Geologie an den höheren Schulen Sachsens

Ohne Zusammenfassung     

Advanced Technology Solar Telescope: A status report

Magnetic fields control the inconstant Sun. The key to understanding solar variability and its direct impact on the Earth rests with understanding all aspects of these magnetic fields. The Advanced Technology Solar Telescope (ATST) has been design specifically for magnetic remote sensing. Its collecting area, spatial resolution, scattered light, polarization properties, and wavelength performance all insure ATST will be able to observe magnetic fields at all heights in the solar atmosphere from photosphere to corona. After several years of design efforts, ATST has been approved by the U.S. National Science Foundation to begin construction with a not to exceed cost cap of approximately $298M. Work packages for major telescope components will be released for bid over the next several months. An application for a building permit has been submitted (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Learning from (small) disasters

In this article, disasters are understood as processes that have different impacts on social routines in terms of scale, scope and duration. The extent of adaptive processes in society can provide the ground for a rough classification of disaster types. Such classification has, on the one hand, practical and analytical advantages. On the other hand, they harbour the danger of overlooking transitions of scale and discourage comprehensive scale-related learning forms. Based on the disaster scale by Fischer (Int J Mass Emerg Disasters 1:91–107, 2003), flash floods in mountain rivers and torrents are described as extreme emergencies or small-town disasters. Three given examples will clearly show that learning rarely takes place within an institutional setting that is subjected to small disasters, because the stakeholder’s focus remains on only one level. Therefore, we propose to implement a system of self-organised and scale-independent learning, so called deutero learning, within the political subsystem. Following a damaging event, participative processes that involve all levels should be initialised. Their task would be to assess the combination of causes and draw conclusions for mitigation measures. An aggregation of these assessments would help the responsible political subsystems to adapt the current natural disasters policy to the changing environmental conditions.     

Threshold behavior of karst aquifers: the example of the Lurbach karst system (Austria)

Threshold behavior in hydrological systems generally involves a qualitative change of a single process, the system response or the functioning of the system. Different types of thresholds and their underlying controls are examined using the example of the Lurbach karst system (Austria). This karst system receives allogenic recharge from the sinking stream Lurbach, which under low-flow conditions only resurges at the Hammerbach spring. Yet, under medium- to high-flow conditions an overflow toward another spring, the Schmelzbach outlet occurs. Thresholds in physicochemical spring responses and their underlying controls are identified from the analysis of heat and solute transport processes in karst conduits. Applying this concept to the Hammerbach spring suggests that the threshold controlling the response of the spring water temperature was changed in the time period from 2006 to 2009 relative to the years before. At the same time, changes are observed in the behavior of the spring hydrograph and the discharge threshold at which the overflow to the Schmelzbach system is activated. All of these observations can be consistently explained by a decreased diameter of the conduit pathways within the indicated time period, presumably caused by the redistribution of sediments due to a flood event in 2005. Thus, thresholds in the physicochemical spring response were successfully employed to support the identification of a change in the functioning of the Lurbach karst system, which occurred possibly because a threshold related to the sediment transport within the karst conduits was crossed.     

Whipple telescope observations of LS I +61 303: 2004–2006

In this paper we present the results of the past two years observations on the galactic microquasar LS I +61 303 with the Whipple 10 m gamma-ray telescope. The recent MAGIC detection of the source between 200 GeV and 4 TeV suggests that the source is periodic with very high energy (VHE) gamma-ray emission linked to its orbital cycle. The entire 50-hour data set obtained with Whipple from 2004 to 2006 was analyzed with no reliable detection resulting. The upper limits obtained in the 2005–2006 season covered several of the same epochs as the MAGIC Telescope detections, albeit with lower sensitivity. Upper limits are placed on emission during the orbital phases of 0→0.1 and 0.8→1, phases which are not included in the MAGIC data set.      

Absorption of nuclear γ-rays on the starlight radiation in FR I sources: the case of Centaurus A

Several BL Lac objects are confirmed sources of variable and strongly Doppler-boosted TeV emission produced in the nuclear portions of their relativistic jets. It is more than probable that also many of the Fanaroff–Riley type I (FR I) radio galaxies, believed to be the parent population of BL Lacs, are TeV sources, for which Doppler-hidden nuclear γ-ray radiation may be only too weak to be directly observed. Here we show, however, that about 1 per cent of the total time-averaged TeV radiation produced by the active nuclei of low-power FR I radio sources is inevitably absorbed and re-processed by photon–photon annihilation on the starlight photon field, and the following emission of the created and quickly isotropized electron–positron pairs. In the case of the radio galaxy Centaurus A, we found that the discussed mechanism can give a distinctive observable feature in the form of an isotropic γ-ray halo. It results from the electron–positron pairs injected to the interstellar medium of the inner parts of the elliptical host by the absorption process, and upscattering starlight radiation via the inverse-Compton process mainly to the GeV–TeV photon energy range. Such a galactic γ-ray halo is expected to possess a characteristic spectrum peaking at ∼0.1 TeV photon energies, and the photon flux strong enough to be detected by modern Cherenkov Telescopes and, in the future, by GLAST. These findings should apply as well to the other nearby FR I sources.     

