Deterioration Of Quality Of Groundwater From Suani Wellfield,Tripoli, Libya 1976–93

The Suani wellfield, consisting of 52 pumping wells, is located about six kilometers south of Tripoli and its continuously pumped to supply the city of Tripoli with public supplies. In 1976, total disolved-solids content ranged from 265-675 mg/l; however, sea water has moved inland as a result of heavy exploitation of the Miocene-Quaternary aquifer in order to meet the increasing water demand. Dissolved-solids content now exceeds 10,000 mg/l. RÉSUMÉ: Le champ captant de Suani, composé de 52 puits de pompage, est situé à environ 6 km au sud de Tripoli; le pompage continu est destiné à l'adduction d'eau potable de Tripoli. En 1976, la minéralisation de l'eau variait entre 265 et 675 mg/l. La surexploitation de l'aquifère mio-quaternaire a provoqué une intrusion de l'eau de mer, du fait de l'accroissement de la consommation. La minéralisation de l'eau atteint maintenant 10 g/l. RESUMEN: El campo de pozos de Suani, situado a unos 6 kilómetros al sur de Trípoli, presenta 52 pozos de extracción que son bombeados de forma continua para el abastecimiento de dicha ciudad. En 1976, el contenido total de sólidos disueltos oscilaba entre 265-675 mg/l. Sin embargo, se ha producido un proceso de intrusión de agua marina como resultado de la sobreexplotación del acuífero Miocénico-Cuaternario para absorbar la creciente demanda de agua. El contenido de sólidos disueltos alcanza ahora un valor superior a los 10000 mg/l.     

The Relationship of Green-Line Transients to White-Light Coronal Mass Ejections

We report observations by the Large Angle Spectrometric Coronagraph (LASCO) on the SOHO spacecraft of three coronal green-line transients that could be clearly associated with coronal mass ejections (CMEs) detected in Thomson-scattered white light. Two of these events, with speeds >25 km s^-1, may be classified as ‘whip-like’ transients. They are associated with the core of the white-light CMEs, identified with erupting prominence material, rather than with the leading edge of the CMEs. The third green-line transient has a markedly different appearance and is more gradual than the other two, with a projected outward speed <10 km s^-1. This event corresponds to the leading edge of a ‘streamer blowout’ type of CME. A dark void is left behind in the emission-line corona following each of the fast eruptions. Both fast emission-line transients start off as a loop structure rising up from close to the solar surface. We suggest that the driving mechanism for these events may be the emergence of new bipolar magnetic regions on the surface of the Sun, which destabilize the ambient corona and cause an eruption. The possible relationship of these events to recent X-ray observations of CMEs is briefly discussed. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1004981125702     

The Leonard Award Address Presented 1996 July 25, Berlin,Germany: The elemental composition of stony cosmic spherules

Abstract— Five hundred stony cosmic spherules collected from deep-sea sediments, polar ice, and the stratosphere have been analyzed for major and some minor element composition. Typical spherules are products of atmospheric melting of millimeter sized and smaller meteoroids. The samples are small and modified by atmospheric entry, but they are an important source of information on the composition of asteroids. The spherules in this study were all analyzed in an identical manner, and they provide a sampling of the solar system's asteroids that is both different and less biased than provided by studies of conventional meteorites. Volatile elements such as Na and S are depleted due to atmospheric heating, while siderophiles are depleted by less understood causes. The refractory nonsiderophile elements appear not to have been significantly disturbed during atmospheric melting and provide important clues on the elemental composition of millimeter sized meteoroids colliding with the Earth. Typical spherules have CM-like composition that is distinctively different than ordinary chondrites and most other meteorite types. We assume that C-type asteroids are the primary origin of spherules with this composition. Type S asteroids should also be an important source of the spherules, and the analysis data provide constraints on their composition. A minor fraction of the spherules are melt products of precursor particles that did not have chondritic elemental compositions. The most common of these are particles that are dominated by olivine. The observed compositions of spherules are inconsistent with the possibility that an appreciable fraction of the spherules are simply chondrules remelted during atmospheric entry.     

A moment method for radiative transfer in an anisotropically-scattering slab medium with space-dependent albedoω(x)

The moment method is used to solve the radiative transfer problem in an anisotropic scattering plane medium with arbitrary space-dependent albedo(x). The results are compared with those obtained recently by Cengel and Özisik.     

Disk-instability model for outbursts of dwarf novae: Fine mesh calculations

We have executed fine mesh calculations which can almost fully resolve the transition front in the accretion disk of dwarf novae. Results show that the effects of thermal diffusion become very important only when the heating wave passes by. But it is unlikely that they cause drastic changes in the situation of wave propagation. The validity of the localized front approximation is examined. It is found that this approximation is relatively good for heating waves but it is marginal for cooling waves.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

The energy distributions of magnetic variables: The effects of inhomogeneous accretion columns

Previous shock models for the AM Herculis-type magnetic variables have assumed homogeneous accretion columns, with constant infall densities out to a characteristic column radius. The resulting energy distributions are strongly peaked in the visible to ultraviolet and are in disagreement with observations. We report the preliminary results of calculations with more general radial functions of the infall density. Exponential and gaussian profiles yield continua profiles produce continua which are flatter and in better agreement with observations. Comparisons are made to data for AM Her and E2003+225.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

The ultrashort period dwarf nova SW ursae majoris

SW UMa is an unusual dwarf nova in several respects. Recent observations by Robinsonet al. (1986) have established that SW UMa is an SU UMa system, while Shafter, Szkody, and Thorstensen (1986) have presented evidence suggesting that SW UMa may be a DQ Her system as well. If the DQ Her classification is confirmed then SW UMa will be the only system to have this dual classification. Finally, time resolved spectroscopy of SW UMa has revealed the presence of an S-wave component in the H emission which has an unexpected phasing relative to the line wings.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Age distribution of open clusters as a function of their linear diameter and age-dependence of cluster masses

From the well-observed data of star clusters, the age distribution of galactic clusters is obtianed as a function of their linear diameter and it is concluded that the observed age distribution of clusters for different linear diameter intervals within 1500 pc, is not seriously affected by the selection effects. If we assume that the rate of formation of clusters is constant, the lifetimes _1/2 of the clusters for different linear diameter intervals have been obtained and it is found that the clusters with a linear diameter in the range 0–1.9 pc have longer lifetimes than the clusters having linear diameters larger than 2.0 pc.Total masses of 57 clusters have been obtained using the catalogues of Piskunov (1983) and Myakutinet al. (1984). A study of age-dependence of cluster masses, based on the total masses of the clusters obtained in the present study and the cluster masses given by Bruch and Sanders (1983) and Lynga (1983b), shows that there is a decreasing trend in the total mass with the age, however, there is an increasing trend after the age of about 10⁸ yr. It is also concluded that the initial rate of formation of rich clusters was relatively higher than the present rate of formation.     

Implications from the shape of the viscosity-surface density relation

We present results of new vertical structure computations for cool, convective accretion disks. The influence of the uncertainty in the low temperature opacities on the cool branch of the viscosity-surface density relation is investigated. We discuss how the shape of this relation allows a prediction of temperatures in the accretion disk during the onset of an outburst and we compare this with observations for VW Hydri by Hassall (1984).Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.