• 대한화학회지
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• 제29권1호
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• pp.52-60
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• 1985

본 연구는 대기중의 질소산화물(이하 NO$_x$로 약기)을 신속 정확하게 측정하기 위해 현 방법을 개선한 것으로써, 대기중의 NO$_x$를 0.03${\%}$ 과산화수소(H$_2$O$_2$)를 함유한 0.1N수산화나트륨의 알칼리성 흡수액에 흡수 시킴으로써, 정량이 가능했다. 완전한 흡수를 위해서는 100ppm정도의 NO$_x$인 경우 흡수액과 2분간의 진탕이 필요했으나, 고농도의 NO$_x$ (>200 ppm 이상)인 경우에는 산화제로 공기나 산소기체를 첨가시켜 반응물을 맹렬히 진탕시켜 줌으로써 30분이내에 완전한 산화흡수가 가능했다. 남아있는 여분의 H$_2$O$_2$는 흡광도에 미치는 영향이 매우 크지만 아연분말 0.5g으로서 완전히 분해할 수 있었으며, 시료용액은 질산이온에서 아질산이온으로의 환원이 가능하도록 완충용액으로 액성이 pH 6.1~6.6으로 조정되어야 했다. 흡수된 NO$_x$는 sulfanilamide와 NEDA로서 diazo coupling 반응시켜 비색 정량하였다. 이상의 방법은 몰흡광계수가 크며(4.48 ${\times}$ 10$^4$), 한국공업규격에 채택된 O$_3$산화-아연 환원 NEAD 법보다 훨씬 신속, 간편할 뿐 아니라. 측정값의 재현성이 우수한 배기가스중의 NO$_x$분석법임이 확인되었다.

• 한국해양환경ㆍ에너지학회지
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• 제9권3호
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• pp.160-167
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• 2006

저서성 요각류 Tigriopus japonicus 는 한국연안에 널리 분포하며, 영양단계에서 1차 소비자로서 중요한 역할을 담당한다. 본 연구에서는 해양생태독성평가를 위한 표준 실험생물로서 가능성을 구명하기 위하여 T. japonicus 유생($100{\sim}200{\mu}m$)을 이용하여 염분 및 수소이온농도(pH) 내성실험과 2종의 표준독성물질(황산구리, 카드뮴) 및 3종의 산업폐수오니(피혁, 염색, 염료공장폐수오니)에 대한 48시간 사망률 실험을 실시하였다. T. japonicus 유생은 $5.0{\sim}35.0psu$ 염분과 pH $6.3{\sim}8.2$ 범위에서 90% 이상 생존하여 염분 및 pH에 대한 강한 내성을 보였다. 또한 표준독성물질에 대한 48시간 $LC_{50}$은 황산구리의 경우 $3.6{\pm}0.7ppm$, 카드뮴은 $1.7{\pm}0.8ppm$ 이었으며, 각각의 반복구간의 사망률 편차는 10% 이하였다. 황산구리에 대한 T. japonicus 유생의 독성반응은 요각류를 포함한 소형 갑각류에 비해 낮은 것으로 나타났다. 그러나 카드뮴에 대한 T. japonicus 유생의 독성반응은 요각류 T. japonicus, Paracalanus parvus 및 윤충류 Brachinonus plicatilis 성체 보다 훨씬 민감하였다. 산업폐수오니의 경우, 염료오니 추출액을 제외한 피혁과 염색오니 추출액은 농도-반응 사이의 선형관계가 뚜렷하였다. 산업폐수오니 추출물에 대한 T. japonicus의 48시간 $LC_{50}$은 피혁 추출물의 경우, $31.1{\pm}1.1%$ 이었으며, 염색 추출물은 $54.4{\pm}15.1%$로 산출되었다. 상기의 실험결과들에 의하면, 요각류 T. japonicus 유생을 이용한 생물검정법은 산업폐수나 화학물질에 대한 해양생태독성평가 시 유용한 평가 수단인 것으로 판단된다. 광범위한 염분 및 pH에 대한 내성, 농도-반응(사망률) 사이의 뚜렷한 선형관계는 본 종이 표준시험종으로써 충분한 가치가 있음을 입증하였다.

