Time-resolved electron detachment imaging of the I- channel in I2Br- photodissociation

The evolution of the I(-) channel in I(2)Br(-) photodissociation is examined using time-resolved negative-ion photoelectron imaging spectroscopy. The 388 nm photodetachment images obtained at variable delays following 388 nm excitation reveal the transformation of the excess electron from that belonging to an excited trihalide anion to that occupying an atomic orbital localized on the I(-) fragment. With increasing pump-probe delay, the corresponding photoelectron band narrows on a approximately 300 fs time scale. This trend is attributed to the localization of the excess-electron wave function on the atomic-anion fragment and the establishment of the fragment's electronic identity. The corresponding band position drifts towards larger electron kinetic energies on a significantly longer, approximately 1 ps, time scale. The gradual spectral shift is attributed to exit-channel interactions affecting the photodetachment energetics, as well as the photoelectron anisotropy. The time-resolved angular distributions are analyzed and found consistent with the formation of the asymptotic I(-) fragment.     

Study of acid pyridine-3-carboxylic acid dodecatungstenphosphate of the composition (C6NO2H5)2H[PW12O40]·2H2O

Acid pyridine-3-carboxylic acid dodecatungstenphosphate (C₆NO₂H₅)₂H[PW₁₂O₄₀]·2H₂O is synthesized. The compound is studied by chemical analysis, IR spectroscopy, X-ray crystallography, and thermogravimetry. The compound is found to crystallize at 290 K in a hexagonal crystal system (space group \(R\bar 3\) ) (I) with the unit cell parameters: a = 33.015(6) Å, c = 12.010(2) Å, γ = 120°, V = 11337(4) ų, Z = 9. When the temperature decreases to 100 K, a phase transition is observed leading to an increase in symmetry to \(R\bar 3m\) (II), with the unit cell parameters: a = 33.072(1) Å, c = 24.234(1) Å, γ = 120°, V = 22955(2) ų, Z = 18.     

Lead and cadmium atomic absorption determination in solid carbonized food samples using flame-furnace atomizer

Direct atomic absorption solid sampling analysis using flame-furnace atomizer enables a significant decrease in the analysis duration, to avoid sample pollution and to exclude toxic reagents. The selection of the chemical modifiers decreasing the detection limit and improving the results repeatability is based on the analyte’s free atoms formation mechanism. The developed kinetic approach has allowed to determine pre-exponential factors k₀ and apparent activation energies E_a of atomization processes for Pb(II) and Cd(II) compounds and to propose effective chemical modifiers sodium N,N-diethyldithiocarbamate and urea for food samples. The express and precision technique for lead and cadmium determination in food, using proposed chemical modifiers and carbonization techniques was developed.      

Synthesis of 2,3-bis(perfluoroalkyl)quinoxalines and 2,3-bis(perfluoroalkyl)-1,4-benzoxazines from oxides of internal perfluoroolefins

The reactions of oxides of internal trans-, cis-perfluoroolefins with o-phenylenediamine and 2-aminophenol in dioxane gave 2,3-bis(perfluoroalkyl)quinoxalines and 2,3-bis(perfluoroalkyl)-2H-1,4-benzoxazin-2-ols respectively in yields of 23-67%. When N,N-dimethylacetamide was used as a solvent an anionic isomerization of the oxides into ketones, which further yielded 2-(perfluoroalkyl)benzimidazoles in the case of o-phenylenediamine and 2-hydroxy-N-perfluoroalkanoylanilines in the case of 2-aminophenol, became the main path of these reactions. Unusual cyclization resulting in 2-pentafluoroethyl-2-pentafluoropropanoylbenzoxazolidine occurs on interaction between dodecafluoro-3,4-epoxyhexane and 2-aminophenol in N,N-dimethylacetamide.     

Quivers of Associative Rings

The concept of a quiver, i.e., a direct graph of a finite-dimensional algebra, was introduced by Gabriel in connection with problems of representation theory of such algebras. The notion of a scheme (=quiver Q(A)) of a semiperfect, right Noetherian ring A was introduced by the author and was applied to the study of the structure of serial rings. We give a short review of some results on structural ring theory, which were obtained by using the graph technique. __________ Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 14, Algebra, 2004.