• 미생물학회지
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• 제51권4호
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• pp.355-363
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• 2015

본 연구에서는 염소 소독제를 함유한 수돗물을 수리학적 체류시간 2시간 수준으로 공급한 모델 상수관망에서 형성된 초기 생물막의 생장에 대해 연구하였다. PVC slide 표면에 형성된 세균 생물막의 비생장률(specific growth rate, ${\mu}$)은 총세균수와 종속영양세균수 기준으로 각각 $0.14{\pm}0.09day^{-1}$와 $0.16{\pm}0.08day^{-1}$로 측정되었으며, 생물막 형성 정도는 실험 개시 10일 후에 각각 $3.1{\times}10^4cells/cm^2$와 $6.6{\times}10^3CFU/cm^2$에 이르렀다. Bulk-phase 세균에 비해 훨씬 높은 생물막 형성 세균의 비생장률(${\mu}$)은 관망내에서 생물막 세균의 증식이 세균 재생장의 주된 요인으로 작용함을 의미하였다. 분리 배양된 생물막 균주들은 acetate 농도를 달리한 생장배지에서 얻어진 Monod 모델에서 특징적인 ${\mu}_{max}$와 $K_S$값을 보여주었다. 가장 낮은 ${\mu}_{max}$값을 보여준 Methylobacterium 균주는 느린 생장을 통해 염소 소독제 처리(0.5 mg/L, 10분간)에 대해 높은 내성을 나타내었다. 반포화상수(half-saturation constant) $K_S$값은 Sphingomonas 균주에서 다른 분리 균주들에 비해 100배 정도 낮게 측정되어 기질친화도가 매우 높게 나타났다. 이는 수돗물과 같이 영양물질의 농도가 매우 낮은 조건에서 생존할 수 있도록 적응된 절대 빈영양성 세균의 특징으로 판단된다. 비록 특징적인 ${\mu}_{max}$와 $K_S$값을 보이는 균주 만을 대상으로 수행되었지만, 이상의 결과는 상수관망에서 초기에 형성되는 복합 세균종으로 구성된 생물막에 대한 이해와 조절에 도움을 줄 수 있을 것으로 기대된다.

• 농촌의학ㆍ지역보건
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• 제9권1호
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• pp.56-66
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• 1984

Giardia lamblia is a pathogenic flagellate causing intestinal disorders such as diarrhea, abdominal pain and malabsorption of nutrients. Giardia is mainly infected by the ingestion of contaminated foods per os. Craun (1979) has recently reported that mass infection of this flagellate through the contaminated water supply systems is one of public health hazards. Also, so-called traveller's diarrhea is sometimes caused by Giardia infection (CDC, U.S.A., 1971). However, a few epidemiological studies figuring out the mode of infection or control measures of Giardia infection has been done so far in Korea. The present study was aimed to know the prevalence of Giardia infection in several Korean populations, detectability of this flagellate in water systems and the viability of the cysts against sewages and disinfectants applying to drinking water. In the present study, 388 stool specimens from orphanage children in Chun-joo, Chung-joo, On-yang and Chun-an areas and 538 stool specimens from inhabitants in Woo-do, In-chon, and Chun-joo were examined by formalin-ether concentration technique to detect out Giardia cysts. On the other hand, water samples from 14 sites of Han River and its tributaries were collected in May through July, 1984. Fifty liter of water sample in each sampling site was then filtered through water filtering system deviced by U.S. Environmental Proutection Agency and the sediments rinsed out from the thread rolls, a part of water filtering system, were examined to detect out the Giardia cysts. In order to observe the viability of Giardia cysts in the sewage samples, the cysts were treated in it at $4^{\circ}C$ or $25^{\circ}C$ for 7 through 28 days. For this purpose, the cysts were also exposed to various concentrations of disinfectants such as chlorine, iodine and ozone gas for proper time intervals. After treatment, the viability test of the Giardia cysts were carried out by method of Rice and Schaefer (1981) with minor modification. The results obtained in this study were as follows : 1) The detection rates of G lamblia cysts in the stool specimens were 18.3% in orphans and 4.3% in general examinees. 2) The prevalences of Giardia Infection were higher in the young age groups than in-adults. The highest positive rate was 18.4% in the age group less than 10. 3) Of 14 water specimens sampled from Han River system and its tributaries around the Seoul area, the Giardia cysts were detected from 4 samples, and no cyst was found in the water supply systems. 4) The cysts treated in the sewage survived for 28 days at $4^{\circ}C$ and for 13 days at $25^{\circ}C$. 5) The cysts were completely destroyed within 60 minutes by exposure to 8 mg/l of residual chlorine at 4g and within 30 minutes by exposure to the same concentration of chlorine at $25^{\circ}C$. 6) The cysts were all dead when exposed to 1 mg/1 of iodine for 60 minutes at $4^{\circ}C$ or $25^{\circ}C$. 7) The cysts were destroyed after 10 minute exposure in 0.15 mg to 0.25mg of residual ozone gas per liter. Summarizing the above results, it is considered that Giardia infection is regarded as water-borne disease and the cysts are able to be controlled by the application with the disinfectants in the water supply systems.

