Objective: This study was conducted to evaluate the insertion properties and intracochlear trajectories of three perimodiolar electrode array designs and to compare these designs with the standard CochlearlMelbourne array. Background: Advantages to be expected of a perimodiolar electrode array inclu<;le both a reduction in stimulus thresholds and an increase in dynamic range, resulting in a more localized stimulation pattern of the spiral ganglion cells, reduced power consumption, and, therefore, longer speech processor battery life. Methods: The test arrays were implanted into human temporal bones. Image analysis was performed on a radiograph taken after the insertion. The cochleas were then histologically processed with the electrode array in situ, and the resulting sections were subsequently assessed for position of the electrode array as well as insertion-related intracochlear damage. Intracochlear multichannel cochlear implants have successfully provided auditory information for profoundly deaf patients by electrically stimulating discrete populations of auditory nerve fibers via a scala tympani electrode array. The straight, yet flexible, tapered Melbourne/Cochlear electrode array can be safely implanted into the human cochlea. However, histologic and radiologic examination of implanted temporal bones showed that the electrode array is usually positioned along the outer wall of the scala tympani (1-5). The array is, therefore, some distance from the spiral ganglion cells in the Rosenthal canal and their peripheral processes. However,

Ultrafast transient absorption spectroscopy is performed on a novel donor-acceptor-donor triad made of two identical bisthiophene derivatives as electron donors and a central perylenediimide moiety as electron acceptor. The triad is extended at both ends by covalently bound siloxane chains that confer self-organisation into thin smectic films at ambient temperature. When diluted in chloroform, selective excitation of the donor moiety leads to resonance energy transfer within 130 fs to the acceptor moiety, followed by the formation of a charge transfer (CT) state in ~3 ps. The CT state recombines entirely on a 55 ps time scale. In the liquid crystal films, excitonic intermolecular coupling leads to significant changes in the dynamics. Most remarkably, ultrafast intra- and intermolecular CT state formation occurs in about 60 fs, i.e. on a time scale comparable to electronic coherence times. While the intra-molecular CT states recombine on the same time scale as in solution or even faster, inter-molecular CT states live for about 1 ns. Last, triplet states of the perylenediimide moiety dominate the differential absorption after ~1 ns. We anticipate that the fast recombination of intra-molecular CT states and the triplet state formation may severely limit the photo-current in these materials.

When bound to a protein, the coenzyme NAD+/NADH typically exists in an extended conformation, while in aqueous solutions it can be characterized by an equilibrium of folded and unfolded structures. It was recognized long ago that in the folded conformation light absorption at the adenine ring initiates an effective energy transfer (ET) toward the nicotinamide group, but the mechanism of this process is still unexplored. Here we apply ultrafast transient absorption measurements on NADH combined with compartmental model analysis for following the kinetics of the ET. We find that the actual ET is extremely rapid (∼70 fs). The high rate can be well described by a Förster-type mechanism, promoted by both the special photophysical properties of adenine and the subnanometer inter-ring distance. The rapid ET creates a vibrationally hot excited state on nicotinamide, the vibrational and electronic relaxation of which is characterized by 1.7 and 650 ps, respectively.

Conjugated donor-acceptor block co-oligomers that self-organize into D-A mesomorphic arrays have raised increasing interest due to their potential applications in organic solar cells. We report here a combined experimental and computational study of charge transfer (CT) state formation and recombination in isolated donor-spacer-acceptor oligomers based on bisthiophene-fluorene (D) and perylene diimide (A), which have recently shown to self-organize to give a mesomorphic lamellar structure at room temperature. Using femtosecond transient absorption spectroscopy and Time-Dependent Density Functional Theory in combination with the Marcus-Jortner formalism, the observed increase of the CT lifetimes is rationalized in terms of a reduced electronic coupling between D and A brought about by the chemical design of the donor moiety. A marked dependence of the CT lifetime on solvent polarity is observed, underscoring the importance of electrostatic effects and those of the environment at large. The present investigation therefore calls for a more comprehensive design approach including the effects of molecular packing.

Singlet exciton diffusion was studied in the efficient organic photovoltaic electron donor material DTS(FBTTh2)2. Three complementary time-resolved fluorescence measurements were performed: quenching in planar heterojunctions with an electron acceptor, exciton–exciton annihilation, and fluorescence depolarization. The average exciton diffusivity increases upon annealing from 1.6 × 10–3 to 3.6 × 10–3 cm2 s–1, resulting in an enhancement of the mean two-dimensional exciton diffusion length (LD = (4Dτ)1/2) from 15 to 27 nm. About 30% of the excitons get trapped very quickly in as-cast films. The high exciton diffusion coefficient of the material leads to it being able to harvest excitons efficiently from large donor domains in bulk heterojunctions.

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A post processing method of solvent vapor annealing (SVA) enhances the diffusion length (LD) and domain size in small molecule organic semiconductors which leads to an enhancement in device performance in bulk heterojunction organic photovoltaics.

We demonstrate the implementation of a broadband fluorescence up-conversion set-up with high signal-to-noise ratio and dynamic range allowing for the detection of weak luminescence from triplet states in Fe(II) NHC complexes. Based on the experimentally determined radiative rates and the emission spectra, these states have dominant MLCT character.