Spider colonization of former brown coal mining areas — time or structure dependent?

Colonization of former mining areas by a highly mobile arthropod group, spiders (Arachnida), is studied based on a comparative analysis of four mining areas of different age and habitat structure including adjacent undisturbed areas. Species number was lowest in sparsely vegetated sites, and highest in dense vegetation regardless of age. Species number may exceed that of undisturbed adjacent sites after 70 years. Similarity among the sites ranges from 26 to 75% (Sörensen index). A DCA ordination of sites revealed a grouping into three relatively distinct clusters, one including the vegetation free sites, the second the sparsely vegetated short grass sites, and the third both the plant species rich, mature, short grass sites and the tall grass stands. Environmental variables were related to the species composition by means of CCA. However, most of these relations proved to be spurious being either not significant or if so, showing a low contribution to variance explanation. The influence of scale parameters such as area size and distance (when analysing all data, data from mining areas only, or data from one mining area separately) becomes visible in all analyses. A detailed analysis including age as an independent variable shows that age has some influence on the structure of the whole data set including undisturbed sites, but not within the subset of the mining areas. Using data from one mining area only it is shown that the influence of age and spatial autocorrelation effects cannot be properly distinguished on the larger scales. A more detailed account on the known autecology of the species encountered showed that biological spectra of the communities remain similar in the course of development. Initial colonization occurs very rapidly during the first years after dumping. The most decisive aspect of population establishment is the structure of the vegetation, as expressed by height or volume amenable for colonization. Despite some developmental trends such as increase in species number clearly separated successional stages cannot be distinguished.     

The Metrology Light Source of PTB – a Source for THz Radiation

The Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute, operates the low-energy electron storage ring Metrology Light Source (MLS) in Berlin-Adlershof in close cooperation with the Helmholtz-Zentrum Berlin (HZB). The MLS is designed and prepared for a low-α machine optics mode based on a sextupole and octupole correction scheme, for the production of coherent synchrotron radiation in the far-IR and THz region. In our contribution we present commissioning results, which clearly indicate that the MLS, in combination with dedicated beamlines, offers intense, stable, and well-focused THz radiation. We discuss the planned use of the MLS for metrology in the THz spectral range.     

Effect of frying parameters on crispiness and sound emission of cassava crackers

Cassava crackers, based in cassava starch and water, were produced by deep-fat frying in oil at 140, 150 and 160 °C. Physical properties of cassava crackers were monitored at 5, 10 and 15 s of the frying process, moisture contents, bulk density, linear expansion and penetration forces and sound emission were evaluated. The results showed that with increasing frying (time and temperature), the moisture content, the linear expansion, the number of force and sound peaks significantly increased while the density and maximum and mean of force peaks decreased. Further it could be seen that with higher temperature the number of small size air cells increased. Correlations were found between physical and textural properties and sound emission. Moisture content, bulk density, maximum of sound peak, maximum force and mean force were negatively correlated with linear expansion, number of sound peaks and number of force peaks.     

The collisions of high-velocity clouds with the galactic halo

Spiral galaxies are surrounded by a widely distributed hot coronal gas and seem to be fed by infalling clouds of neutral hydrogen gas with low metallicity and high velocities. We numerically study plasma waves produced by the collisions of these high-velocity clouds (HVCs) with the hot halo gas and with the gaseous disk. In particular, we tackle two problems numerically: 1) collisions of HVCs with the galactic halo gas and 2) the dispersion relations to obtain the phase and group velocities of plasma waves from the equations of plasma motion as well as further important physical characteristics such as magnetic tension force, gas pressure, etc. The obtained results allow us to understand the nature of MHD waves produced during the collisions in galactic media and lead to the suggestion that these waves can heat the ambient halo gas. These calculations are aiming at leading to a better understanding of dynamics and interaction of HVCs with the galactic halo and of the importance of MHD waves as a heating process of the halo gas.