Tetrathiafulvalenes as π-Electron Donors for Intramolecular Charge-Transfer Materials

Although tetrathiafulvalene (TTF) and its derivatives have been extensively studied for more than 25 years as π-electron donors in intermolecular charge-transfer materials, the intriguing potential of TTF as a donor in an intramolecular sense has only recently been developed. Many versatile, functionalized TTF building blocks are now readily available, and this article will review a range of compounds in which TTF is covalently linked to an electron acceptor moiety by a variety of linking units, sometimes giving rise to an intramolecular charge-transfer (ICT) interaction, which is most frequently manifested in the optical and electrochemical properties. In this context, acceptor subunits include: tetracyano-p-quinodimethane, quinones, electron-deficient aryl groups, pyridinium and bipyridinium units, fullerenes, phthalocyanines, and mesomerically conjugated carbonyl, thiocarbonyl, ester, and related groups. This work paves the way for more systematic and detailed studies of TTF–spacer–A molecules (where A is an acceptor) in which there is increased control of the structural, electronic, optical, and magnetic properties arising from ICT interactions in the ground state, or in the excited state.     

Explosive Performance Properties of Erythritol Tetranitrate (ETN)

Erythritol tetranitrate (ETN) is a melt‐castable explosive with impressive performance, similar to the well‐known related nitrate ester, pentaerythritol tetranitrate (PETN). Though ETN has been known since 1849, its properties have not been thoroughly investigated. We report here the first 1/2′′ copper cylinder tests of ETN, compared with PETN. We discuss detonation and wall expansion velocity, along with diameter effect information in unconfined rate stick tests. The detonation velocity of ETN is 99 % that of PETN in the same test setup, showing that performance properties are very similar for the two nitrate esters.     

Epitaxial,electro-optically active barium titanate thin films on silicon by chemical solution deposition

Recent progress in the integration of BaTiO₃ thin films with silicon has shown great promise for the development of on-chip photonic devices. However, the highest performing thin films in the literature are deposited by costly and/or complex vacuum techniques. In this study, epitaxial BaTiO₃ thin films are deposited on thin SrTiO₃ template layers on Si(001) from an alkoxide-based chemical solution under atmospheric conditions and yield an effective Pockels coefficient of 27 ± 4 pm/V for an ~85 nm film. Film crystallinity, microstructure, and defect nature are examined by X-ray diffraction and high-resolution transmission and scanning electron microscopy techniques and discussed within the context of the growth method as well as the observed electro-optical response.     

A comparison of vector autoregressive forecasting performance: spatial versus non-spatial Bayesian priors

The Annals of Regional Science - Forecasting performance of spatial versus non-spatial Bayesian priors applied to a large vector autoregressive model that includes the 48 lower US states plus and...     

MASS TRANSFER EFFECTS ON THE ETCH RATE OF GAAS IN FLOW SYSTEMS

In industrial wet etching reactors, the fluid contacts the substrate surface as a spray of flowing stream, thus introducing mass-transfer resistances to the reaction rate. The etching of gallium arsenide in H₂O₂-NH₄OH-H₂O solutions was studied using an open-channel flow reactor to simulate the industrial conditions. The etch rate was always lower than that obtained under kinetic control, and the dependence of etch rate on H₂O₂ concentration shifted closer to first order. From the calculation of the ratio of rate constant to mass-transfer coefficient, the reaction-rate and mass-transfer resistances were both significant in this system. When the mass-transfer coefficient was calculated from equations for flow past a flat plate, the prediction of etch rate was good, particularly when the starting length for velocity boundary layer development ahead of concentration boundary layer development was taken into account. Another approach for the calculation of mass-transfer coefficient, based on the assumptions for flow between parallel plates, best represented the relative insensitivity of etch rate to fluid velocity.