Interfacial electronic structure of vanadyl naphthalocyanine on highly ordered pyrolytic graphite

We present a core and valence region spectroscopic analysis of the interfacial electronic structure of thin films of vanadyl naphthalocyanine (VONc) deposited onto highly oriented pyrolytic graphite (HOPG). X-ray photoelectron spectroscopy indicates the predominantly ionic character of the vanadyl metal center coordinated by the heterocycle and affords the bandgap in the thin VONc films. Valence band photoelectron spectroscopy points to the existence of three different adsorption geometries of VONc on the HOPG surface. The distribution of the different geometries can be systematically influenced in a simple post-deposition processing step, with an immediate effect on the interfacial electronic environment. We find spectroscopic evidence in the valence levels that VONc grows on HOPG most likely in a 2D-gas fashion rather than by nucleation and growth of islands. These data allow us to predict accurately the interface dipole in the case of a broad class of dipolar organic semiconductors, based simply on molecular dipole moment, polarizability and molecular diameter. This ability provides an important step towards rational optimization of energy level alignment in organic electronics.     

Existence, Regularity, and Properties of Generalized Apparent Horizons

We prove a conjecture of Tom Ilmanen and Hubert Bray on the existence of the outermost generalized apparent horizon in an initial data set and that it is outer area minimizing.     

Close-loop three-laser scheme for chaos-encrypted message transmission

In this paper, we numerically evaluate private data transmission using a three-laser scheme, consisting of a pair of twin semiconductor lasers, driven to chaos by delayed optical feedback in a short cavity, and optically injected by a third chaotic laser which forces them to synchronize. This laser is selected with different internal parameters with respect to the twin pair, so that the emissions of the synchronized, matched lasers, are highly correlated, whereas their correlation with the driver is low. The digital message modulates the emission of the transmitter, as in a standard Chaos Modulation scheme. Message recovery is then obtained by subtracting, from the transmitted chaos-masked message, the chaos, locally generated by the synchronized receiver laser. Simulations have been performed with the Lang-Kobayashi model, and, in view of application to private transmission, we have investigated the effect of the parameter mismatch, between transmitter and receiver, on message recovery. A preliminary experimental evaluation has been also performed using specially designed InP integrated modules.     

Erratum to “Unique continuation results for Ricci curvature and applications” [J. Geom. Phys. 58 (2008) 179–207]

Corrections are given to some of the proofs of the paper mentioned in the title.     

Fluorescent Triphenyl Substituted Maleimide Derivatives: Synthesis,Spectroscopy and Quantum Chemical Calculations

In this paper we describe a semi-empirical quantum method for predicting the wavelength of maximum fluorescence excitation and emission for several known and new maleimide derivatives. All new maleimides, containing a N-Benzyl attachment, were successfully synthesised via a tandem Suzuki reaction with aryl boronic acids containing either an electron donating, electron withdrawing functional groups. Absorption and emission spectra calculated using the semi-empirical AM1 method with excited state ZINDO calculations proved more reliable than either Hartree-Fock Configuration interaction or time dependent density functional methods. Calculated absorption and emission wavelengths were compared with 26 experimental spectra from known or newly synthesised maleimides and found to have provide reasonable predictions, with an average deviation of less the 6% for absorption maxima and less than 4% for emission peaks. The described method provides a strong benchmark for the accuracy that can be expected from theoretical predictions of fluorescence spectra.