• Bulletin of the Korean Chemical Society
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• 제22권4호
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• pp.337-348
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• 2001

This article gives an overview of a recently developed channel system, frit-inlet asymmetrical flow field-flow fractionation (FI-AFlFFF), which can be applied for the separation of nanoparticles, proteins, and water soluble polymers. A conventiona l asymmetrical flow FFF channel has been modified into a frit-inlet asymmetrical type by introducing a small inlet frit near the injection point and the system operation of the FI-AFlFFF channel can be made with a great convenience. Since sample components injected into the FI-AFlFFF channel are hydrodynamically relaxed, sample injection and separation processes proceed without interruption of the migration flow. Therefore in FI-AFlFFF, there is no requirement for a valve operation to switch the direction of the migration flow that is normally achieved during the focusing/relaxation process in a conventional asymmetrical channel. In this report, principles of the hydrodynamic relaxation in FI-AFlFFF channel are described with equations to predict the retention time and to calculate the complicated flow variations in the developed channel. The retention and resolving power of FI-AFlFFF system are demonstrated with standard nanospheres and protreins. An attempt to elucidate the capability of FI-AFlFFF system for the separation and size characterization of nanoparticles is made with a fumed silica particle sample. In FI-AFlFFF, field programming can be easily applied to improve separation speed and resolution for a highly retaining component (very large MW) by using flow circulation method. Programmed FI-AFlFFF separations are demonstrated with polystyrene sulfonate standards and pululans and the dynamic separation range of molecular weight is successfully expanded.

• 한국독성학회:학술대회논문집
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• 한국독성학회 2006년도 추계학술대회
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• pp.65-74
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• 2006

Modem drug discovery requires rapid pharmacokinetic evaluation of chemically diverse compounds for early candidate selection. This demands the development of analytical methods that offer high-throughput of samples. Naturally, liquid chromatography / tandem mass spectrometry (LC-MS/MS) is choice of the analytical method because of its superior sensitivity and selectivity. As a result of the short analysis time(typically 3-5min) by LC-MS/MS, sample preparation has become the rate- determining step in the whole analytical cycle. Consequently tremendous efforts are being made to speed up and automate this step. In a typical automated 96-well SPE(solid-phase extraction) procedure, plasma samples are transferred to the 96-well SPE plate, internal standard and aqueous buffer solutions are added and then vacuum is applied using the robotic liquid handling system. It takes only 20-90 min to process 96 samples by automated SPE and the analyst is physically occupied for only approximately 10 min. Recently, the ultra-high flow rate liquid chromatography (turbulent-flow chromatography)has sparked a huge interest for rapid and direct quantitation of drugs in plasma. There is no sample preparation except for sample aliquotting, internal standard addition and centrifugation. This type of analysis is achieved by using a small diameter column with a large particle size(30-5O ${\mu}$m) and a high flow rate, typically between 3-5 ml/min. Silica-based monolithic HPLC columns contain a novel chromatographic support in which the traditional particulate packing has been replaced with a single, continuous network (monolith) of pcrous silica. The main advantage of such a network is decreased backpressure due to macropores (2 ${\mu}$m) throughout the network. This allows high flow rates, and hence fast analyses that are unattainable with traditional particulate columns. The reduction of particle diameter in HPLC results in increased column efficiency. use of small particles (<2 urn), however, requires p.essu.es beyond the traditional 6,000 psi of conventional pumping devices. Instrumental development in recent years has resulted in pumping devices capable of handling the requirements of columns packed with small particles. The staggered parallel HPLC system consists of four fully independent binary HPLC pumps, a modified auto sampler, and a series of switching and selector valves all controlled by a single computer program. The system improves sample throughput without sacrificing chromatographic separation or data quality. Sample throughput can be increased nearly four-fold without requiring significant changes in current analytical procedures. The process of Bioanalytical Method Validation is required by the FDA to assess and verify the performance of a chronlatographic method prior to its application in sample analysis. The validation should address the selectivity, linearity, accuracy, precision and stability of the method. This presentation will provide all overview of the work required to accomplish a full validation and show how a chromatographic method is suitable for toxirokinetic sample analysis. A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method developed to quantitate drug levels in dog plasma will be used as an example of tile process.

