• Korean Journal of Mathematics
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• v.26 no.1
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• pp.75-85
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• 2018

In this paper, we study nonconstant warping functions on an Einstein warped product manifold $M=B{\times}_{f^2}F$ with a warped product metric $g=g_B+f(t)^2g_F$. And we consider a 2-dimensional base manifold B with a metric $g_B=dt^2+(f^{\prime}(t))^2du^2$. As a result, we prove the following: if M is an Einstein warped product manifold with a 2-dimensional base, then there exist generally nonconstant warping functions f(t).

• The Korean Journal of Malacology
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• v.15 no.1
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• pp.31-39
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• 1999

This study was aimed to describe the population dynamics and secondary production of Tapes philppinarum on Chohwa and Toksan tidal flats in Kwangyang Bay, from June 1994 to July 1995. The size distributions in shell length showed bimodal patterns from June 1994 to April 1995. Thereafter the distribution changed to the passage of time, indicating an increase in shell length. The mean densities decreased gradually with month. Chohwa A sustained highestdensity, followed by Chohwa B, Toksan C, and Toksan D. The recruitment of new year class occurred first on the upper tidal flat, and then moved to the lower tidal flat. The mean biomass in flesh dry weight of each year class increased in spring just before the spawning period, and thereafter decreased progressively. Annual mean biomass wasrecorded as 170.7 g m$\^$-2/ at Chohwa A, 220.7 g m$\^$-2/ at Chohwa B, 21.8 g m$\^$-2/ at Toksan C, and 45.2 g m$\^$-2/ at toksan D. Annual productions of Ruditapes philippinarum were estimated as 259.72 g m$\^$-2/ yr$\_$-1/ at Chohwa A, 359.79 g m$\^$-2/ yr$\_$-1/ at Chohwa B, 45.02 g m$\^$-2/ yr$\_$-1/ at Toksan c, 68.88 g m$\^$-2/ yr$\_$-1/ at Toksan D. Annual productions were much higher on Chohwa tidal flat than those on Toksan tidal flat. While P:B ratio were higher on Toksan tidal flat as 1.70 than those on Chohwa tidal flat as 1.58. In conclusion, the Chohwa tidal flat showed higher biomass and producion of Ruditapes philippinarum, whereas the Toksan tidal flat showed higher P:B ratio. The total amount of potential food might influence on the density, biomass nad produciton, whereas the amount of food and space per individual might influence on the growth rate and P:B ratio.

• Korean Journal of Microbiology
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• v.49 no.2
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• pp.191-194
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• 2013

The fresh fruit bodies of Pleurotus eryngii var. ferulae was irradiated with ultraviolet (UV)-B (280-320 nm) in order to increase vitamin $D_2$ contents, which was assayed using HPLC (Waters 1525, USA). The vitamin $D_2$ contents were $3.5{\mu}g/g$ after 3 min UV-B irradiation ($21.6KJ/m^2$) and $6.02{\mu}g/g$ after 5 min UV-B irradiation ($36KJ/m^2$), respectively, which showed the significant increase considering the vitamin $D_2$ content ($0.01{\mu}g/g$) before UV-B irradiation. This increasing effect was confirmed also for other edible mushrooms; Pleurotus eryngii, from $0.09{\mu}g/g$ to $2.75{\mu}g/g$ (3 min) and $5.21{\mu}g/g$ (5 min); Lentinus edodes, from $0.021{\mu}g/g$ to $3.02{\mu}g/g$ (3 min) and $3.78{\mu}g/g$ (5 min); Pleurotus ostreatus, from $0.19{\mu}g/g$ to $9.63{\mu}g/g$ (3 min) and $11.6{\mu}g/g$ (5 min). Although the original content of vitamin $D_2$ was the highest in P. ostreatus, the extent of increase by UV irradiation was remarkably high in P. eryngii var. ferulae.

• Applied Biological Chemistry
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• v.51 no.3
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• pp.159-163
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• 2008

Xylogone sphaerospora ${\beta}$-mannanase was purified by Sephadex G-100 column chromatography. The specific activity of the purified enzyme was 8.44 units/ml protein, representing an 56.27-folds purification of the original crude extract. The final preparation thus obtained showed a single band on SDS-polyacrylamide gel electrophoresis. The molecular weight was determined to be 42kDa. Konjac glucomannan was hydrolyzed by the purified ${\beta}$-mannanase, and then the hydrolysates was separated by activated carbon column chromatography. The main hydrolysates were composed of D.P. (Degree of Polymerization) 3 and 4 glucomannooligosaccharides. For elucidate the structure of D.P 3 and 4 glucomannooligosaccharides, sequential enzymatic action was performed. D.P 3 and 4 were identified as M-G-M and M-M-G-M (G- and M- represent glucosidic and mannosidic link-ages). To investigate the effects of konjac glucomannooligosaccharides on in vitro growth of Bifido-bacterium longum, B. bifidum, B. infantis, B. adolescentis, B. animalis, B. auglutum and B. breve. Bifidobacterium spp. were cultivated individually on the modified-MRS medium containing carbon source such as D.P. 3 and D.P. 4 glucomannooligosaccharides, respectively. B. longum and B. bifidum grew up 3.9-fold and 2.8-fold more effectively by the treatment of D.P. 4 glucomannooligosaccharides, compared to those of standard MRS medium. Especially, D.P. 4 was more effective than D.P. 3 glucomannooligosaccharide on the growth of Bifidobacterium spp.

