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41.
Naeem Khan Nargis Jamila Yun MiDang Cheong Mi Lee Yu Min Park Ga Hyun Lee 《Analytical letters》2017,50(15):2426-2446
This study reports the concentrations of eight trace essential (Zn, Mn, Cu, Ni, Cr, Co, V, and Se) and four toxic elements (Pb, As, Cd, and Hg) in commonly consumed stone fruits from South Korea. The samples were digested by microwave-induced combustion and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of mercury were analyzed by direct mercury analysis (DMA). The analytical techniques were validated by linearity, limits of detection and quantification, precision, recovery, and for accuracy by analyzing a spinach leave-certified reference material; satisfactory results were obtained in all cases. The concentrations of essential trace elements varied considerably among the stone fruits. Generally stone fruits contained comparatively high concentrations of Zn (0.946 to 7.86?µg/g) and Mn (below the limit of detection to 1.66?µg/g), while lower contents of Cu (0.214 to 1.24?µg/g), Cr (0.032 to 0.114?µg/g), Ni (0.006 to 0.091?µg/g), Co (0.004 to 0.016?µg/g), V (below the limit of detection to 0.023?µg/g), and Se (0.0002 to 0.005?µg/g) were obtained. The concentrations (µg/g) of toxic metals were 0.007 (peach) to 0.016 (cherry) for Pb, 0.001 (plum) to 0.007 (cherry) for As, 0.002 (apricot and cherry) to 0.003 (peach) for Cd, and 0.0003 (peach) to 0.0016 (jujube) for Hg. The values for the estimated dietary intakes, target hazard quotients, and hazard indices were lower than the recommended safety limits by World Health Organization. Therefore, the analyzed stone fruits were deemed to be safe for human consumption. 相似文献
42.
Zou L Cheong WL Chung WH Leung YC Wong KY Wong MK Chan PH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(45):13367-13371
Herein is described the development of a novel switch-on fluorescence assay for detecting β-lactamases. The fluorescence assay comprises two components: solid beads coated with a β-lactam antibiotic, which is linked to an environment-sensitive fluorophore (dansylaminothiophenol, DTA), and amyloid fibrils of hen lysozyme (acting as fluorescence enhancer and visual tool). In the presence of the clinically significant TEM-1 β-lactamase, the DTA-antibiotic complex on the solid beads is hydrolyzed, thus releasing the DTA dye into solution. The DTA dye is only weakly fluorescent in solution but gives strong green fluorescence upon binding to lysozyme fibrils. These strongly fluorescent DTA-bound fibrils can be easily visualized by the naked eye upon illumination of the sample with a simple UV lamp. The fluorescence assay can detect TEM-1 at low concentration (0.01 nM). In contrast, no observable fluorescence appears when the fluorescence assay is performed on samples without the TEM-1 β-lactamase. 相似文献
43.
Shen ZL Goh KK Cheong HL Wong CH Lai YC Yang YS Loh TP 《Journal of the American Chemical Society》2010,132(45):15852-15855
The first water-tolerant, ketone-type indium homoenolate was synthesized via the oxidative addition of In/InCl(3) to enones. The reaction proceeds exclusively in aqueous media. Both indium and indium(III) chloride are necessary for the smooth conversion of the reaction. Similar results were obtained when InCl or InCl(2) was used in place of In/InCl(3). The synthetic utility of the indium homoenolate was demonstrated through the synthesis of 1,4-dicarbonyl compounds via palladium-catalyzed coupling of indium homoenolate with acid chloride. 相似文献
44.
Electrospinning fabrication and characterization of poly(vinyl alcohol)/montmorillonite/silver hybrid nanofibers for antibacterial applications 总被引:1,自引:0,他引:1
Jae Hyeung Park Mohammad Rezaul Karim In Kyo Kim In Woo Cheong Jong Won Kim Do Gyu Bae Jin Won Cho Jeong Hyun Yeum 《Colloid and polymer science》2010,288(1):115-121
Poly(vinyl alcohol) (PVA)/montmorillonite clay (MMT)/silver (Ag) nanoparticles have been electrospun for fabricating PVA/MMT/Ag
nanofiber in aqueous solutions. Since PVA is a water-soluble and biocompatible polymer, it is one of the best materials for
preparation of antibacterial nanofiber. MMT has been used as an inorganic filler to enhance properties of homopolymeric nanofiber.
The PVA/MMT/Ag nanofiber diameter increases with increasing contents of MMT clay and Ag nanoparticles. In preservation test,
the PVA/MMT/Ag nanofiber confirms an excellent antibacterial performance, elucidating for practical uses as a new preservative.
Moreover, the PVA/MMT/Ag nanofiber shows improved thermal properties. 相似文献
45.
