Synthesis of mesoporous γ-alumina by sol–gel process and its characterization and application for sorption of Pu(IV)

Mesoporous γ-alumina samples were prepared by the sol–gel process from the boehmite sol having different template solutions. Copper doped material was also prepared from sol containing template solution along with copper nitrate. Studies were performed to understand the influence of templates on the morphology of the synthesized samples particularly with respect to specific surface area and porosity. Synthesized samples were used to study sorption of Pu(IV) from nitric acid–oxalic acid solutions. Distribution ratios (D) for Pu(IV) were determined using the γ-alumina samples with an objective to employ these for the recovery of Pu.     

A note on maximizing the permanent of a positive definite hermitian matrix,given the eigenvalues ∗

As a step toward understanding the unsolved problem of determining how large the permanent of a positive semi-definite matrix can be, given the eigenvalues, we note that a necessary condition for A to be a permanent maximizing matrix is that A commute with its permanental adjoint.     

Kinetics of carbon monoxide methanation on nickel catalysts

The kinetics of CO methanation in excess H₂ on CaO- and CeO₂-doped nickel catalysts supported on Al₂O₃ and TiO₂ was studied at atmospheric pressure in a temperature range of 180–240°C. It was found that the same rational fractional rate equation corresponding to the reaction taking place at high surface coverages, is valid for all of the catalysts. The activity of nickel catalysts in the methanation reaction and their adsorption capacity with respect to reaction mixture components depend on the nature of the support and dopants.     

Theoretical Studies on the Binding of Cd~（2＋） to Uracil and Its Thio-derivatives

The interaction of Cd2+ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory(DFT) calculations.For uracil and 2,4-dithiouracil,where the two basic sites are the same,Cd2+ attachment to the heteroatom at position 4 is preferred.However,for the systems where both types of basic centers,a carbonyl and a thiocarbonyl groups,are present,Cd2+ association with sulfur is favorable.The enhanced stability of these enolic and thiol forms comes from Cd2+ interaction with two basic sites simultaneously,which thereby triggers a significant aromatization of the ring.More significantly,the Cd2+ binding energy with uracil and its thio-derivatives is larger than the tautomerization barriers connecting the diketo-like forms with the corresponding enolic-like tautomers.Consequently,when associated with Cd2+,all tautomers are energetically accessible and should be observed in the gas phase.     

Flat 3-webs via semi-simple Frobenius 3-manifolds

We construct flat 3-webs via semi-simple geometric Frobenius manifolds of dimension three and give geometric interpretation of the Chern connection of the web. These webs turned out to be biholomorphic to the characteristic webs on the solutions of the corresponding associativity equation. We show that such webs are hexagonal and admit at least one infinitesimal symmetry at each singular point. Singularities of the web are also discussed.     

On the state of Mn impurity implanted in Si

The state of manganese impurity in implanted silicon at implantation doses of up to 5 × 10¹⁶ cm^?2 has been investigated by X-ray diffraction and transmission electron microscopy. It is established that, after short-term vacuum annealing at 850°C, most of the implanted manganese impurities are in microinclusions up to 20 nm in size formed by a tetragonal silicide phase of the Mn₁₅Si₂₆ type.     

Boson-fermion mixed site states

It is shown that an essential aspect in the study of polarons, which belong to multiparticle systems, is a correct selection of the Fock space from a manifold of unitarily inequivalent representations. Using the quantum field theory, we have studied a single-site polaron model with an allowance for the electron correlations at a lattice site. This model takes into account the formation of a charged site boson state in addition to the single-particle fermion states. It is demonstrated that, provided the initial site sates are half-occupied, the formation of boson-polaron mixed site states takes place. The thermodynamics of these states is considered.     

Halobenzenes in the Duff reaction

Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, p. 228, January, 1993.     

A note on maximizing the permanent of a positive definite hermitian matrix, given the eigenvalues

As a step toward understanding the unsolved problem of determining how large the permanent of a positive semi-definite matrix can be, given the eigenvalues, we note that a necessary condition for A to be a permanent maximizing matrix is that A commute with its permanental adjoint.