• 대한예방의학회:학술대회논문집
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• 대한예방의학회 1994년도 교수 연수회(환경)
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• pp.651-657
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• 1994

To assess quantitatively the association between benzene exposure and leukemia, we examined the mortality rate of a cohort with occupational exposure to benzene. Cumulative exposure for each cohort member was estimated from historical air-sampling data and, when no sampling data existed, from interpolation on the basis of existing data. The overall standardized mortality ratio (a measure of relative risk multiplied by 100) for leukemia was 337 (95 percent confidence interval, 154 to 641), and that for multiple myeloma was 409 (95 percent confidence interval, 110 to 1047). With stratification according to levels of cumulative exposure, the standardized mortality ratios for leukemia increased from 109 to 322, 1186, and 6637 with increases in cumulative benzene exposure from less than 40 parts per million-years (ppm-years), to 40 to 199, 200 to 399, and 400 or more. respectively. A cumulative benzene exposure of 400 ppm years is equivalent to a mean annual exposure of 10 ppm over a 40-year working lifetime; 10 ppm is the currently enforceable standard in the United States for occupational exposure to benzene. To examine the shape of the exposure-response relation, we performed a conditional logistic-regression analysis, in which 10 controls were matched to each cohort member with leukemia. From this model, it can be calculated that protection from benzene induced leukemia would increase exponentially with any reduction in the permissible exposure limit.

• Journal of Microbiology and Biotechnology
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• 제24권12호
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• pp.1728-1735
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• 2014

Scrub typhus, caused by infection with Orientia tsutsugamushi, is a mite-borne zoonotic disease endemic to the Asian-Pacific region. In Korea, the incidence of this disease has increased with climate changes, and over 10,000 cases of infection were reported in 2013. Although this infection is treatable with antibiotics such as doxycycline and azithromycin, an effective prophylactic vaccine against O. tsutsugamushi would be more desirable for preventing scrub typhus in endemic areas. In this study, we investigated the 56-kDa type-specific antigen (TSA56), which is a major outer membrane protein of O. tsutsugamushi, as a vaccine candidate. Intranasal immunization of recombinant TSA56 (rec56) induced a higher level of TSA56-specific IgG than that induced by intramuscular immunization of tsa56-expressing DNA (p56). Both types of immunization induced a cell-mediated immune response to TSA56, as demonstrated by the splenic cell proliferation assay. Mice immunized with p56, followed by rec56 plus heat-labile enterotoxin B subunit from E. coli, had a stronger protection from a homologous challenge with the O. tsutsugamushi Boryong strain than with other combinations. Our preliminary results suggest that an effective human vaccine for scrub typhus can include either recombinant TSA56 protein or tsa56-expressing DNA, and provide the basis for further studies to optimize vaccine performance using additional antigens or different adjuvants.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 2003년도 Annual Meeting of KSAP : International Symposium on Pharmaceutical and Biomedical Sciences on Obesity
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• pp.65-65
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• 2003

The aim of this study was to investigate the effect of resveratrol on the oxidative stress-induced inhibition of gap junctional intercellular communication (GJIC) in HaCaT keratinocyte. Anti-oxidative activity of resveratrol was measured by a,a-diphenyl-b-picrylhydrazyl (DPPH) assay and dichlorodihydrofluorescein diacetate oxidation assay. GJIC of HaCaT keratinocyte was assessed using the scrape loading/dye transfer technique. Western blots and reverse transcription-polymerase chain reaction were also analyzed for Connexin 43 protein and mRNA expression, respectively. Resveratrol scavenged directly the stable DPPH radical over a concentration range of 4 mg/$\mell$ (78.2 $\pm$ 2.7% of control) to 500 mg/$\mell$ (29.9 $\pm$ 4.2% of control) and prevent to increase the intracellular fluorescence induced by oxidative stress significantly. Ultraviolet A irradiation (UVA) and 12-O-tetradecanoylphorbol-13-acetate markedly reduced GJIC, which was restored by resveratrol. There were no significant differences in the level of Connexin 43 protein and mRNA expression among any of the experimental groups. Our data suggests that resveratrol has the protective effect on the oxidative stress-induced inhibition of gap junctional intercellular communication in HaCaT keratinocyte and this protection is likely due to the scavenging of reactive oxygen species.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.337-341
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• 2001