• 산업기술연구
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• 제7권
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• pp.27-47
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• 1987

Fine anthracite is very difficult to upgrade by conventional processes such as gravity concentration or froth flotation, because large quantities of fine coals are generated at the mining and preparation stages and a significant portion of these fine coals are mixed with gangue minerals. This study, therefore, was carried out for the purpose of improving recovery of low ash clean coal, effective beneficiation of low-grade coking coal and removal of sulphur from high-sulphur coals by employing the method of selective agglomeration using oil or polystrene flocculants, for coals which are generally hydrophobic in nature will be extracted by using flocculants. Studies were performed by varying solid concentration, concetration of bridging liquid, mixing speed and mixing time, balling speed and balling time, dispersant dosage, flocculant dosage, pulp pH, and particle size. The results were : when the methods of the oil agglomeration and selective flocculation were employ(in the two process the sample was ground to the size of -74 micron), 1) ash content of the agglomerated coal was 9.85, 7.83%, 2) combustibel recovery of it was 98.5%, 93.5%, respectively. It was observed in selective flocculation that polystyrene is an effective flocculant for coal, De-entrapment of shale from the concentrate flocculated by mechanical agitation was necessary for substantional reductions in final ash content.

• 대한기계학회논문집
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• 제17권12호
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• pp.2995-3006
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• 1993

An automatic mesh generation scheme has been developed for finite element analysis with two-dimensional, quadrilateral elements. The basic strategies of the method are to transform the analysis domain into loops with key nodes and the loops are recursively subdivided into subloops with the use of best split lines. Finally by using the basic loop operators, the meshes are completed. In this algorithm an eight-node loop operator is proposed, which is useful in the area where the change of element size is large and the splitting criteria for subdividing the loops have also been modified to the existing algorithms. Lines, arcs, and cubic spline curves are used to define the boundaries of analysis domain. Sample meshes for several geometries are presented to demonstrate the robustness of the algorithm.

• 한국환경농학회지
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• 제30권3호
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• pp.323-329
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• 2011

BACKGROUND: The conazoles, difenoconazole, diniconazole, hexaconazole, penconazole and tetraconazole are a large class of synthetic fungicides used extensively for foliage and seed treatments in agricultural crops. The extensive use of conazoles has brought concerns on the potentiality of environmental contamination and toxicity. Thus studies on the development of methods for monitoring the conazoles are required. METHODS AND RESULTS: A modified quick, easy, effective, rugged and safe (QuEChERS) method was involved in sample preparation. Quadrapole time of flight mass spectrometer (Q-TOF MS) in electron spray ionization (ESI) mode was employed to determine conazoles in garlic samples. The limit of detection (LOD) and limit of quantification (LOQ) of conazoles by Q-TOF-MS ranged from 0.001 to 0.002 mg/L and 0.002 to 0.005 mg/L, respectively. Q-TOF-MS analysis exhibited less than 2.6 ppm error of accurate mass measurements for the detection of conazoles spiked at 0.05 mg/L in garlic matrix. Recovery values of conazoles fortified in garlic samples at 0.02, 0.05 and 0.1 mg/L were between 79.2 and 106.2% with a maximum 11.8% of standard deviation. No detectable conazoles were found in the domestic market samples by using the Q-TOF-MS method. CONCLUSION(s): High degree of confirmation for conazoles by accurate mass measurements demonstrated that Q-TOF-MS analysis combined with a QuEChERS method may be applicable to simultaneous determination of conazoles in garlic samples.