• 한국균학회소식:학술대회논문집
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• 한국균학회 2014년도 추계학술대회 및 정기총회
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• pp.25-25
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• 2014

Three species of Fusarium, F. fujikuroi, F. verticillioides and F. proliferatum, are known to be associated with bakanae disease of rice [1, 2]. F. fujikuroi infects rice flowers and survive in endosperm and embryo of the seeds. Infected seed is an important source of primary inoculum of pathogens [3]. Seeds of rice (Oryza sativa cv. Boramchan) collected from bakanae-infected field were found to be 96% infected with Fusarium sp., 52% with F. fujikuroi, 42% with F. verticillioides, and 12% with F. proliferatum as determined by incubation method and species-specific PCR assays. F. fujikuroi was detected at lemma/palea, endosperm and embryo whereas F. verticillioides and F. proliferatum were recovered only from lemma/palea by means of component plating test. Seed disinfection methods have been developed to control bakanae disease and prochloraz has been most widely used for rice seeds. Two chemicals formulated with prochloraz (PC 1) and prochloraz + hexaconazole (PC 2) that inhibit biosynthesis of ergosterol strongly reduced the incidence of Fusarium spp. on selective media to 4.7% and 2.0%, respectively. Disease symptoms of rice seedlings in nursery soil were alleviated by chemical treatment; seedlings with elongated leaves or wide angle between leaf and stem were strikingly reduced from 15.6 to 3.2% (PC 1) and 0 (PC 2), stem rots were reduced from 56.9 to 26.2% (PC 1) and 32.1% (PC 2), and normal seedling increased from 0.4 to 13.3% (PC 2). Prochloraz has some disadvantages and risks such as the occurrence of tolerant pathogens [4] and effects on the sterol synthesis in animals and humans [5]. For these reasons, it is necessary to develop new disinfection method that do not induce fungal tolerance and are safe to humans and animals. Chlorine dioxide ($ClO_2$), that is less toxic, produces no harmful byproducts, and has high oxidizing power, has been reported to be effective at disinfection of several phytopathogenic fungi including Colletotrichum spp. and Alternaria spp. [6]. Gaseous $ClO_2$ applied to rice seeds at a concentration of 20 ppm strongly suppressed mycelial growth of Fusarium fujikuroi, F. verticillioides and F. proliferatum. The incidence of Fusarium spp. in dry seed with 8.7% seed moisture content (SMC) tended to decrease as the concentration of $ClO_2$ increased from 20 to 40 ppm. Applying 40 ppm $ClO_2$ at 90% relative humidity, incidence was reduced to 5.3% and resulted in significant reduction of disease symptoms on MS media. In nursery soil, stem rot was reduced from 56.9 to 15.4% and the number of normal seedlings increased from 0.4 to 25.5%. With water-soaked seeds (33.1% SMC) holding moisture in the endosperm and embryo, the effectiveness of disinfection using $ClO_2$ increased, even when treated with only 20 ppm for four hours. This suggests that moisture was a key element for action of $ClO_2$. Removal of the palea and lemma from seeds significantly decreased the incidence of Fusarium spp. to 3.0%. Seed germination appeared to decrease slightly by water-soaking at $30^{\circ}C$ because of increased SMC and by physical damage of embryos from hulling. These results indicate that the use of gaseous $ClO_2$ was effective as a means to disinfect rice seeds infected with Fusarium spp. and that moisture around the pathogens in the seed was an important factor for the action of $ClO_2$. Further investigations should be conducted to ascertain the best conditions for complete disinfection of Fusarium spp. that infect deep site of rice seeds.