A new method to extract gold from pyrite roster cinder, which combines ultra-fine-grinding with resin-in-pulp, has been studied in this paper. Compared with traditional leaching technology, it can short leaching time, avoid complex filter process, lower sodium cyanide consumption and increase gold recovery by 35%. During leaching, aluminium oxide ball was used as stirred medium, hydrogen peroxide as leaching aid and sodium hexametaphosphate as grinding aid. With the high efficiency and chemistry effect of ultra-fine-grinding, the leaching process was developed and the gold leaching rate may reach 88%. With AM-2 Б resin as abosorber and sulfocarbamide (TU) as eluent, gold was recovered from cyanide pulp by resin-in-pulp. AM-2 Б resin has good adsorbability in cyanide solution(pH=10). It was easy to elude gold from the loaded resin with 0.1㏖/L cholhydric acid and 1㏖/L sulfocabamide. The effect of contact time, temperature and acidity etc. on the gold absorption had been examined with static methods. The results showed that the adsorption and desorption of gold could both reach over 98%. The effects of flow rate of solution on dynamic adsorption and elution of gold had been examined with dynamic methods. Breakthrough curve and elution curve had been drawn in this paper. A mild condition was determined through a number of experiments: leaching time 2 hours, liquid solid ratio 4:1, sodium cyanide 3kg/t, hydrogen peroxide 0.05%, sodium hexametaphosphate 0.05%; adsorption time 30 minutes, temperature 10-3$0^{\circ}C$, resin($m\ell$) solid(g) ratio 1:10, eluent resin ratio 10-20:1, velocity of eluent $1.5m\ell$/min. Under the mild condition, the gold recovery may reach 85%.

• 한국수산과학회지
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• 제39권spc1호
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• pp.142-150
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• 2006

We examined the effect of predation by observing the changes in macrobenthic communities in a tidal flat at Seonjae, Korea, following the exclusion of large predators such as birds, fishes and crustaceans using protective screens. We conducted two interference experiments in the field from April to November 2004: (1) Experiment 1 was conducted at a mid-tidal flat in the western part of Seonjae-do, Incheon, Korea, (2) Experiment 2 was set up at a low tidal flat in the eastern part of Seonjae-do. predator exclusion showed different effects in the two experiments. Both the number of species and density were reduced by 20% in Experiment 1. Whereas in Experiment 2, they increased by up to 13% and 69%, respectively. In Experiment 1, a high density of brachyuran crabs observed in the treatment may have caused the difference in community composition between the treatment and the control, and this probably resulted from active predation of macrofauna (e.g., small crabs) under protection from megafaunal predators such as birds and fishes. However, in Experiment 2, as typically observed in other predator exclusion experiments, a lower density of benthic predators and the subsequent reduction of over predation probably resulted in a more diverse and abundant benthic community in the treatment. We confirmed that predation was a contributing factor in the formation of the macrobenthic community. We also demonstrated relationships that exist among different trophic groups (large predators, macrobenthic predators and prey) and what effects and responses occur in each component of the tidal flats.

• 한국식품영양과학회지
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• 제28권4호
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• pp.924-933
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• 1999

This study investigated the effects of vitamin E supplementation on immune responses and antioxidant status in healthy Korean old and young women. Blood samples were obtained from 15 healthy old women (over 60 years old) and from 15 healthy young women(20 years old) before and 4 weeks after vitamin E( tocopherol acetate) supplementation(400IU/day). Daily nutrient intakes were calculated, and plasma vitamin E concentration, numbers and percentages of white blood cell and their subpopulation, percentages of lymphocytes and subpopulation, NK cell percentages, plasma immunoglobulin A, G, M and C3 concentration, proliferation of PMN with mitogen were measured. Also plasma TBARS concentration and radical scavenger activity of erythrocytes were investigated. Plasma vitamin E concentrations were significantly increased after supplementation in both groups. In elderly women, vitamin E supplementation restored the per centages of neutrophils, lymphocytes, and eosinophils which had been out of normal ranges before supple mentation. And after vitamin E supplementation, helper T cell percentages significantly increased in elderly. Plasma immunoglobulin and complement C3 concentrations were not affected by vitamin E supplementation in both groups. PMN proliferations with mitogen were significantly lower in old women than in young women, and there was no effect of vitamin E supplementation. Vitamin E supplementation significantly decreased plasma TBARS concentrations in old and young women. RSA of erythrocytes was increased in both groups, but the statistical significant was only found in young women group. Therefore, these results suggest that the moderate vitamin E supplementation in old women improves immune responses, especially nonspecific immunity and cell mediated immunity, via protection of oxidant stress.

• 한국환경농학회지
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• 제34권1호
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• pp.1-5
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• 2015

BACKGROUND: The stabilities of the two alkaloidal insecticides of S. flavescens including matrine and oxymatrine are important factor to establish expiry date and usage manual for crop protection. However, the environmental stability of the compounds had not been studied with the extract and its commercial biopesticide. METHODS AND RESULTS: The environmental stabilities of the two alkaloids were performed with extract of S. flavescens, and its two commercial biopesticides both in controlled aquatic and soil conditions. The half-lives of the total matrines for the extract and its two commercial biopesticides were estimated over 200 days both under aerobic and anaerobic water condition. Under dry soil condition, the initial decay rates of the matrines were calculated 0.0804-0.1275 ($t_{1/2}$ 5.4-8.6 days), and the half-lives under wet soil condition were calculated 33.0-231 days. Total soil bacteria on the wet soil ranged 6.0-8.0 log CFU/g-soil during the experiments period. CONCLUSION: The aquatic mixture of the extract showed excellent stability both with the extract and its biopesticides, however, the stability of soil mixture were shorter than the aquatic mixture, suggesting that soil metal consider as a catalyst for the degradation of the two alkaloids.

