• Animal Bioscience
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• 제36권6호
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• pp.869-878
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• 2023

Objective: Hyperketonemia remains a major metabolic issue of serious milk production and a major health concern in early lactation cows. Oral supplementation of glucose precursors (GP) can be used to prevent hyperketonemia in dairy cows. The objective of this study was to compare the beneficial effects of orally supplementing a mixture of GP on metabolic health indicators and milk production status of primiparous (PP) and multiparous (MP) dairy cows. Methods: Twenty-eight Holstein cows were blocked by expected date of parturition, previous lactation yield, and parity. The cows were randomly allocated to one of the four treatment groups (n = 7 cows/group) based on their parity and GP supplementation: i) PP cows fed basal diet only (PP-CON), ii) PP cows with oral supplementation of GP (PP-GP), iii) MP cows fed basal diet only (MP-CON), and iv) MP cows with oral supplementation of GP (MP-GP). Glucose precursor (glycoline liquid) was orally drenched (300 mL/d) in GP cows from 7 days prepartum through 7 days postpartum. Other than GP supplementation, all cows were fed similar pre- and postpartum basal diets. Results: In both pre- and postpartum periods, serum glucose concentration was increased, whereas β-hydroxybutyrate and free fatty acids were decreased in GP cows compared with the CON cows. Milk yield and milk components were statistically not different between GP and CON cows over the first 9 week of lactation. The yield of actual milk, energy-corrected milk, 63-days cumulative milk, colostrum yield, and calf birth weight remained higher in MP cows compared with PP cows. Conclusion: Oral drenching of GP around calving can be recommended to successfully improve the metabolic health and reduce the negative effects of hyperketonemia not only in MP but also in PP dairy cows.

• Carbon letters
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• 제28권
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• pp.47-54
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• 2018

High surface carbon aerogels with hierarchical and tunable pore structure were prepared using ionic liquid as carbon precursor via a simple salt templating method. The as-prepared carbon aerogels were characterized by nitrogen sorption measurement and scanning electron microscopy. Through instant visual observation experiments, it was found that salt eutectics not only serve as solvents, porogens, and templates, but also play an important role of foaming agents in the preparation of carbon aerogels. When the pyrolyzing temperature rises from 800 to $1000^{\circ}C$, the higher temperature deepens the carbonization reaction further to form a nanoporous interconnected fractal structure and increase the contribution of super-micropores and small mesopores and improve the specific surface area and pore volume, while having few effects on the macropores. As the mass ratio of ionic liquid to salt eutectics drops from 55% to 15%, that is, the content of salt eutectics increases, the salt eutectics gradually aggregate from ion pairs, to clusters with minimal free energy, and finally to a continuous salt phase, leading to the formation of micropores, uniform mesopores, and macropores, respectively; these processes cause BET specific surface area initially to increase but subsequently to decrease. With the mass ratio of ionic liquids to salts at 35% and carbonization temperature at $900^{\circ}C$, the specific surface area of the resultant carbon aerogels reached $2309m^2g^{-1}$. By controlling the carbonization temperature and mass ratio of the raw materials, the hierarchically porous architecture of carbon aerogels can be tuned; this advantage will promote their use in the fields of electrodes and adsorption.

• 한국재료학회지
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• 제24권7호
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• pp.351-356
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• 2014

A spherical $Sr_4Al_{14}O_{25}:Eu^{2+}$ phosphor for use in white-light-emitting diodes was synthesized using a liquid-state reaction with two precipitation stages. For the formation of phosphor from a precursor, the calcination temperature was $1,100^{\circ}C$. The particle morphology of the phosphor was changed by controlling the processing conditions. The synthesized phosphor particles were spherical with a narrow size-distribution and had mono-dispersity. Upon excitation at 395 nm, the phosphor exhibited an emission band centered at 497 nm, corresponding to the $4f^65d{\rightarrow}4f^7$ electronic transitions of $Eu^{2+}$. The critical quenching-concentration of $Eu^{2+}$ in the synthesized $Sr_4Al_{14}O_{25}:Eu^{2+}$ phosphor was 5 mol%. A phosphor-converted LED was fabricated by the combination of the optimized spherical phosphor and a near-UV 390 nm LED chip. When this pc-LED was operated under various forward-bias currents at room temperature, the pc-LED exhibited a bright blue-green emission band, and high color-stability against changes in input power. Accordingly, the prepared spherical phosphor appears to be an excellent candidate for white LED applications.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권9호
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• pp.423-429
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• 2002

RuOx thin films were fabricated by the method of liquid delivery MOCVD using Ru(C$_{8}$ $H_{13}$ $O_2$)$_3$ as the precursor and their thermal effects and conductivity were investigated. Ru films deposited at 25$0^{\circ}C$ were annealed at $650^{\circ}C$ for 1min with Ar, $N_2$ or N $H_3$ ambient. The changes of the micro-structure, the surface morphology and the electrical resistivity of the Ru films after annealing were studied. Ar gas was more effective than $N_2$ and N $H_3$ gases as an ambient gas for the post annealing of the Ru films, because of smaller resistivity and denser grains. The X-ray diffraction and X-ray photoelectron spectroscopy results indicate that the Ru $O_2$ phase and the silicidation are not observed regardless of the ambient gases. The minimum resistivity of the Ru film is found to have the value of 26.35 $\mu$Ω-cm in Ar ambient. Voids were formed at Ru/TiN interface of the Ru layer after annea1ing in $N_2$ ambient. The $N_2$ gas generated due to the oxidation of the TiN layer accumulated at the Ru/TiN interface, forming bubbles; consequently, the stacked film may peel off the Ru/TiN interface.e.

