On the Energetics of Ions in Carbon and Gold Nanotubes

We investigate the insertion of halide and alkali atoms into narrow single‐walled carbon nanotubes with diameters <9 Å by density functional theory; both chiral and non‐chiral tubes are considered. The atoms are stored in the form of ions; the concomitant charge transfer affects the band structure and makes originally semiconducting tubes conducting. The electrostatic interaction between a charge and the walls of the tube is explicitly calculated. The insertion energies and the positions of the ions are determined by a competition between electrostatic energy and Pauli repulsion. For comparison, we consider ions in gold nanotubes. Alkali ions follow the same principles in gold as in carbon tubes, but chloride is specifically adsorbed inside gold tubes.     

Removable singularities of solutions of linear uniformly elliptic second order equations

Let L be a uniformly elliptic linear second order differential operator in divergence form with bounded measurable real coefficients in a bounded domain G ? ?ⁿ (n ? 2). We define classes of continuous functions in G that contain generalized solutions of the equation L? = 0 and have the property that the compact sets removable for such solutions in these classes can be completely described in terms of Hausdorff measures.     

Removable Singularities of Solutions of the Minimal Surface Equation

Suppose that G is a bounded domain in ? ⁿ (n ? 2), E ≠ G is a relatively closed set in G, and 0 < α < 1. We prove that E is removable for solutions of the minimal surface equation in the class C ^1,α(G)_loc if and only if the (n ? 1 + α)-dimensional Hausdorff measure of E is zero.     

Investigation of double sulfates of potassium and rare earth elements with composition KRE(SO4)2

We have established the formation of anhydrous double sulfates of KRE(SO₄)₂ for the entire series of rare earth elements, which crystallize in five different structural types. The parameters of the unit cells of the double sulfates KRE(SO₄)₂ (RE = LaTb) have been determined. The thermal stability and character of decomposition of the double sulfates of potassium and rare earth elements have been investigated.     

Synthesis of 2′,3′-didehydro-3′-deoxythymidine and its activity against HIV

2,3-Didehydro-3-deoxythymidine has been obtained with an overall yield of 10% by the condensation of 1,2-di-O-acetyl-3,5-di-O-benzoyl-D-xylofuranose with bis-(dimethylsilyl)thymine and a series of subsequent transformations. The anti-HIV activity of the compound obtained was studied on the model of MT-4 lymphoid cells primarily infected with HIV-1. It was found that the substance effectively inhibits the reproduction of HIV-1 in a cell culture.Institute of Organic Chemistry, Ural Branch, Russian Academy of Sciences, Ufa. Vector Scientific-Production Association, Kil'tsovo, Novosibirsk Province. Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 133–136, January–February, 1993.