no statistically important differences. 4. Combi group showed the highest degree of penetration. Walk group showed lower penetration than Combi group. Thermo group & Dw group showed lower than Walk group. 5. Cervical root permeability to hydrogen peroxide varied from 0 to 35 %.

• The Korean Journal of Physiology and Pharmacology
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• v.17 no.1
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• pp.57-64
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• 2013

Cells can resist and even recover from stress induced by acute hypoxia, whereas chronic hypoxia often leads to irreversible damage and eventually death. Although little is known about the response(s) to acute hypoxia in neuronal cells, alterations in ion channel activity could be preferential. This study aimed to elucidate which channel type is involved in the response to acute hypoxia in rat pheochromocytomal (PC12) cells as a neuronal cell model. Using perfusing solution saturated with 95% $N_2$ and 5% $CO_2$, induction of cell hypoxia was confirmed based on increased intracellular $Ca^{2+}$ with diminished oxygen content in the perfusate. During acute hypoxia, one channel type with a conductance of about 30 pS (2.5 pA at -80 mV) was activated within the first 2~3 min following onset of hypoxia and was long-lived for more than 300 ms with high open probability ($P_o$, up to 0.8). This channel was permeable to $Na^+$ ions, but not to $K^+$, $Ca^+$, and $Cl^-$ ions, and was sensitively blocked by amiloride (200 nM). These characteristics and behaviors were quite similar to those of epithelial sodium channel (ENaC). RT-PCR and Western blot analyses confirmed that ENaC channel was endogenously expressed in PC12 cells. Taken together, a 30-pS ENaC-like channel was activated in response to acute hypoxia in PC12 cells. This is the first evidence of an acute hypoxia-activated $Na^+$ channel that can contribute to depolarization of the cell.

• Food Science and Preservation
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• v.12 no.5
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• pp.482-488
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• 2005

Oxidant stress is well-known for a pivotal parameter related to neuro-inflammatory diseases including Alzheimer's disease, Parkinson's disease, and ALS (Lou Gehrig's disease). In order to effectively screen for anti-inflammatory agents, we first established the infrastructure of high throughput screening for anti-oxidant agents from medicinal insect library extracted with water, methanol, ethanol, and dimethyl sulfoxide. By the screening system, we found that Tenodera angustipennis Saussure, Pyrocoela rupa Olivier and Papilio maackii Mntris had strong anti-oxidant activity. Moreover, Tenodera angustipennis Saussure and Tenodera aridifolia (Stoll) exhibited protection effects of cellular damage by treatment of an oxidant hydrogen peroxide. Together, the results suggest that some selected hits could be a potential agent against neuro-inflammation, although the in vivo studies should be clearly tested.

• Journal of Ecology and Environment
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• v.29 no.3
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• pp.305-321
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• 2006

Atmospheric Acid Deposition: Nitrogen Saturation of Forests: Volume weighted annual average wet deposition of nitroge at 33 sites in Korea during 1999-2004 ranged 7.28 to $21.05kgN{\cdot}ha^{-1}{\cdot}yr^{-1}$ with average $12.78kgN{\cdot}ha^{-1}{\cdot}yr^{-1}$, which values are similar level with nitrogen deposition of Europe and North America. The temperate forests that suffered long-term high atmospheric nitrogen deposition are gradually saturated with nitrogen. Such nitrogen saturated forest watersheds usually leach nitrate ion ($NO_3^-$) in stream water and soil solution. It may be likely that Korean forest ecosystems are saturated by much nitrogen deposition. In leaves with nitrogen saturation ratios of N/P, N/K and N/Mg are so enhanced that mineral nutrient system is disturbed, suffered easily frost damage and blight disease, reduced fine-root vitality and mycorrhizal activity. Consequently nitrogen saturated forests decrease primary productivity and finally become forest decline. Futhermore understory species are replaced the nitrophobous species by the nitrophilous one. In soil with nitrogen saturation uptake of methane ($CH_4$) is reduced and emission of nitrogen monoxide (NO) and nitrous oxide ($N_{2}O$) are increased, which gases are greenhouse gas accelerating global warming.

• Journal of Environmental Science International
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• v.5 no.6
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• pp.813-826
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• 1996

The toxic effects of aluminium (Al) on growth, chlorophyll content, $\delta-aminolevulinic$ acid dehydratase (ALAD) activity and anatomy of root and shoot were investigated in 7-day-old azuki bean (Vigna angularis) seedlings. Significant depressions in root elongation was observed in the low concentrations of Al (50, 100 $\muM)$ and increasing Al concentrations caused a sharp decline of root and shoot growth. The degree of inhibition was dependent upon Al supply. Exposure to 50 $\muM$ Al or more inhibited root elongation within 1 day. In the 50 $\muM$ Al treatments, a recovery of root growth was seen after 7 days exposure. In contrast, lateral root initials was little affected by Al exposure. Al toxicity symptoms and growth responses were more well developed in the roots than in the shoots. Analysis of Al localization in root cells by hematoxylin stAlning showed that Al entered root apices and accumulated in the epidermal and cortical cells immeadiately below the epidermis. There was a good positive correlation between the level of chlorophyll and ALAD activity. Increasing Al concentrations caused a decrease in total chlorophyll contents, accompanied by proportional changes in ALAD activity, suggesting a cootr-dinated reduction of a photosynthetic machinery. Al exerted specific influence on the morphology of root ann shoot. At higher concentrations of Al the roots induced drastic anatomical changes. The epidermal cells were disorganized or destructed while the cortical cells exhibited distortion of cell shape and/or disintegration. The diameter of root and transectional area of cortical cells decreased considerably with Al treatment. In the shoot Al also enhanced reduction of diameter of shoot and cell size. Gross anatomy of leaves treated with Al did not differ significantly from the controls, except for fewer and smaller chloroplast. Our results indicate that toxic effect of Al appear to be manifested primarily in roots and secondarily on shoots, and changes in root morphology are related to changes in the root growth patterns. Results are further discussed in re181ion to the findings in other plant species, and it is concluded that Al causes morphological, structural and, presumably, functional damage to the roots of the species investigated.