Temperature dependence and anisotropy of the hole drift mobility in monoclinic tetracyanoethylene

The tensor of the hole drift mobility is determined in monoclinic tetracyanoethylene by the transient photoconductivity technique. The principal tensor components amount to μ₁ = 0.21, μ₂ = 0.10 and μ₃ = 0.15 cm²/V s at room temperature. Above 250 K the mobility is a decreasing function of temperature and follows an exp(E/kT) dependence (E = 0.08 eV) which is inconsistent with both band and hopping models. Below 250 K the mobility is controlled by a hole trapping level of 0.28 eV deep. The photogeneration efficiency is found to be independent of temperature and proportional to the light intensity.     

Diastereomeric non-equivalence of (−)-ω-camphanic esters of chiral secondary alcohols in 13C NMR spectroscopy

The diastereomeric differences (Δδ) were measured by ¹³C NMR spectroscopy for a series of 11 (?)-ω-camphanic esters of secondary alcohols of known absolute configuration. This method cannot be used for the determination of the absolute configuration, but it can be applied to the estimation of the enantiomeric purity of chiral alcohols.     

On resolvable tree-decompositions of complete graphs

A partition of the edge set of a graph H into subsets inducing graphs H₁,…,H_s isomorphic to a graph G is said to be a G-decomposition of H. A G-decomposition of H is resolvable if the set {H₁,…,H_s} can be partitioned into subsets, called resolution classes, such that each vertex of H occurs precisely once in each resolution class. We prove that for every graceful tree T of odd order the obvious necessary conditions for the existence of a resolvable T-decomposition of a complete graph are asymptotically sufficient. This generalizes the results of Horton and Huang concerning paths and stars.     

Neue Methode zur Kontrolle der Sulfonierung von einigen aromatischen Kohlenwasserstoffen

Zusammenfassung Es wurde eine schnelle und genaue volumetrische Methode zur Kontrolle des Sulfonierungsverfahrens von Benzol, Toluol und Naphthalin ausgearbeitet.     

Formation of radical anions and not deprotonation starts the reaction of gamma-butyrolactone with potassium anions

A mechanism is proposed for the reaction of gamma-butyrolactone with the potassium anion as a two-electron-transfer reagent. Potassium hydride and potassium 4-potassiobutyrate are formed in this process as intermediates. These compounds deprotonate gamma-butyrolactone. Potassium lactone enolate, potassium butyrate, and hydrogen are the final reaction products.     

Kinetics of the esterification of maleic anhydride with octyl, decyl or dodecyl alcohol over dowex catalyst

Summary Esterification of maleic anhydride over acid ion exchange resin catalyst has been investigated in an isothermal semi batch reactor. Although this is a bimolecular reaction, first order kinetics with respect to acid has been observed.     

Nature of the chemical bond between metal atoms and oxide surfaces: new evidences from spin density studies of K atoms on alkaline earth oxides

We have studied the interaction of K atoms with the surface of polycrystalline alkaline-earth metal oxides (MgO, CaO, SrO) by means of CW- and Pulsed-EPR, UV-Vis-NIR spectroscopies and DFT cluster model calculations. The K adsorption site is proposed to be an anionic reverse corner formed at the intersection of two steps, where K binds by more than 1 eV, resulting in thermally stable species up to about 400 K. The bonding has small covalent and large polarization contributions, and the K atom remains neutral, with one unpaired electron in the valence shell. The interaction results in strong modifications of the K electronic wave function which are directly reflected by the hyperfine coupling constant, (K)a(iso). This is found to be a very efficient "probe" to measure the degree of metal-oxide interaction which directly depends on the substrate basicity. These results provide an original and general model of the early stages of the metal-support interaction in the case of ionic oxides.     

On the projectivity of threefolds

Let be a smooth complete three-dimensional algebraic variety (defined over an algebraically closed field ). We show that is projective if it contains a divisor which is positive on the cone of effective curves.

     

A model for so(5) = sp(4) lie algebra

The paper is the continuation of a previous one [Physica Scripta22 (1980), 545–555] devoted to quadrupling in the shell model. We consider here a simple model of the ten- dimensional quasi-spin Lie algebra which is spectrum generating for the quadrupling Hamiltonian. The model allows us to investigate many concrete aspects of the theory of linear representations of the quasi-spin algebra. In particular, we present an explicit construction of the irreducible representation module for the finite dimensional representations, and we consider the direct product of the such irreducible modules.