• 한국식품영양과학회지
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• 제34권8호
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• pp.1258-1264
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• 2005

꽁치를 이산화염소 용액 처리하여 미생물에 대한 살균 효과와 pH, 지방산패, 휘발성 염기 질소 함량, 관능평가에 대한 이산화염소의 농도별 효과를 측정하였다. 4$^{\circ}C$에서 저장한 꽁치의 초기 미생물수는 이산화염소의 농도에 따른 유의적인 차이 없이 1.8$\∼$2.4 log CFU/g이었으나,저장 기간이 경과함에 따라 뚜렷한 차이를 보여 저장 4일에 대조구의 총균수가 6.43 log CFU/g에 도달한 반면 50 ppm 이산화염소를 처리한 시료에서는 저장 9일에 5.47 log CFU/g의 총균수에 도달하였다 또한 4$^{\circ}C$에서 저장한 꽁치의 저온균수도 저장 기간이 경과할수록 유의적인 차이를 보이며 증가하였고, 저장 4일에 대조구와 3 ppm은 각각 6.72, 6.34 log CFU/g을 나타내었으나, 이산화염소 농도 10 ppm과 50 ppm은 5.02, 4.13 log CFU/g으로 이산화염소 용액의 농도가 증가함에 따라 저온균수가 감소하는 경향을 보였다. -20$^{\circ}C$에서는 저장 마지막 날까지 총균수의 큰 변화를 보이지 않아 신선도 유지가 가능하였다. 꽁치의 pH는 저장 6일에 급격히 증가하여 저장 9일에는 대조구의 pH 7.05, 50 ppm의 이산화염소 처리구에서는 6.73으로 측정되었으며, 휘발성 염기 질소 함량을 측정한 VBN 값은 저장 4일까지 큰 변화를 보이지 않다가, 저장 5일에 증가하여 높은 값을 나타내었다. -20$^{\circ}C$에서 저장한 꽁치의 pH와 VBN 값은 미생물수와 마찬가지로 큰 변화를 보이지 않았다. 지방산패 정도를 측정한 TBARS 값은 저장 기간에 따라 증가하였는데 이산화염소 농도에 따른 큰 차이는 없었고, 관능검사를 실시한 결과 이산화염소 용액의 농도가 증가할수록 평가 점수가 높음을 확인할 수 있었다 따라서 이산화염소 용액의 처리가 꽁치의 미생물학적 안전성을 증가시켜 유통기간을 증대한다고 판단된다.

• 한국가축번식학회지
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• 제5권1호
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• pp.43-63
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• 1981

This study aimed to determine the effects of adrenalectomy on the sexual gland, the thyroid gland and the serum components. A total of 192 Wister strain albino rats were evenly divided into 4 sexually equal groups for the comparisons. Each groups was divided into a control and a treatment group by sexuality. Each tissue of the sexual gland and the thyroid gland was microscopically examined, and at the same time body weight and serum components were also examined on the 1st, 7th, 14th, 28th, 42nd, 56th, 70th and 84th day respectively following adrenalectomy. The results obtained were as follows: 1. The body weight was sufficiently retarded in decreasingly after the adrenalectomy as compared to that of control. 2. The histological change of testis started atrophy of spermatogonia and degeneration of spermatocyte. There was a, pp.ared no cell division activity. Spermatozoa in the seminiferous tuble was not noticed but degeneration of interstitial cell was started and spermatozoa in the epididymal duct disa, pp.ared. 3. Degeneration of oocyte and follicular cell was noticed as the histological change of ovary. There was not a, pp.arance of primary follicle and corpus Iuteum but interstitial cell was proliferated. 4. For the effect of adrenalectomy on the histological change of the thyroid gland, the number of small follicle decreased and that of large follicle increased as the time passed following the adrenalectomy. And the follicular epithelial cell became squamous as typical condition of functional decreased. 5. It was shown that in the total contents of serum protein no difference with control occurred with in the 70th day for male and female adrenalectomized, respectively. But the differences in protein contents were significanly decreased on the 70th day. 6. No difference occurred in the total serum lipids on the 7th day, but they decreased significantly on the 42nd day, and (P<0.01) on the 56th, and 70th day. A tendency to decrease was noted as time elapsed following adrenalectomy. 7. Increase and decrease were intercrossed in the serum cholesterol contents between the control and th treatment groups on the 28th day. But the difference significantly decreased on the 42nd, 56th, and 70th day after adrelalectomized. The contents showed tendency to decrease as time elapsed following adrenalectomy. 8. The blood glucose contents rapidly decreased with time. The difference were significant on the 28th and 42nd day, and highly significant on the 56th and 70th day for male adrenalectomized. 9. In case of solium, there was no noticeable sexual distinction. There was slight in creasing or decreasing for the control group. But the treatment group tended continuously to decrease for male and female. 10. It was shown that potassium contents tended to increase on the 28th day for male and female, but the differences were small. 11. As for chlorine, it tended to decrease rapidly on 7th day for male and female adrenalectomized, and the tendency continued.

