Non-local exchange correlation energy in quasi-two-dimensional electron layers

We introduce a simple, non-local approximation for the exchange-correlation energy of an inhomogeneous electron gas. This approximation is shown to be quantitatively accurate in several important limiting cases. The method is used to calculate the non-local exchange-correlation energy for density distributions representing quasi-two-dimensional electron layers. These energies are compared to the widely used three-dimensional local-density approximation and suggest that the latter approximation may contain errors on the order of 10–30% for layer profiles typical of real systems.     

Production characteristics of the F meson

Inclusive cross sections of η production by e⁺e^- annihilation for c.m. energies between 4.0 and 5.0 GeV are presented. The η production is shown to be correlated with the production of a weakly decaying particle, indicating that its main source is F production. At the 4.42 GeV resonance it is correlated with a low energy photon, suggesting or production. A mass determination of the F is made at 4.42 GeV using the F → ηπ decay channel.     

Ultrarotdurchlässigkeit und Struktur abschreckend kondensierter Schichten von PbS,PbSe und PbTe

Thin films of the lead chalcogenides PbS, PbSe and PbTe are condensed from the vapor onto substrates at low temperature. After condensation and during heating the infrared transmission between 0.8 and 18 μ is measured. Debye-Scherrer-diagrams also are sketched for investigating the structure of the layers. After condensation at 20° K the thin films are amorphous. Depending on the conditions of evaporation the layers crystallize at 83° K or at 115° K (PbS at 135° K) into the normal structure of NaCl-type. During crystallisation the infrared absorption edge moves to longer wavelengths. The high amount of covalent bond seems to be essential for the appearence of the amorphous phase when the substances are condensed on a substrate at low temperature.     

Synthesis of stable derivatives of c(62): the first nonclassical fullerene incorporating a four-membered ring

A rational synthetic approach to the first four-membered ring-containing derivatives of C(62) is reported. They were synthesized by an inverse electron demand Diels-Alder reaction of 3,6-diaryl-1,2,4,5-tetrazines with C(60) in o-dichlorobenzene, followed by visible light irradiation at reflux. The structure of these nonclassical fullerenes derivatives was determined by X-ray single-crystal diffraction.     

Pipette mit Verschluss

Ohne Zusammenfassung     

Lower bounds for numbers of ABC-hits

By an ABC-hit, we mean a triple (a,b,c) of relatively prime positive integers such that a+b=c and rad(abc)<c. Denote by N(X) the number of ABC-hits (a,b,c) with c?X. In this paper we discuss lower bounds for N(X). In particular we prove that for every ?>0 and X large enough N(X)?exp((logX)^1/2−?).     

A bound for tridiagonal matrices

Novosibirsk. Translated from Sibirskii Matematicheskii Zhurnal, Vol. 30, No. 4, pp. 171–173, July–August, 1989.     

Über die Bestimmung des Gipsgehaltes von Sulfitablaugen

Analytical and Bioanalytical Chemistry -