Influence of geomagnetic field on the motion of low satellites

The first aim of the present work is to compute a more accurate and recent model for the Earth’s magnetic field. The second aim is to determine the effects of the Earth’s magnetic field on the motion of a charged artificial satellite to evaluate the variations of the orbital elements of the satellite due to these effects. The magnetic field and its variation with time have been studied at different heights, longitudes and latitudes. The geomagnetic field is considered as a multiple potential field and the electrical charge of the satellite is assumed to be constant. A new computer code has been constructed to follow the components of the magnetic field in spherical harmonic models. The Gauss equations are solved numerically. The results concentrate on the computation of the numerical values of orbital perturbation for the case of a low Earth satellite. RS-1 satellite and space craft gravity probe B (GPB) are chosen as cases of studies for a detailed numerical analysis.     

Rift to post-rift evolution of a ��passive�� continental margin: the Ponta Grossa Arch, SE Brazil

Low-temperature thermochronology was applied at the Brazilian passive continental margin in order to understand and reconstruct the post-rift evolution since the break-up of southwestern Gondwana. Thermochronological data obtained from apatite fission-track analysis of Neoproterozoic metamorphic and Paleozoic to Mesozoic siliciclastic rocks as well as Mesozoic dikes and alkaline intrusions from the Ponta Grossa Arch provided ages between 66.2 (1.3) and 5.9 (0.8) Ma. These data clearly indicate a post-rift reactivation during Late Cretaceous and Paleogene times. Integrating the results of older thermochronological studies, the reactivation of the southeastern Brazilian margin could be described in three main phases related to the rift to post-rift evolution of SE Brazil. Furthermore, the spatial distribution of age data indicates the presence of two age groups: a NE age-group (NE of Curitiba), with ages around 20?Ma and a SW age-group (Curitiba and NW) with ages of around 50?Ma. The change of ages follows the NW?CSE trending S?o Jer?nimo-Curi??va fault zone that can be traced offshore into the southern end of the Santos basin. Within the Santos basin, this lineament ends up to the salt occurrence in the south and seams to play a major role in the structural evolution of the Santos basin and the Rio Grande Rise. Sedimentological studies in the Santos basin evidenced that the transport direction changed in Miocene from WNW to WNW/NNW. During the Oligocene and earlier, the sediments were transported mainly from southeastwards to the direction of the ??Curitiba area?? into the Santos basin. Within the Miocene, an additional transport direction from an area north of Curitiba developed.     

Core Sediments from Lake Brollus (Bahra el Burullus), Egypt

Nine short cores were taken from different regions of Lake Brollus, an Egyptian large shallow brackish-water Delta lake connected with the Mediterranean Sea. The core samples were subjected to some investigations in order to know the vertical variations in the values of different constituents of the deposits. The variations of water content of the sediments are mainly due to the nature and type of these sediments. An inverse relation was found between the density of wet mud and the water content of some core samples. The sediments of the lower parts of the cores taken from the central region of Lake Brollus were enriched with organic matter and black in color. These black sediments may be remains of dense land vegetation entered into Lake Brollus by drainage and fresh water. They may be also remains of massive plankton organisms which survived for a long period in this lake under favourable conditions. The amounts of diatom-silica estimated from the sediments can be used as a rough indicator for the amounts of diatoms which were found in the lake at the time of deposition. The allochthonous materials, the organic matter, the calcareous substances and the diatomsilica generally were deposited in variable amounts at various depths of the cores. The quantitative distribution of these components in the core sediments was found to depend mainly upon certain factors which were discussed.     

Permittivity in the microwave region of some natural minerals

The permittivity measured at a frequency of 10 GHz normalized to constant density is the same within the experimental error for talc, baryte and dolomite. In the case of clay and kaolin, it is about 10% higher. This is attributed to the high content of Al₂O₃ (30–40%) in them, which interpretation is proved by experiment.     

