Biradical with the “non-linear” diacetylene fragment

The nitronyl nitroxide biradical, 2,2′-[1,1′-(hexa-2,4-diyne-1,6-diyl)bis(1H-pyrazole-4,1-diyl)]bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide 1-oxyl), was synthesized. The structure and magnetic properties of the biradical were studied. In the solid state, this nitroxide contains the nonlinear C^S-C≡C-C≡C-C^S fragment. The C^S-C≡C and C≡C-C≡ angles are 172.4(5) and 171.1(3)°, respectively. Dedicated to Academician G. A. Tolstikov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 385–390, February, 2008. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 385–390, February, 2008.     

On reductibility of degenerate optimization problems to regular operator equations

We present an application of the p-regularity theory to the analysis of non-regular (irregular, degenerate) nonlinear optimization problems. The p-regularity theory, also known as the p-factor analysis of nonlinear mappings, was developed during last thirty years. The p-factor analysis is based on the construction of the p-factor operator which allows us to analyze optimization problems in the degenerate case. We investigate reducibility of a non-regular optimization problem to a regular system of equations which do not depend on the objective function. As an illustration we consider applications of our results to non-regular complementarity problems of mathematical programming and to linear programming problems.     

Kinetics and mechanism of nickel ferrite formation under high temperature ultrasonic treatment

The effect of simultaneous ultrasonic and thermal treatment on kinetics and mechanism of nickel ferrite formation was studied. It was established that sonication leads to notable increase of the mean rate of this reaction and decrease of effective activation energy from 190+/-5 to 125+/-7 kJ/mol. XRD data show that ultrasonic treatment significantly affects the microstructure of both initial reagent (Fe(2)O(3)) and reaction product (NiFe(2)O(4)) thus promoting formation of well developed reaction zone. A general model of ferrite formation mechanism under high temperature ultrasonic treatment was proposed.     

Scanning X-ray fluorescence microanalysis of annual layers in samples of Lake Shira bottom sediments

The interannual and interseasonal variations in the trace element composition of annual layers in bottom sediments of Lake Shira (Khakassia) are studied by means of X-ray scanning microanalysis with synchrotron radiation on the VEPP-3 (Novosibirsk) and BESSY-II (Berlin) storage rings. The relationship between sediment composition and weather and climatic conditions is established. The possibility of paleoclimatic reconstructions with annual temporal resolution is demonstrated.     

Molecular magnets based on chain polymer complexes of copper(II) bis(hexafluoroacetylacetonate) with isoxazolyl-substituted nitronyl nitroxides

First isoxazolyl-substituted nitronyl nitroxides (L and $L^{Me_2 }$ ) were synthesized and characterized. Their reactions with Cu(hfac)₂ and Mn(hfac)₂ (hfac is hexafluoroacetylacetonate) afford the heterospin complexes [Cu(hfac)₂L] _n , [Cu₂(hfac)₄L] _n , $\left[ {Cu_2 (hfac)_4 L^{Me_2 } } \right]_n$ , $\left[ {Cu(hfac)_2 L^{Me_2 } } \right]_n$ , $\left[ {Cu(hfac)_2 L^{Me_2 } _2 } \right]$ , $\left[ {Cu(hfac)_2 L^{Me_2 } (MeCN)} \right]$ , [Mn(hfac)₂]₃L₄, and $\left[ {Me(hfac)_2 L^{Me_2 } } \right]_2$ . In the ligand L, the N atom of the isoxazole ring (NIz) has weak electron-donating properties. For example, the paramagnetic ligand in the chain polymer complex [Cu(hfac)₂L] _n acts as a bidentate bridging ligand coordinated through both O atoms of the nitronyl nitroxide group (O_N-O); the N_Iz and O_Iz atoms are not involved in the coordination. The introduction of Me groups into the isoxazole substituent results in an increase in the electron density on the N_Iz atom and enables the synthesis of the chain polymer complex $\left[ {Cu(hfac)_2 L^{Me_2 } } \right]_n$ , in which the bidentate bridging ligand $L^{Me_2 }$ is coordinated through the O_N-O and N_Iz atoms. In the mononuclear complexes $\left[ {Cu(hfac)_2 L^{Me_2 } _2 } \right]$ and $\left[ {Cu(hfac)_2 L^{Me_2 } (MeCN)} \right]$ , the paramagnetic ligand is coordinated only through the N_Iz atom. The solid heterospin Mn complexes [Mn(hfac)₂]₃L₄ and $\left[ {Mn(hfac)_2 L^{Me_2 } } \right]_2$ have a molecular structure. In these complexes, strong antiferromagnetic intracluster exchange interactions arise. The residual magnetic moments of the exchange clusters in the complex [Mn(hfac)₂]₃L₄ are ferromagnetically coupled, resulting in the increase in the effective magnetic moment (??_eff) of the complex with decreasing temperature in the range of 300??30 K. The thermomagnetic study of the complexes [Cu(hfac)₂L] _n , [Cu₂(hfac)₄L] _n , and $\left[ {Cu_2 (hfac)_4 L^{Me_2 } } \right]_n$ in the range of 2?C300 K revealed the ferromagnetic ordering at temperatures below 5 K. The ESR study of the solid complex $\left[ {Cu(hfac)_2 L^{Me_2 } } \right]_n$ showed that the decrease in its ??_eff in the temperature range of 30?C300 K is associated with the direct exchange interaction between the unpaired electrons of the nitronyl nitroxides of adjacent chains, whereas at temperatures below 30 K, only Cu²⁺ ions contribute to the magnetic susceptibility of the complex.     