• 응용통계연구
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• 제18권2호
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• pp.355-369
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• 2005

마이크로어레이 실험에서는 유전자의 기능과 상호작용의 이해를 돕기 위한 방안으로 유전자발현자료의 시각화방법이 많이 사용되고 있다. 행렬도는 유전자와 샘플들을 동시에 그려볼 수 있어서, 유전자 또는 샘플의 군집이나 유전자-샘플간 연관작용을 알아보는데 더욱 유용하게 쓰일 수 있다. 본고에서는 마이크로어레이실험에서 행렬도를 이용하여 유전자의 군집 및 연관성을 알아보는 방법을 소개하고, 추가점기법을 이용하여 새로운 샘플을 분류하는 방법을 제안하였다. Golub et al.(1999)의 백혈병 데이터와 Alizadeh et al. (2000)의 림프구데이터, Ross et al.(2000)의 NCI60 종양조직데이터를 이용하여 유용성을 살펴보았으며, 계층적 군집분석 및 k-평균 군집분석 등 다른 기법을 이용한 결과와 비교하고 이러한 기법을 행렬도와 연계하는 방안을 살펴보았다.

• 한국토양비료학회지
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• 제30권4호
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• pp.361-369
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• 1997

본 연구는 질산태 질소 정량을 위한 기존의 E. coli 효소법을 개량하여 한국과학기술연구원(KIST) 생명공학연구소 유전자은행의 KCTC 1116 야생종 대장균(K12 wildtype)을 사용하는 E. coli 세포법으로 개량하였는바, (1) formate적정농도는 0.1mol/l formate를 넣은 0.4ml 보관모액조건에서 도달하였으며, (2) 질산환원에 소요되는 항온배양시간은 보관모액의 주입량에 따라 좌우되었고 (3) 20분 항온배양시간조건하에서 최고 $25{\mu}g$의 $NO_3{^-}-N$을 정량적으로 환원시키는데 충분하였다. (4) 항온배양용액내 NR활성도는 $N_2$가스 공급 및 얼음 냉수 조건하에서 저하정도가 120분간까지 거의 저하되지 않았고 (5) 보관모액은 $N_2$가스로 포화된 무산소조건의 냉장상태($+4^{\circ}C$)에서 최대 6개월까지 NR활성도의 저하가 없어 안정적 보관이 가능하였다. (6) 주입된 질산염은 본 분석조건에서 E. coli에 의해 99%가 아질산으로 환원되었고, 이후 아질산은 60분간의 배양조건하에서도 암모니아로 전혀 전환되지 않아 안정적이었다는 점 등을 토대로 본 $NO_3{^-}$ 분석방법을 확립하였다. 새로이 개발된 본 미생물적 질산태질소 분석방법의 장단점 몇가지를 적시하면, (1) 식물체, 토양, 수질시료를 동시에 그리고 동일한 분석방법으로 정확도 높게 분석할 수 있고, (2) Cd환원법, Salicylate법, Rhenium법 등의 타 분석방법 결과와 높은 상관관계가 있으며, (3) Cd환원법에 비해 질산환원이 더욱 효과적이고 완전하며, 실험과정이 분석종사자에게 전혀 유해하지 않고, 중금속 또는 유기화합물에 의한 실험폐수 분리수거가 필요 없으며, (4) 자동분석에서 뿐만아니라 수동분석에서도 활용될 수 있고, 분석과정이 간단하므로 일시에 다량의 시료분석이 가능하다는 등의 장점이 있으나 (5) 다만 년 1~2회의 세포배양에 장시간이 요구된다는 단점이 있다.

• 핵의학기술
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• 제12권1호
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• pp.66-73
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• 2008