• 대한소아치과학회지
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• 제47권4호
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• pp.397-405
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• 2020

이 연구의 목적은 불소 민감성(fluoride-sensitive) Streptococcus mutans (FS S. mutans ) 와 불소 저항성(fluoride-resistant) Streptococcus mutans (FR S. mutans )의 우식원성 특성을 비교하는 것이다. S. mutans ATCC 25175 균주를 NaF (70 ppm)를 포함한 trypticase soy broth에서 40일 동안 배양하여 FR S. mutans를 획득하였다. 2% 자당 유무에 따른 FS와 FR S. mutans의 성장과 산 생성 변화를 비교하였고, 타액 세균을 이용하여 FS와 FR S. mutans 바이오필름을 형성하여 공초점 레이저 현미경으로 관찰하고 세균 수를 측정하였다. 또한 RT-PCR을 통해 FS와 FR S. mutans의 gtf 유전자 발현 정도를 비교하였다. FR S. mutans는 FS S. mutans 보다 자당을 이용한 성장과 산 생성이 모두 낮았다. 타액 세균과 단일 균주 바이오필름의 형성 또한 FR S. mutans가 FS S. mutans 보다 적었고, 더 낮은 gtfB, gtfC 및 gtfD 발현을 보였다. 이 연구를 통해 FR S. mutans는 FS S. mutans 보다 감소된 우식원성 특성을 가지고 있음을 관찰하였고, 불소의 주기적 사용은 S. mutans 세균의 활성을 낮추어 우식 발생을 줄이는데 도움이 될 수 있을 것이다.

• Steel and Composite Structures
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• 제5권2_3호
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• pp.181-192
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• 2005

The effective length method for flexural (column) buckling has been used for many decades but its use is somewhat limited in various contemporary design codes to moderately slender structures with elastic critical load factor (${\lambda}_{cr}$) less than 3 to 5. In pace with the use of higher grade steel in recent years, the influence of buckling in axial buckling resistance of a column becomes more important and the over-simplified assumption of effective length factor can lead to an unsafe, an uneconomical or a both unsafe and uneconomical solution when some members are over-designed while key elements are under-designed. Effective length should not normally be taken as the distance between nodes multiplied by an arbitrary factor like 0.85, 1.0, 2.0 etc. Further, the classification of non-sway and sway-sensitive frames makes the conventional design procedure tedious to use and, more importantly, limited to simple regular frames. This paper describes the practical use of second-order analysis with section capacity check allowing for $P-{\delta}$ and $P-{\Delta}$ effects together with member and system imperfections. Most commercial software considers only the $P-{\Delta}$ effect, but not member and frame imperfections nor $P-{\delta}$ effect, and engineers must be very careful in their uses. A verification problem is also given for validation of software for this type of powerful second-order analysis and design. It is a trend for popular and advanced national design codes in using the second-order analysis as a norm for analysis and design of steel structures while linear analysis may only be used in very simple structures.

• 대한환경공학회지
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• 제38권3호
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• pp.150-153
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• 2016

본 연구는 $TiCl_4$의 농도(0.25-0.59 mM)와 급속교반속도(100-250 rpm), 완속교반속도(30-60 rpm)의 변화가 인 제거효율에 미치는 영향을 알아보고자 하였다. 응집제 농도가 $0.25{\leq}[TiCl_4]{\leq}0.39mM$ 범위에서 인 제거 효율은 $TiCl_4$의 농도가 증가 할수록 증가하였으며 처리후 인의 농도는 0.2 mg/L 이하였다. 응집제 농도 0.39 mM, 급속교반속도 100 rpm, 완속교반속도 30 rpm에서 인 제거효율이 약 99%로 가장 높았다. $TiCl_4$의 농도가 낮을 경우(0.25-0.27 mM) 인제거효율의 편차는 급속교반속도 변화(2-3%)보다 완속교반속도 변화(7-10%)에서 더 민감하였다.

