A detached binary system BK Pegasi

TheUBV photometry of the detached F-type eclipsing binary BK Pegasi is presented. The light curve solution by a simple spherical model assumption suggests that a slightly hotter, larger and more luminous primary was eclipsed during the primary minimum. Combined with the radial velocity curves in Popper (1983), it was used to determine anew the system's parameters. The age and the metal abundance of the system were estimated as (3.3 ± 0.2) × 10⁹ yr andz = 0.028 ± 0.003 from a comparison with the new grids of stellar models and the isochrones by Schalleret al. (1993). The distance of the system was estimated as 290 pc.     

Female circumcision and ethnic identification in Sudan with special reference to the Berti of Darfur1

This article assesses the state of female circumcision in the Sudan with the primary emphasis being placed on the Berti of Darfur. Among other things, the article examines the factors that have so far led to the perpetuation of the practice and the failure of the anti-circumcision campaign. The author suggests a renewal of the campaign through the use of a comprehensive approach which encompasses the social, aesthetic, medical, identificational and religious variables involved in the practice. This revised version was published online in July 2006 with corrections to the Cover Date.     

Islam and cultural identity among the Berti of Sudan1

Focusing on the Berti of Sudan, this article assesses the role of Islam and Arabism as important variables in the social construction of cultural identity of the studied people. In line with most relevant recent literature, the author looks at cultural identity as a social construct, a dynamic ideology of shifting borders and a historical process that is grounded on diachronic social formation. The article argues that the present Berti identity is a conscious reflection of their subordinate position vis-à-vis the kingdoms and states which have dominated Sudan over the past few centuries. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fourier techniques for an analysis of eclipsing binary light curves: III

The aim of the present paper will be to present a new approach to the light changes of eclipsing binary systems. The light changes have been expanded into the Fourier-Bessel and Dini series. The coefficients of these expansions which are the Hankel transforms of the order of the loss of light (1–l) have been expressed in terms of the eclipse elements. These discrete Hankel transformsH (j _m ) andH ( _m ) valid for only the positive real zerosj _m and _m of the functionsJ and [xJ(x)+J (x)] have been generalized for any positive value of andy. Thus, these general expressions for the Hankel transforms of the light curves which are valid for all types of eclipses, for any arbitrary degree of the adopted limb-darkening law and, moreover, for any positive value of the free parameters andy, may be used for the solution of the elements of eclipsing binary systems.     

The effect of biological and physical disturbances on the transport of arsenic from contaminated estuarine sediments

From the distribution of dissolved and solid arsenic species in a contaminated estuarine sediment and measured rates of flux of the various arsenic species we propose an empirical model for the cycling of arsenic between sediments and water column. The chemical form of arsenic in the sediment was largely determined by the redox state of the sediment. Arsenite was the dominant dissolved and solid species in the deeper reduced sediment, and arsenate was dominant in the oxidized surface layer. Arsenite in the interstitial water diffused toward the surface layer, where it was mostly oxidized to arsenate prior to leaving the sediments. Some arsenate adsorbed to the surface sediments and produced a surface layer enriched in arsenic. Small concentrations of methyl and dimethyl arsenic were produced in the sediments, and these also diffused into the overlying water.Nereis succinea, a burrowing polychaete, affected distribution and flux of arsenic from the sediments by its production of irrigated burrows. These burrows increased both the effective surface area of the sediment and the diffusion of arsenic by a factor of five. When the relative effects of the activities of Nereis succinea and physical resuspension are compared, results indicate that although physical resuspension can produce large pulses of materials from contaminated sediments, continuous biological activity is likely to be more important in the mobilization of contaminants from sediments in many estuarine environments.     

Forward Modeling with Forced Neural Networks for Gravity Anomaly Prof?le

In this paper, we introduce a new method called Forced Neural Network (FNN) to find the parameters of the object in geophysical section respect to gravity anomaly assuming the prismatic model. The aim of the geological modeling is to find the shape and location of underground structure, which cause the anomalies, in 2D cross section. At the first stage, we use one neuron to model the system and apply back propagation algorithm to find out the density difference. At the second level, quantization is applied to the density differences and mean square error of the system is computed. This process goes on until the mean square error of the system is small enough. First, we use FNN to two synthetic data, and then the Sivas–Gürün basin map in Turkey is chosen as a real data application. Anomaly values of the cross section, which is taken from the gravity anomaly map of Sivas–Gürün basin, are very close to those obtained from the proposed method.