15N and17O NMR spectra of vinyl ethers of pyridine and quinoline

Conclusions ¹⁵N (¹⁴N) and¹⁷O NMR spectra have been obtained on vinyl ethers of pyridine and quinoline, with unenriched samples. The principal factor determining the chemical shifts is p- conjugation of the unshared pairs of the heteroatom with the unsaturated fragments of the molecule; an additional contribution in the case of the¹⁵N signals comes from interaction of the nitrogen atom with a proton through space.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 769–773, April, 1987.     

A sensitive 3–4-mm radiometer

Improving the parameters of the Schottky barrier mixing diodes has permitted us to improve the sensitivity of the 3–4-mm radiometer described in [1]. The authors were able to achieve a fluctuation sensitivity of no worse than 0.15K for double-sideband reception with an output RC filter time constant of =1 sec by using, with several changes, the high-frequency part of this receiver. The sensitivity reached 0.1K at several points in the 3–4-mm range. Figure 1 shows a calibration record of a standard load, cooled in liquid nitrogen. The amplification while recording the noise was 30 times greater than for the calibration signal.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 11, pp. 1702–1703, November, 1978.     

PMR of complexes of organohalostannanes with N-vinyl-N-ethylimidazole

The chemical shifts and spin-spin coupling constants of the protons of the vinyl and ethyl groups and of the imidazole ring in the PMR spectra of complexes R_4–n·SnX_n · mB, where R=C₂H₅, C₄H₉;X=Cl, Br, I; B is N-vinylimidazole or N-ethylimidazole; and n=1 (m=1) and 2 (m=2), are compared. The electronic and geometrical structures of these complexes are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 391–394, March, 1973.     

Pulsed discharge in a hollow cathode with the detection of ions in a time-of-flight mass spectrometer: Analytical capabilities in the analysis of solid samples

The results of a study of a new analytical system that includes an ion source with a hollow-cathode pulsed gas discharge and a time-of-flight mass spectrometer are reported. It was found that such a system can be successfully used for the direct analysis of metal and dielectric solid samples. The results of the optimization of various ionizer parameters, such as the delay of an ejecting pulse with respect to a discharge pulse and the bias voltage of the anode-cathode pair, are given. It was proposed to use an additive of hydrogen as a reaction gas for a considerable decrease in the intensities of gas components in the mass spectrum, and the effectiveness of this approach was demonstrated. The possibility of the rapid and efficient direct analysis of solid samples with the use of a hollow-cathode pulsed glow discharge was demonstrated using an example of the analysis of high-purity copper samples and the glassy slag of molten lead.     

New synthesis of tert-butyl peroxycarboxylates

tert-Butyl peroxyacetate, tert-butyl peroxybutyrate, tert-butyl phenylperoxyacetate, and tert-butyl peroxyundecanoate were obtained in nearly quantitative yields by the esterification of the corresponding carboxylic acids with tert-butyl hydroperoxide in the presence of trifluoroacetic anhydride and pyridine in nonaqueous medium at 0–5°C. No tert-butyl peroxytrifluoroacetate was formed as a by-product during the process. A possible reaction mechanism is discussed.     

Hydrodynamic conditions for growth of large KDP crystals

Three-dimensional mass transfer is simulated. The factors determining the hydrodynamic conditions for efficient mass transfer in growth of large KDP single crystals (cross sections up to 45 × 45 cm²) from solutions in a real 300-l-crystallizer are established. The conditions for the motion of the supersaturated solution to the surface of a growing crystal in the direction opposite to that of gravitation are attained. The growth mode developed provides growth rates that are five times higher of large high-quality optical KDP crystals.     

Surface precrystallization of normal C24 alkane in porous glass

The behavior of the enthalpy and specific heat of normal C24 alkane in the bulk and in porous glasses is investigated using an adiabatic scanning microcalorimeter. Enthalpy jumps, which precede a phase transition in the entire volume of the pores, are found in porous glass with characteristic pore size 1000 Å at a transition from the isotropic liquid into the rotator phase RII. The enthalpy jumps are interpreted as a layerwise growth of a crystal phase on the surface of porous glass. It is also found that porous glass substantially changes the phase behavior of alkanes.     

Near-field effect in two-atom system

The self-consistent problem is solved for the interaction of two dipole atoms situated at arbitrary distance from one another with the field of quasiresonant light wave. Atoms are considered to be linear Lorenz oscillators. Polarizing fields inside the system include both Coulomb and retarding parts. The solutions obtained are investigated for the case when atoms have the same polarizabilities and interatomic distance is much less than external light wavelength. Formulas for electric fields inside and outside of small object are obtained. It is shown that longitudinal and transverse optical oscillations are possible to exist inside small two-atom object. Dispersion laws of these oscillations depend upon interatomic distance and upon angle between axis of the system and the direction of propagation of external wave. The field outside the small object in wave zone is linearly polarized with the choice of linear polarization of external field. However, the directions of polarization of these waves are different and depend essentially upon frequency. The amplitude of field outside small object in wave zone is shown to depend essentially on the frequency of external field and interatomic distance. The results obtained are treated as near-field effect in the optics of small objects making it possible to investigate the structure of small objects with optical radiation. Received 26 October 1998 and Received in final form 26 January 2000     

Peculiarities of NMR spectra of heterospin complexes

Experimental investigation and theoretical simulation of the unusual phenomenon of multiple broadening and narrowing of NMR signals due to the temperature variation of a solution of the stereochemically non-rigid heterospin Ni²⁺ complex with stable nitroxide were performed. The investigation of the temperature dependence of the NMR signals of stereochemically non-rigid heterospin systems can be used for choosing conditions for growing heterospin single crystals containing molecules in a definite conformation.     

Preparation of Chemically Cross-Linked Swollen Gels from Spent Rubbers and Their Use as Components of Rubber Stocks

A study was made of cross-linking of gelatinous compositions to obtain products classed with gels of the first type in which a part of the plasticizer is firmly retained by the gel structure of the elastomer. The elastic-hysteresis properties of the rubbers were studied.