• 환경영향평가
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• 제21권6호
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• pp.841-857
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• 2012

Preliminary ecological environmental assessments including physico-chemical constituents, water quality, fish fauna analysis, physical habitat health, and ecological health assessment were conducted as a primary step for Jeungchon micro-habitat ecosystem restoration in 2012. Water chemistry analysis of conductivity, dissolved oxygen, chlorophyll-a and etc. indicated that there were no significant differences(p < 0.05) among 6 sites between the headwaters and downstream. Multi-metric model analysis of Qualitative Habitat Evaluation Index(QHEI) showed that brooklets were at "good condition" as a mean QHEI of 158.7(n = 6) and the longitudinal differences of the model values between the sites were minor(QHEI range: 153 - 165). Total fish species and the number of individuals were 12 and 481, respectively, and dominant species were Zacco platypus(49.5%) and Zacco koreanus(36.8%). Tolerance guild analysis showed that the proportion of sensitive species($S_S$) had a negative linear function[$S_S=86.35-0.31(D_H)$; $R^2$ = 0.892, p < 0.01] with a distance from the headwaters, while the proportion of tolerant species($T_S$) had a positive linear function($R^2$ = 0.950, F = 90.28, p < 0.001) with the distance. Trophic feeding guild analysis showed that the proportion of insectivore species($I_n$) had a negative linear function($R^2$ = 0.934, p < 0.01) with a distance from the headwaters, while the proportion of omnivore species($O_m$) had a positive linear function($R^2$ = 0.958, p < 0.001) with the distance. Index of Biological Integrity(IBI) model, based on fish assemblages, showed a "fair condition" as a mean IBI of 23(n = 6), and there was a distinct differences of ecological health between the headwaters(S1 = 30; "good condition") and the downstreams(S6 = 14; "poor condition"). Overall, the preliminary environmental impact assessments suggest that water quality, physical habitat conditions(QHEI model), and ecological health(IBI model) were maintained well, even if the state was not an excellent conditions.

• 한국식품영양과학회지
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• 제26권5호
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• pp.901-907
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• 1997

The purpose of this study was to investigate the effects of green tea catechin o n free radical generation system and peroxidative damage in the liver of streptozotocin(STZ)-induced diabetic rats. Spragu-Dawley male rats weighing 150$\pm$10gm were randomly assigned to one normal and three STZ-induced diabetic groups; diabetic groups were classified to catechin free diet(DM-oC group), 0.5% catechin diet(DM-0.5C group) and 1% catechin diet(DM-1C group) according to the levels of dietary catechin supplementation. Diabetes was experimentally induced by intravenous injection of 55mg/kg of body wt of STZ in citrate buffer(pH 4.3) after feeding of three experimental diet for 4 weeks. Animals were sacrificed at the 6th day of diabetic states. Activities of serum glutamic oxaloacetic transaminase(GPT) in DM-oC groups were higher than those of the normal group, and those in catechin supplementation group were similar to those of the normal group. Liver lipid peroxide values increased by 153%, 49%, and 27% in Dm-oC, DM-0.5C and DM-0C and Dm-1C but was not significantly different in catechin supplementation groups compared with the normal group, and liver cytochrome $P_{450}$ contents was similar to result of XOD activity. In electron microscopic examination of liver, lysosome was relatively scattered in Dm-oC and Dm-0.5C group and preserved normal shapes in DM-1C group. The present results indicate that STZ-induced diabetic rats are more sensitive to oxidative stress, leading to the acceleration of lipid peroxidation process, but this was reduced by anti-oxidative effect of high level of dietary catechin. It is concluded that dietary catechin serves as powerful antioxidant against lipid peroxidation in diabetic rats.

