General laws of X-ray reflection from rough surfaces: I. Optical theorem and energy conservation law

The optical theorem is generalized for the general case of X-ray wave reflection from an arbitrary layered rough medium. It is proven strictly that in the absence of absorption the energy conservation law is exactly satisfied within the distorted wave Born approximation if the angular scattering distribution is calculated taking into account only the single wave scattering from the inhomogeneities of the medium and if the specular reflectance and transmittance are calculated with allowance for both single and double scattering.     

Inverse and implicit function theorems on carnot manifolds

We obtain some analogs of the Euclidean inverse and implicit function theorems for continuously hc-differentiable mappings on Carnot manifolds.     

On Minimum Static Breakdown Voltage for a Gasfilled Gap

Russian Physics Journal - Relying on the condition of the discharge self-sustainment, a theoretical analysis is performed aimed at identifying the lowest possible discharge voltage. It is shown...     

Channeling of Neutrons in a Planar Waveguide

The propagation of neutrons in the middle layer of a planar waveguide in the form of a three-layer thin film has been investigated. The microbeam from the end face of the film has been registered. The neutron channeling length has been measured as a function of the thickness of the upper waveguide layer and the resonance order. The experimental data have been compared with theoretical results.     

Barkhausen jumps in the motion of a single ferroelectric domain wall

It is shown that the motion of a domain wall in the improper ferroelectric-ferroelastic gadolinium molybdate Gd₂(MoO₄)₃ demonstrates a self-organized critical behavior under polarization reversal. Barkhausen pulses are measured experimentally during the jumpwise motion of a single plane domain wall in monocrystalline plates with artificial pinning centers of the “field inhomogeneity” type.     

5-Acylmethyl-3-(2-pyridyl)-1,2,4-triazines: Synthesis and Complexes with Cu(II)

5-Acylmethyl-3-(2-pyridyl)-1,2,4-triazines are easily prepared from accessible 3-(2-pyridyl)-1,2,4-triazine 4-oxides by reaction of the latter with acetophenone or trifluoroacetone in the presence of NaH. The compounds obtained behaved as efficient ligands in reaction with CuCl₂ furnishing dimeric neutral complexes with Cu(II) whose structure was investigated by means of X-ray diffraction analysis.     

Oxidation of primary alcohols to aldehydes with oxygen catalysed by tetra-n-propylammonium perruthenate

The liquid-phase oxidation of a series of saturated and unsaturated non-allylic alcohols to aldehydes with oxygen or air catalysed by tetra-n-propylammonium perruthenate (TPAP, represented as [(n-Pr)₄N]RuO₄) at 80–110 °C is shown to proceed with selectivities of 72–91% at 55–80% alcohol conversion. The unsaturated alcohols, such as 9-decenol, 9-octadecenol and β-citronellol, give the corresponding unsaturated aldehydes without competing double bond attack. The time course of oxidation indicates a complex reaction mechanism. The results on oxidation of a test alcohol, t-Bu(Ph)CHOH, suggest that one-electron processes do not play an important role in the TPAP-catalysed aerobic oxidation of alcohols.     

The thermodynamic properties of weakly bound oxygen and electron transport in Sr3Fe2O6+δ under oxidizing conditions

The content of oxygen, electrical conductivity, and thermal electromotive force were measured for ferrite Sr₃Fe₂O_6+δ over the oxygen partial pressure range 10^?4–0.5 atm at 650–950°C. The partial molar thermodynamic functions of weakly bound oxygen in the oxide structure were determined. Labile oxygen ions were characterized as an ensemble of weakly interacting particles. The predominant charge carriers under experimental conditions were electron holes. An analysis of conductivity was performed using the data on the oxygen content. The concentration, activation energy, and mobility of charge carriers were determined. The results can be satisfactorily interpreted using the polaron transfer model of conductivity taking into account the charge disproportionation reaction for iron ions, 2Fe⁴⁺ = Fe³⁺ + Fe⁵⁺.     

Phosphorescence vs fluorescence in cyclometalated platinum(II) and iridium(III) complexes of (oligo)thienylpyridines

Two newly prepared oligothienylpyridines, 5-(2-pyridyl)-5'-dodecyl-2,2'-bithiophene, HL(2), and 5-(2-pyridyl)-5'-dodecyl-2,2':5',2'-ter-thiophene, HL(3), bind to platinum(II) and iridium(III) as N∧C-coordinating ligands, cyclometallating at position C(4) in the thiophene ring adjacent to the pyridine, leaving a chain of either one or two pendent thiophenes. The synthesis of complexes of the form [PtL(n)(acac)] and [Ir(L(n))(2)(acac)] (n = 2 or 3) is described. The absorption and luminescence properties of these four new complexes are compared with the behavior of the known complexes [PtL(1)(acac)] and [Ir(L(1))(2)(acac)] {HL(1) = 2-(2-thienyl)pyridine}, and the profound differences in behavior are interpreted with the aid of time-dependent density functional theory (TD-DFT) calculations. Whereas [PtL(1)(acac)] displays solely intense phosphorescence from a triplet state of mixed ππ*/MLCT character, the phosphorescence of [PtL(2)(acac)] and [PtL(3)(acac)] is weak, strongly red shifted, and accompanied by higher-energy fluorescence. TD-DFT reveals that this difference is probably due to the metal character in the lowest-energy excited states being strongly attenuated upon introduction of the additional thienyl rings, such that the spin-orbit coupling effect of the metal in promoting intersystem crossing is reduced. A similar pattern of behavior is observed for the iridium complexes, except that the changeover to dual emission is delayed to the terthiophene complex [Ir(L(3))(2)(acac)], reflecting the higher degree of metal character in the frontier orbitals of the iridium complexes than their platinum counterparts.