Radial velocities of the components of Trapezium type multiple stellar systems. II

Translated fromAstrofizika, Vol. 37, No. 4, 1994.     

Beach accretion and erosion, Burullus-Gamasa coast, Egypt

Several areas of erosion and accretion were observed along the Burullus-Gamasa beach. The accreted sands are coarser and less sorted than the eroded ones. Differentiation between them could be achieved on the basis of their grain-size fractions, shape of grain-size distribution curves and statistical grain-size parameter relationships.     

A nonlinear tensor field and the second metric tensor

In our preceding paper {see [L. Sh. Grigorian and S. Gottlöber, Astrofizika (in press)]} we investigated a self-gravitating system consisting of a scalar field and a linear tensor field _ik= _ki with minimal coupling and with allowance for the action of vacuum polarization effects. In the present paper we investigate the case of a nonlinear tensor field _ik. The action S ⁽⁾ of the field _ik is determined by the difference R_ik — _ik, where R_ik is the space-time Ricci tensor and Rik is the analogous quantity constructed using the metric _ik=g_ik+_ik induced by _ik ( is a free parameter). Here S ⁽⁾ coincides with the previously known expression for the action of a linear field _ik. Equations of motion are derived for _ik in curved space-time. The energy-momentum metric tensor, determining the contribution of _ik to the gravitational field equations, is calculated.Translated from Astrofizika, Vol. 39, No. 1, pp. 135–144, January-March, 1996.     

Neutron stars in the multidimensional einstein theory of gravitation

The radius, mass, total number of baryons, and other parameters of static, spherically symmetric, superdense stars are calculated. A model with one Ricci-flat inner space of arbitrary dimensionality and the approximation p₁=?0.5ε + ap for additional components of the energy — momentum tensor are used (ε and ρ are the total energy density and the pressure of the stellar matter and a is a fitting parameter). In the case of white dwarfs, the results of the multidimensional theory do not depend on the dimensionality D of space-time for ?10 ? a ? 10 and coincide with the analogous data of the general theory of relativity (GTR). For neutron stars there is a dependence on D and a. For D>4, in particular, the greatest mass M_max of a neutron star as a function of a has a maximum at 3<a(D) ? 4, which exceeds the greatest mass M _max ⁰ =2.14 M_⊙ in the GTR. A comparison of theoretical results with observational data determines the allowable values of a. Data for PSR 1913 + 16 lead to 0.2 ≤ a ≤ 9.2 in the case of D=26, while the results of [P. C. Joss and S. A. Rappaport, Annu. Rev. Astron. Astrophys.,22, 537 (1984)] lead to the stricter limits 1 ≤ a ≤ 7.4.     

A Yohkoh search for “black-light flares”

Calculations which predict that a phenomenon analogous to stellar negative pre-flares could also exist on the Sun were published by Hénouxet al. (1990), and Aboudarhamet al., (1990), who showed that at the beginning of a solar white-light flare (WLF) event an electron beam can cause a transient darkening before the WLF emission starts, under certain conditions. They named this event a black light flare (BLF). Such a BLF event should appear as diffuse dark patches lasting for about 20 seconds preceding the WLF emission, which would coincide with intense and impulsive hard X-ray bursts. The BLF location would be at (or in the vicinity of) the forthcoming bright patches. Their predicted contrast depends on the position of the flare on the solar disc and on the wavelength band of the observation.TheYohkoh satellite provided white-light data from the aspect camera of the SXT instrument (Tsunetaet al., 1991), at 431 nm and with a typical image interval of 10–12 s. We have studied nine white-light flares observed with this instrument, with X-ray class larger than M6. We have found a few interesting episodes, but no unambiguous example of the predicted BLF event. This study, although the best survey to date, was not ideal from the observational point of view. We therefore encourage further searches. Successful observations of this phenomenon on the Sun would greatly strengthen our knowledge of the lower solar atmosphere and its effects on solar luminosity variations.     

On the rotation of rigid Venus

According to A.A. Khentov Venus' rotation is in the quasi-stationary state as a result of the balance interaction of the solar tidal torque with the aerodynamical torque of the rotating Venus' atmosphere. In case of the nonconservative forces are negligible and the solar attraction is the stabilizing factor, the rotation of the rigid Venus may be assumed as the first approximation. The theory of the rotation of the rigid Venus in the coordinates,, had been constructed. It have been found that Venus rotates almost uniformly and the libration harmonics are negligible.     

Phenomenological theory of gravitational vacuum

An idea is developed that the vacuum in the gravitational field acquires properties of an elastic medium described by a definite tension _ik . The vacuum is stated to also participate in the formation of the space-time metric, together with the usual matter. So, the matter, vacuum and metric form a complex unity determined by the solution of the field equations. The vacuum may prove to play an essential role in the extremely strong fields existing in superdense celestial bodies. The tensor _ik is not to be identified with the pseudo-tensor of the energy-momentum of the gravitational field the idea of which is preserved.The problem of vacuum is investigated in the case of the central symmetry static field. A number of properties of the tensor _ik is found using the symmetry of the field and comparison with the post-Newton limit. The external and internal problems, as well as the procedure of joining the solutions on the surface of a celestial body, have been formulated. The stellar surface is determined in the usual way:P(r) = 0 whereP is the matter pressure. The theory includes three dimensionless parametersa=p/,b=p / (,p, p are the density of the vacuum energy and of its pressures in the radial and transverse directions) and determining the vacuum elastic properties. Generally speaking, they depend on the valueP/c² in the stellar centre where is the mass density. From general physical considerations it is shown that 0 1 + lim _P (l/q). The field equations are solved for the simple version of the theoryb=–a. There are solutions corresponding to superdense celestial bodies with masses considerably exceeding that of the Sun.     

The removal of color and COD from wastewater containing water base color by coagulation process

In this study acrylic water base color was removed from synthetic wastewater using coagulation process. Experiments were conducted on the sample containing 100 mg/L and 400 mg/L of acrylic water base color. Destruction of color by means of coagulation/flocculation techniques using ferrous sulfate, alum, lime and polyelectrolyte (cationic, anionic and non ionic). The study was performed in a systematic approach searching optimum values of alum and FeSO₄ concentration, pH and temperature. All the experiments were run in a laboratory scale.The obtained results show that treatment with alum and ferrous sulfate alone proved to be very effective in removing the color (> 99 %) and part of COD (60–70 %) from aqueous solution. Lime alone did not significant change on COD and color removal.     

Assessment of sand encroachment in Kuwait using GIS

Assessment of sand encroachment in Kuwait using Geographical Information System (GIS) technology has been formulated as a Multi-Criteria Decision Making problem. The Delphi method and Analytical Hierarchy Process were adopted as evaluating techniques, in which experts’ judgments were analyzed for objectively estimating and weighting control factors. Seven triggering factors, depicted in the form of maps, were identified and ordered according to their priority. These factors are (1) wind energy; (2) surface sediment; (3) vegetation density; (4) land use; (5) drainage density; (6) topographic change and (7) vegetation type. The factor maps were digitized, converted to raster data and overlaid to determine their possible spatial relationships. Applying a susceptibility model, a map of sand encroachment susceptibility in Kuwait was developed. The map showed that the areas of very high and high sand encroachment susceptibility are located within the main corridor of sand pathway that coincides with the northwesterly dominant wind direction.