Laboratory simulation of geogas microbubble flow

Preliminary laboratory tests provided first data on the behavior of gas microbubbles through porous media in the framework of the geogas theory. Under experimented conditions with laboratory equipment arranged for pressure controlled gas-tracer injection and sampling, gas microbubbles moved up to ten times faster than singlephase flow in dry media under the same injection pressure. Microbubbles were determined to be very sensitive to changes in injection pressure and their terminal velocity seems to be described with good approximation by the Stokes formula. The capability of microbubbles to pick up and transport upward for short distances solid ultra-small particles (metallic and radionuclide compounds) has been proved. Results are consistent with a time-dependent process linked to the transport properties of microbubbles (e.g., flotation), such as that reported by some authors.     

Winter severity in Europe: The fourteenth century

The fourteenth century is known to include a period of winter cooling in Central and Western Europe, but its timing and magnitude are not clearly established. An attempt to obtain a coherent picture from verified documentary evidence yielded 2133 records from a region covering Central Europe and Northern Italy, mostly originating from the Monumenta Germaniae Historica. Temperatures were assessed using semi-quantitative indices on the basis of proxy information on snow-cover, ice and untimely activity of vegetation. Results: A run of cold winters from 1303 to 1328 was followed by a run of average winters up to 1354. Then winter temperatures were extremely variable up to 1375. For the rest of the century they fluctuated somewhat below the average of the twentieth century. The pattern in the first five decades is compared to that in the Late Maunder Minimum (1675–1715). The possible role of forcing factors (variations in solar output, North Atlantic Deep Water formation) is briefly discussed.     

Photometric investigation of the evolved contact binary system DN Aur

We present here the photometric light curve analyses of the eclipsing binary star DN Aur. The CCD photometry, performed at the Behlen observatory using the 0.76 m automated telescope gave 646 individual data points inV andR bandpass filters. From this data we have determined a new epoch and an orbital period of 0.6168891 days. The published spectral classification is F3.The Wilson-Devinney model was used to derive the photometric solutions. DN Aur is a W UMa type contact binary system. The mass ratio, (q=m ₂/m ₁0.210, where star 2 is eclipsed at the primary minimum) suggests that the system has A-type configuration. The computed light curve has a third light of about 22 percent and a total eclipse in the secondary minimum. A solution with a cool spot on the secondary component is also found. We recommend spectroscopic study of DN Aur even though the light curve analysis show it to be a single line spectroscopic system. Generally contact systems of spectral type F3 have periods ranging from 0.25 to 0.5 days. The longer period of DN Aur suggests that it is an evolved contact system with case A mass transfer.     

Hydromagnetic Rayleigh problem for a porous wall in slip flow regime

An analysis of the Rayleigh problem in MHD for a porous wall in a slip flow regime is considered. The normal velocity of suction/injection at the wall is assumed to be time dependent. The solution of the problem is obtained in the form of a power series, in terms of known functions. The variations of the velocity field and the skin friction are shown graphically and are followed by a quantitative discussion.Science Update, The Pioneer, India, 21 July 1995 edition     

On estimates of lower and upper limits for the masses of compact components in close binaries

A method of determination of limits for a compact component mass on the base of disk emission lines parameters is described. Lower limit of the mass depends upon the distance between maxima in double peaked lines, the upper the full width of the line. The method is tested for some cataclysmic variables with well known masses of compact components. We obtain a lower limit for the mass of the compact object in the close binary SS433 is 4.9M . This component is apparently a black hole.     

The GEM project: An international collaboration to survey galactic radiation emission

The GEM (Galactic Emission Mapping) project is an international collaboration established with the aim of surveying the full sky at long wavelengths with a multi-frequency radio telescope. A total of 745 hours of observation at 408 MHz were completed from an Equatorial site in Colombia. The observations cover the celestial band 0 ^h <<24 ^h , and –24° 22<<+35° 37. Preliminary results of this partial survey will be discussed. A review of the instrumental setup and a 10° resolution sky map at 408 MHz is presented.Presented by S. Torres at the UN/ESA Workshop on Basic Space Sciences: From Small Telescopes to Space Missions, Colombo, Sri Lanka 11–14 January 1996     

An analysis of 1983 observations of facular contrast with an extreme limb photometer

Analysis of facular contrast I/I _qs from Extreme Limb Photometer (ELP) data of the summer of 1983 yield a mean contrast of 0.91 ± 0.19% and 1.57 ± 0.16% for apertures 1 and 2 located at = 0.198 and at = 0.111, respectively. The ratio of the mean contrast in the outer aperture (closer to the limb) to that of the inner one is 1.71 ± 0.40, indicating an increase in the mean facular contrast toward the limb. This result is in agreement with observations made in 1975, 1979, and 1982. The errors are dominated by the random presence of solar active regions. The combined results from all seasons follow an approximately ^–1 curve. Facular excess solar oblateness signals for 1983 are 33.8 ± 6.6 arc ms and 16.5 ± 2.1 arc ms for ELP apertures 1 and 2, respectively, in reasonable agreement with the 1983 excess solar oblateness results of Dicke, Kuhn, and Libbrecht (1985).     

Propagation of solar cosmic rays: Diffusion versus focused diffusion

This paper is designed to bring to the attention the fact that the effect of focusing of solar energetic particles is always essential as compared with scattering, no matter how small the value of the mean free path may be. That is why, an ordinary (focusing-free) diffusion approach can not be applied to the solar cosmic ray transport. In the case of high-energy solar particles, the focused diffusion is demonstrated to lead to a power law decay of energetic particle intensity much like an ordinary diffusion. However, the power law index of the decay is renormalized by the focusing.     

Planetary boundary layer and surface layer sensitivity to land surface parameters

The sensitivity of the development of the convective planetary boundary layer (PBL) and the surface layer are examined using a coupled surface parameterization and detailed PBL model. First, the coupling is verified against observations from the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE). Results of the sensitivity experiments indicate that the PBL is most sensitive to the amount of soil water content, and the proximity of the soil water content to critical soil texture values (field capacity and wilting point). While vegetation cover is not the most sensitive parameter at the surface, its influence on the surface energy and hydrologic balance is crucial. Model sensitivity to minimum stomatal resistance, type of soil parameterization and canopy height (surface roughness and displacement depth) is also discussed.