Electron ionization mass spectra of alkylated sulfabenzamides

Mono‐, di‐ and trialkyl derivatives of 'sulfabenzamide' (N‐4‐aminophenylsulfonylbenzamide) have been prepared and their electron ionization (EI) mass spectra examined. It is found that the fragmentation of N‐alkylsulfabenzamides (alkyl = CH₃ to n‐C₅H₁₁) proceeds via a very specific rearrangement process. The proposed mechanism involves an intermediate formation of distonic molecular ions, and the driving force for this process is the formation of stable N‐alkylphenylcyanide cations [R‐N⁺ ? CC₆H₅]. The findings are confirmed by exact mass measurements, tandem mass spectrometry (MS/MS) experiments and deuterium labeling. Published in 2011 by John Wiley & Sons, Ltd.     

Pb3+ radiation defects in Ca9Pb(PO4)6(OH)2 hydroxyapatite nanoparticles studied by high-field (W-band) EPR and ENDOR

W-band pulsed EPR and ENDOR investigations of X-ray irradiated nanoparticles of synthetic hydroxyapatite Ca(9)Pb(PO(4))(6)(OH)(2) are performed. It is shown that in the investigated species lead ions probably replace the Ca(1) position in the hydroxyapatite structure.     

Cosmology in modified <Emphasis Type="Italic">f</Emphasis>(<Emphasis Type="Italic">R</Emphasis>, <Emphasis Type="Italic">T</Emphasis>)-gravity

In the present paper we propose a further modification of f(R, T)-gravity (where T is trace of the energy-momentum tensor) by introducing higher derivatives matter fields. We discuss stability conditions in the proposed theory and find restrictions for the parameters to prevent appearance of main type of instabilities, such as ghost-like and tachyon-like instabilities. We derive cosmological equations for a few representations of the theory and discuss main differences with conventional f(R, T)-gravity without higher derivatives. It is demonstrated that in the theory presented inflationary scenarios appear quite naturally even in the dust-filled Universe without any additional matter sources. Finally, we construct an inflationary model in one of the simplest representation of the theory, calculate the main inflationary parameters and find that it may be in quite good agreement with observations.     

Investigation of cold rubidium Rydberg atoms in a magneto-optical trap

This paper reports on the results of experiments with cold rubidium Rydberg atoms in a magneto-optical trap. The specific feature of the experiments is the excitation of Rydberg atoms in a small volume within a cloud of cold atoms and the sorting of measured signals and spectra according to the number of detected Rydberg atoms. The effective lifetime of the 37P Rydberg state and its polarizability in a weak electric field are measured. The results obtained are in good agreement with theoretical calculations. It is demonstrated that the localization of the excitation volume in the vicinity of the zero-magnetic-field point makes it possible to improve the spectral resolution and to obtain narrow microwave resonances in Rydberg atoms without switching off the quadrupole magnetic field of the trap. The dependence of the amplitude of dipole-dipole interaction resonances in Rydberg atoms on the number of atoms is measured. This dependence exhibits a linear behavior and agrees with the theory for a weak dipole-dipole interaction.     

Directional radiation pattern of luminescent photonic crystals at frequencies near the second photonic stop band

The possibility of the directional enhancement of luminescence at frequencies near the edge of the second photonic bandgap of opal-type photonic crystals has been demonstrated both theoretically and experimentally. The directional patterns of radiation have been simulated by calculating the angular dependences of the density of optical states. The calculation results are compared to the experimental data obtained for the thin-film opals with terbium-containing complexes. Good agreement is achieved after the strong smoothing of the calculated curves; this smoothing is necessary because of the imperfection of the structure of actual samples.