7-Azabicyclo[2.2.1]heptadienes in electrophilic chalcogenation reactions

Russian Chemical Bulletin - Reactions of electrophilic chalcogenation (sulfenylation and selenenylation) of 7-azabicyclo[2.2.1]heptadiene derivatives with electron-withdrawing substituents at the...     

Influence of Medium Parameters and Acrylate Ionic Terpolymer Concentration on the Toms Effect

The influence of the solution ionic strength (up to 1.89 M), temperature (up to 413 K) and acidity (pH down to 1.65) on the drag reduction DR and flow rate increment ΔQ of an aqueous solution of the terpolymer containing 71.6 mol % acrylamide, 10.5 mol % acrylonitrile, and 17.9 mol % sodium 2-acrylamido-2-methylpropanesulfonate was studied by capillary turbulent viscometry. The intrinsic performance and the optimum concentrations of the terpolymer under these conditions were determined. The temperature dependence of the flow rate increment for the terpolymer solution passes through a maximum. The turbulence drag reduction for water flows at temperatures exceeding 373 K was demonstrated.     

Dual reactivity of N-heterocyclic carbenes towards copper(II) salts

Complexes of N-heterocyclic carbenes (NHCs) with copper(II) halogenides are unstable. Upon formation, these complexes decompose to give haloamidinium salts. Contrastingly, O-substituted copper(II) NHC complexes are fairly stable. A series of new five-, six- and seven-membered ring NHC complexes of Cu(OAc)(2) have been synthesised and characterised in the solid state.     

Skew linear recurring sequences of maximal period over galois rings

Let p be a prime number, and R = GR(q ^d , p ^d ) be a Galois ring of q ^d = p ^rd elements and of characteristic p ^d . Denote by S = GR(q ^nd , p ^d ) a Galois extension of the ring R of dimension n and by ? the ring of all linear transformations of the module _R S. We call a sequence v over the ring S with the law of recursion $$ {\mathrm{for}\ \mathrm{all}\ }i \in {\mathbb{N}_0}:v\left( {i + m} \right) = {\psi_{m - 1}}\left( {v\left( {i + m - 1} \right)} \right) + \cdots + {\psi_0}\left( {v(i)} \right),\quad {\psi_0}, \ldots, {\psi_{m - 1}} \in \textit{\v{S}} $$ (i.e., a linear recurring sequence of order m over the module _? S) a skew LRS over S. It is known that the period T(v) of such a sequence satisfies the inequality T(v) ?? ?? = (q ^nm ?1)p ^d?1. If T(v) = ?? , then we call v a skew LRS of maximal period (a skew MP LRS) over S. A new general characterization of skew MP LRS in terms of coordinate sequences corresponding to some basis of a free module _R S is given. A simple constructive method of building a big enough class of skew MP LRS is stated, and it is proved that the linear complexity of some of them (the rank of the linear recurring sequence) over the module _S S is equal to mn, i.e., to the linear complexity over the module _R S.     

Random ballistic growth and diffusion in symmetric spaces

Sequential ballistic deposition (BD) with next-nearest-neighbor (NNN) interactions in a N  -column box is viewed as a time-ordered product of (N×N)$(N\times N)$-matrices consisting of a single _sl2${\mathit{sl}}_2$-block which has a random position along the diagonal. We relate the uniform BD growth with the diffusion in the symmetric space _HN=SL(N,R)/SO(N)$H_N=\mathit{SL}(N,R)/\mathit{SO}(N)$. In particular, the distribution of the maximal height of a growing heap is connected with the distribution of the maximal distance for the diffusion process in _HN$H_N$. The coordinates of _HN$H_N$ are interpreted as the coordinates of particles of the one-dimensional Toda chain. The group-theoretic structure of the system and links to some random matrix models are also discussed.     

Investigation of temperature dependence of neutron yield and electron screening potential for the d(d, n)3He reaction proceeding in deuterides ZrD2 and TiD2

The temperature dependence of the enhancement factor for the dd reaction proceeding in TiD₂ and ZrD₂ is investigated. The experiments were carried out at the Hall pulsed ion accelerator (INP, Polytechnic University, Tomsk, Russia) in the deuteron energy interval 7.0?C12.0 keV and at temperatures ranging from 20 to 200°C. The values obtained for the electron screening potentials indicate that the dd reaction enhancement factor does not depend on the target temperature in the range 20?C200°C. This result contradicts the conclusions drawn by the LUNA Collaboration from their work.     

Effect of point defects on phase transitions in ferroelectric nanocrystals

The dependences of the phase transition temperature of ferroelectric nanocrystals in a dielectric matrix on the point charged defect concentration have been obtained. The influence of point defects on the nonlinear characteristics of ferroelectric nanocrystals has been studied as a function of the strength and direction of an external electric field with the adequate inclusion of depolarizing electric fields and nonlocal effects.     

Interpretation of the vibrational spectra of polycrystalline adenine

The infrared and Raman spectra of the tetramer of the adenine N₉H are calculated and analyzed. The vibrational spectra of polycrystalline adenine are interpreted. It is demonstrated that the method for calculating the vibrational spectra of molecular complexes formed by hydrogen bonds can be used for interpreting the vibrational spectra of polyatomic molecules in the solid state.     

Study of the possibility of solving cosmological lithium problem in an accelerator experiment

Within the standar dmodel of Big Bang Nucleosynthesis (BBN), there is a cosmological lithium problem, which consists in a substantial difference between calculated data on the abundances of the isotopes ⁶Li and ⁷Li and those that were found from observational astronomy. An attempt at measuring the cross section for the main 6Li production reaction ²H(⁴He, γ)⁶Li induced by the interaction of ⁴He⁺ ions with deuterons at collision energies less than the lower boundary of the BBN energy range was made in the present study. Upper limits on the cross sections for the reaction in question were set.     

The role of size effects in shaping the properties of heterogeneous ferroelectric active systems

The effect of the sizes and shapes of ferroelectric particles, one component of a dielectric composite, on the ferroelectric phase-transition temperature was studied within the phenomenological Landau theory. The metastable temperature range in which ferro- and paraelectric phases can coexist was determined. The temperature dependences of composite permittivity were calculated within the effective-medium approximation taking into account the sizes and concentration of ferroelectric particles.