Loss of electrons by fast H− ions in gases

The characteristic angles and cross sections for a (\mathop 1^- 0) + (\mathop 1^- 1)(\mathop 1\limits^ - 0) + (\mathop 1\limits^ - 1) reaction in which H⁻ atoms with an energy of 0.1–10 000 MeV lose electrons when scattered on C, N, or O atoms were calculated for the relativistic case of the Bethe scattering theory. The cross sections for N₂, O₂, and CO₂ molecular targets were obtained using the additivity rule. The results presented are compared with known experimental and theoretical data.     

Trends in the kinetic and magnetic properties of Pb0.8Sn0.2Te single crystals of high structural perfection

In the temperature interval 4.2–300K and magnetic fields up to 4 T, we have investigated the electrical, thermal-electrical, thermal-magnetic, and magnetic properties of single crystals of the solid solution Pb_0.8Sn_0.2Te. It is shown that an enhancement of its level of structural perfection leads to the appearance of a second structural phase transition (SPT), and also to an increase in the temperature of the first structural phase transition. Fiz. Tverd. Tela (St. Petersburg) 41, 1750–1752 (October 1999)     

Control of sp2/sp3 carbon ratio and surface chemistry of nanodiamond powders by selective oxidation in air

The presence of large amounts of nondiamond carbon in detonation-synthesized nanodiamond (ND) severely limits applications of this exciting nanomaterial. We report on a simple and environmentally friendly route involving oxidation in air to selectively remove sp(2)-bonded carbon from ND. Thermogravimetric analysis and in situ Raman spectroscopy shows that sp(2) and sp(3) carbon species oxidize with different rates at 375-450 degrees C and reveals a narrow temperature range of 400-430 degrees C in which the oxidation of sp(2)-bonded carbon occurs with no or minimal loss of diamond. X-ray absorption near-edge structure spectroscopy detects an increase of up to 2 orders of magnitude in the sp(3)/sp(2) ratio after oxidation. The content of up to 96% of sp(3)-bonded carbon in the oxidized samples is comparable to that found in microcrystalline diamond and is unprecedented for ND powders. Transmission electron microscopy and Fourier transform infrared spectroscopy studies show high purity 5-nm ND particles covered by oxygen-containing surface functional groups. The surface functionalization can be controlled by subsequent treatments (e.g., hydrogenization). In contrast to current purification techniques, the air oxidation process does not require the use of toxic or aggressive chemicals, catalysts, or inhibitors and opens avenues for numerous new applications of nanodiamond.     

Energy version of the kinetic equations of isothermal creep and long-term strength

Energy-type kinetic equations of inelastic rheological deformation are proposed in which the elastic, plastic, and creep strains are the additive components of the total strain, and the damage parameter is taken into account. A model of viscoelastic material with a creep kernel of exponential type is considered. The Lyapunov stability of solutions under constant stress is studied. The stability range of the solutions of the differential equations of the mathematical model corresponding to asymptotically bounded creep is established. It is shown that the instability range of the solutions corresponds to the onset of the third stage of creep. The relationship is determined between the Lyapunov stability of the solutions and the stability of the computational algorithm for the numerical solution of the system of equations. The proposed model is experimentally verified. It is shown that the calculated and experimental data are in good agreement.     

Heat equation with a general stochastic measure on nested fractals

A stochastic heat equation on an unbounded nested fractal driven by a general stochastic measure is investigated. Existence, uniqueness and continuity of the mild solution are proved provided that the spectral dimension of the fractal is less than 4/3.     

Mathematical model of creep for a microinhomogeneous nonlinearly elastic material

A mathematical model is proposed to describe the experimentally observed creep effect on the instantaneous elastic deformation of physically nonlinear elastic microinhomogeneous materials. Using a structural model of the medium, it is shown that, during unloading of a sample after creep at constant stress, the elastic strain can be both larger and smaller than the elastic strain during loading. It is shown that calculation results for a biocomposite material are in good agreement with experimental data. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 157–163, May–June, 2008.     

Synthesis and Evaluation of a Macrocyclic Actinium-225 Chelator,Quality Control and In Vivo Evaluation of 225Ac-crown-αMSH Peptide

Targeted alpha-therapy (TAT) has great potential for treating a broad range of late-stage cancers by delivering a focused and lethal radiation dose to tumors. Actinium-225 (²²⁵Ac) is an emerging alpha emitter suitable for TAT; however, the availability of chelators for Ac remains limited to a small number of examples (DOTA and macropa). Herein, we report a new Ac macrocyclic chelator named ‘ crown’ , which binds quantitatively and rapidly (<10 min) to Ac at ambient temperature. We synthesized ²²⁵Ac- crown -αMSH, a peptide targeting the melanocortin 1 receptor (MC1R), specifically expressed in primary and metastatic melanoma. Biodistribution of ²²⁵Ac- crown -αMSH showed favorable tumor-to-background ratios at 2 h post injection in a preclinical model. In addition, we demonstrated dramatically different biodistrubution patterns of ²²⁵Ac- crown -αMSH when subjected to different latency times before injection. A combined quality control methodology involving HPLC, gamma spectroscopy and radioTLC is recommended.     

Investigation of Glasses and Glaze Coats of Composition R2O–RO–Fe2O3(FeO)–Al2O3–B2O3–SiO2 by the EPR Method

The valence state and the coordination environment of the paramagnetic centers of iron ions in glasses and vitreous coats of composition R₂O–RO–Fe₂O₃(FeO)–Al₂O₃–B₂O₃–SiO₂ have been investigated by the EPR method. The tetrahedral and octahedral coordinations of Fe³⁺ ions have been revealed. The character of change in the EPR spectra of the materials studied in the vitreous and vitrocrystalline state has been determined. It is shown that the coordination number of iron ions is dependent on the crystallization processes.     

Fedosov supermanifolds

We study the properties of the symplectic curvature tensor on supermanifolds. Using the method of normal coordinates, we establish higher-order relations between affine extensions of the curvature tensor and of the symplectic structure tensor. We find a generating function for higher-order relations. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 149, No. 2, pp. 202–227, November, 2006.     

Dielectric constant of polymer matrices containing isolated inclusions: Giant dielectric enhancement instead of collective resonance

A giant increase in the static dielectric constant and a giant dielectric relaxation are predicted for a heterogeneous medium consisting of matrix-isolated spheroids and described by the Maxwell-Garnett formula. The possibility of observing collective dielectric resonance in such a medium is also discussed.