Taxonomische Studien über Cyanophyceen aus Oxydationsteichen

Zusammenfassung Die Cyanophyceen aus 8 Oxydationsteichen Südschwedens wurden untersucht. Drei Arten kamen regelm?ssig vor:Phormidium autumnale, Oscillatoria chalybea undO. tenuis. Letztere war in allen Teichen vorhanden und trat oft massenhaft auf. Es wurden statistische Messungen der Trichombreite, in erster Linie beiO. tenuis, die eine erhebliche Breitenvariation in ein und derselben Probe aufwies, vorgenommen. Die gr?sste Variationsbreite betrug 3,5 bis 10 μ. Trotzdem mussO. tenuis als eine gute Art betrachtet werden. Sie ist leicht identifizierbar, und die Kleinformen (Mikrotaxa) sind statistisch nicht auseinander zu halten. Wahrscheinlich stellen auch dievar. natans undtergestina solche Kleintypen dar und sollten daher in die Hauptart eingezogen werden. Eine schmale Form aus Humleb?cken (kein Oxydationsteich) weicht ausser der Zellbreite in weiteren Merkmalen von der Hauptart ab und k?nnte deshalb als eine Variet?t betrachtet werden.

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Summary The Cyanophyta found in 8 oxydation ponds in the South of Sweden were analysed. Three species appeared regularly:Phormidium autumnale, Oscillatoria chalybea andO. tenuis. The last species was present in all of the ponds and often in very large quantities. Statistical measures were made of the trichom width, especially ofO. tenuis for which considerable variations were observed in a single sample. The largest differences in width varied from 3·5 to 10 μ. Nevertheless,O. tenuis must be considered as a good species. It is easy to identify and its microtaxa cannot statistically be held apart. Thevar. natans andtergestina should probably be considered as microtaxa and included in the main species. A smaller type from Humleb?cken (not from an oxydation pond) differs from the main species not only in the width of its cells, but also in other characteristics and could therefore be considered as a variety.

     

The hyperthermal ionization and high absolutemeteor velocities observed with HPLA radars

High Power Large Aperture (HPLA) radars generally observe very high meteor velocities averaging over 50 km s⁻¹. There are only a few events recorded around 30 km s⁻¹, while meteors at 20 km s⁻¹ or slower are very rare. This is a clear and debated contradiction to specular meteor radar results. A high plasma density condition contributes, but the dominating phenomenon is the hyperthermal ionization mechanism due to chemical dynamics of the ionization process. The observed high velocities can be explained in terms of high hyperthermal ionization cross-sections for collisions between ablated meteoroid metal atoms such as Na and/or Fe and atmospheric species.     

Meteor fluxes and visual magnitudes from EISCAT radar event rates: a comparison with cross-section based magnitude estimates and optical data

Incoherent scatter radars (ISR) are versatile instruments for continuous monitoring of ionisation processes in the Earths atmosphere. EISCAT, The European Incoherent Scatter facility has proven effective also in meteor studies. The time resolution of the radar can be reduced to a few milliseconds, sufficient to resolve the passage of individual meteors through the narrow ISR beam. Methods for group and phase velocity determination of the meteoroids and the discrepancy between the results related to the target behaviour are presented. The radar cross sections of echoes associated with moving meteoroids (–meteor head echoes) are very small and increase with decreasing wavelength. The parent meteoroids are found to have visual magnitudes far below the detection limit of most optical observations. The equivalent visual magnitude limit of the smallest objects observed by EISCAT in the current experiments has been estimated by two different methods, both from the cross-section measurements and from the measured event rates. Both methods give a limit value of +10 for the smallest objects while the upper limit is +4. The lower limit of the visual magnitude for the collocated optical measurement system is +4. Thus the two detection systems observe two different meteor size ranges, with the radar almost reaching micrometeorite population. Meteor fluxes estimated from the event rates and the radar system parameters agree well with previous extrapolated values for this size range.     

Trust Matters – Social Capital in Herding Cooperation in Finland

Reindeer herding is a nature-based livelihood of the indigenous Sámi people in northern parts of Europe and Russia. During the last decades, reindeer herding has become a more significant issue in the context of the market economy: the livelihood has transformed toward entrepreneurship, and the subsidies demand growth in the scale of herding. According to the national administration, the market values are highlighted. However, for herders, market economies are only one part of their livelihood. Another important part is their experience of reindeer herding as a way of life; for many reindeer herders trust in their livelihood and the social relations associated with their way of life are of equal or greater importance than economic aspects. In this paper, the role of social trust in the changing process of reindeer herding is discussed. Inherited tacit and cultural knowledge, as a part of social capital, strengthen reindeer herders’ experience of trust.     

Latitudinal Variations of Diurnal Meteor Rates

The presence of a diurnal variation in meteor activity is well established. The sporadic meteor count rates are higher on the local dawn side and lower on the local dusk side. This phenomenon is caused by the Earth’s orbital motion and rotation. Meteor radar measurements have been compared from Esrange, Kiruna, Sweden, at 68° N, from Juliusruh, Germany, at 55° N, and from Ascension Island, at 8° S, to investigate how the diurnal variation depends on season at different latitudes. Data have been used from vernal and autumnal equinoxes and summer and winter solstices to locate the largest seasonal differences.     

Estimated Visual Magnitudes of the EISCAT UHF Meteors

We have investigated the conditions for simultaneous meteor observations with the EISCAT UHF radar system and telescopic optical devices. The observed characteristics of 410 meteors detected by all three UHF receivers are compared with model simulations and their luminosity is calculated as a part of a meteoroid ablation model using a fifth order Runge–Kutta numerical integration technique. The estimated absolute visual magnitudes are in the range of +9 to +5. The meteors should therefore be observable using intensified CCD or EMCCD (Electron Multiplying CCD) cameras with telephoto lenses. A possible setup of a coordinated radar and optical campaign is suggested.     

Simultaneous oxidation of arsenic and antimony at low and circumneutral pH,with and without microbial catalysis

Arsenic and Sb are common mine-water pollutants and their toxicity and fate are strongly influenced by redox processes. In this study, simultaneous Fe(II), As(III) and Sb(III) oxidation experiments were conducted to obtain rates under laboratory conditions similar to those found in the field for mine waters of both low and circumneutral pH. Additional experiments were performed under abiotic sterile conditions to determine the biotic and abiotic contributions to the oxidation processes. The results showed that under abiotic conditions in aerated Fe(III)–H₂SO₄ solutions, Sb(III) oxidizes slightly faster than As(III). The oxidation rates of both elements were accelerated by increasing As(III), Sb(III), Fe(III), and Cl⁻ concentrations in the presence of light. For unfiltered circumneutral water from the Giant Mine (Yellowknife, NWT, Canada), As(III) oxidized at 15–78 μmol/L/h whereas Sb(III) oxidized at 0.03–0.05 μmol/L/h during microbial exponential growth. In contrast, As(III) and Sb(III) oxidation rates of 0.01–0.03 and 0.01–0.02 μmol/L/h, respectively, were obtained in experiments performed with acid unfiltered mine waters from the Iberian Pyritic Belt (SW Spain). These results suggest that the Fe(III) formed from microbial oxidation abiotically oxidized As(III) and Sb(III). After sterile filtration of both mine water samples, neither As(III), Sb(III), nor Fe(II) oxidation was observed. Hence, under the experimental conditions, bacteria were catalyzing As and Sb oxidation in the Giant Mine waters and Fe oxidation in the acid waters of the Iberian Pyrite Belt.