• Nuclear Engineering and Technology
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• 제56권9호
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• pp.3804-3811
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• 2024

The study focuses on creating new boro-silicate glasses doped with SnO₂ for radiation shielding. It examines how substituting Na₂O with SnO₂ affects their structural, optical, and shielding properties. Density increases from 2.406 to 2.488 g/cm³ with rising SnO₂, measured via the Archimedes Method. The examination for the glassy phase was performed using the XRD diffractometer. UV/Vis spectrophotometer analysis reveals reduced refractive index (2.412-1.976) and increased optical absorption-band gap (direct: 3.648-5.662 eV; indirect: 2.994-5.163 eV) with SnO₂ concentrations of 0-9 mol.%). The effectiveness of the radiation shielding was assessed over the 0.059-1.408 MeV gamma-ray energy interval. The analysis demonstrates that when the concentration of SnO₂ increases, the synthesized glasses' linear attenuation coefficient improves. As the SnO₂ content was raised between 0 and 9 mol%, the linear attenuation coefficient rose between 0.489 and 2.892 cm^-1 (at energy of 0.059 MeV) and between 0.126 and 0.128 cm^-1 (at energy of 1.408 MeV), respectively. As the SnO₂ content was raised between 0 and 9 mol%.

• 한국태양에너지학회 논문집
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• 제28권2호
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• pp.64-69
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• 2008

As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, these have raised potential problems of network protection on electrical power system. One of the numerous problems is an Islanding phenomenon. There has been an argument that it may be a non-issue in practice because the probability of islanding is extremely low. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an islanding can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficiently to cause a trip, plus the time required to execute a trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. Third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an islanding. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. Therefore the verification of anti-islanding performance is strongly needed. In this paper, improved RPV method is proposed through considering power quality and anti-islanding capacity of grid-connected single-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"). And the simulation results are verified.

• 농약과학회지
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• 제4권3호
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• pp.40-46
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• 2000

Phoma sp.에 의한 대추나무 점무늬병 방제용 살균제를 선발하기 위하여 모두 26종의 살균제를 대상으로 $250{\mu}g\;a.i./m{\ell}$ 의 농도에서 균사생장을 조사한 결과 benomyl 등 8종의 살균제가 균사생장 억제효과를 보였다. 이들 8종의 살균제에 대하여 균사 최소생장억제농도 (MIC)와 포자발아억제력을 조사하였는데, myclobutanil 등 3종은 포자발아억제력은 우수하였으나 포장에서 사용시의 권장농도보다도 높은 MIC 값을 보여 이들을 제외한 5종 (benomyl, iminoctadine-triacetate (IT), iprodione과 propineb 합제 (IP), thiophanate-methyl과 triflumizole 합제 (TT), carbendazim과 kasugamycin 합제 (CK)에 대하여 온실에서 예방효과와 치료효과를 검정하였다. Benomyl, CK, TT 등의 MIC는 $10-50{\mu}g\;a.i./m{\ell}$ 사이에 있음이 확인되었으며, IP와 IT의 MIC는 $50-250{\mu}g\;a.i./m{\ell}$이었다. 또한 포자발아 억제시험 결과 IT는 $0.4{\mu}ga\;.i./m{\ell}$의 농도에서 99%, 그리고 CK와 TT는 $10{\mu}g\;a.i./m{\ell}$에서 90% 이상의 포자발아를 억제하였으나, benomyl과 IP는 $10{\mu}g\;a.i./m{\ell}$에서 각각 22.8%와 9.2%라는 낮은 억제율을 보였다. 예방효과시험에서 CK와 TT는 모두 권장 농도 (1,000 ppm)에서 70% 내외, 배량 농도 (2,000 ppm)에서 90% 내외의 방제 효과를 보였고, benomyl은 2,000 ppm, IP는 4,000 ppm, IT는 8,000 ppm에서 70% 내외의 병 방제 효과를 보였다. 치료효과시험에서는 각 살균제를 1,000 ppm으로 처리하였을 때 benomyl이 90% 이상의 방제가를, 그리고 CK와 TT가 70-80%의 방제가를 보였다. 반면에 IP는 2,000 ppm에서도 방제가가 6.7%로 매우 낮았으며, IT는 전혀 방제효과가 없었다. 더구나 IT 는 예방 효과 시험과 치료 효과 시험 모두에서 약해를 보였다. 따라서 대추나무 점무의병의 방제약제로는 benomyl이 가장 적합한 것으로 밝혀졌으며, 저항성 균의 출현 등을 저지하기 위해서 병이 발생하기 전에는 CK나 TT를 사용하고, 병이 발생한 이후에는 benomyl을 사용하는 것이 바람직할 것으로 생각한다.