• 한국응용곤충학회지
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• 제7권
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• pp.39-51
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• 1969

The study involved determination of resistance levels of spider mites ta argano-phosphates using topical application and slide dip techniques; laboratory serening tests of alternative acaricides using an O/P resistant strain and a field trial of the screened materials. 1. Strains of Tetranychus were from Timaru(TR), Havelock Narth (HNR), Lincaln (LN). Germany (GR, GN). Comparisons of the resistant strains and normal strains at the LD50 and LC50 levels were as follows : (a) Using the topical application tochnique; with Parathian. resistant levels of the GR. TR and HNR strains of T. urticae were respeativuly, 1035. 484 and 452 times as resistant' as the LN strain. (b) Using the slide dip technique; with Phosdrin, resistant of GR, TR and HNR strains of T. urticae were 635, 274 and 266 times greater respeativuly, than the GN strain. 2. The laboratory sereaning tests were carried out far their contact plus stomach and residual effect to assess the toxicities of eleven alternative materials which would be used far control of O/P resistant strain of T. urticae. The acaricide groups represented were 3 organo-chlorines (Spidex, Kelthane and C 8514), 2 nitrophenyls (UC 19786 and Morocide), 2 cyclic carbonates(Eradex and Morestan). I carbamate (UC2004 7A), 1 mixture of carbamate and orano-chlorine and 2 other chemicals (C 8677 and M2527). From all acaricide tested. Kelthane and Morocide were the most effective, folowed by Spidex and M2527. Morestan, C8514. C8677 and RS 143 were intermediate, but Eradex, UC 19786 and UC 20046A were poor. 3, The number of sapmles required for estimation of the population in the field evaluation of acaricidal effects was one giving the highest practical precision. It was decided, after preliminary sampling trials. to use samples of 30 leaves per replicate which gave a $5.7\%$ standard error. 4. In the field trials, Morocide applied at the $0.05\%\;and\; 0.04\%$ a. i. conc. to black currant trees gave excellent control of O/P resistant population of T. urticae for about 12 days, but Morocide 0.025 and Kel thane $0.02\%$ a. i. cone. gave efficient control for about 6 days. In other words. first applications of Kel thane ane Moroeide gave very high degrees of control of O/P resistant population of the two-spotted spider mite. However, the results indicate that secondary application would sometimes be necessary. There was no foliage damage of black Currants and strawberries by either acaricides at the concentrations used. Acknowledgment ... The authors are grateful to: Dr. R. P. pottinger, Senior Lecturer in Agricultural Zoology. Lincoln college. New Zealand. for his helpful assistance in aiding with the organization of thd field work. Department of agriculture officers for mite colonies. Mr. D. A. Slade, Technical Advisor. Fruitgrowers' Federation (now at Massey University) for his assistance and provision of mites for testing. Mr T. McRae of Timaru for permission to use his crops for field tests. The following chemical companies and I or their New Zealand agents for so readily supplying samples of acarides; Ivan Watkins-Dow Limited. Fruitgrowers Chemical Company Limited. Henry H. York & company (New Zealand). Shell Oil (New Zealand) Limited.

• 한국식품영양과학회지
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• 제45권4호
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• pp.619-624
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• 2016

이전 연구에서 이산화염소 가스 훈증처리가 수확 후 파프리카의 미생물학적 안전성을 향상할 수 있다고 보고한 바 있다. 이에 관한 후속 연구로써 본 연구에서는 파프리카의 장기 저장성 확보를 목적으로 저장 중 품질 유지와 부패 감소를 위해 고농도 이산화염소 가스 처리된 파프리카를 $8{\pm}1^{\circ}C$, 상대습도 90%의 조건에서 저장하면서 저농도 서방형 이산화염소 가스 발생제(팜이톡, 3 ppmv)를 이용한 추가적인 병합처리를 수행하였다. 저장 초기 이산화염소 가스 병합처리구의 총 호기성 세균은 대조구와 비교하여 3.04 log CFU/g의 감소를 했고, 효모와 곰팡이는 2.70 log CFU/g의 감소를 나타내었으며, 이러한 이산화염소 가스 병합처리의 미생물 저감 효과는 저농도 서방형 이산화염소 가스 발생제 처리로 저장 기간 유지되었다. 특히, 부패율에서 병합처리구가 대조구보다 유의적으로 낮았다. 파프리카의 품질 변화지표(비타민 C 함량, 경도, 색도)와 관련하여 이산화염소 가스 병합처리구와 대조구 모두 저장 기간 차이를 나타내지 않았으나, 저장 중 중량감소율은 병합처리구가 대조구보다 낮은 수준을 유지하였다. 따라서 본 연구 결과, 수확 후 파프리카에 두 가지 형태의 이산화염소 가스를 병합처리 하는 것이 단일처리보다 저장과 유통과정 중 파프리카의 품질을 유지하면서 부패율을 낮출 수 있는 더 효과적인 처리 방법이라고 판단된다.

