A Study of the Optical Properties of a Multimode Silica Optical Fiber with a Reflective Shell from a Fluorinated Thermoplastic Polymer

Optics and Spectroscopy - The optical properties of a silica–polymer optical fiber with a light-guide core with a diameter of 430 μm and a reflecting shell with a thickness of 70 μm...     

Complex formation of pyridine <Emphasis Type="Italic">N</Emphasis>-oxides with iodine

Complex formation of N-oxides of pyridine, 2- and 3-picolines, 4-nitropyridine, and 2,6-lutidine with iodine in benzene solutions and binary solid mixtures gives rise to equimolar complexes. In the solid phase, 1 : 2 and 2 : 1 complexes are also formed. Most solid complexes are polymorphous, and the enthalpies of intermolecular bonds in different crystal modifications are different. In solutions, external complexes pass into more stable internal complexes. The formation enthalpies of external and internal complexes with 2,6-lutidine N-oxides differ two times. Exposure of solid complexes to sun or UV light endows them with several types of coloration centers.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 12, 2004, pp. 2048–2055.Original Russian Text Copyright © 2004 by Ponomarenko, Borovikov, Sivachek, Makovetskii.This revised version was published online in April 2005 with a corrected cover date.     

Reaction of zero-valent cobalt and nickel with ethyl bromide

Conclusions A study was made of the composition of the gaseous products that are formed when zero-valent Co and Ni, complexed with C₂H₅MgBr, are reacted with C₂H₅Br, and it was shown that the latter is decomposed quantitatively to give ethane and ethylene in an equimolar ratio, and a certain amount of butane. The formation of the reaction products is not related to the development of free radical steps in solution.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1170–1172, May, 1973.     

Reaction of allene cyclodimers with alkyllithium compounds

Conclusions 1,3-Dimethylenecyclobutane and 1-methyl-3-methylenecyclobutene are metallated in the presence of THF by alkyllithium compounds under mild conditions with the formation of one and the same organolithium compound of the -pentadienyl type. Under the same conditions, 1,2-dimethylenecyclobutane adds alkyllithium compounds, to form a -alkenyl complex.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1996–1999, September, 1988.The authors wish to express their gratitude to E. R. Dolinskaya and her fellow workers for recording the spectra on the Bruker HX-270 spectrometer.     

Magnetic phase transitions in the Mn1-xCrxSe (x ≦ 0.4) system

Neutron diffraction and magnetic investigations have been made on the Mn_1-xCr_xSe (0 ≦ x ≦ 0.4) system solid solutions. Evidence is found of the appearance of magnetization in the samples with composition 0.05 ≦ x ≦ 0.4, exceeding in value that of antiferromagnet. The temperatures of magnetic transition, obtained from the magnetic measurements, do not fit the temperatures of disappearance of antiferromagnetic ordering obtained from the neutron diffraction studies. The antiferromagnetic structure with compositions 0.03 ≦ x ≦ 0.3 is analogous to the α-MnSe structure. The results are discussed under assumption of simultaneous coexistence of phases with different type of magnetic ordering.     

Generation of coherent phonons in ruby

In conditions of inversion of spin-level populations at T = 1.7° K the resonant stationary coherent phonon emission has been revealed in ruby at frequency ν = 9.12 GHz. The intensity of emission is I_S ≈ 10^?6 W·cm^?2. The frequency spectrum consists of very narrow lines generated simultaneously on several modes of hypersonic ruby cavity. Monochromatism of emission in each line is Δν/ν ? 2 × 10^?6. The spectrum nature permits to suppose the levelwidth of elementary spin excitation to be Δν_s < 3 × 10⁵ Hz, i.e. at least 2–3 orders it is narrower than the inhomogeneously broadened resonant line in ruby. The lifetime of resonant phonons in ruby was defined: τ = 7 × 10^?6 sec.     

Kinetics of austenite decomposition upon cooling of low-alloy pipe steel from the intercritical temperature range

High-rate dilatometry is used to study the kinetics of decomposition of undercooled austenite of low-alloy pipe steel 13KhFA obtained upon heating into the single-phase γ field and the intercritical temperature range. The complex effect of the austenitizing in the intercritical temperature range on the decomposition of the undercooled austenite is revealed (the initial temperature of decomposition falls while the temperature of decomposition termination rises).