80 research outputs found
Formation of coloring complexes in glass colored with cerium and titanium oxides
The valence state of cerium and titanium ions in barium-strontium aluminosilicate glass with a different ratio of cerium and titanium oxides was investigated and the possible composition of the cerium-titanium complexes formed in silicate glass was analyzed. It was found that an active separate reaction between cerium and titanium
oxides with the appearance of complex color centers takes place in synthesis of the glass. It is hypothesized that color centers primarily form between tetravalent cerium and tetravalent titanium in glass-forming melts
Non-Weyl asymptotics for quantum graphs with general coupling conditions
Inspired by a recent result of Davies and Pushnitski, we study resonance
asymptotics of quantum graphs with general coupling conditions at the vertices.
We derive a criterion for the asymptotics to be of a non-Weyl character. We
show that for balanced vertices with permutation-invariant couplings the
asymptotics is non-Weyl only in case of Kirchhoff or anti-Kirchhoff conditions,
while for graphs without permutation numerous examples of non-Weyl behaviour
can be constructed. Furthermore, we present an insight helping to understand
what makes the Kirchhoff/anti-Kirchhoff coupling particular from the resonance
point of view. Finally, we demonstrate a generalization to quantum graphs with
nonequal edge weights.Comment: minor changes, to appear in Pierre Duclos memorial issue of J. Phys.
A: Math. Theo
Electrochemical reactions of white phosphorus
The main electrochemical transformations of elemental (white) phosphorus were considered. Special attention was given to the recently developed processes of preparation of organophosphorus compounds (OPCs) with phosphorus-carbon bonds. The electrochemical approaches to the synthesis of OPCs from white phosphorus using organonickel and organozinc reagents are described. The importance of using the electrochemical methods for the generation of highly reactive phosphorus intermediates was shown for phosphine oxide H3PO obtained for the first time. This provides significant prospects for the electrochemical approaches that could be applied for the development of technologies of the chlorine-free synthesis of OPCs from white phosphorus. © 2012 Springer Science+Business Media New York
Effect of a sacrificial anode material on the electrochemical generation of phosphane oxide (H3PO)
The highest yields of phosphane oxide in the title process were obtained in electrochemical cells supplied with aluminium (49%), tin (36%) or zinc (67%) anodes
Thermal stability of primary and secondary phosphine oxides formed as a reaction of phosphine oxide with ketones
© 2016 Taylor & Francis Group, LLC.We present the study of reactivity of electrochemically generated in situ from white phosphorus P4 phosphine oxide H3PO toward various ketones (acetone, methylethylketone, methyl-n-propylketone). This interaction was found to give a selective formation of mono- and bis-(α-oxyalkyl)phosphine oxides RRʹC(OH)P(O)H2 (1) and (RRʹC(OH))2P(O)H (2) where R = Me; Rʹ = Me, Et, n-Pr. Thermal properties of the formed primary and secondary phosphine oxides have been studied and quantum chemical calculations of thermodynamic stability of these compounds were performed
Spin dependent point potentials in one and three dimensions
We consider a system realized with one spinless quantum particle and an array
of spins 1/2 in dimension one and three. We characterize all the
Hamiltonians obtained as point perturbations of an assigned free dynamics in
terms of some ``generalized boundary conditions''. For every boundary condition
we give the explicit formula for the resolvent of the corresponding
Hamiltonian. We discuss the problem of locality and give two examples of spin
dependent point potentials that could be of interest as multi-component
solvable models.Comment: 15 pages, some misprints corrected, one example added, some
references modified or adde
Reactivity of phosphine oxide H<inf>3</inf>PO in the reactions with ketones
© 2016, Springer Science+Business Media New York.The reactivity of the electrochemically generated phosphine oxide H3PO towards ketones (acetone, ethyl methyl ketone, methyl n-propyl ketone, and tert-butyl methyl ketone) has been studied. It was found that this reaction led to the formation of mono- and bis(hydroxyalkyl)phosphine oxides of the formulas RRĆ(OH)P(O)H2 and [RRĆ(OH)]2P(O)H (R = Me; R´ = Me, Et, Pr) and represents the first example of the P—C bond formation involving the intermediate H3PO
Polymorphism and thermodynamic properties of chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium(II) complex
© 2016 Elsevier B.V. All rights reserved. A new crystalline polymorph of known chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium(II) complex [RuCl(PPh3)2(η5-C5H5)] was obtained and characterized by various analytical methods including single-crystal and powder X-ray diffraction (XRPD) and differential scanning calorimetry (DSC) in combination with thermo-gravimetric analysis (TG-DSC). The obtained crystals of new polymorph are monoclinic, space group P21/n, with a = 11.125(4), b = 19.184(6), c = 15.946(5) Å, α = 90, β = 100.174(5), γ = 90, and Z = 4. It has been found that real melting point of the complex (M.p. = 252-253 °C) can be determined only in inert atmosphere while an apparent melting is observed in the range 142-150 °C due oxygen promoted oxidative dissociation of triphenylphosphine ligand
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