HI observations ofHII-galaxies

High-resolution observations of the star forming dwarf galaxies Haro 21 and Markarian 314 are presented and are compared with a set of narrow band (H) CCD images. TheHi system related to Haro 21 measures about 12 kpc in diameter and is much more extended than the optical emission. The optical light follows that of an exponential disk and has a scale length of only 600 pc. TheHi distribution shows a lack of neutral gas near its centre where most of the H emission is found. The velocity field is regular and shows the characteristics of a disk in differential rotation. The rotation curve is rising out to the last measured point and the total mass is estimated to be about 1.5×10¹⁰ M . This implies that Haro 21 is a galaxy which is dominated by Dark Matter.Partly based on observations collected at the European Southern Observatory, La Silla, Chile.     

Ökologische und physiologische Untersuchungen an der planktischen BlaualgeOscillatoria rubescens D.C. unter besonderer Berücksichtigung von Licht und Temperatur

Zusammenfassung Der Vierwaldst?ttersee (Horwer Bucht), Thunersee (H?he Faulensee), Luganersee (Bucht von Lugano) und Mauensee (ein Kleingew?sser im Schweizerischen Mitelland) wurden im Zeitabschnitt 1965 bis 1967 periodisch untersucht. Durch die chemische Analyse wurden die folgenden Komponenten erfasst: Sauerstoff, Nitrat— Stickstoff, Phosphat— Phosphor (PO₄−P), partikul?rer Phosphor (PP), SBV und pH-Wert. Das Phytoplankton wurde im umgekehrten Mikroskop ausgez?hlt, wobei der quantitativen Verteilung vonOscillatoria rubescens D. C. in den verschiedenen Tiefenstufen besondere Beachtung geschenkt wurde. Gleichzeitig wurden Temperatur und subaquatische Ver?nderungen des lichtes gemessen sowie mit der C¹⁴-Methode die Prim?rproduktion bestimmt. In mehr als 80% aller F?lle fielen dieOscillatoria rubescens-Maxima mit jenen Tiefenstufen zusammen, in denen weniger als 14°C gemessen wurde. In diesen Tiefenstufen wurde gleichzeitig in mehr als 65% aller F?lle weniger als 4% der Oberfl?chen-intensit?t des grünen Lichtes (VG 9) beobachtet. Der Einfluss von Licht und Temperatur auf das Wachstum vonOscillatoria rubescens wurde in einem Lichtthermostat experimentell untersucht. Bei temperaturabh?ngigenI _k-Werten zeigte sich, dass sich diese Alge bei einer Lichtintensit?t von 1500 Lux erst im Bereich von 30°C optimal entwickelt. Oberhalb 29°C wirkte sich eine Steigerung über 1500 Lux hinaus wieder hemmend aus. Aus diesen Beobachtungen wurde abgeleitet, dass es sich beiOscillatoria rubescens um eine eurytherme und oligophote Form handelt, und dass das Auftreten vonOscillatoria rubescens-Maxima in der vertikalen Verteilung des Phytoplanktons in einem See durch das Zusammenspiel der beiden Faktoren Licht und Temperatur bedingt wird.

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Summary The Lakes of Lucerne (Horw Bay), Thoune (Faulensee region), Lugano (Lugano Bay) and Lake Mauen, a small lake in central Switzerland, were investigated periodically from 1965 to 1967. The water was analysed in view of determining the following components: oxygen, nitrate-nitrogen, phosphate-phosphorus (PO₄−P), phosphorus incorporated in cell mass (PP), Langlier index. Phytoplankton was counted in an inverted microscope with special consideration to quantitative distribution ofOscillatoria rubescens D. C. at various depths. Temperature and light variations in function of depth were measured simultaneously and the production rate was determined by means of the C-14 method. In over 80% of all cases, theOscillatoria rubescens-maxima coincided with depths showing temperatures under 14°C. In over 65% of all cases, the intensity of green light (VG9) in such depths was less than 4% of the surface intensity. The influence of light and temperature on the growth ofOscillatoria rubescens was tested with a light thermostat. It was shown that maximum growth occurred at temperatures around 30°C and light intensities of 1500 Lux. Increase of light intensities above 1500 Lux had a negative effect on the growth rate at temperatures higher than 29°C. Our investigations lead to the conclusion thatOscillatoria rubescens is a eurythermal, oligophotic species and that the occurrence ofOscillatoria rubescens-maxima in the vertical distribution of the phytoplankton in a lake is caused by the combined effects of light and temperature.