Purpose: CA 19-9 need to examine a number of sample volume, and the postwar 200 U/ml concentration hook effect appears slight. Thus, the antibody-antigen reaction, and by reducing the amount of (sample volume), they can hook effect to minimize the impact of the sample volume and relevance know, I saw the hook effect. In addition, the current maximum of using the standard concentration of the reagent in 240 U/ml increase more than the standard concentration can be seen knows. Material and Method: 5 U/ml and under, make a few low concentration of serum pool from the high concentration of the sample hook effect together with a standard concentration of about 500 to meet the production. The reagents used in experiments are currently using SNUH NM experiment. Orignal method along with the experiment is to 25 ul sample volume (1 / 4), 50 ul (1 / 2), 100 ul (Orignal method) in the experiment. My greatest concentration of the reagent concentration of approximately two times the standard concentration of production. When was the last to make the first experiment, as measured by the standard concentration after that. The new inspection information through a standard solution modified by entering values in them. Results: 100 ul, and to apply the new standard concentration y = 1.3021x - 10.97, $R^2$ = 0.9844. Overall, the results showed a similar orignal method. Because of the concentration in the value of more than 240 U/ml, but it is an overall value that can be made out of a similar value When I put the 50 ul y = 1.045x + 9.5861, $R^2$ = 0.9428. Overall orignal method and the results of a similar value. 50 ul, and to apply the new standard concentration y=1.2006x+11.252, $R^2$=0.9423. Showing a slightly lower value compared with orignal method. Because of the concentration in the value of more than 240 U/ml, but it is an overall value that can be made out of a similar value. When I put the man 25 ul y=0.6012x+24.755, $R^2$=0.4033. Results showed that very small amounts of sample are insecure inside and showed a lower middle cpm orignal method and showed a lot of mismatched. Conclusions: 25 ul of the sample volume is not possible to use the instability had, when I put the 50 ul of the orignal method can be used to show a similar concentration. The new values are slightly lower concentration, The new values are slightly lower concentration, concentration, which are likely due to the lack of data has had a little gap between the sample showed 80 to 200 U/ml additional experiments seem to do. Apply a new 100 ul concentration values are applied to a large crowd is not even in sight. But this way the concentration of 100 to more 400 U/ml gather further experiments should possible adds.

• 간호행정학회지
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• 제13권2호
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• pp.156-166
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• 2007

Purpose: The purpose of the present study was to examine the causal relationships among hospital nursing organizational characteristics (organizational climate, workload), individual characteristics (experience, education) and outcome variables (job satisfaction, job stress, task performance) by constructing and testing a conceptual framework. Method: Five large general hospitals located in Seoul were selected to participated. The total sample of 245 registered nurses represents a response rate of 94 percent. Data for this study was collected from January to February in 2006 by questionnaire. Path analyses with LISREL program were used to test the fit of the proposed model to the data and to examine the causal relationships among variables. Result: Both the proposed model and the modified model fit the data excellently. The model revealed relatively high explanatory power of work stress (40%), job satisfaction (46%) and task performance (27%) by predicted variables. In predicting work stress, job satisfaction and task performance, the finding of this study clearly demonstrate organizational climate might be the most important variable. Conclusion: Based on the findings of the study, it was suggested that desirable organizational climate was needed to increase the nurses' mental and physical health as well as qualified task performance.

• 대한간호학회지
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• 제32권5호
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• pp.643-653
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• 2002

The purpose of this study was to identify factors that influence the functional status of chronic lung disease patients. Method: A descriptive, correlational study design was used. The study was conducted at the outpatient respiratory clinic of the large university hospital in Korea. A convenience sample of 128 chronic lung patients (age = 64.2 yrs; 106 COPD, 17 bronchiectasis, 5 DILD) with mean FEV1 64.4 % predicted. Functional status was measured with SIP. Physical variables (FEV1% predicted, dyspnea, fatigue, pulmonary symptom distress), psychological variables (mood, stress), and situational variable (sleep quality) were examined. Dyspnea was measured by the BDI, fatigue was measured with the MFI. Mood was measured with the modified Korean version of POMS. Sleep quality was measured with the Pittsburgh Sleep Quality Index. Potential independent variables for the regression were age, gender, years since diagnosis, FEV1% predicted, dyspnea, fatigue, pulmonary symptom distress, stress, and sleep quality. Result: In general, functional status was relatively good. In regression analysis, functional status were significantly influenced by dyspnea, mood, age and fatigue. These variables explained 70 % of the variances in functional status. Conclusion: The results suggest that psychophysiologic symptom management should be a focus to enhance the functional status in this group.