Sedimentary and tectonic evolution of Lake Ohrid (Macedonia/Albania)

Lake Ohrid, located on the Balkan Peninsula within the Dinaride–Albanide–Hellenide mountain belt, is a tectonically active graben within the South Balkan Extensional Regime (SBER). Interpretation of multichannel seismic cross sections and bathymetric data reveals that Lake Ohrid formed during two main phases of deformation: (1) a transtensional phase which opened a pull‐apart basin, and (2) an extensional phase which led to the present geometry of Lake Ohrid. After the initial opening, a symmetrical graben formed during the Late Miocene, bounded by major normal faults on each side in a pull‐apart type basin. The early‐stage geometry of the basin has a typical rhomboidal shape restricted by two sets of major normal faults. Thick undisturbed sediments are present today at the site where the acoustic basement is deepest, illustrating that Lake Ohrid is a potential target for drilling a long and continuous sediment core for studying environmental changes within the Mediterranean region. Neotectonic activity since the Pliocene takes place along the roughly N–S‐striking Eastern and Western Major Boundary Normal Faults that are partly exposed at the present lake floor. The tectono‐sedimentary structure of the basin is divided into three main seismic units overlying the acoustic basement associated with fluvial deposits and lacustrine sediments. A seismic facies analysis reveals a prominent cyclic pattern of high‐ and low‐amplitude reflectors. We correlate this facies cyclicity with vegetation changes within the surrounding area that are associated with glacial/interglacial cycles. A clear correlation is possible back to ca. 450 kyrs. Extrapolation of average sedimentation rates for the above mentioned period results in age estimate of ca. 2 Myrs for the oldest sediments in Lake Ohrid.     

Colloidal Stability and Toxicity of Gold Nanoparticles and Gold Chloride on <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

Here we have examined interactions of gold nanoparticles differing in primary particle size and coating with the green algae Chlamydomonas reinhardtii as function of the colloidal stability of the particles in the experimental media used for toxicity studies. Interactions of dissolved Au³⁺ ions with algae were also examined. Included endpoints were photosynthetic yield and algal growth. Morphological and structural effects were examined microscopically and by flow cytometry. The results indicate no significant toxicity of gold nanoparticles to C. reinhardtii. Analysis of published data suggests toxicity of gold nanoparticles on algal growth to relate rather to particular coatings than to the gold core.     

3XMM J185246.6+003317 as transient neutron star

We performed an X‐ray timing and spectral analysis of the variable source 3XMM J185246.6+003317 to investigate its physical nature. The data from all observations of 3XMMJ185246.6+003317 conducted by XMM‐Newton EPIC MOS1 and MOS2 with the same instrumental setup in 2004–2009 were reprocessed to form a homogenous data set of solar barycenter corrected photon arrival times and high S/N spectra of 3XMM J185246.6+003317. A Bayesian method for the search, detection, and estimation of the parameters of a periodic signal of unknown shape was employed, as developed by Gregory & Loredo (1992, 1993). The results show that 3XMM J185246.6+003317 is a transient neutron star with the genuine spin‐period of 23.11722 (23.11711–23.11727) s and its derivative of 5.3(0.3–5.5)×10^–11 s s^–1, implying a characteristic age of 7 (6–104) kyr, if the period derivative can be ascribed to the genuine spin‐down rate of the neutron star. The rotational‐phase averaged X‐ray spectra at the different brightness periods can be fitted with a highly absorbed blackbody model with different temperatures. The phase‐folded light curves in different energy bands with high S/N ratio show a double‐peaked profile; the variations depend on time and energy, indicating that radiation emerges from at least two emitting areas. The spectra at the phases corresponding to the maxima in the phase‐folded light curve show different spectral parameters of absorbed blackbody radiation, i.e. the hotter one has a smaller size. The source is detected only from September 2008 to April 2009 with persistently decreasing brightness, but not before, even though it was observed by XMM. Hence, it is a transient neutron star or a binary system hosting it. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)