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34 results on '"Yee, K.J."'

4. Optical studies of carrier and phonon dynamics in Ga(sub 1-x)Mn(sub x)As

Author

Yee, K.J., Lee, D., Liu, X., Lim, W.L., Donrowolska, M., Furdyna, J.K., Y.S. Lim, K.G. Lee, Ahn, Y.H., and Kim, D.S.

Subjects
Phonons -- Atomic properties, Gallium arsenide -- Atomic properties, Physics
Abstract

A time-resolved optical study of the dynamics of carriers and phonons in Ga(sub 1-x)Mn(sub x)As layers for a series of Mn and hole concentrations. The direct observation on lattice vibrations in Ga(sub 1-x)Mn(sub x)As layers through the reflective electro-optic sampling technique.

Published
2005

5. Development and validation of liquid chromatography tandem mass spectrometry method quantitative determination of polymyxin B1, polymyxin B2, polymyxin B3 and isoleucine-polymyxin B1 in human plasma and its application in clinical studies

Author

Yee K.J. Leaw, Kim Hor Hee, Lawrence S. Lee, and Jun L. Ong

Subjects
Polymyxin B1, Formic acid, Clinical Biochemistry, Pharmaceutical Science, Tandem mass spectrometry, Mass spectrometry, 030226 pharmacology & pharmacy, 01 natural sciences, Analytical Chemistry, 03 medical and health sciences, chemistry.chemical_compound, 0302 clinical medicine, Tandem Mass Spectrometry, Liquid chromatography–mass spectrometry, Drug Discovery, medicine, Humans, Protein precipitation, Polymyxins, Isoleucine, Spectroscopy, Chromatography, 010401 analytical chemistry, Selected reaction monitoring, 0104 chemical sciences, chemistry, Polymyxin B, Chromatography, Liquid, medicine.drug
Abstract

Polymyxin B (PB) is an antibiotic consisting of a cyclic heptapeptide and a tripeptide side chain used in treatment of infections caused by Gram-negative bacteria. Commercial formulations of PB contain multiple structurally related components with major constituents of PB1, PB2, PB3 and ile-PB1. To understand the pharmacokinetics of these major components, we have developed and validated a LC-MS/MS method to quantify PB1, PB2, PB3 and ile-PB1 in human plasma. PB was extracted from plasma by protein precipitation using trichloroacetic acid followed by chromatographic separation on Zorbax Bonus-RP column (100mm×2.1mm, 1.8μm) using stepwise gradient elution of water containing 0.1% of formic acid and 0.1% of trichloroacetic acid (mobile phase A) and 90% acetonitrile with 0.1% formic acid (mobile phase B). Despite of structural similarities, these PBs were completely resolved in the analytical run time of 6.5min. Detection and quantification of PBs were performed by selected reaction monitoring (SRM) under positive ionization mode in the mass spectrometer. Separation of PB1 and ile-PB1, as well as PB2 and PB3, before quantification is crucial because they are structural isomers detected based the same SRM. Excellent linearity was achieved (r2>0.99) in the calibration curves of PB. The developed method was accurate (95.3-111.7%) and precise (CV

Published
2017
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12. Microstructure, magnetic, and spin-dependent transport properties of (Zn,Cr)Te films fabricated by magnetron sputtering

Author

Wang, Weigang, Yee, K.J., Kim, Dongho, Han, Kangjeon, Wang, Xiangrong, Ni, Chaoying, Moriyama, Takahiro, Mathew, Anoop, Opila, Robert L., Zhu, Tao, Xiao, John Q., Wang, Weigang, Yee, K.J., Kim, Dongho, Han, Kangjeon, Wang, Xiangrong, Ni, Chaoying, Moriyama, Takahiro, Mathew, Anoop, Opila, Robert L., Zhu, Tao, and Xiao, John Q.

Abstract

Chromium doped zinc telluride thin films with various doping concentrations are fabricated by magnetron sputtering. These films are ferromagnetic and the Curie temperature increases with Cr concentration. X-ray diffraction, transmission electron microscopy, and magnetic circular dichroism characterizations show that the films are free of Cr1-xTex impurities and the ferromagnetism is intrinsic. The transport study shows that the resistivity and magnetoresistance are governed by variable range hopping at low temperatures. A negative magnetoresistance as large as -57% is observed at 5 K. The magnetoresistance and its temperature dependence can be well explained by a model involving an increase in the localization length of carriers with a magnetic field in the hopping region. An anomalous Hall effect is also observed and a possible origin of the sign difference between the anomalous Hall resistance and ordinary Hall resistance is discussed.

Published
2008

33. Photoluminescence of high energy Ar+-irradiated SrTiO3 single crystal

Author

Sung, K.D., Kumar, Ravi, Pratap Singh, Abhinav, Kim, C.S., Yee, K.J., and Jung, J.H.

Subjects
*PHOTOLUMINESCENCE, *FORCE & energy, *ION bombardment, *STRONTIUM compounds, *MOLECULAR structure, *ELECTRON microscopy, *AMORPHOUS substances, *ELECTRIC conductivity
Abstract

Abstract: We report the structural and photoluminescence characteristics of a high energy Ar+-irradiated SrTiO3 single crystal. High resolution X-ray reciprocal space mapping, cross-section scanning electron microscopy and photoluminescence measurements suggest that thick amorphous and oxygen-deficient SrTiO3 layers are formed after irradiation. Due to the highly accelerated Ar+ (∼100keV), electrical conductivity of the oxygen-deficient SrTiO3 layer seems to be highly reduced, which results in the absence of 440nm (blue-light) emission at 300K, and broad and weak 380nm emission at 20K. [Copyright &y& Elsevier]

Published
2010
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34. Structural and magnetic properties of Ge0.7Mn0.3 thin films

Author

Kim, Sung-Kyu, Son, Jong Yeog, Shin, Young-Han, Jo, Moon-Ho, Park, S., Hong, Tae Eun, and Yee, K.J.

Subjects
*GERMANIUM alloys, *METALLIC films, *CHEMICAL structure, *MAGNETIC properties of thin films, *MAGNETRON sputtering, *SUBSTRATES (Materials science), *TRANSITION temperature, *FERROMAGNETISM
Abstract

Abstract: Ge0.7Mn0.3 thin films were fabricated on Al2O3 (0001) and glass substrates at growth temperatures ranging from room temperature to 500 °C by a radio frequency magnetron sputtering. We found that the Ge0.7Mn0.3 thin films showed a polycrystalline-to-amorphous transition at about 360 °C, and the ferromagnetic transition temperature of each thin film depends on its structure — crystalline or amorphous states. Particularly, the Ge0.7Mn0.3 thin films showed room temperature ferromagnetism when they were fabricated at temperatures above the crystallization temperature. [Copyright &y& Elsevier]

Published
2010
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