     

A one dimensional wind model for diffusion calculations

Summary A simple one dimensional wind model, designed for diffusion calculations in flat environments with obstructions, is proposed. It covers the surface layer and up to a maximum height of 500 m with three levels. The lowest level is the internal boundary layer, in which the influence of the immediate environment is manifest. The second is the surface layer in which the wind profile is characterized by the fetch conditions further upstream. The third is the spiral layer, where the wind turns with height. The actual depth of the surface layer is estimated by the model. In both the surface layer and the internal boundary layer, Monin-Obukhov theory is applied. The spiral layer is represented by a classical Ekman-Taylor solution matched at the top of the surface layer. This conceptual model is then tested with data from a meteorological mast at Garching (near Munich, Germany).With 11 Figures     

Mass transfer during sub-seafloor alteration of the upper Troodos crust (Cyprus)

Five major alteration zones in the Extrusive Series and the Sheeted Dike Complex of the Troodos Ophiolite are each characterized by (a) distinct elemental changes compared to the original composition and (b) secondary mineralogy. The upper ca. 300 m of the extrusive crust, the highly oxidatedcold seawater alteration zone (CSA), is strongly enriched in K₂O and depleted in Na₂O. It is followed downwards by alow temperature alteration zone (<170° C) which is most widespread in the Troodos extrusives and where Na₂O and K₂O are enriched, the latter less strongly than in the CSA zone. Three types ofhigh temperature alteration zones (<440° C; HTA I–III) are found in the Sheeted Dike Complex. All are marked by thorough leaching of K₂O, while the behavior of Na₂O (e.g. unchanged in type III) and CaO (depleted in type I, enriched in types II, III) is variable. Mass budgets of elemental changes are quantified by calibration of whole rock analyses via systematic stable element variations of fresh glasses found throughout the extrusive section. The Troodos extrusive crust and upper Sheeted Dike Complex are a major sink for MgO, K₂O, and Na₂O, and a source for CaO; the overall scale of fluxes drastically exceeds estimates based on fresh basalt compositions from present ocean crust.     

Dipole moment scaling for convection-driven planetary dynamos

Scaling laws are derived for the time-average magnetic dipole moment in rotating convection-driven numerical dynamo models. Results from 145 dynamo models with a variety of boundary conditions and heating modes, covering a wide section of parameter space, show that the time-average dipole moment depends on the convective buoyancy flux F. Two distinct regimes are found above the critical magnetic Reynolds number for onset of dynamo action. In the first regime the external magnetic field is dipole-dominant, whereas for larger buoyancy flux or slower rotation the external field is dominated by higher multipoles and the dipole moment is reduced by a factor of 10 or more relative to the dipolar regime. For dynamos driven by basal heating, the dipole moment M increases like M  F^1/3 in the dipolar regime. Reversing dipolar dynamos tend to cluster near the multipolar transition, which is shown to depend on a local Rossby number parameter. The geodynamo lies close to this transition, suggesting an explanation for polarity reversals and the possibility of a weaker dipole earlier in Earth history. Internally heated dynamos generate smaller dipole moments overall and show a gradual transition from dipolar to multipolar states. Our scaling yields order of magnitude agreement with the dipole moments of Earth, Jupiter, Saturn, Uranus, Neptune, and Ganymede, and predicts a multipolar-type dynamo for Mercury.     

