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101.
102.
B. Hwang J. Kwon M. Lee S.J. Lim S. Jeon S. Kim U. Ham Y.J. Song Y. Kuk 《Current Applied Physics》2013,13(7):1365-1369
It has been known that a good quality h-BN layer can only be grown within a narrow temperature window of 1020–1100 K on a copper substrate. We found that the growth temperature window on Cu(111) surface could be lowered up to 100 K by ionizing and/or exciting borazine precursor gas with an electron-beam. The structures of a hexagonal boron nitride (h-BN) layers grown at various substrate temperatures on a Cu(111) were examined using scanning tunneling microscopy. We found that the grown h-BN film exhibits highly inert behavior with wide bandgap semiconductor characteristics. 相似文献
103.
Ham DJ Pak C Bae GH Han S Kwon K Jin SA Chang H Choi SH Lee JS 《Chemical communications (Cambridge, England)》2011,47(20):5792-5794
The strong interaction between PdNi alloys and WC makes PdNi/WC a novel Pt-free electrocatalyst for the anode hydrogen oxidation reaction of polymer electrolyte membrane fuel cells with activity and stability comparable to those of the conventional Pt/C catalysts. 相似文献
104.
105.
Ham H Park NH Kang I Kim HW Shim KB 《Chemical communications (Cambridge, England)》2012,48(53):6672-6674
Catalyst-free graphene nanosheets without substrates were synthesized using pure solid carbon sources of multiwalled carbon nanotubes (MWCNTs) and a spark plasma sintering (SPS) process. Single and few-hundred-nanometer graphene nanosheets were formed from gas-phase carbon atoms which were directly evaporated from MWCNTs at a local high temperature. 相似文献
106.
The remarkable catalytic effects of Fe(OTf)(3) in the context of the Pd(ii)-catalyzed conjugate addition of arylboronic acids to chromones were observed to yield a variety of flavanones under mild conditions. The addition of catalytic amounts of DDQ and KNO(2) to the reactions exclusively yielded flavone analogs. The reaction scope for the transformation was fairly broad, affording good yields of a wide range of flavanones and flavones, which are privileged structures in many biologically active compounds. 相似文献
107.
Young Jin Ham Hana Yu Nam Doo Kim Jung-Mi Hah Khalid B. Selim Hwan Geun Choi Taebo Sim 《Tetrahedron》2012,68(7):1918-1925
A Rh-catalyzed diastereoselective reductive cyclization, mediated by hydrogen, of optically active 1,6-enynes using chiral BINAP was successfully applied to the total synthesis of four stereoisomers of the proposed structure of lucentamycin A. In order to synthesize two of these four stereoisomers, we successfully constructed chiral proline derivatives bearing cis-carbon substituents at C2 and C3 positions based on Krische’s methodology, which has very rarely been reported. Anti-proliferative activities on HCT-116 cell line and NMR data of these four stereoisomers were compared with those of naturally occurring lucentamycine A. The results show that the proposed structure of lucentamycin A needs revision. 相似文献
108.
Seunghon Ham Chungsik Yoon Euiseung Lee Kiyoung Lee Donguk Park Eunkyo Chung Pilje Kim Byoungcheun Lee 《Journal of nanoparticle research》2012,14(9):1-17
Although task-based sampling is, theoretically, a plausible approach to the assessment of nanoparticle exposure, few studies using this type of sampling have been published. This study characterized and compared task-based nanoparticle exposure profiles for engineered nanoparticle manufacturing workplaces (ENMW) and workplaces that generated welding fumes containing incidental nanoparticles. Two ENMW and two welding workplaces were selected for exposure assessments. Real-time devices were utilized to characterize the concentration profiles and size distributions of airborne nanoparticles. Filter-based sampling was performed to measure time-weighted average (TWA) concentrations, and off-line analysis was performed using an electron microscope. Workplace tasks were recorded by researchers to determine the concentration profiles associated with particular tasks/events. This study demonstrated that exposure profiles differ greatly in terms of concentrations and size distributions according to the task performed. The size distributions recorded during tasks were different from both those recorded during periods with no activity and from the background. The airborne concentration profiles of the nanoparticles varied according to not only the type of workplace but also the concentration metrics. The concentrations measured by surface area and the number concentrations measured by condensation particle counter, particulate matter 1.0, and TWA mass concentrations all showed a similar pattern, whereas the number concentrations measured by scanning mobility particle sizer indicated that the welding fume concentrations at one of the welding workplaces were unexpectedly higher than were those at workplaces that were engineering nanoparticles. This study suggests that a task-based exposure assessment can provide useful information regarding the exposure profiles of nanoparticles and can therefore be used as an exposure assessment tool. 相似文献
109.
Kwang-Soo HuhMin-Chang Jeong Moon-Ho HamJae-Min Myoung Woo-Young LeeJeung-Mi Lee Suk-Hee Han 《Solid State Communications》2003,128(4):119-123
Effects of Mn flux on the magnetic properties of (Ga,Mn)N films grown on sapphire substrate by plasma-enhanced molecular beam epitaxy (PEMBE) discussed. The (Ga,Mn)N thin films were found to exhibit ferromagnetic ordering at room temperature without any secondary phases by X-ray diffraction and alternating gradient magnetometer. It is found that, although the surface morphology and the electrical properties are degraded with increasing Mn concentration, the magnetic properties of the films improve. 相似文献
110.
H. Genten S.W. Ham B.R. Kim S.K. Oh 《Zeitschrift fur Physik C Particles and Fields》1997,76(1):117-125
We consider the Higgs sector of a nonlinear supersymmetric standard model. Analytic solutions for some useful mass relations are derived. We investigate physical consequences of the model for LEP 1, LEP 2, and 500, 1000 resp. 2000 GeV LCs, and show that the neutral scalar Higgs bosons will most probably enable LC 500, 1000, 2000 to test the model conclusively, whereas at LEP 1, 2 only a part of the parameter space can be explored. As for the two pseudoscalar Higgs bosons the lighter one cannot be detected at any of the considered colliders, whereas the heavier one could possibly be detected with about “10 percent probability” at LC 1000 and LC 2000. 相似文献