• Development and Reproduction
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• v.9 no.1
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• pp.49-52
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• 2005

The effects of cytochalasin B was studied for the cleavage and development of in vitro matured porcine follicular oocytes. The follicular oocytes were collected from slaughtered pig ovaries and matured for 65 hours. The matured oocytes were activated by 7% ethanol(v/v) in DPBS and the activated oocytes were subjected to cytochalasin B concentrations of 2.5, 5.0 and $7.5\;{\mu}g/mL$ for 3, 5 and 7 hours, and then the treated oocytes were cultured in NCSU23 with 0.4% BSA for 7 days. The cleavage rates were not different significantly in each treatment. However, the oocytes treated with $5.0\;{\mu}g/mL$ for 5 hours yielded a significantly higher morula rate(19.7%) than oocytes treated with $2.5\;{\mu}g/mL$ for 3 and 5 hours(9.4%). The sum rate of $2.5\;{\mu}g/mL$ concentration(10.5%) by hour was also significantly lower than those of 5.0(18.0%) and $7.5\;{\mu}g/mL$ concentration(14.6%). The blastocyst rate in oocytes treated with $5.0\;{\mu}g/mL$ for 3(9.4%) and 5 hours(9.0%) was significantly higher than the rate in oocytes treated with $2.5\;{\mu}g/mL$ for 3 hours(0%). The sum rate of $5.0\;{\mu}g/mL$ concentration also significantly higher than those of 2.5 and $7.5\;{\mu}g/mL$ concentration. The results demonstrated that the treatment of oocytes with cytochalasin B of $5.0\;{\mu}g/mL$ for $3{\sim}5$ hours was the optimal concentration and duration for parthenogenetic activation and blastocyst formation of in vitro matured porcine oocytes.

• Food Science and Preservation
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• v.21 no.2
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• pp.193-198
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• 2014

The quality and antioxidative characteristics of drinks prepared with different mixing ratios of black garlic and Oenanthe javanica DC., BD-1 (black garlic only), BD-2 (black garlic:Oenanthe javanica DC.=2:1), BD-3 (black garlic:Oenanthe javanica DC.=1:1), and BD-4 (black garlic:Oenanthe javanica DC.=1:2), were studied. The pH increased with the increasing concentration of Oenanthe javanica DC. extract in all the tested drinks, but the sugar contents decreased. The total polyphenol contents of the drinks were 28.48 ${\mu}g/mL$ (BD-1), 41.91 ${\mu}g/mL$ (BD-2), 42.36 ${\mu}g/mL$ (BD-3), and 46.96 ${\mu}g/mL$ (BD-4). The SOD-like activity was highest for BD-4 (18.60%), followed by BD-3 (15.53%), BD-2 (12.53%), and BD-1 (10.27%). The thiobarbituric acid reactive substances (TBARS) was highest for BD-4 (52.51%), followed by BD-3 (45.70%), BD-2 (39.44%), and BD-1 (28.72%). The ferrous ion chelating activity increased with the increasing concentration of Oenanthe javanica DC extract, and BD-4 showed the best activities among all the tested drinks. The water-soluble vitamin content (vitamins B1, B2, B6, and C) of BD-4 (1197.77 ${\mu}g/mL$) was higher than those of the other drinks (BD-1, 213.02 ${\mu}g/mL$; BD-2, 477.87 ${\mu}g/mL$; BD-3, 914.72 ${\mu}g/mL$), and the vitamin C (806.21 ${\mu}g/mL$) content of the water-soluble vitamins at BD-4 was higher than those of vitamins B1 (68.04 ${\mu}g/mL$), B2 (312.51 ${\mu}g/mL$), and B6 (11.01 ${\mu}g/mL$). BD-4 showed the best score in the sensory evaluations, such as in the evaluation of the color, flavor, taste, and overall acceptability.

