Elastic waves at the (0 0 1) and (1 1 0) surfaces of AlN, GaN and InN

We have studied the acoustic waves in the (0 0 1) and (1 1 0) surfaces of AlN, GaN and InN. We have employed the surface Green function matching method and different sets of calculated elastic constants available in the literature for these materials, because no experimental values are available. Important differences are found for the velocities of the bulk and surface acoustic waves coming from these sets of elastic constants, in such a way that they could be easily measured by ultrasonic and Brillouin techniques. These results together with the expressions obtained here for the velocities of the acoustic waves in high symmetry directions could be used to determine the elastic coefficients of these materials.     

Water-Chain intervention in the ketonization of vinyl alcohol. An ab initio study

The ketonization of vinyl alcohol in aqueous solution has been studied by means of ab initio calculations, using the STO -3G basis set. The intervention of a chain of two water molecules reduces dramatically the potential barrier. This result agrees with experimental facts.     

Carleson's counterexample and a scale of Lorentz-BMO spaces on the bitorus

We introduce a full scale of Lorentz-BMO spaces BMO _L ^p,q on the bidisk, and show that these spaces do not coincide for different values ofp andq. Our main tool is a detailed analysis of Carleson's construction in [C]. The first author gratefully acknowledges support by the LMS and Proyecto BFM2002-04013. The second author gratefully acknowledges support by EPSRC and by the Nuffield Foundation.     

Sui fasci di cubiche a modulo costante

An improvement of the uniqueness theorem of Wintner for the differential equationx ⁽ⁿ⁾(t)=f(t, x) is given.     

Die Trennung der Alkalien in der Silicatanalyse

Zusammenfassung Die alte Berzelius-Methode zur Alkalibestimmung in Silikaten wird bedeutend vereinfacht, wenn man nach dem Flusss?ure-Aufschluss die Schwefels?ure vollst?ndig verjagt, die Sulfate schwach glüht, und die Masse mit heissem Wasser auszieht.     

Ueber die Entstehung der Myelin-Formen

Ohne ZusammenfassungVom Verfasser mitgetheilt.     

Isomeric effects on the self‐assembly of a plausible prebiotic nucleoside analogue: A theoretical study

The self‐assembly properties of N(9)‐(2,3‐dihydroxypropyl adenine) (DHPA), a plausible prebiotic nucleoside analogue of adenosine, were investigated using density functional theory. Two different isomers were considered, and it is found that while both isomers can form a variety of structures, including chains, one of them is also able to form cages and helixes. When these results were put in the context of substrate supported molecular self‐assembly, it is concluded that gas‐phase self‐assembly studies that consider isomer identity and composition not only can aid interpreting the experimental results, but also reveal structures that might be overlooked otherwise. In particular, this study suggest that a double‐helical structure made of DHPA molecules which could have implications in prebiotic chemistry and nanotechnology, is stable even at room temperature. For example electrical properties (energy gap of 4.52eV) and a giant permanent electrical dipole moment (49.22 Debye) were found in our larger double‐helical structure (3.7 nm) formed by 14 DHPA molecules. The former properties could be convenient for construction of organic dielectric‐based devices.