Venture capital : U.S.-amerikanisches Modell und deutsches Aktienrecht

Der deutsche Markt für Venture Capital (VC) ist trotz erfreulicher Fortschritte insbesondere in den letzten drei Jahren im Vergleich zum weltweit größten VC-Markt in den USA unterentwickelt. Venture Capital-Investitionen beliefen sich in Deutschland im Jahr 1996 auf 0,04% des Bruttoinlandsproduktes, weniger als ein Drittel des U.S.-amerikanischen Niveaus. Obwohl seither ein deutlicher Anstieg zu verzeichnen ist, hat der deutsche VC-Markt mit einem Fondsvolumen von ca. 18,6 Milliarden DM nach jüngsten Angaben nur etwa ein Achtel der Größe des amerikanischen Marktes

Cavity-enhanced Raman Microscopy of Individual Carbon Nanotubes

Raman spectroscopy reveals chemically specific information and provides label-free insight into the molecular world. However, the signals are intrinsically weak and call for enhancement techniques. Here, we demonstrate Purcell enhancement of Raman scattering in a tunable high-finesse microcavity, and utilize it for molecular diagnostics by combined Raman and absorption imaging. Studying individual single-wall carbon nanotubes, we identify crucial structural parameters such as nanotube radius, electronic structure and extinction cross-section. We observe a 320-times enhanced Raman scattering spectral density and an effective Purcell factor of 6.2, together with a collection efficiency of 60%. Potential for significantly higher enhancement, quantitative signals, inherent spectral filtering and absence of intrinsic background in cavity-vacuum stimulated Raman scattering render the technique a promising tool for molecular imaging. Furthermore, cavity-enhanced Raman transitions involving localized excitons could potentially be used for gaining quantum control over nanomechanical motion and open a route for molecular cavity optomechanics

Manual application of insecticidal dust in semi-field experiments with honeybees

Manuelle Applikation von Insektizidstäuben in Halbfreilandversuchen mit Honigbiene

A scanning cavity microscope

Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a high-finesse scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1, 700-fold signal enhancement compared with diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1 nm(2);we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for optical studies of nanomaterials, molecules and biological nanosystems