Mass spectrometric decomposition of 2-dimethylamino-4-methoxy-6-polynitromethyl-1,3,5-triazines

Fragmentation of 6-fluoro(chloro, bromo)dinitromethyl-, 6-trinitromethyl-, 6-(1,1-dinitroethyl)-, and 6-(2-hydroxy-1,1-dinitroethyl)-2-dimethylamino-4-methoxy-1,3,5-triazines under electron impact was studied. The stability of the molecular ions and main fragmentation pathways are discussed.     

Trinitromethylation reactions of chloro-1,3,5-triazines

Reactions of chloro-1,3,5-triazines with trinitromethane salts were studied. Depending on conditions, trinitromethane salts used and special additives, six types of 2,4,6-trichloro-1,3,5-triazine trinitromethylation reactions were revealed, namely, bis-trinitromethylation-nitro-nyloxylation, bis-trinitromethylation-amination, bis-trinitromethylation-hydroxylation, trinitromethylation-dialkoxylation, trinitromethylation-diaryloxylation, and trinitromethylation-alkoxylation-aryloxylation. The mechanisms of reactions are proposed.     

Effect of Li doping on the critical temperature and glass formation in the Bi-Sr-Ca-Cu-O system

A study has been made of the glass-forming ability, structure, and superconducting properties of Bi_2.2Sr_1.8Ca_1.05Cu_2.15Li_xO_y and Bi_2.2Sr_1.8Ca_1.05Cu_2.15−x Li_xO_y (x=0;0.3;0.5;0.7). The compounds were melted by rf at T=1300–1500 °C. Rapid quenching produces glassy alloys whose glass-forming ability is the highest when lithium is substituted for copper. Glass annealing at 700–800 °C results in the formation of the HTSC phase 2212 with a critical temperature of up to 91 K. In lithium-doped samples the HTSC phase forms at lower temperatures and shorter anneals and it depends on the cooling rate following the anneal. The composition and properties of the 2212 phase depend nonmonotonically on the anneal time. The lattice parameter C of the 2212 phase increases with increasing lithium content. Fiz. Tverd. Tela (St. Petersburg) 41, 18–21 (January 1999)     

Specificities of Spin Wave Focusing in EuO and EuS Crystals

Physics of the Solid State - Specificities of spin wave focusing in EuO and EuS crystals are studied. It is shown that spin wave focusing is absent in the long-wave approximation: it is observed...     

Nuclear spin dynamics in the quantum regime of a single-molecule magnet

We show that the nuclear spin dynamics in the single-molecule magnet Mn12-ac below 1 K is governed by quantum tunneling fluctuations of the cluster spins, combined with intercluster nuclear spin diffusion. We also obtain the first experimental proof that-surprisingly-even deep in the quantum regime the nuclear spins remain in good thermal contact with the lattice phonons. We propose a simple model for how T-independent tunneling fluctuations can relax the nuclear polarization to the lattice that may serve as a framework for more sophisticated theories.     

Crystal and molecular structure of the potassium salt of 2,4-di-<Emphasis Type="Italic">iso</Emphasis>-propoxy-6-dinitromethyl-1,3,5-triazine

An X-ray diffraction study of the potassium salt of 2,4-di-iso-propoxy-6-dinitromethyl-1,3,5-triazine was performed. Monoclinic crystals, C₁₀H₁₄N₅O ₆ ^? ·K⁺; M = 339.36; a = 9.645(2) Å, b = 8.803(2) Å, c = 17.686(3) Å; β = 92.50(2)°; V = 1500.2(5) Å ³, d _c = 1.50 g/cm³, Z = 4, space group P2₁/a. The 2,4-di-iso-propoxy-6-dinitromethyl-1,3,5-triazine anion is nonplanar. The 1,3,5-triazine heterocycle is planar; the angle between the ring and the dinitromethyl fragment is 87.9(5)°. The potassium cation is in the general position; its coordination number is 7. The cation is bonded to four 2,4-di-iso-propoxy-6-dinitromethyl-1,3,5-triazine molecules. Infinite layers are formed due to the coordination bonds in crystal.     

Crystal and molecular structures of the potassium salt of 2-methoxy-4-dimethylamino-6-dinitromethyl-1,3,5-triazine

The X-ray diffraction study of the potassium salt of 2-methoxy-4-dimethylamino-6-dinitromethyl-1,3,5-triazine is carried out. The crystals are triclinic; C₇H₉N₆O ₅ ^? ·2K⁺·2H₂O; a = 7.645(7) Å, b = 8.230(7) Å, c = 12.435(9) Å; α = 99.99(8)°, β = 91.52(7)°, γ = 113.86(8)°; V = 701(1) ų, ρ_calc = 1.58 g/cm³, Z = 2, space group P-1. The compound crystallizes as a crystalline hydrate with two water molecules. Two planar fragments of dinitromethyl and 2-methoxy-4-dimethylamino-1,3,5-triazine construct the anion. Their geometrical parameters are explored. The coordination of potassium cations and numerous hydrogen bonds are found which result in the development of a complex 3-D framework.     

Low-temperature anisotropy of the thermal conductivity of single-crystal nanofilms and nanowires

The effect of phonon focusing on the phonon transport in single-crystal nanofilms and nanowires is studied in the boundary scattering regime. The dependences of the thermal conductivity and the free path of phonons on the geometric parameters of nanostructures with various elastic energy anisotropies are analyzed for diffuse phonon scattering by boundaries. It is shown that the anisotropies of thermal conductivity for nanostructures made of cubic crystals with positive (LiF, GaAs, Ge, Si, diamond, YAG) and negative (CaF₂, NaCl, YIG) anisotropies of the second-order elastic moduli are qualitatively different for both nanofilms and nanowires. The single-crystal film plane orientations and the heat flow directions that ensure the maximum or minimum thermal conductivity in a film plane are determined for the crystals of both types. The thermal conductivity of nanowires with a square cross section mainly depends on a heat flow direction, and the thermal conductivity of sufficiently wide nanofilms is substantially determined by a film plane orientation.     

Parametric Studies of a Globus-3 Spherical Tokamak with Various Options of Electromagnetic Systems Based on Copper Alloys Using the GLOBSYS Code

Physics of Atomic Nuclei - The engineering part of the GLOBSYS code is presented, and the parameters of the Globus-3 facility, which is a development of the Globus program, are analyzed. The...