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991.
P. Allenspach B. W. Lee D. A. Gajewski V. B. Barbeta M. B. Maple G. Nieva S. -I. Yoo M. J. Kramer R. W. McCallum L. Ben-Dor 《Zeitschrift für Physik B Condensed Matter》1995,96(4):455-464
Low temperature heat-capacity measurements have been performed to study the magnetic ordering in NdBa2Cu3O
x
and DyBa2Cu3O
x
. In order to investigate the type of ordering, magnetic fields up to 6 T and hydrostatic pressures up to 4.5 kbar were applied. While for NdBa2Cu3O
x
and DyBa2Cu3O
x
both the fully oxidized and the fully oxygen reduced samples display long rang antiferromagnetic ordering, only magnetic short range interaction could be found for samples in an intermediate range of oxygen concentration. For NdBa2Cu3O
x
, where superexchange is believed to be the dominant magnetic interaction,T
N
is three times higher in the sample withx=6.26 compared to the one withx=6.98. In contrast,T
N
of DyBa2Cu3O
x
is almost oxygen independent as expected for this mainly dipolar interacting system. 相似文献
992.
A highly sensitive assay method for phenylethanolamine N-methyltransferase in rat adrenal medulla and brain is described which employs high-performance liquid chromatography with fluorescence detection. Epinephrine formed enzymatically from the substrate norepinephrine and isoproterenol (internal standard), after chromatography on a small cartridge of a cation exchanger, Toyopak SP, are converted into the corresponding fluorescent compounds by reaction with 1,2-diphenylethylenediamine, a selective fluorescence derivatization reagent for catechol compounds. The derivatives are separated by reversed-phase chromatography on TSK gel ODS-120T. The detection limit for epinephrine formed enzymatically is 0.66 pmol per assay tube. 相似文献
993.
Luis Echegoyen George W. Gokel Lourdes E. Echegoyen Zhi-Hong Chen Hyunsook Yoo 《Journal of inclusion phenomena and macrocyclic chemistry》1989,7(2):257-266
The evolution of lariat ethers from relatively simple, substituted crown ethers into electrochemically sensitive ligands is presented. Although nitrogen-pivot lariats were observed to be better binders than the corresponding parent crowns and to retain considerable flexibility after complexation, overall stability constants were not favorable for cation transport applications. This led to the syntheses of nitrobenzene- and anthraquinone-substituted systems capable of reversible redox behavior and drastically enhanced cation binding abilities when reduced. Application of these in enhanced cation transport processes has been demonstrated. 相似文献
994.
J. Y. Yoo J. H. Shin Y. H. Lee H. -H. Park B. -S. Yoo 《Optical and Quantum Electronics》1995,27(5):421-425
Precision etch-depth control is realized by a chemically assisted ion-beam etching system incorporated within situ laser reflectometry. By counting the number of interference fringes, etch-depth control better than a quarter-wave thickness is easily obtained. Optimized etching conditions for highly anisotropic etching of bulk GaAs and AlGaAs/GaAs distributed Bragg reflectors are obtained. With the ability to etch-stop just below the active region by thein situ monitoring, InGaAs vertical-cavity surface-emitting lasers with CW threshold current density as low as 380 A cm-2 with output power >11 mW are fabricated. Spatial uniformity is 5% over a 1-cm2 sample, which corresponds to one pair over 20 pairs of quarter-wave stacks of AlGaAs/GaAs distributed Bragg reflectors. 相似文献
995.
996.
Self-assembled arrays of zinc oxide nanoparticles from monolayer films of diblock copolymer micelles 总被引:1,自引:0,他引:1
A hexagonal array of optically active ZnO nanoparticles was synthesized in situ on the solid substrate by utilizing a single-layered film of diblock copolymer micelles as a nanostructured template. 相似文献
997.
998.
999.
J.H.?SongEmail author Y.Z.?Yoo T.?Chikyow H.?Koinuma 《Applied Physics A: Materials Science & Processing》2004,79(3):457-460
Epitaxial growth of non-polar wurtzite (11-20) AlN thin films was achieved on a Si(100) substrate by inserting an MnS buffer layer. The a-plane AlN film and MnS buffer layer were fabricated by pulsed KrF excimer laser deposition, and their micro- and interfacial atomic structures were investigated by transmission electron microscopy. The epitaxial relationship between films and substrate was found to be AlN(11-20)MnS(100)Si(100) with in-plane alignment of AlN[1-101]MnS[011]Si[011]. AlN[11-20] grown on Si is perpendicular to AlN[0001] and parallel to MnS[100]. The MnS/Si interface is abrupt enough to inherit the orientation of the Si(100) surface. A sharp interface was also observed for AlN/MnS without any intermediate layer. PACS 81.05.Ea; 81.05.Zx; 81.15.Fg; 68.37.Lp 相似文献
1000.
A high-definition analysis based on flow topology is made on the vortex motions under natural and lock-on conditions in the
near-wake region of a circular cylinder, where two-dimensional flow fields in the wake-transition regime are measured by a
time-resolved PIV system. The Reynolds stress distributions are examined in view of the mean separation streamline and the
trajectory ofthe vortex center. It is shown that, by the lock-on, the Reynolds stresses become stronger and their dispositions
match well with the shortened wake bubble, indicating perfect synchronization of shedding to the oscillatory forcing flow
in the near field, which causes increased lift and drag forces. 相似文献