• Proceedings of the PSK Conference
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• 2003.10b
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• pp.182.1-182.1
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• 2003

Flavonoids with oxygen atoms are known to have potent biological effect.They have been studied long as major antioxidants which protect cell membranes. Recent medical surveys show that increased intake of selenium decreases the risk of breast, colon, lung and prostrate cancer by preventing free radical generation. The flavonoids, isoflavonoids, and coumarins which form the bulk of these compounds are very polar and have limited use as drugs which have to pass through BBB(Brain Blood Barrier)The non-polar property is increased by exchange oxygen to selenium as a part of heterocyclic compound. (omitted)

• Journal of Korean Society of Environmental Engineers
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• v.35 no.3
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• pp.165-170
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• 2013

In this study, physico-chemical properties and environmental fate were investigated and ecotoxicity tests using fish, daphnia and algae were conducted for an initial ecological risk assessment of 1,2-Benzisothiazol-3-one. Due to low volatility of the test substance under environmental conditions, it is likely to distributed in soil and water environment. The compound has low adsorption in the soil, with low bioconcentration potential. Acute toxicity results showed that 96 h-$LC_{50}$ for Oryzias laties was 4.7 mg/L (measured) and 48h-$EC_{50}$ for Daphnia magna was 3.3 mg/L (measured). In a growth inhibition test with Pseudokirchneriella subcapitata, 72 h-$EC_{50}$ was 0.456 mg/L (growth rate, nominal) and 0.262 mg/L (yield, nominal). Using the acute toxicity value of algae, predicted no-effect concentration (PNEC) in the aquatic environment was determined to be 2.62 ${\mu}g/L$ using an factor of 100. According to globally harmonized system (GHS), the compound was categorized as aquatic acute 1 for algae, while it was categorized as aquatic acute 2 for fish and daphnia. This screening assessment suggests that the test substance may pose ecological risks in the aquatic environment.

• The Journal of the Korean dental association
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• v.49 no.3
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• pp.153-158
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• 2011

Oral precancerous lesion is a morphologically altered tissue in which oral cancer is more likely to occur than is apparently normal counterpart. As dentists always do oral examination and dental treatment, with fundamental knowledge and attention of this lesion, it is relatively easy to find one. If followed by proper treatment and management, it is possible to minimize its oral cancer progression, or at least delay it. Even if it were to progress to oral cancer, very early detection is possible. However, no specific biomarkers are present at the moment that could reveal oral precnacerous lesion that is high risk of oral cancer progression. Since early detection of oral cancer followed by treatment could show good prognosis with just a simple ablative surgery. Dentists should also instruct people to avoid risk factor related oral cancer progression and take natural compound having anticancer effect. Hereby, As a primary care givers, dentists play an important role in prevention of oral cancer.

• The Korean Journal of Applied Statistics
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• v.24 no.4
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• pp.575-586
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• 2011

In this paper, we study an asymptotic behavior of the finite-time ruin probability of the compound Poisson model in the case that the initial surplus is large. To compare an exact ruin probability with an approximate one, we place the focus on the exact calculation for the ruin probability when the claim size distribution is regularly varying tailed (i.e. exponential claims and inverse Gaussian claims). We estimate an adjustment coefficient in these examples and show the relationship between the adjustment coefficient and the safety premium. The illustration study shows that as the safety premium increases so does the adjustment coefficient. Larger safety premium means lower "long-term risk", which only stands to reason since higher safety premium means a faster rate of safety premium income to offset claims.

• The Korean Journal of Applied Statistics
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• v.25 no.1
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• pp.81-87
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• 2012

A continuous time risk model is considered, where the premium rate is constant and the claims form a compound Poisson process. We assume that an injection is made, which is an immediate increase of the surplus up to level u > 0 (initial level), when the level of the surplus goes below ${\tau}$(0 < ${\tau}$ < u). We derive the formula of the ruin probability of the surplus by establishing an integro-differential equation and show that an explicit formula for the ruin probability can be obtained when the amounts of claims independently follow an exponential distribution.

