• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1593-1603
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• 2023

In deterministic and Monte Carlo transport codes, b-delayed emission is included using a group structure where all of the precursors are grouped together in 6 groups or families, but given the increase in computational power, nowadays there is no reason to keep this structure. Furthermore, there have been recent efforts to compile and evaluate all the available b-delayed neutron emission data and to measure new and improved data on individual precursors. In order to be able to perform a transient Monte Carlo simulation, data from individual precursors needs to be implemented in a transport code. This work is the first step towards the development of a tool to explore the effect of individual precursors in a fissile system. In concrete, individual precursor data is included by expanding the capabilities of the open source Monte Carlo code OpenMC. In the modified code - named Time Dependent OpenMC or OpenMC(TD)- time dependency related to β-delayed neutron emission was handled by using forced decay of precursors and combing of the particle population. The data for continuous energy neutron cross-sections was taken from JEFF-3.1.1 library. Regarding the data needed to include the individual precursors, cumulative yields were taken from JEFF-3.1.1 and delayed neutron emission probabilities and delayed neutron spectra were taken from ENDF-B/VIII.0. OpenMC(TD) was tested in a monoenergetic system, an energy dependent unmoderated system where the precursors were taken individually or in a group structure, and in a light-water moderated energy dependent system, using 6-groups, 50 and 40 individual precursors. Neutron flux as a function of time was obtained for each of the systems studied. These results show the potential of OpenMC(TD) as a tool to study the impact of individual precursor data on fissile systems, thus motivating further research to simulate more complex fissile systems.

• 한국세라믹학회지
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• 제53권3호
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• pp.317-324
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• 2016

Continued miniaturization and increasingly exact requirements for thin film deposition in the semiconductor industry is driving the search for new effective, efficient, selective precursors and processes. The requirements of defect-free, conformal films, and precise thickness control have focused attention on atomic layer deposition (ALD). ALD precursors so far have been developed through a trial-and-error experimental approach, leveraging the expertise and tribal knowledge of individual research groups. Precursors can show significant variation in performance, depending on specific choice of co-reactant, deposition stage, and processing conditions. The chemical design space for reactive thin film precursors is enormous and there is urgent need for the development of computational approaches to help identify new ligand-metal architectures and functional co-reactants that deliver the required surface activity for next-generation thin-film deposition processes. In this paper we discuss quantum mechanical simulation (e.g. density functional theory, DFT) applied to ALD precursor reactivity and state-of-the-art automated screening approaches to assist experimental efforts leading toward optimized precursors for next-generation ALD processes.

• Animal Bioscience
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• 제34권10호
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• pp.1684-1694
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• 2021

Objective: This study investigated the association between feed efficiency, physicochemical properties, flavor precursors and biomolecules in the thigh meat of Korat (KR) chickens. Methods: The feed intake and body weight of individual male KR chickens were recorded from 1 to 10 weeks old to calculate the individual residual feed intake (RFI) of 75 birds. At 10 weeks of age, chickens with the 10 highest (HRFI) and lowest RFI (LRFI) were slaughtered to provide thigh meat samples. The physicochemical properties (ultimate pH, water holding capacity [WHC], drip loss) and flavor precursors (guanosine monophosphate, inosine monophosphate (IMP), adenosine monophosphate and inosine) were analyzed conventionally, and Fourier transform infrared spectroscopy was used to identify the composition of biomolecules (lipids, ester lipids, amide I, amide II, amide III, and carbohydrates) and the secondary structure of the proteins. A group t-test was used to determine significant differences between mean values and principal component analysis to classify thigh meat samples into LRFI and HRFI KR chickens. Results: The physicochemical properties of thigh meat samples from LRFI and HRFI KR chickens were not significantly different but the IMP content, ratios of lipid, lipid ester, protein (amide I, amide II) were significantly different (p<0.05). The correlation loading results showed that the LRFI group was correlated with high ratios of lipids, lipid esters, collagen content (amide III) and beta sheet protein (rg loading >0.5) while the HRFI group was positively correlated with protein (amide I, amide II), alpha helix protein, IMP content, carbohydrate, ultimate pH and WHC (rg loading >0.5). Conclusion: The thigh meat from chickens with different RFI differed in physiochemical properties affecting meat texture, and in the contents of flavor precursors and biomolecules affecting the nutritional value of meat. This information can help animal breeders to make genetic improvements by taking more account of traits related to RFI.

• Bulletin of the Korean Chemical Society
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• 제25권2호
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• pp.243-248
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• 2004

As diverse synthetic precursors of cyclic adenosine diphosphate ribose (cADPR), several adenosine derivatives in which azido or amino group is introduced at 2'- or 3'-position of the sugar moiety of adenosine were prepared from readily available adenosine via conventional protocols. These synthetic sequence employs very efficient reactions conditions that proceed at or below ambient temperature with actual yields of >80% for each individual step.

• Journal of Plant Biology
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• 제36권3호
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• pp.293-296
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• 1993

Effects of dark treatment and N1-dichlorophenyl-N3-dimethylurea (DCMU) on the desaturation of galactolipids of Dunaliella salina were investigated to see whether light-driven photosynthetic electron transport is involved in in vivo desaturation of galactolipids. The incorporation of radioactive fatty acid precursors ([14C]lauric acid) into galactolipids, mainly composed of prokaryotic molecular species, was most affected among different polar lipid classes by both treatments. The analysis of specific radioactivities of individual galactolipid molecular species revealed that their synthesis was greatly inhibited by the treatments except for eukaryotic molecular species, 18 : 3/ 18 : 3 digalactosyldiacylglycerol, whose desaturation occurs in endoplasmic reticulum.

