Enhancing the Accuracy of Numerical Integration of the Equations of Asteroid Motion with Perturbations from Major Planets and the Moon from the DE Ephemerides

The discontinuous behavior of coordinates of planets and the Moon and their derivatives, which are determined from their modern ephemerides, at the boundaries of adjacent interpolation intervals is illustrated using the example of the DE436 ephemerides. The numerical integration of the equations of motion of two asteroids demonstrates that the integration accuracy increases by several orders of magnitude if the step of numerical integration is matched to the boundaries of ephemeris interpolation intervals. In addition, an algorithm for ephemeris smoothing at the boundaries of interpolation intervals is developed and applied in order to eliminate the jumps of coordinates and their first-order derivatives emerging in extended- and quadprecision calculations. This algorithm allows one to remove the jumps of coordinates and their derivatives up to any given order. It is demonstrated that the use of ephemerides smoothed to the first-order derivatives in quad-precision calculations increases the accuracy of numerical integration by ~10 orders of magnitude.     

Variations in the composition of the ferromanganese concretions of the Kara Sea

It has been found when studying the distribution of 57 elements in flattened, pellet-shaped, and pipelike iron-manganese concretions of the Kara Sea, that the F₂O₃ and MnO₂ contents in them are 52.5 and 5.30%; 18.3 and 24.2%; and 13.0 and 0.44%, respectively. The pellet-shaped concretions are enriched with nonferrous metals and microelements (especially with arsenic, cobalt, molybdenum, and animony) to the highest degree relative to the sediments, the flattened concretions are enriched to a lesser degree, and the pipelike ones are enriched to the least degree. The relative enrichment with the medium elements and a negative cerium anomaly are observed in the distribution of the rare-earth elements, which is also revealed in the host sediments to a lesser degree. The low content of ore and rare elements in the iron-manganese concretions of the Kara Sea relative to oceanic concretions is related mostly to the high sedimentation rates and short exposition period of the concretions on the sea bottom.     

Low heavy-element photospheric abundance: a challenge for solar modeling

Recent spectroscopic data pointing to low heavy-element abundances Z pose a severe problem for solar-structure modeling. The low-Z abundances imply a lower opacity and a relatively shallow convective zone, both of which are in obvious contradiction with the observed helioseismic sound-speed profile. This paper presents a series of solar models with different heavy-element abundances. The SAHA-S equation of state and OPAL opacities properly take into account the respective heavy-element abundances. Diffusion of individual elements is also included in the models. Sound-speed profiles are compared with inversion results and it is shown that the models with low Z are in disagreement with the inversion data. Even combining the effect of diffusion, overshooting and mixing for the sound-speed profile did not lead to a solution of the low-Z problem. Models with varied neon abundance have also been computed. It turned out that a substantial increase of the neon abundance could produce a model in agreement with the sound-speed inversion but the required abundance increase would be unrealistic. The effect of the neon enhancement on the adiabatic exponent profile in the convection zone is also presented.     

Species of molybdenum,thallium, and tellurium in ferromanganese crusts of oceanic Seamounts

The species of molybdenum, thallium, and tellurium in standard technological samples of ferromanganese crusts from the Magellan Seamounts in the Pacific Ocean were studied by means of analytical electron microscopy and chemical analysis. In the initial samples and in the products of their acid treatment, some ultramicroscopic inclusions of molybdenite, thallium oxide and chlorite, and tellurium oxide were found. The origin of the molybdenite is supposedly related to the sedimentation of organic matter particles from oceanic water, thus, forming a local reducing environment. The presence of thallium chloride in the crusts correlates with the existence of this compound in oceanic waters; the same is true for thallium and tellurium oxides. The data presented show that, in ferromanganese crusts, along with the sorbed forms of the microelements considered, their own mineral phases are present.     

Issue of the relationship between primary productivity of organic carbon in ocean and phosphate accumulation (Holocene-Late Jurassic)

By analogy with the present-day ocean, the primary productivity of paleoceans can be reconstructed using calculations based on the content of organic carbon in sediments and their accumulation rates. Results of calculations based on literature data show that the primary productivity of organic carbon, the mass of phosphorus involved in the process, and the content of phosphorus in oceanic waters were relatively stable in the Mesozoic and Late Mesozoic. Prior to precipitation on the seafloor together with the biogenic detritus, the dissolved phosphorus could repeatedly be involved in the biogeochemical cycle. Therefore, only less than 0.1% of phosphorus is retained in bottom sediments. The bulk phosphorus accumulation rate in oceanic sediments is partly consistent with the calculated primary productivity. Some epochs of phosphate accumulation also coincide with maximums of primary productivity and minimums of the fossilization coefficient of organic carbon. The latter fact can testify to episodes of the acceleration of organic matter mineralization and the release of phosphorus from sediments, leading to increase in the phosphorus reserve in paleoceans and phosphate accumulation in some places.