A novel dual-plasma system has been developed to combine the synthesis of silicon nanocrystals (Si-NCs), the etching to controllably tailor the Si-NC size, and the surface functionalization of Si-NCs into one simple all-gas-phase process. Si-NCs are synthesized in SiH(4)-based plasma; they then travel through CF(4)-based plasma, where Si-NCs are etched and passivated by C and F. The resulting Si-NCs exhibit air-stable emission across the full visible spectrum. Structural and optical characterization indicates that the emission in the red-to-green range is based on the recombination of quantum-confined excitons in Si-NCs, while the blue emission originates from defect states. The quantum yields of stabilized photoluminescence from Si-NCs range from 16% at the red end to 1% at the blue end.

Individual nanoparticles of silicon and titanium having diameters in the range of 40-140 nm have been repeatedly compressed by a nanoindenter. Even at low loads, the small tip-particle and particle-substrate contacts generate extreme pressures within the confined particle, influencing its stiffness and fracture toughness. The effect of these high pressures on the measured modulus is taken into account by invoking a Murnaghan equation-of-state-based analysis. Fracture toughness of the silicon particles is found to increase by a factor of 4 in compression for a 40-nm-diam particle when compared to bulk silicon. Additionally, strain energy release rates increase by more than an order of magnitude for particles of this size when compared to bulk Si.

The clarification of complete cell lineages, which are produced by specific stem cells, is fundamental for understanding mechanisms, controlling the generation of cell diversity and patterning in an emerging tissue. In the developing Central Nervous System (CNS) of Drosophila, neural stem cells (neuroblasts) exhibit two periods of proliferation: During embryogenesis they produce primary lineages, which form the larval CNS. After a phase of mitotic quiescence, a subpopulation of them resumes proliferation in the larva to give rise to secondary lineages that build up the CNS of the adult fly. Within the ventral nerve cord (VNC) detailed descriptions exist for both primary and secondary lineages. However, while primary lineages have been linked to identified neuroblasts, the assignment of secondary lineages has so far been hampered by technical limitations. Therefore, primary and secondary neural lineages co-existed as isolated model systems. Here we provide the missing link between the two systems for all lineages in the thoracic and abdominal neuromeres. Using the Flybow technique, embryonic neuroblasts were identified by their characteristic and unique lineages in the living embryo and their further development was traced into the late larval stage. This comprehensive analysis provides the first complete view of which embryonic neuroblasts are postembryonically reactivated along the anterior/posterior-axis of the VNC, and reveals the relationship between projection patterns of primary and secondary sublineages.

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