• 한국환경농학회지
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• 제34권3호
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• pp.230-237
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• 2015

BACKGROUND: To identify the sources of inaccuracy in LC/MS/MS methods used in the routine quantitation of small molecules are described and discussed. METHODS AND RESULTS: Various UPLC coupled to triple quadrupole mass spectrometer and time of flight (TOF) were used to identify the potential sources of inaccuracy and inducing the pitfalls of qualification and quntitation during the veterinary drug residue analysis. Some of stable isotope labelled veterinary drugs, which were used as internal standards, presented "cross-talk", regardless of manufactures of mass spectrometer and types of spectrometer. Group of sulfonamides also presented inaccuracy qualification and quantitation due to the multi-residue analytical method with the same fragment ions at the close retention times. CONCLUSION: The phenomena of "cross-talk" occurring between subsequently monitored transition from stable isotope labelled and isotope non-labelled authentic chemical were identified. To prevent errors and achieve more accurate data during the analysis of small molecules by LC/MS/MS SRM method, Followings should be taken care of and kept checking; purity and concentration of stable isotope as an internal standard, prevention of carry-over during the separation in column, minimizing the ion suppression by matrix effect, identification of retention time, precursor ion and product ion, and full knowledge of data processing including smoothing and peak integration.

• Biomolecules & Therapeutics
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• 제27권2호
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• pp.193-200
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• 2019

Ceramide metabolism is known to be an essential etiology for various diseases, such as atopic dermatitis and Gaucher disease. Glucosylceramide synthase (GCS) is a key enzyme for the synthesis of glucosylceramide (GlcCer), which is a main ceramide metabolism pathway in mammalian cells. In this article, we developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine GCS activity using synthetic non-natural sphingolipid C8-ceramide as a substrate. The reaction products, C8-GlcCer for GCS, could be separated on a C18 column by reverse-phase high-performance liquid chromatography (HPLC). Quantification was conducted using the multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m/z $588.6{\rightarrow}264.4$ for C8-GlcCer at positive ionization mode. The calibration curve was established over the range of 0.625-160 ng/mL, and the correlation coefficient was larger than 0.999. This method was successfully applied to detect GCS in the human hepatocellular carcinoma cell line (HepG2 cells) and mouse peripheral blood mononuclear cells. We also evaluated the inhibition degree of a known GCS inhibitor 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) on GCS enzymatic activity and proved that this method could be successfully applied to GCS inhibitor screening of preventive and therapeutic drugs for ceramide metabolism diseases, such as atopic dermatitis and Gaucher disease.

• Progress in Superconductivity
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• 제4권1호
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• pp.94-98
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• 2002

Two kinds of multifilament Bi-2223／Ag tapes, which are different in the precursor calcination temperatures, were heat treated for different time (12, 20, 30, 50, 70, or 100 h) firstly to obtain varied B2223 contents, and then followed by the same pressing and sintering cycles. The relation of the 2223 phase contents after the first sintering and the transport property of the fully processed tapes was studied. The results show that 75-80% 2223 phase formed in tapes before the first cold pressing is beneficial to get a high $I_{c}$ in the final tapes. Compensating the total heat treatment time of the tapes first sintered for 20 h to the same length as that first sintered for 50 h in the subsequent sintering stages, different $I_{c}$ enhancements were observed in these two tapes. No improvement on $I_{c}$ was found in the tape made from the powder calcined at higher temperature, whereas for the tape prepared with the lower temperature calcined powder, the $I_{c}$ was increased to the same level as that first sintered for 50 h. The 2223 contents before the intermediate mechanical work is related to the residual reactants, especially to the liquid phase, which is of vital importance to the phase conversion and healing microcracks, meanwhile, to the size and distribution of the non-superconducting secondary phases. The lower temperature calcined powder resulted in slow formation of 2223 phase, but also provided more reactants and liquid phase for the further phase conversion, as a consequence, for the Improvement of $I_{c}$. c/.

