2-(2-Pyridyl)indandione-1,3 and its zinc(II) and nickel(II) complexes: Synthesis and physicochemical characterization

Inner complex compounds (ICCs) and molecular adducts based on 2-(2-pyridyl)indandione-1,3 have been synthesized for the first time. The structure of the ligand (the preferred tautomer) and the complexes has been studied using X-ray crystallography, 1H NMR spectroscopy, and IR spectroscopy.     

IR-Spectroscopic Analysis of Hard Tissues of Lower “Wisdom” Teeth at the Eruption Stage of Connective Tissue Dysplasia

Journal of Applied Spectroscopy - A spectral analysis of the enamel, the enamel–dentin junction, and the dentin of human teeth with and without dysplasia of the connective tissue was carried...     

Finite-temperature perturbation theory for the random directed polymer problem

We study the random directed polymer problem—the short-scale behavior of an elastic string (or polymer) in one transverse dimension subject to a disorder potential and finite temperature fluctuations. We are interested in the polymer short-scale wandering expressed through the displacement correlator 〈[δu(X)]²〉, with δu(X) being the difference in the displacements at two points separated by a distance X. While this object can be calculated at short scales using the perturbation theory in higher dimensions d > 2, this approach becomes ill-defined and the problem turns out to be nonperturbative in the lower dimensions and for an infinite-length polymer. In order to make progress, we redefine the task and analyze the wandering of a string of a finite length L. At zero temperature, we find that the displacement fluctuations 〈[δu(X)]²〉 ∝ LX ² depend on L and scale with the square of the segment length X, which differs from a straightforward Larkin-type scaling. The result is best understood in terms of a typical squared angle 〈α²〉 ∝ L, where α = ? _x u, from which the displacement scaling for the segment X follows naturally, 〈[δu(X)]²〉 ∝ 〈α²〉 X ². At high temperatures, thermal fluctuations smear the disorder potential and the lowest-order results for disorder-induced fluctuations in both the displacement field and the angle vanish in the thermodynamic limit L → ∞. The calculation up to the second order allows us to identify the regime of validity of the perturbative approach and provides a finite expression for the displacement correlator, albeit depending on the boundary conditions and the location relative to the boundaries.     

Molecule-induced alkane homolysis with dioxiranes.

The mechanisms of C-H and C-C bond activations with dimethyldioxirane (DMD) were studied experimentally and computationally at the B3LYP/6-311+G**//B3LYP/6-31G* density functional theory level for the propellanes 3,6-dehydrohomoadamantane (2) and 1,3-dehydroadamantane (3). The sigma(C-C) activation of 3 with DMD (Delta G(*) = 23.9 kcal mol(-1) and Delta G(r) = -5.4 kcal mol(-1)) is the first example of a molecule-induced homolytic C-C bond cleavage. The C-H bond hydroxylation observed for 2 is highly exergonic (Delta G(r) = -74.4 kcal mol(-1)) and follows a concerted pathway (Delta G(*) = 34.8 kcal mol(-1)), in contrast to its endergonic molecule-induced homolysis (Delta G(*) = 28.8 kcal mol(-1) and Delta G(r) = +9.2 kcal mol(-1)). The reactivities of 2 and 3 with CrO(2)Cl(2), which follow a molecule-induced homolytic activation mechanism, parallel the DMD results only for highly reactive 3, but differ considerably for more stable propellanes such as 4-phenyl-3,6-dehydrohomoadamantane (1) and 2.     

Several features of the Ar<Superscript>+</Superscript>-ion irradiation of vanadium and its alloys

Changes in the surface properties of vanadium and its alloys irradiated by Ar⁺ ions with the energy 20 keV, to a dose of 10²² m⁻² at T _irr ≈ 700K have been studied. The radiation effect consists of material surface hardening, increasing the lattice parameters of the irradiated samples, and radiation erosion of the surface layers in the form of flaking. Features of radiation damage to the material’s surface irradiated by gas ions with high sputtering coefficients are discussed.     

Molecular dynamics investigation of the helical structure of smectic C*

The numerical simulation of the behavior of the molecules of the DOBAMBC liquid crystal by the molecular dynamics method allowed us to find the change of the the conformation of molecules as a function of temperature and to reveal the helical structures with various pitches in the smectic phase C*. These results explained the anomalous temperature dependences of the order parameter at the molecular level, as well as the optical second harmonic generation in the region of smectic A.