Shock-induced formation mechanism of seifertite in shergottites

The Martian meteorites Shergotty, Zagami and Dhofar 378 have been re-investigated in order to elucidate the shock-induced formation of seifertite. The occurrence of orthorhombic seifertite (α-PbO₂ structured SiO₂) has been confirmed for the mesostasis of Shergotty and Zagami by transmission electron microscopy with lattice parameters of a = 4.05(1) Å, b = 5.05(1) Å and c = 4.45(1) Å. Seifertite crystals are interpreted as shock-induced transformation products occurring together with maskelynite of both plagioclase and alkali-feldspar composition in a largely preserved eutectic crystallisation texture. Shock-induced microstructures in accessory minerals demonstrate that these regions cannot have been completely re-molten. No further features indicating shock-pressures above ~30 GPa are detected. Hence, seifertite must have been formed below its stability field by a fast solid-state process. Significantly higher shock-pressures of Dhofar 378 indicate an inhibition of a potential seifertite crystallisation by resulting high post-shock temperatures. Crystallographic considerations reveal that a direct formation of seifertite from a high-pressure derivate of cristobalite is possible without breaking any silicon-oxygen bonds. Important implications arise from the existence of such a non-equilibrium pathway. Inferring shock-pressures from metastably formed phases appears implausible, and the transition pressure could be even below 30 GPa. Furthermore, the transformation product is determined by the precursor phase. Epitaxial intergrowth with other silica high-pressure polymorphs should be induced by certain features of the precursor, for example, planar defects, or heterogeneous strain conditions. Due to symmetrical considerations, seifertite will get amorphous during a potential back-transformation, which provides an explanation for the formation of numerous amorphous lamellae.     

Regional and interannual variability of ecosystem dynamics in the Southern Ocean

To investigate regional and interannual variability of the ecosystem in the Southern Ocean, a coupled circumpolar ice–ocean–plankton model has been developed. The ice–ocean component (known as BRIOS-2) is based on a modified version of the s-coordinate primitive equation model (SPEM) coupled to a dynamic–thermodynamic sea-ice model. The biological model (BIMAP) comprises two biogeochemical cycles – silica and nitrogen – and a prognostic iron compartment to include possible effects of micronutrient limitation. Simulations with the coupled ice–ocean–plankton model indicate that the physical–biological interaction is not limited to the effect of a varying surface mixed-layer depth. In the Pacific sector, large anomalies in winter mixed-layer depth cause an increased iron supply and enhance primary production and plankton biomass in the following summer, whereas in the Atlantic sector variability in primary production is caused mainly by fluctuations of oceanic upwelling. Thus, the Antarctic Circumpolar Wave (ACW) induces regional oscillations of phytoplankton biomass in both sectors, but not a propagating signal. Furthermore, interannual variability in plankton biomass and primary production is strong in the Coastal and Continental Shelf Zone and the Seasonal Ice Zone around the Antarctic continent. Interannual variability induced by the ACW has large effects on the regional scale, but the associated variability in biogenic carbon fluxes is small compared to the long-term carbon sequestration of the Southern Ocean.     

On the history of chloride concentrations in the River Lippe (Germany) and the impact on the macroinvertebrates

The River Lippe is situated at the northern part of the rhenish-westphalian coal mining area, Germany and has a long history of being affected by mining water discharge. There has, however, been a massive decrease in the discharge of mining water over the past few decades. While early in the last century concentrations of up to 3500 mg l⁻¹ of chloride were observed, the mean concentration is now below 400 mg l⁻¹. At the same time the water quality has improved greatly so factors other than chloride concentration may be influencing the macroinvertebrate community.Macroinvertebrate data collected from three sites along the River Lippe was analyzed for a change in the occurrence of salt tolerant species in an area where mining water discharge ended in 2000. It was found that also during the period of discharges the macroinvertebrate community was dominated by freshwater species and therefore the impact of mining water discharges in the upper River Lippe is considered to be minor.It was also found that for some species (Nais elinguis, Bithynia tentaculata and Gammarus tigrinus) their proposed salinity preference did not correlate with their occurrence in the field. This may be an area that requires further research.