• Mass Spectrometry Letters
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• 제5권2호
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• pp.42-48
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• 2014

A specific and sensitive liquid chromatography-electrospray ionization tandem mass spectrometry method (LC-ESI-MS/MS) was developed and validated for the simultaneous quantification of porphyrins (coproporphyrin, pentacarboxylporphyrin, hexacarboxylporphyrin, heptacarboxylporphyrin, and uroporphyrin) in human plasma and urine. Acidified plasma samples and urine samples were prepared by using liquid-liquid extraction using ethyl acetate and protein precipitation with acetonitrile, respectively. The separation was achieved onto a Synergi Fusion RP column ($150mm{\times}2.0mm$, $4{\mu}m$) with a gradient elution of mobile phase A (0.1% formic acid in 2 mmol/L ammonium acetate, v/v) and mobile phase B (20% methanol in acetonitrile, v/v) at a flow rate of $450{\mu}L$/min. Porphyrins and the internal standard (IS), coproporphyrin I-$^{15}N_4$, were detected by a tandem mass spectrometer equipped with an electrospray ion source operating in positive ion mode. Multiple reaction monitoring (MRM) transitions of the protonated precursor ions and the related product ions were optimized to increase selectivity and sensitivity. The proposed method was validated by assessing selectivity, linearity, limit of quantification (LOQ), precision, accuracy, recovery, and stability. The calibration curves were obtained in the range of 0.1-100 nmol/L and the LOQs were estimated as 0.1 nmol/L for all porphyrins. Results obtained from the validation study of porphyrins showed good accuracy, precision, recovery, and stability. Finally, the proposed method was successfully applied to clinical studies on the autism spectrum disorder (ASD) diagnosis of 203 Korean children.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1990년도 제2차 학술발표초록집
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• pp.36-37
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• 1990

In the past, facile dissolution of cellulose has been hampered by the lack of suitable nondegrading solvents. Recently, this problem has been solved in our laboratory by the discovery of an inexpensive, convenient solvent system, that is the mixture of $NH_3\;and\;NH_4SCN$, for cellulose. Also, the $cellulose/NH_3/NH_4SCN$ solution system has been found to form the anisotropic, i.e., liquid crystalline phase. It is believed that both the cholesterio and the nematic phase occur. This finding has prompted extensive on-going researoh on the formation of the liquid crystalline phase from an inexpensive natural source such as cellulose since the nematic phase is envisioned as an excellent precursor sources for products with desirable properties, for example, high modulus and high strength. This interest naturally leads to a desire to understand the theological properties of the nematic phase so that the transformation of the nematic phase to the solid state with desirable properties can be efficiently accomplished, ;From this point of view, the theological behavior of the $cellulose/NH3_/NH_4SCN$ system has been studied as a function of shear rate and shear stress over a wide range of solvent compositions, cellulose concentration, centrifugation and urea contents, Results indicate that the viscosity decreases with increasing shear rate. A marked shear thinning behavior and a quasi-Newtonian behavior were observed in the low shear rate region and in the high shear rate region, respectively for all solvent compositions. The $cellulose/NH_3/NH_4SCN$ solution system only exhibited the viscosity increase with increasing cellulose concentration and failed to show the viscosity drop generally observed at the point of incipience of liquid crystal formation, This may be due to the gel-like nature of the solution by the association of the rodlike molecules into bundles which may serve as crosslinking points giving the cellulose solution a network structure. Also, simply hydrogen bonding may be so restrictive of molecular mobility that a viscosity drop is blocked. In addition to the above results, yield stress and thixotropy were also observed in the $cellulose/NH_3/NB_4SCN$ solution system which are characteristics of liquid crystal and gel, The results of the effect of centrifugation on viscosity show that viscosity decreases by the application of centrifugation. This may be explained by the change of the piled polydomain structure to the dispersed polydomain structure due to the pressure gradient generated during centrifugation.ation.

• 분석과학
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• 제20권2호
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• pp.138-146
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• 2007

본 연구에서는 비글견 혈장 중의 파록세틴을 액체상추출법(LLE)으로 전처리하고 액체크로마토그래피-탠덤질량분석기(LC-MS/MS)로 신속하게 분석하는 방법을 개발하였다. 파록세틴과 내부표준물질로 사용한 플루오세틴을 TBME(tert-butyl methyl ether)로 추출하고 상층액을 취하여 건조시킨 후, 이동상 $100{\mu}L$로 재분산하여 LC-MS/MS에 주입하였다. HPLC 분석조건으로 Capcell Pak UG120($2.0{\times}150mm$, $5{\mu}m$) 컬럼을 사용하였으며, 이동상은 50% 아세토니트릴(pH 3, formic acid로 조정) 용액을 사용하였고, 유량은 0.2 mL/min으로 하였다. MS/MS의 SRM(selective reaction monitoring) 방법으로 파록세틴과 플루오세틴의 선구 이온, 생성 이온을 각각 m/z $330{\rightarrow}192$, m/z $310{\rightarrow}148$로 분석한 결과 0.02~5 ng/mL의 농도범위에서 상관계수($R^2$) 0.9993으로 좋은 직선성을 나타내었다. 또한 정량한계는 0.02 ng/mL이며, 정밀성은 일내 및 일간 변동계수가 7.67% 이하이고, 정확도는 92.96~102.99%로 비글견 혈장 중의 파록세틴의 약물동력학 연구에 이용될 수 있는 충분한 감도와 특이성, 직선성, 정밀성 및 정확성을 갖고 있음을 확인하였다.