• 대한간호학회지
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• 제44권2호
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• pp.198-208
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• 2014

Purpose: This research was an empirical study designed to identify precursors and interaction effects related to nurses' patient identification behavior. A multilevel analysis methodology was used. Methods: A self-report survey was administered to registered nurses (RNs) of a university hospital in South Korea. Of the questionnaires, 1114 were analyzed. Results: The individual-level factors that had a significantly positive association with patient identification behavior were person-organization value congruence, organizational commitment, occupational commitment, tenure at the hospital, and tenure at the unit. Significantly negative group-level precursors of patient identification behavior were burnout climate and the number of RNs. Two interaction effects of the person-organization value congruence climate were identified. The first was a group-level moderating effect in which the negative relationship between the number of RNs and patient identification behavior was weaker when the nursing unit's value congruence climate was high. The second was a cross-level moderating effect in which the positive relationship between tenure at the unit and patient identification behavior was weaker when value congruence climate was high. Conclusion: This study simultaneously tested both individual-level and group-level factors that potentially influence patient identification behavior and identified the moderating role of person-organization value congruence climate. Implications of these results are discussed.

• 분석과학
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• 제8권4호
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• pp.807-814
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• 1995

Accurate measurements of ozone precursors are required to understand the process and extent of ozone formation in rural and urban areas. Nonmethane hydrocarbons (NMHCs) have been identified as important ozone precursors. Identification and quantification of NMHCs are difficult because of the large number present and the wide molecular weight range encountered in typical air samples. A major plan of the research team of the Climate and Air Quality Taiwan Station (CATs) was the measurement of atmospheric nonmethane hydrocarbons. An analytical method has been development for the analysis of the individual nonmethane hydrocarbons in ambient air at ppb (v) and subppb(v) levels. The whole ambient air samples were collected in canisters and analyzed by GC-FID with $Al_2O_3$/KCl PLOT column. Our targeted for quantitative analysis 43 compounds that may be substantial contributors to ozone formation. The retention indices and molar response factors of some commercially available $C_2{\sim}C_{10}$ hydrocarbons were determined and used to identify and quantify air samples. A quality assurance program was instituted to ensure that good measurements were made by participating in the International Nonmethane Hydrocarbon Intercomparison Experiments (NOMHICE).

• Mass Spectrometry Letters
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• 제5권2호
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• pp.35-41
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• 2014

Gas chromatography-mass spectrometry (GC-MS) methods have been used extensively in clinical steroid analyses. Evaluating the metabolic ratios of precursors to products by accurate quantification of individual steroid levels in biological samples can reveal the activities of enzymes associated with steroid metabolism. This review article discusses the impact of GC-MS-based steroid profiling on our understanding of the biochemical role of steroids and their metabolic enzymes in hormone-dependent diseases, such as congenital adrenal hyperplasia (CAH), cortisol-mediated hypertension, apparent mineralocorticoid excess (AME), male-pattern baldness, and breast and thyroid cancers. Steroid profiling is a comprehensive analytical technique that can be applied whenever the highest specificity is required and may be a reasonable initial diagnostic approach.

• 한국자기학회지
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• 제5권5호
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• pp.589-596
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• 1995

In the present paper some of the magnetic properties of the nanocrystalline Fe-based magnets produced by an appropriate annealing of their metallic glass precursors are reviewed. These properties are discussed on the grounds of their characteristics measured at the elevated temperatures. It is shown that the effective magnetostriction these magnets display, results from the competition among two contributions of the opposite sign originating from the individual magnetic phases, crystalline phase and the residual glassy matrix in which the nanocrystallites are embedded. It is also shown that at certain conditions the magnets considered expose superparamagnetic behavior and that their isothermal magnetization characteristics can successfully be used to calculate the distribution of the particle volumes. Application of the recently invented new genetic algorithm method, a powerful tool to calculate these distributions is, finally, presented.

• 한국연초학회지
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• 제30권1호
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• pp.33-38
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• 2008

This study was carried out to determine the analytical methods for heterocyclic amines(HAs) of the tobacco smoke by LC/MS/MS. HAs have been found in pyrolysate of protein and cooked food including protein, were known the Sugimura compound. HAs content of the smoke were known to exist very low ppb level. Especially, some of HAs are mutagenic and carcinogenic compounds. In according to IARC, the toxicity of N-heterocyclic amines classified IARC class 2A or 2B group. Precursors of these compounds are glutamic acid, protein and free amino acids including tryptophan, therefore, the precursors have been proved in cooked food continuously. This study was investigate multiple analysis methods for HAs and HAs contents of some commercial products. In this study, we used the linear type smoking machine for HAs analysis. At the ISO conditions, mainstream smoke was collected on cambridge filter pad, and then cambridge filter pad was extracted by 0.1% acetic acid. The extracted solution were passed cation exchange SPE cartridge to remove matrix, samples were analyzed using LC/MS/MS on MRM mode. From the result that optimized this methods, the correlation coefficient(R) of the individual compounds were good linearity over 0.999, recovery rate over 96% and the limit of detection were good values between 0.06 to 0.37 ng/mL, In addition, HAs content of some commercial products were in range of 0.02 to 43.8 ng/cig.