First-Order Complexity of Subgraph Isomorphism via Kneser Graphs

Mathematical Notes - The problem of finding the least number of variables of a first-order formula expressing the statement that an input-graph contains a subgraph isomorphic to a given...     

On the relative role of GCR intensity variations and the Suess’ effect in the data on <Superscript>14</Superscript>C isotope content in tree rings

The relative contribution from GCR intensity variations and anthropogenic carbon dioxide emissions into the atmosphere (the Suess effect) to the variation of ¹⁴C isotope content in annual tree rings is considered. The contribution from a reduction in GCR intensity to the lowering of the cosmogenic ¹⁴C isotope content in tree rings from the middle of the 19th century to the middle of the 20th century is shown to be comparable to the contribution from the Suess effect.     

The connection between cosmic rays and changes in the geomagnetic field and the Earth’s climate

The possible influence of changes in cosmic ray fluxes on climate variability has been the subject of wide speculation in recent years. New studies show that the interrelation between the parameters of the geomagnetic field and climate can also be followed on time scales of different lengths. We present our analysis of data on cosmic rays and changes in climate and the geomagnetic field obtained from different natural archives.     

Zinc-containing zeolite catalysts for ethane aromatization prepared by solid-state modification

Solid-state modification was used to prepare zinc-containing zeolite catalysts based on pentasils with different framework SiO₂/Al₂O₃ ratios. The catalysts were studied by X-ray diffraction analysis and IR spectroscopy. The activity and selectivity of the Zn—pentasil systems prepared by the solid-state modification and impregnation methods were compared in the aromatization of ethane. The active and stable zeolite catalysts modified by transition metal ions can be obtained by the topochemical method.     

Changes in the geomagnetic dipole moment over last 12 thousand years,the concentration of cosmogenic isotopes,and optimization of <Superscript>14</Superscript>C exchange parameters between atmosphere and ocean

The long-term variations in the production rate of ¹⁰Be and ¹⁴C in the Earth’s atmosphere during the last 10 thousand years caused by the geomagnetic-field effect have been investigated. It is shown that the difference in the correlation coefficient between the production rate of ¹⁰Be and ¹⁴C and variations in the dipole magnetic moment of the Earth is due to the lack of knowledge about the ¹⁴C exchange parameter for the carbon reservoir. The optimal parameters of the reservoir model of radiocarbon exchange, averaged over 10 thousand years, are found.     

The high-energy heavy-particle fluences in the orbits of manned space stations

The results are presented of measurements high-energy particles in a customary manned space station orbit (a 350-450-km altitude, a 51.6 degrees inclination; Salyut-6 and 7, MIR). The particles were recorded by the chambers composed of the Lavsan (polyethyleneterephtalate) solid-state nuclear track detector layers mounted outside a spacecraft for 1-3 years. A high resolution has been attained in the charge and energy spectra of 30-200 MeV/n Fe group particles. The results of measuring the particle fluxes in the space station orbits are used to restore the initial particle energy spectra in terms of the models that describe the galactic and solar cosmic rays and their penetration to the Earth's magnetosphere. The analysis demonstrates a high effectiveness of the described methods when applied to quite a number of space physics problems.     

Investigation of heavy cosmic-ray nuclei by solid-state track detectors on orbiting platforms

Results are presented from investigations of Fe-group nuclei in galactic and solar cosmic rays in the energy ranges 30–210 MeV/n and 7–210 MeV/n in various phases of the solar cycles. Spectra of Fe particles have been obtained with high energy resolution as a result of exposing PLATAN chambers, made up of layers of a polyethyelene terephthalate solid-state track detector, for between one and three years on the Salyut-6, Salyut-7, and Mir space stations, orbiting at an inclination of 51.6° to the plane of the equator and at an altitude of 350–400 km. Measurements were made of the energy spectra of Fe particles from a unique event, the series of solar flares of September 29 and October 19–29, 1989, which is the most powerful of those recorded and measured over the entire history of cosmic ray research. A modern model of particle penetration inside the Earth’s magnetosphere, developed at the Institute of Nuclear Physics at Moscow State University, is used to compare the measured spectrum with measurements made using the solid-state track detector in the HIIS experiment on the LDEF station, and with extramagnetospheric measurements made using electronic equipment on the IMP-8 satellite and the Galileo space station. It is shown that the solid-state track detector technique has advantages for obtaining the characteristics of the energy spectrum. Zh. Tekh. Fiz. 69, 94–98 (September 1999)