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991.
992.
Two new 8,4′-oxynorneolignans were produced by elicitation of Echinacea purpurea cell suspension cultures with yeast elicitor. Their structures with an unusual (hydroxy)acetyl group were elucidated by spectroscopic methods including gas chromatography (GC) and electrospray ionization (ESI) mass spectrometry. 相似文献
993.
994.
Wolfgang S.M. Werner 《Surface science》2003,526(3):L159
Reflection electron energy loss spectra have been measured for a semiconductor and some metals (Si, Cu, Ag and Au). A novel procedure is presented to rigorously decompose the spectra into contributions corresponding to surface and volume excitations. The resulting distributions of energy losses in an individual surface loss are in good agreement with theory. In particular, the begrenzungs effect occurring at the boundary of a solid state plasma, i.e. the reduction of the intensity of bulk modes due to the coupling with surface modes, can be clearly observed in the retrieved energy loss distribution. 相似文献
995.
We prove the existence of entire functions which are universal under translations and bounded on certain prescribed sets.
It is also shown that the family of all these universal functions is a dense but not a Gδ-subset in the space of entire functions provided with a natural metric.
Received: 24 November 2004; revised: 12 April 2005 相似文献
996.
We study the nucleation phase of molecular beam epitaxy of (hexagonal) MnAs on (cubic) GaAs (0 0 1) using reflection high-energy electron diffraction (RHEED) azimuthal scans. The nucleation proceeds from a non-reconstructed initial stage through randomly oriented small nuclei and two orientation stages to the final single-phase epitaxial orientation. The fascinatingly complex nucleation process contains elements of both Volmer-Weber and Stranski-Krastanov growth. The measurement demonstrates the potential of high-resolution RHEED techniques to assess details of the surface structure during epitaxy. 相似文献
997.
998.
999.
Wolfgang Denzer Gus Hancock John C Pinot de Moira Phillip L Tyley 《Chemical physics letters》1997,280(5-6)
Time-of-flight measurements have been made of the O(1D) fragment following the photolysis of ozone in the near-UV. At 321.9 nm fragments are seen with kinetic energies the values of which are those expected from spin-forbidden dissociation with ground state O2(X3Σg−) molecules as the co-product. Spin-allowed dissociation of internally excited ozone molecules is also seen to produce translationally cold O(1D) and O2(a1Δg) products. The implications for the dissociation of tropospheric ozone are briefly discussed. 相似文献
1000.