Total dissolved and particulate lead in the Western Harbor of Alexandria,a Mediterranean basin under stress

The Western Harbor of Alexandria, the largest harbor of Egypt on the Mediterranean Sea, receives different internal and external untreated pollutants affecting dramatically its water, sediments and biota. Surface and bottom water samples were collected bimonthly from this harbor for studying vertical, regional and monthly distributions of total suspended matter (TSM), total dissolved lead (TDPb) and total particulate lead (TPPb). The high surface TSM values coincided with air-borne dust, organic aggregates, plankton productivity and discharged wastes. The high TSM averages in winter resulted mainly from turbulence of the water column by wind action. The highest averages of TDPb in the petroleum and coal basins in the Western Harbor reflect their effects on the water column, while the lowest averages of TDPb and TPPb were found at a location far away from pollution sources. For the water column, the maximum and minimum monthly averages of TPPb and TDPb respectively in June reflect the increase in the rate of lead uptake by phytoplankton abundant in summer, favored by temperature elevation. The annual mean concentration of TPPb was nearly double that of TDPb, indicating that lead was transported to the Western Harbor mainly in particulate form. This reflects the high TSM content in the harbor water onto which a considerable part of lead was adsorbed.     

Facies analysis of tertiary alluvial fan deposits in the Jundiaí region, São Paulo, southeastern Brazil

This article presents an analysis of facies of sedimentary sequences that occur as discontinuous bodies in the Jundiaí region, west of the main Tertiary continental basins of the southeastern Brazil continental rift. Nine identified sedimentary facies, grouped into four associations, suggest the existence of an ancient alluvial fan system whose source area was the Japi mountain range (Serra do Japi). The deposits are considered Tertiary in age and chronocorrelated with those identified in the Atibaia region and at other sites up to 100 km east and northeast of Jundiaí. The depositional model adopted to explain the filling of the basin proposes that the alluvial fans, which directly derive from the source area, terminated in a braided channel longitudinal to the basin axis that flowed to northwest, in a similar configuration to that of the present day. This basin may have extended to the Atibaia region or formed a set of small basins laterally contiguous to the faults associated with the rift. Such occurrences show that the formation of rift basins was broader than the area presently occupied by the main deposits.     

Geotectonic significance of the Neoproterozoic ophiolitic metagabbros of Muiswirab area,South Eastern Desert,Egypt: constraints from their mineralogical and geochemical characteristics

Acta Geochimica - Petrological and geochemical studies of Neoproterozoic metagabbros were carried out in the Muiswirab area, South Eastern Desert of Egypt. The Muiswirab area comprises of...     

Near-surface foundation level assessment from seismic measurements: a case study of north Jeddah City,Saudi Arabia

In this study, a comprehensive assessment on the generation mechanism, distribution characteristics, and extension rules of structure cracks was conducted by in situ monitoring and field investigation in the Chengchao Iron Mine. Structure cracks are affected by many factors, e.g., surface deformation, structure strength, occurrence position, and machine vibration. They initially occur in a structure when the strength of the structure is not enough to resist the inner strain as surface deformation increases. In contrast, increases in width and length of structure crack exert stress release in the structure and thus decrease structure deformation surrounding the crack. A great ground crack may adversely aggravate structure cracking and release the stress of surrounding rock masses. In addition, micro cracks in rock masses provide favorable conditions for the generation and extension of cracks, resulting that cracks occur in shaft walls more easily and extend towards the deeper. The initial distribution of cracks is generally consistent with such micro cracks. Subsequently, cracks in deep rock masses will extend along the strike of the mined-out area as surface deformation increases. Sensibilities to cracking of structures are changed by their different strain resistances and become stronger from bolt-shotcrete shaft, bolt-shotcrete tunnel, and brick-concrete building to brick wall. Based on distribution characteristics of cracks and wave velocity in rock masses, the overlaying strata affected by underground mining can be divided into four zones: broken zone, broken transition zone, crack generation zone, and micro deformation zone.     

Analytical expansion of the earth's zonal potential in terms of ks regular elements

In this paper, the expansion of the Earth's zonal potential is established analytically in terms of KS regular elements whatever the power of the eccentricity e(e < l) and the number of the zonal harmonics may be.