Oxidative Reactions of Azines. 11. The Influence of Manganese Dioxide on the Reaction of Tetrahydropyridines with Formaldehyde: Synthesis and Molecular Structures of 3-Oxa-7-azabicyclo[3.3.1]- and 6-Oxa-2-azabicyclo[3.2.1]octanes

New derivatives of piperidino[4,5-d]dioxane and 3-oxa-7-bicyclo[3.3.1]nonane were obtained by the oxidatively catalysed condensation of 4-aryl-1,2,3,6-tetrahydropyridines with formaldehyde. The direction of this reaction is sharply altered in the presence of manganese dioxide to give 6-oxa-2-azabicylo[3.2.1]octan-4-one — the product of the oxidative condensation of a new type.     

Numerical and experimental investigations of the effect of repeated cyclic thermal loads on the strength of materials of recoverable liquid-propellant rocket engines

Elements of the liquid-propellant rocket engines (LPREs) are subject to the action of intense mechanical and thermal loads, which are temporally related to the start-up, normal regime, and switch-off periods of the working cycle. Recoverable LPREs experience these loads many times. Repeated (cyclic) loads lead to the manifestation of processes typical of fatigue, whereby residual stresses and (plastic) deformations are retained and accumulated in the LPRE materials. Numerical investigations using models of the nonstationary thermal and stressed-strained state and the plastic behavior of materials have been performed in order to determine the limiting numbers of loading cycles for the structural materials employed in various units of LPREs. A special computational-experimental procedure is described, which allows these materials to be studied in a stressed-strained state close to that in real LPREs.     

EHD flows at large electric Reynolds numbers

The motion of a medium consisting of neutral particles and charged particles of single sign is studied under the assumption that the electric Reynolds number (R_q=u/bE) is large. We calculate the freezingin integral and the Bernoulli and Cauchy-Lagrange integrals, study the fluid motion in a stream tube, and formulate the boundary layer problem.     

Submillimeter-wave Josephson spectroscopy

A Josephson high-temperature superconducting (HTSC) submillimeter-wave spectrometer is designed, built, and experimentally investigated. The integrated detection structure of the spectrometer includes a YBCO Josephson junction on a bicrystalline boundary, a double-slot or log-periodic antenna, and a low-inductance resistive shunt. The selective detector response and the response at an intermediate frequency of 1.4 GHz are measured under the action of a signal in the frequency range 350–1250 GHz. Three methods of spectroscopy are investigated using this setup: 1) a method of Hilbert spectroscopy with processing of the detector response is implemented; 2) it is found that for a wide Josephson line at intermediate frequency (IF) the response has the same form as the detector response, making it possible to obtain a spectrum and the width of the generation line from IF response measurements; 3) for a narrow Josephson line the IF response corresponds to the regime of conversion with self-pumping. A new method is proposed for calculating the emission spectrum. The method consists of simple shift, summation, and subtraction operations. The advantages of the method are simplicity, high sensitivity, and high resolution. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 5, 338–343 (10 September 1999)     

Influence of barocryodeformation on the hydrogen concentration and acoustic emission in VT1-0 commercial titanium

The concentration of hydrogen with different binding energies and acoustic emission initiated by indentation in VT1-0 commercial titanium in the initial state and after barocryodeformation are measured. The acoustic parameters are found to correlate with the hydrogen concentration in the material.     

One-Pot Synthesis of 6,7-Dehydro-1-aza-3-oxabicyclo[3.3.1]nonanes by Condensation of α-Methylstyrenes with Formaldehyde and Ammonia

Russian Journal of Organic Chemistry -     

Cover-free codes and separating system codes

A set \(T\subset {GF(q)}\), \(q=p^h\) is a super-Vandermonde set if \(\sum _{y\in T} y^k=0\) for \(0< k <|T|\). We determine the structure of super-Vandermonde sets of size \(p+1\) (almost small) and size \(q/p-1\) (almost large).     

Investigation of a dense,chemically reacting plasma by the high-frequency probe potential modulation method

A method is proposed for investigating a chemically reacting plasma by means of an electric probe whose potential is modulated by a high-frequency sinusoidal voltage. The method is based on the use of a numerical solution of the problem of an electric probe introduced under negative potential into a steady-state low-temperature plasma formed in a mixture of chemically reacting molecular gases. The conditions under which the charged particle concentration in the region undisturbed by the probe is constant as a result of equilibrium between the ionization and recombination rates are examined.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 114–119, November–December, 1987.