• Korean Chemical Engineering Research
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• 제50권5호
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• pp.837-842
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• 2012

폐기물 고형연료의 순환유동층 연소기술의 시범을 위하여 파일롯트 규모 순환유동층 연소보일러를 설계하고 건설하였다. 보일러의 규모는 출력기준 약 6 MWth에 해당하며 증기질은 $400^{\circ}C$, 38 ata로 설계하였다. 최대 증기출력은 약 8 ton/h에 해당한다. 연료는 RDF로 휘발분을 주성분으로 하며 점화가 빠르고 연소성이 매우 뛰어났으며 보일러의 연소효율은 99.5%를 능가하였다. 순환유동층 RDF 연소의 안정성은 연료중 회분 이외의 이물질의 존재 여부와 신속한 배출 가능성에 크게 의존하였다. 오염물질의 배출농도는 염소를 제외하고는 법적 기준치 이내에 들었다. 또한 60% 정도의 연료중 염소는 비산재에 흡수되는 것으로 나타났다. HCl을 국내 법 규제에 맞추어 제어하기 위해서는 건식 또는 습식 흡수 장치와 같은 별도의 환경설비가 필요하였다.

• Computers and Concrete
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• 제26권4호
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• pp.367-375
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• 2020

Today, the use of special technologies in the admixture of concrete has made tremendous progress, but the problem that has always existed in the construction of concrete members is the brittleness and lack of loading bearing after cracking, which leads to reduced strength and energy absorption. One of the best ways to fix this is to reinforce the concrete with steel fibers. Steel fibers also control cracks due to dry shrinkage, reduce structural crack width, and improve impact resistance. In this study, recycled steel fibers from worn tires have been used in the manufacture of concrete samples, the secondary benefits of which are the reduction of environmental pollution. One of the disadvantages of steel fiber reinforced concrete is the corrosion of steel fibers and their deterioration in harsh environments such as coastal areas. Corrosion caused by chlorine ions in metal fibers causes deterioration and early decommissioning of structures in corrosive environments. In this study, the effect of the dosage of steel fibers (dosages of 15, 30, and 45 kg of fibers per cubic meter of concrete) and aspect ratio of fibers (aspect ratio of 25 and 50) on compressive and flexural strength of concrete samples are investigated. In the following, the effect of fiber corrosion on the results of the mechanical properties of concrete samples is examined. The results show that the increase in fiber causes a relative increase in compressive strength, and a significant increase in flexural strength, and corrosion of steel fibers without reducing workability reduces compressive strength and flexural strength by up to 6 to 11%, respectively.

• Journal of the Korean Wood Science and Technology
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• 제45권4호
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• pp.382-398
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• 2017

This study was conducted to identify the potential of Quercus mongolica (QUM), Pinus densiflora (PID) and Pinus rigida (PIR) as a raw material for pellet production. Larix kaempferi (LAK), which has mostly been used for pellet production in Korea, was also used as a control. All specimens contained very minimal amounts of sulfur and chlorine. Ash content of LAK was the lowest, followed by PID, PIR and QUM. For the size distribution, the mass fraction between 0.42 mm and 0.25 mm was the highest in PIR. Most fuel characteristics of the produced wood pellets improved with the use of 12% moisture content (MC) particles and the increase of the ratio of length to diameter of a hole in flat-die (L/D ratio). When the MC, bulk density and durability of QUM, PID, PIR and LAK pellets was compared with the standards of the KFRI and ISO, the use of wood particles of 12% MC and flat-die with an L/D ratio of 5.00 for PID particles are suitable for high-quality pellets in the aspects of all fuel characteristics. For PIR and QUM, further work is needed to seek the optimum conditions for the production of high-quality and durable pellets.