Some derivatives of pyrimido [5,4-b]quinoline

10-Chloro-2,4-dioxo derivatives of pyrimido[5,4-b]quinoline have been synthesized, and nucleophilic substitution reactions in these compounds have been studied.     

Inductive sustainment of a field-reversed configuration stabilized by shaping, magnetic diffusion, and finite-Larmor-radius effects

Oblate field-reversed configuration (FRC) plasmas are sustained for up to 350 micros, or approximately 15 poloidal flux-confinement times, in the magnetic reconnection experiment. The diamagnetic equilibrium is maintained in argon plasmas as a balance of an inward pinch and outward diffusion. Numerical and analytic models show that the observed stability is provided by a combination of plasma shaping, magnetic diffusion, and finite-Larmor radius effects. FRCs formed with lighter ions, which benefit less from these stabilizing effects, succumb to rapid instability and cannot be sustained.     

Superlattices consisting of “lines” of adsorbed hydrogen atom pairs on graphene

The structures and electron properties of new superlattices formed on graphene by adsorbed hydrogen molecules are theoretically described. It has been shown that superlattices of the (n, 0) zigzag type with linearly arranged pairs of H atoms have band structures similar to the spectra of (n, 0) carbon nanotubes. At the same time, superlattices of the (n, n) type with a “staircase” of adsorbed pairs of H atoms are substantially metallic with a high density of electronic states at the Fermi level and this property distinguishes their spectra from the spectra of the corresponding (n, n) nanotubes. The features of the spectra have the Van Hove form, which is characteristic of each individual superlattice. The possibility of using such planar structures with nanometer thickness is discussed.     

Hydrolytic Stability and Photostability of Boron Complexes of Dibenzoylmethane with Various Substituents at the Boron Atom

High Energy Chemistry - The basic photophysical characteristics and the hydrolytic stability and photostability of dibenzoylmethanatoboron complexes containing various substituents at the boron...     

Synthesis and structure of (acetylacetonato-κ<Superscript>2</Superscript>-O,O′)(bistriphenylphosphine)palladium tetrafluoroborate as a precursor of catalysts active in the conversion of unsaturated hydrocarbons

An X-ray diffraction analysis is carried out for the complex [Pd(Acac)(PPh₃)₂]BF₄ (I), which is a precursor of the active complexes of styrene dimerization and norbornene additive polymerization in the system [(Acac)Pd(PPh₃)₂]BF₄-BF₃ · OEt₂. In complex I the palladium atom is coordinated by two oxygen atoms of the acetylacetonate ligand and two phosphorus atoms of the triphenylphosphine ligands at the vertices of the distorted square.     

Acid-Catalyzed Isomerization of 1-Halo-2-Arylthioalk-1-Enes

1-Halo-2-arylthioalk-1-enes, the anti-Markovnikov adducts of 1,2-halosulfenylation of terminal alkynes containing propargyl hydrogen atoms, were found to transform into a mixture of E - and Z -isomers of 1-halo-2-arylthioalk-2-enes under acid catalysis conditions. A plausible mechanism of rearrangement is proposed. The Markovnikov adducts 2-halo-1-arylthioalk-1-enes were partially converted into their cis -form under similar conditions. The halosulfenylation products of 1-phenylpent-1-yne did not show the signs of double-bond migration in the presence of an acid; only partial isomerization of the E - to the Z -isomers took place.     

Impact of urbanization and climate warming on energy consumption in large cities

This article considers the urban heat island effect, taking into account peculiarities of energy consumption in large cities. It is shown that energy demand in large cities must be planned, taking into account of the seasonal asymmetry of the impact of anthropogenic heat fluxes on energy demand of the urban economy in the warm and cold seasons of the year. Together with the heat island effect, climate changes in Russian cities should decrease the overall energy demand due to space heating and air conditioning. At the same time, the increasing energy share used for air conditioning always remains one or two orders of magnitude smaller than the energy share used for space heating.     

Electrical conductivity of cation-and anion-exchange membranes in ampholyte solutions

Several laws governing ampholyte transport through ion-exchange membranes are established by a comparative analysis of the concentration dependence of electrical conductivity for homogeneous (CMX, AMX) and heterogeneous (MK-40, MA-41) membranes in NaCl, LysHCl, and NaH₂PO₄ solutions. The increase in the electrical conductivity of membranes in ampholyte solutions as the solutions become more dilute is explained by the increased fraction of divalent ions of the amino acid (cation-exchange membrane) or from phosphoric acid (anion-exchange membrane) in the membrane as a result of Donnan exclusion of hydrolysis products (hydroxide ions or protons, respectively).     

Synthesis and colloidochemical properties of yttrium oxohydroxyde hydrosols

Abstaract  It is shown that hydrosols of oxygen-containing compounds of yttrium may be prepared by the peptization and condensation methods. Basic characteristics of hydrosols, such as the size and shape of particles, their phase compositions, electrophoretic mobility, and the pH range of the dispersion medium where sols are stable with respect to aggregation, are determined. Coagulation thresholds of the sols are estimated in the presence of sodium nitrate and sulfate. It is found that the hydrosols coagulate reversibly. Concentration and aging of the sols give rise to the spontaneous formation of slightly structured thixotropic gels. The nature of the aggregation stability of hydrosols is suggested. Original Russian Text ? I.A. Belova, K.I. Kienskaya, A.S. Grodskii, V.V. Nazarov, 2008, published in Kolloidnyi Zhurnal, 2008, Vol. 70, No. 5, pp. 601–606.