• The Korean Journal of Applied Statistics
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• v.22 no.5
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• pp.937-942
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• 2009

In this paper, a continuous-time risk process in an insurance business is considered, where the premium rate is constant and the claim process forms a compound Poisson process. We say that a ruin occurs if the surplus of the risk process becomes negative. It is practically impossible to calculate analytically the ruin probability because the theoretical formula of the ruin probability contains the recursive convolutions and infinite sum. Hence, many authors have suggested approximation formulas of the ruin probability. We introduce a new approximation formula of the ruin probability which extends the well-known De Vylder's and exponential approximation formulas. We compare our approximation formula with the existing ones and show numerically that our approximation formula gives closer values to the true ruin probability in most cases.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.1
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• pp.42-54
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• 2018

This study is to establish the traffic volume-based warrants of left-turn lanes in unsignalized intersections based on a risk probability methodology. This study applied a risk probability of a potential rear-end collision between a left-turn vehicle and the immediately following through vehicle. With the shifted negative exponential model and the compound probability theorem, the risk probability can be expressed as the function of directional volumes, opposing volumes and the percentage of left-turns for a two-lane and four-land highway, respectively. The warrants of installing left-turn lanes on unsignalized intersections were developed with the risk probability. The warrants define the total approaching and opposing volumes to encourage a left-turn lane as a function of operating speed, percentage of left-turn, and number of lanes.

• Proceedings of the Korean Environmental Health Society Conference
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• 2004.06a
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• pp.173-177
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• 2004

The acute toxicities of two major anti-pathogenic veterinary medicines, i.e., ciprofloxacin and enrofloxacin, and six benzimidazole anthelmintics, i.e., albendazole, thiabendazole, flubendazole, febantel, fenbendazole, and oxfendazole, were evaluated with a marine bacterium, Vibrio fischeri, and invertebrate Daphnia magna. These veterinary medical products have been widely used for farm animals, but their impact on aquatic fauna has seldom been investigated. In general, daphnids responded as much as 3 orders of magnitude more sensitively to the tested pharmaceuticals than the microbes. For Daphnia, the most toxic product among the tested anthelmintics was fenbendazole, followed by flubendazole > albendazole ${\approx}$ febantel > thiabendazole > oxfendazole. Daphnids' EC50 values obtained from 48 to 96 hrs of fenbendazole exposure ranged from 2.7 to 6.3 ug/L. The mixture toxicity of the test pharmaceuticals was generally additive in nature and was well predicted by a concentration addition model. Using the predicted no effect concentrations (PNECs) of the benzimidazole derivatives estimated from this study, and predicted environmental concentrations (PECs) of these pharmaceuticals, the risk quotients of each anthelmintics were calculated. Most of the test anthelmintic compounds resulted in risk quotients greater than 1. Especially, risk quotient for fenbendazole was 2,791, which strongly indicates this compound might cause severe ecological consequences, should no future action be taken. This study is the first report on the aquatic toxicities and potential ecological risk of major anthelmintic and antimicrobial veterinary products in Korea. The result of this study provides information necessary for conducting more detailed ecological risk assessment of pharmaceutical products in ambient water and guiding proper management decision.

• Journal of the Korean Data and Information Science Society
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• v.27 no.4
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• pp.959-967
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• 2016

Distributional assumptions on equity returns play a key role in valuation theories for derivative securities. Elberlein and Keller (1995) investigated the distributional form of compound returns and found that some of standard assumptions can not be justified. Instead, Generalized Hyperbolic (GH) distribution fit the empirical returns with high accuracy. Hu and Kercheval (2007) also show that the normal distribution leads to VaR (Value at Risk) estimate that significantly underestimate the realized empirical values, while the GH distributions do not. We consider saddlepoint approximations to estimate the VaR and the ES (Expected Shortfall) which frequently encountered in finance and insurance as measures of risk management. We supposed GH distributions instead of normal ones, as underlying distribution of linear portfolios. Simulation results show the saddlepoint approximations are very accurate than normal ones.

• Korean Journal of Environmental Agriculture
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• v.22 no.3
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• pp.177-184
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• 2003

Although clay can sorb significant amounts of inorganic contaminants from soils and wastewater, the hydration of exchangeable cations in clay minerals makes it hydrophilic at the clay mineral surfaces and interlayers. Thus, natural clays are often ineffective in complexing and stabilizing toxic organic contaminants in soils and groundwater environment. But, substituting these hydrated cations with cationic surfactant such as QAC(Quaternary ammonium Compound) can change the natural clay from hydrophilic to hydropobic. Furthermore functionalized organoclay can act as a powerful dual function sorbent for both toxic metals and organic compounds. It also can be used as landfill clay liners, slurry walls, nano-composite materials, petroleum tank farms, waste treatment, and filter systems. To use this modified clay minerals effectively, it is required to understand the fundamental chemistry of organoclay, synthetic procedures, its engineering application, bioavailability of sorbed ion-clay complex, and potential risk of organoclay. In this review, we investigate the use, application and historical background of the organoclay in remediation technology. The state-of-the-art of organoclay research is also discussed. Finally, we suggest some future implications of organoclay in environmental research.