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81.
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The absorption of a resonant coupling laser driving a closed degenerate two-level system in an atomic cesium beam was investigated as a function of the detuning of a second laser probing the same transition. The measurements were performed for four different polarization combinations of the two laser beams. Except for the beams of counterrotating polarizations all coupling-laser absorption profiles showed "absorption within transparency," i.e., the absorption in the region around the two-photon resonance was smaller than the absorption corresponding to the one-photon transition induced by the coupling laser, and an extra absorption peak was observed on this curve at the two-photon resonance. With regard to the beams of counterrotating polarizations we observed a switch from absorption within transparency to "transparency within transparency" when the probe-laser power exceeded the constant coupling-laser power. In other words, the cesium ensemble became mostly transparent to the coupling-laser beam at the two-photon resonance. 相似文献
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84.
We study isometric embeddings of a Euclidean space or a Heisenberg group into a higher dimensional Heisenberg group, where both the source and target space are equipped with an arbitrary left-invariant homogeneous distance that is not necessarily sub-Riemannian. We show that if all infinite geodesics in the target are straight lines, then such an embedding must be a homogeneous homomorphism. We discuss a necessary and certain sufficient conditions for the target space to have this ‘geodesic linearity property’, and we provide various examples. 相似文献
85.
86.
Descalzo AB Xu HJ Xue ZL Hoffmann K Shen Z Weller MG You XZ Rurack K 《Organic letters》2008,10(8):1581-1584
A new class of boron-dipyrromethene (BDP or BODIPY) dyes was obtained by phenanthrene fusion to the beta-pyrrole positions, absorbing in the wavelength range of important laser sources. Despite a 'propeller-like' distorted structure in the crystalline state, the chromophore absorbs (log epsilon > or = 5) and fluoresces (Phif > or = 0.8) strongly and can be easily turned into a fluorescence light-up probe. Incorporation into latex beads produces bright and photostable single-dye and F?rster Resonance Energy Transfer (FRET) particles for microscopy applications. 相似文献
87.
Neundorf I Hoyer J Splith K Rennert R Peindy N'dongo HW Schatzschneider U 《Chemical communications (Cambridge, England)》2008,(43):5604-5606
The conjugation of cymantrene CpMn(CO)(3) to cell-penetrating peptide hCT(18-32)-k7 alters the intracellular distribution in MCF-7 cells compared to the unmodified peptide, as visualized by fluorescence microscopy, and leads to an increased nuclear accumulation; the peptide and cymantrene compound themselves are not toxic, but the bioconjugate shows a significant cytotoxicity with an IC(50) value of 36 micromol l(-1). 相似文献
88.
Driller KM Libnow S Hein M Harms M Wende K Lalk M Michalik D Reinke H Langer P 《Organic & biomolecular chemistry》2008,6(22):4218-4223
N-glycosides of 6H-indolo[2,3-b]quinoxalines were prepared and structurally characterized. The synthesis relies on the cyclocondensation of isatine-N-glycosides with 1,2-diaminobenzenes. Some products exhibit weak cytotoxic activity against human ceratinocytes (HaCaT). 相似文献
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