Photoluminescence quantum yields and nonradiative decay of the excitonic S(1) state in length fractionated (6,5) single-wall carbon nanotubes (SWNTs) are studied by continuous wave and time-resolved fluorescence spectroscopy. The experimental data are modeled by diffusion limited contact quenching of excitons at stationary quenching sites including tube ends. A combined analysis of the time-resolved photoluminescence decay and the length dependence of photoluminescence quantum yields (PL QYs) from SWNTs in sodium cholate suspensions allows to determine the exciton diffusion coefficient D = 10.7 ± 0.4 cm(2)s(-1) and lifetime τ(PL) for long tubes of 20 ± 1 ps. PL quantum yields Φ(PL) are found to scale with the inverse diffusion coefficient and the square of the mean quenching site distance, here l(d) = 120 ± 25 nm. The results suggest that low PL QYs of SWNTs are due to the combination of high-diffusive exciton mobility with the presence of only a few quenching sites.

Running neu-trino mass parameters in seesaw scenarios, JHEP 03 (2005) 024, hep-ph/0501272v3. S. Antusch, J. Kersten, M. Lindner, M. Ratz, Neutrino mass matrix running for non-degenerate seesaw scales, Phys. Lett. B538 (2002) 87-95.

Two-dimensional networks made of metal nanowires are excellent paradigms for the experimental observation of electrical percolation caused by continuous jackstraw-like physical pathways. Such systems became very interesting as alternative material in transparent electrodes, which are fundamental components in display devices. This work presents the experimental characterization of low-haze and ultra-transparent electrodes based on silver nanowires. The films are created by dip-coating, a feasible and scalable liquid film coating technique. We have found dominant alignment of the silver nanowires in withdrawal direction. The impact of this structural anisotropy on electrical anisotropy becomes more pronounced for low area coverage. The rod alignment does not influence the technical usability of the films as significant electrical anisotropy occurs only at optical transmission higher than 99 %. For films with lower transmission, electrical anisotropy becomes negligible. In addition to the experimental work, we have carried out computational studies in order to explain our findings further and compare them to our experiments and previous literature. This paper presents the first experimental observation of electrical anisotropy in two-dimensional silver nanowire networks close at the percolation threshold.

We prove a generalized version of the well-known Lichnerowicz formula for the square of the most general Dirac operator D on an even-dimensional spin manifold associated to a metric connection ∇. We use this formula to compute the subleading term Φ 1 (x, x, D 2 ) of the heat-kernel expansion of D 2 . The trace of this term plays a key-rôle in the definition of a (euclidian) gravity action in the context of non-commutative geometry. We show that this gravity action can be interpreted as defining a modified euclidian Einstein-Cartan theory. ⋆ Supported by the European Communities, contract no. ERB 401GT 930224 expansion, Wodzicki residue, gravity for the most general Dirac operator D associated to a metric connection ∇ on a compact spin manifold M with dim M = 2n ≥ 4. We proceed as follows: According to the main theorem of [KW], there is a relation between the Wodzicki residue Res(△ −n+1 ) of a generalized laplacian△ on a hermitian bundle E over M and