Intermittent Trajectories in the 3/1 Jovian Resonance

The statistical behaviour of intermittent trajectories at the 3/1resonance is investigated. The elliptic planar restricted three-body problemis used as a model. Distribution functions for time intervals D betweeneccentricity bursts are obtained and theoretically interpreted. For smallervalues of D the distribution is found to be of Poisson type, while in itstail it is described by a power law D. This change in thedistribution occurs for values of D in the range10⁵10⁶Jupiter periods. The power-lawindexfor the integral distributions lies in the range (-2,-1) and istrajectory dependent. The algebraic decay in the tails of the distributionsis explained by the phenomenon of sticking of orbits to the chaos borderduring long intervals between bursts.     

Hyperboloidal precession of a dynamically symmetric satellite. Construction of normal forms of the Hamiltonian

The Norma specialized program package, intended for normalization of autonomous Hamiltonian systems by means of computer algebra, is used in studies of small-amplitude periodic motions in the neighbourhood of regular precessions of a dynamically symmetric satellite on a circular orbit. The case of hyperboloidal precession is considered. Analytical expressions for normal forms and generating functions depending on frequencies of the system as on parameters are derived. Possible resonances are considered in particular. The 6th order of normalization is achieved. Though the intermediate analytical expressions occupy megabytes of computer's main memory, final ones are quite compact. Obtained analytical expressions are applied to the analysis of stability of small-amplitude periodic motions in the neighbourhood of hyperboloidal precession.     

Hydrological Changes and Their Effect on the Radiological Characteristics in the Chernobyl Abandoned Zone

The effect exerted by the engineering reconstruction activities in the Pripyat River floodplain and changes in the functional state of the melioration systems in the Chernobyl Abandoned Zone on the transformation of runoff characteristics within the period after Chernobyl accident is considered. Multivariate analysis is applied to study the environmental radiological situation resulting from the changes that have taken place. The distribution and migration of radionuclides within ameliorated watersheds are shown to be controlled by the specific features of the current state of melioration systems, cessation of operation, and damming of canals. These factors has affected the area waterlogging; the surface and subsurface water regime, their nutrition, discharge, and secondary pollution.     

Habitat and leaf cytogenetic characteristics of Deschampsia antarctica Desv. in the Maritime Antarctica

Antarctic hairgrass (Deschampsia antarctica Desv.) was studied in the Maritime Antarctica with respect to general ecological characteristics, soil conditions, viral contamination, cell nucleus area, and relative DNA content. Material was gathered in six localities that were highly diverse in terms of the nature of soil-like substrata, presence of viral antigen determinants, and the average nucleus area and relative DNA content in leaf epidermis and parenchyma cells. Our results show that Antarctic hairgrass lives upon soils that are variable with respect to trace elements, pH, and other soil characteristics. The hairgrass is susceptible to a number of viruses, and shows substantial variation in DNA content and nucleus size.     

Sweeping-out of dust from spiral galaxy as a result of “magnetic sling” effect

A new mechanism of sweeping out of dust grains beyond galactic disks both in the radial direction along the galactic plane and in the vertical, cross-disk direction is proposed. The mechanism is driven by the interaction of dust grains with the bisymmetric nonstationary magnetic field of the galaxy, whose lines are curved and corotate with the stellar spiral density wave responsible for the arms. We attribute the radial transfer of interstellar dust grains in the plane of galactic disks to the fact that charged dust grains are “glued” to magnetic field lines and are therefore pushed outward because of the rotation of magnetic field lines and their tilt with respect to the radial direction parallel to the disk plane. In addition, dust is swept out vertically in the cross-disk direction because of the drift motion in crossed magnetic and gravitational fields (both are parallel to the galactic plane). Numerical computations of the motion of dust grains in real magneto-gravitational fields with the allowance for the drag force from interstellar gas show that the time scale of dust grain transport beyond galactic disks is on the order of 1 Gyr or shorter.     

Isotopic and Geochemical Characteristics of Western Arctic Ice-Rafted Sediments

Doklady Earth Sciences - The isotope-geochemical characteristics (LaN/YbN, Sm/Nd, εNd(t), 207Pb/206Pb, and 87Sr/86Sr) of ice-rafted sediments in several areas of the Western Arctic (Fram...     

Preflow stresses in Martian rampart ejecta blankets: A means of estimating the water content

Measurements of extents of rampart ejecta deposits as a function of the size of the parent craters support models which, for craters larger than about 6 km diameter, constrain ejecta blankets to all have a similar maximum thickness regardless of the crater size. These volatile-rich ejecta blankets may have failed under their own weights, then flowed radially outward. Assuming this to be so, we can then determine some of the physicomechanical properties of the ejecta deposits at the time of their emplacement. Finite-element studies of the stress magnitudes, distributions, and directions in hypothetical Martian rampart ejecta blankets reveal that the material most likely failed when the shear stresses were less than 500 kPa and the angle of internal friction was between 26 and 36°. These figures imply that the ejecta has a water content between 16 and 72%. Whether the upper limit or the lower limit is more appropriate depends on the mode of failure which one presumes; namely, viscous flow or plastic deformation.