• Korean journal of food and cookery science
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• v.27 no.1
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• pp.55-62
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• 2011

The aim of this study was to investigate the effects of UV-B irradiation on the physicochemical characteristics of oyster mushrooms (Pleurotus ostreatus). Vitamin $D_2$ concentration, weight loss rate, color value, total plate counts and consumer acceptability of irradiated oyster mushrooms were measured. UV-B irradiation at doses of $0\;kj/m^2$, $20\;kj/m^2$ and $40\;kj/m^2$, significantly increased the vitamin $D_2$ concentrations from $0\;{\mu}g/g$ dry weight (control) to $85.87\;{\mu}g/g$ dw and $116.28\;{\mu}g/g$ dw, respectively, at 5% level. Rate of weight loss was also significantly increased from 0% (control) to 2.21% and 4.31% at $20\;kj/m^2$ and $40\;kj/m^2$ UV-B irradiation, respectively, at 5% level. Although there was no significant difference between the UV-B irradiated groups, total plate counts were significantly decreased from $1.0{\times}10^5$ (control) to $9.4{\times}10^3$ and $1.9{\times}10^3$at $20\;kj/m^2$ and $40\;kj/m^2$ of UV-B irradiation, respectively, at 5% level. There was no significant difference in L values and consumer acceptability between the groups. Therefore, UV-B irradiated oyster mushrooms could be used as health promoting ingredients for many foods.

• Korean Journal of Clinical Laboratory Science
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• v.52 no.3
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• pp.165-171
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• 2020

This study examined the relationship between chronic kidney disease (CKD) and the homeostasis model assessment of insulin resistance (HOMA-IR) and beta-cell function (HOMA-B) in non-diabetic Korean adults. This study included 4,380 adults aged 20 or older (50.32±16.14) using the 2015 Korea National Health and Nutrition Examination Survey (KNHANES) data, which represents the national data in Korea. The present study had several key findings. First, in terms of HOMA-IR, after adjusting for the related variables (Model 4), the HOMA-IR (M±SE, 95% confidence interval [CI]) in group 1 (G1; estimated glomerular filtration rate [eGFR], ≥90 mL/min/1.73 ㎡), group 2 (G2; eGFR, 60~89 mL/min/1.73 ㎡), group 3a (G3a; eGFR, 30~59 mL/min/1.73 ㎡), and ≥group 3b (≥G3b; eGFR, <30 mL/min/1.73 ㎡) were 1.78±0.03 (1.73~1.83), 1.87±0.03 (1.81~1.93), 2.16±0.13 (1.91~2.42), and 2.59±0.24 (2.12~3.06), respectively. The HOMA-IR was positively associated with the progression of CKD (P<0.001). Second, in terms of the HOMA-B, after adjusting for the related variables (Model 4), the HOMA-B (M±SE, 95% CI) in G1, G2, G3a, and ≥G3b were 87.46±1.21 (85.08~89.84), 89.11±1.38 (86.40~91.81), 104.82±5.91 (93.23~116.42), and 123.97±10.87 (102.66~145.29), respectively. HOMA-B was positively associated with the progression of CKD (P<0.001). Both insulin resistance and the beta-cell function were positively associated with CKD in non-diabetic Korean adults.

• Journal of Food Hygiene and Safety
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• v.29 no.1
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• pp.16-20
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• 2014

The prevalence of Bacillus cereus was determined in salad and Kimbab obtained from commercial retailers. Among the 100 salad samples analyzed, 54 samples were negative for B. cereus, whereas the bacterial count was < 10 colony forming units (CFU)/g in 8 samples, < 100 CFU/g in 25 samples, < 1,000 CFU/g in 11 samples, and > 1,000 CFU/g in 2 samples. The mean (standard deviation) was 1.18 log CFU/g (${\pm}0.71$ log CFU/g). In Kimbab, B. cereus was isolated from 20 samples; the mean bacterial count was 1.01 log CFU/g (${\pm}0.71$ log CFU/g). On the basis of the monitoring data, a statistical sampling plan was determined with the NEW sampleplan program (ICMSF), which was used as an analytical tool. To identify the most suitable sampling plan, the microbial limits (m, M) and the maximum allowable number of sample units yielding unsatisfactory test results (c) were varied, but the number of samples units, n = 5, was fixed. Sampling plans showing an acceptable probability (Pa) over 0.95 were considered suitable. Two plans (A and B) were finally suggested. Parameters for plan A are n = 5, c = 0, m = 1,000, and M = 10,000 and for plan B are n = 5, c = 2, m = 100, and M = 1,000. Interestingly, the latter plan was identical to the microbial sampling plan used in New Zealand. Thus, it was concluded that the suggested plan can be used as a sampling plan that is in line with international standards.

• Communications of the Korean Mathematical Society
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• v.38 no.4
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• pp.1281-1298
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• 2023

Let (M^2m, 𝜑, g) be a B-manifold. In this paper, we introduce a new class of metric on (M^2m, 𝜑, g), obtained by a non-conformal deformation of the metric g, called a generalized Berger-type deformed metric. First we investigate the Levi-Civita connection of this metric. Secondly we characterize the Riemannian curvature, the sectional curvature and the scalar curvature. Finally, we study the proper biharmonicity of the identity map and of a curve on M with respect to a generalized Berger-type deformed metric.