Jae Chul Cheong Sung Ill Suh Beom Jun Ko Jin Young Kim Moon Kyo In Won Jo Cheong 《Journal of separation science》2010,33(12):1767-1778
A simple and rapid GC‐MS method has been developed for the screening and quantification of many illicit drugs and their metabolites in human urine by using automatic SPE and trimethylsilylation. Sixty illicit drugs, including parent drugs and their metabolites that are possibly abused in Korea, can be monitored by this method. Among them, 24 popularly abused illicit drugs were selected for quantification. Very delicate optimizations were carried out in SPE, trimethylsilylation derivatization, and GC/MS to enable such remarkable achievements. Trimethylsilylated analytes were well separated within 21 min by GC‐MS. In the validation results, the LOD of all the analytes were in the range of 2–75 ng/mL. The LOQ of the quantified analytes were in the range of 5–98 ng/mL. The linearity (r2) of the quantified analytes ranged 0.990–1.000 in each concentration range between 10 and 1000 ng/mL. The mean recoveries ranged from 62 to 126% at three different concentrations of each analyte. The inter‐day and inter‐person accuracies were within ?13.3~14.9%, and ?10.1~13.0%, respectively, and the inter‐day and inter‐person precisions were less than 12.9%. The method was reliable and efficient for the screening and quantification of abused illicit drugs in routine urine analysis. 相似文献
46.
Kim JH van der Vegte MA Scaramucci A Artyukhin S Chung JH Park S Cheong SW Mostovoy M Lee SH 《Physical review letters》2011,107(9):097401
We studied magnetic excitations in a low-temperature ferroelectric phase of the multiferroic YMn(2)O(5) using inelastic neutron scattering (INS). We identify low-energy magnon modes and establish a correspondence between the magnon peaks observed by INS and electromagnon peaks observed in optical absorption [A. B. Sushkov et al., Phys. Rev. Lett. 98, 027202 (2007).]. Furthermore, we explain the microscopic mechanism, which results in the lowest-energy electromagnon peak, by comparing the inelastic neutron spectral weight with the polarization in the commensurate ferroelectric phase. 相似文献
47.
Ko KT Kim K Kim SB Kim HD Kim JY Min BI Park JH Chang FH Lin HJ Tanaka A Cheong SW 《Physical review letters》2011,107(24):247201
We investigated the magnetic nature of Fe(1/4)TaS2 using x-ray absorption spectroscopy, photoemission spectroscopy, and first principles band calculations. The results show a large unquenched orbital magnetic moment (~1.0 μ(B)/Fe) at intercalated Fe sites, resulting in a gigantic magnetic anisotropy (H(A)?60 T). The magnetic coupling is well understood in terms of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, suggesting a novel RKKY ferromagnet with Ising-type spin states. We also found that this indirect exchange coupling between the neighboring Fe spins is ferromagnetic and maximized at the Fe-Fe distance of 2×2 superstructure. 相似文献
48.
T.A. Tyson Z. Chen S. Yoong S.-W. Cheong 《Journal of magnetism and magnetic materials》2009,321(11):1714-1718
The temperature and magnetic field dependent local structure of RMn2O5 systems was examined. While no significant displacements of the Mn ions are observed, it is found that the R-O distribution exhibits changes at low temperature which are possibly related to the changes in the electric polarization. Density functional computations are used to explore the system dynamics and to link the local structural measurements with anomalous changes in the infrared absorption spectra. The anomalous R-O distribution and observed coupling to magnetic fields point to the need to properly treat the 4f electrons on the R sites in these systems. 相似文献
49.
Kwangmin Park Eungjin Ahn Yu Jin Jeon Hyeonsik M. Cheong Jin Soak Kim Eun Kyu Kim Jungil Lee Young Ju Park Gun-Do Lee Euijoon Yoon 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):169
InAs quantum dots (QDs) were grown on InP substrates by metalorganic chemical vapor deposition. The width and height of the dots were 50 and 5.8 nm, respectively on the average and an areal density of 3.0×1010 cm−2 was observed by atomic force microscopy before the capping process. The influences of GaAs, In0.53Ga0.47As, and InP capping layers (5–10 ML thickness) on the InAs/InP QDs were studied. Insertion of a thin GaAs capping layer on the QDs led to a blue shift of up to 146 meV of the photoluminescence (PL) peak and an InGaAs capping layer on the QDs led to a red shift of 64 meV relative to the case when a conventional InP capping layer was used. We were able to tune the emission wavelength of the InAs QDs from 1.43 to 1.89 μm by using the GaAs and InGaAs capping layers. In addition, the full-width at half-maximum of the PL peak decreased from 79 to 26 meV by inserting a 7.5 ML GaAs layer. It is believed that this technique is useful in tailoring the optical properties of the InAs QDs at mid-infrared regime. 相似文献
50.
This paper presents a study to describe the behaviour of a non-equilibrium bubble in a fluid (Fluid 1) that is in contact with another fluid (Fluid 2). Fluid 2 is assumed to incorporate some elastic properties, which are modelled through a pressure term at the fluid–fluid interface. The Laplace equation is assumed to be valid in both fluids and the boundary integral method is employed to simulate the dynamics of the bubble and the fluid–fluid interface. Interesting characteristic phenomena concerning bubble oscillations and the deformation of the fluid–fluid interface are studied for a range of parameters (distance from the fluid–fluid interface, density ratios of the two fluids and elastic properties of Fluid 2). Some of the phenomena observed are jet formation in the bubble, bubble splitting, a ring bubble separating from the main bubble, mushroom-shaped bubbles and the dynamic elevation of the elastic interface. Most of these phenomena are only observed when Fluid 2 possesses some elastic properties (besides the usual formation of a high speed liquid jet). Comparisons with experimental observations confirm the validity of our simulations. 相似文献