• Journal of Pharmaceutical Investigation
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• 제35권4호
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• pp.265-271
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• 2005

A rapid, selective and sensitive reversed-phase HPLC method for the determination of etodolac in human serum was developed, validated, and applied to the pharmacokinetic study of etodolac. Etodolac and internal standard, ibuprofen were extracted from human serum by liquid-liquid extraction with hexane/isopropanol (95:5, v/v) and analyzed on a Luna C18(2) column with the mobile phase of 1% aqueous acetic acid-acetonitrile (4:6, v/v). Detection wavelength of 227 nm and flow rate of 1.0 mL/min were fixed for the study. The assay robustness for the changes of mobile phase pH, organic solvent content, and flow rate was confirmed by $3^3$ factorial design using a fixed etodolac concentration $(1\;{\mu}g/mL)$ with respect to its peak area and retention time. And also, the ruggedness of this method was investigated at three different laboratories using same quality control (QC) samples. This method showed linear response over the concentration range of $0.05-40\;{\mu}g/mL$ with correlation coefficients greater than 0.999. The lower limit of quantification using 0.5 mL of serum was 0.05 ${\mu}g/mL$, which was sensitive enough for pharmacokinetic studies. The overall accuracy of the quality control samples ranged from 92.00 to 110.00% for etodolac with overall precision (% C.V.) being 1.08-10.11%. The percent recovery for human serum was in the range of 76.73-115.30%. Stability studies showed that etodolac was stable during storage, or during the assay procedure in human serum. The peak area and retention time of etodolac were not significantly affected by the changes of mobile phase pH, organic solvent content, and flow rate under the conditions studied. This method showed good ruggedness (within 15% C.V.) and was successfully used for the analysis of etodolac in human serum samples for the pharmacokinetic studies of orally administered Lodin XL tablet (400 mg as etodolac) at three different laboratories, demonstrating the suitability of the method.

• 대한화학회지
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• 제58권6호
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• pp.575-579
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• 2014

종양 조직으로 약물을 효과적으로 전달하기 위하여 리포솜의 개발이 활발이 연구되고 있다. 그러나 리포솜이 종양조직에 효과적으로 축적됨에도 불구하고, 낮은 약물 방출 때문에 리포솜의 치료 효과가 제한적이다. 따라서 우리는 외부 자극에 의하여 약물방출을 최대화 시킬 수 있는 온도민감성 리포솜을 개발하였다. 모델약물인 독소루비신은 pH 전위차 방법에 의하여 리포솜 내부에 봉입하였다. 리포솜의 입자 크기는 $142.0{\pm}6.24nm$ 이었고, 표면전하는 $-10.55{\pm}1.12mV$ 이었다. 온도민감성 리포솜으로부터 약물의 방출은 형광광도계로 측정하였으며 $42^{\circ}C$ 이상에서 5분 이내에 80% 이상의 방출률을 나타냈다. 초음파에 의해 온도민감성 리포솜으로부터 방출된 독소루비신의 세포독성은 초음파를 조사하지 않은 온도민감성 리포솜보다 월등히 우세하였다. 이번 연구에서 우리는 초음파에 의하여 온도민감성 리포솜으로부터 온도에 민감한 약물방출을 증명하였고, 이것은 외부 자극에 의한 종양조직의 약물 농도를 증가시킬 수 있는 암치료에 효과적일 것이다.

• 분석과학
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• 제29권5호
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• pp.219-224
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• 2016

A sensitive method to detect trace anions in hydrofluoric acid (HF) by solid-phase extraction (SPE) clean-up and ion chromatography (IC) was described. Fluoride in HF solution was eliminated with solid-phase extraction, and residual fluoride, acetate, chloride, bromide, nitrate, phosphate and sulfate were consecutively separated with IC. The SPE parameters (selection of adsorbent, sample volume and pH, elution solvent and its volume) were optimized and selected. The removal effect of fluoride in HF solution was the best on Oasis WAX column, and the optimum conditions (1.0 mL of 25 % HF solution and 50 mM ammonium acetate 5 mL as elution solvent) were established by the variation of parameters. Under the established condition, the method detection limits of chloride, bromide, nitrate, phosphate, and sulfate were 0.04~0.30 µg/L in 25 % HF solutions (w/w) and the relative standard deviation was less than 5 % at concentrations of 20.0 and 40.0 µg/L. The concentrations of anions in a 25 % HF had detectable levels of 4.2 to 47.5 µg/L. The method was sensitive, reproducible and simple enough to permit the reliable routine analysis of anions in HF solution used in the process of producing semiconductors.