Analysis of lightning-induced forest fires in Austria

Besides human-caused fires, lightning is the major reason for forest fire ignition in Austria. In order to analyse the causes of ignition and to characterise lightning-induced forest fires, fire records were compared with the real appearance of lightning events by using the Austrian Lightning Detection and Information System for the period from 1993 to 2010. A probability was estimated for each forest fire being caused by lightning by using a decision tree and decision matrices based on flash characteristics (e.g. amplitude, time, location). It could be shown that 15 % of documented forest fires were lightning-caused. Nearly all lightning-caused fires were found during the summer months, whereas almost 40 % of all fires occurring from June to August were naturally caused. Most lightning-caused fires took place in the south and east of Austria. Lightning fires were more frequent at higher altitudes and primarily affected conifer forests. The median burned area was lower than that for anthropogenic forest fires.     

DRIVING FORCES OF ISLAND BIODIVERSITY: AN APPRAISAL OF TWO THEORIES

The avifauna of three oceanic islands of the Revillagigedo archipelago in the eastern Pacific Ocean consists of 14 endemic landbird taxa and 3 recent continental colonists. This study analyzes the origin, areography of continental relatives, ecological characteristics, and role of immigration and extinction factors as regulators of the islands' species. Only two natural extinctions have been detected on this archipelago in more than 130 years. The endemic nature of the pristine avifauna is interpreted as an indication of high stability over thousands of years. The MacArthur–Wilson (1967) “equilibrium theory of island biogeography” cannot explain or predict the persistence of this avifauna adapted to stable and unique island ecosystems. Lack's (1976) “theory of ecological poverty” regulating island avifaunas, however, predicts stability and a resource-limited bird community. The Revillagigedo avifauna can be understood as an interactive community of a few highly adapted and competitive ecological generalists that have effectively filled all niche spaces and closed off the islands to further colonization. Catastrophic change or anthropogenic landscape degradation may, however, create novel niche spaces and open affected islands to new colonists. This appraisal lends support to the call for a shift away from application of the equilibrium model of island biogeography in conservation science. [Key words: island biogeography, equilibrium theory, island stability, island avifauna, MacArthur-Wilson, Lack, Revillagigedo Islands, Socorro Island.]     

The photospheric barium spectrum: Solar abundance and collision broadening of Baii lines by hydrogen

A study of the solar Ba ii spectrum leads to a solar abundance of barium of log ba = = 2.11±0.12, on the scale log h = 12. The observed asymmetry of the resonance line 4554 is consistent with an isotopic abundance ratio equal to the terrestrial one. The meteoritic Ba/Si abundance ratio found in carbonaceous chondrites appears to exceed the solar ratio by 0.1 to 0.2 dex (Section 5).The broadening by collisions with hydrogen atoms is determined from the solar spectrum (Section 4). Damping half-widths, h, of the three stronger Ba ii lines turn out to be larger by a factor of about 3.0 than predicted from pure van der Waals interaction of dipoles. Departures from LTE appear to be present in the cores of the resonance lines and of the lines arising from the metastable 5D levels (Section 6). The equivalent widths, however, remain practically unaffected.Equivalent widths of neutral barium lines are predicted and some new identifications of photospheric Ba i lines are suggested (Section 7).     

The composite galaxy NGC 6764: Nuclear activity and circumnuclear star formation

We investigated the kinematics and ionization mechanism of the innermost arc seconds of the nucleus of NGC 6764 (SBb), using spatially-resolved optical spectra. The observed radial variations of the emission line ratios cannot be explained by one single-ionizing agent, but are consistent with circumnuclear ionizeation by hot stars in addition to a central power-law source. We conclude that NGC 6764 is a Composite Galactic Nucleus (CGN).Visiting Astronomer, German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie in Heidelberg jointly with the Spanish National Commission for Astronomy.     

Sedimentology and geochemistry of an exceptionally preserved last interglacial sapropel S5 in the Levantine Basin (Mediterranean Sea)

A combined study of lithological, geochemical and physical sediment properties is reported from a completely laminated S5 sapropel, recovered in three gravity cores (M40-4 SL67, M51-3 SL103, M51-3 SL104) from the Pliny Trench region of the eastern Mediterranean. The thickness of the studied sapropel S5 varies between 85 and 91 cm and tops most S5-sapropels in the Mediterranean. Based on optical features like color and thickness of laminae, the sapropels were subdivided into thirteen distinct lithostratigraphic zones. These zones, as well as the finer layering pattern within them, could be followed exactly among the three cores, indicating that the processes responsible for this variation acted at least on a regional scale. The sapropel sediment is characterized by exceptionally high porosity, which is strongly correlated with Si/Ca. This relationship implies that the sapropel is in essence an organic-matter rich diatomite and its exceptional thickness can be explained by preservation of diatoms forming a loosely packed sediment fabric. Compared to other S5 sapropels, the preservation of diatoms has apparently led to a twofold increase in the thickness of the sapropel layer. Relative abundances of 10 elements were determined at ultra-high resolution (0.2 mm) by XRF-scanner over the complete length of each sapropel including several cm of enclosing marl. An analysis of the chemical data indicates that the lowermost 13 cm of the sapropel is chemically more similar to the underlying marl and that the sediment chemistry shows different signals at different scales. The strongest pattern is the contrast between the sapropel and the surrounding marl, which is accentuated in elements indicative for redox conditions as well as terrigenous sediment input and productivity. Within the sapropel, a mm- to cm-scale layering is observed. The abundances of many elements are systematically linked to the pattern of these layers, indicating a common origin, related to productivity and/or terrigenous sediment and/or redox conditions. This pattern indicates a link to a regional climatic process, making the S5 sapropel horizon in M40-4 SL67, M51-3 SL103 and M51-3 SL104 a potential high-resolution archive of climatic variability during the last interglacial in the Mediterranean Sea and its adjacent landmasses.     

The magnetic anisotropy of hematite bearing rocks

Summary The high field torque curves of hematite bearing rocks are not caused by directional differences in the energy of magnetization to saturation, but rather by the couple between the ferromagnetic moment and the applied field. An expression, derived for the high field torque curve of a single crystal of hematite, whose basal plane makes an arbitrary angle with the plane of rotation of the applied field, is found to be in excellent agreement with experiment. Furthermore it is shown that the Fourier spectrum of hematite bearing rocks should in general contain significant higher harmonics and that therefore the high field method is not particularly suitable for determining the preferred crystalline alignment of hematite bearing rocks.     

Geology,petrography, and petrology of Pinzon Island,galapagos archipelago

Three stratigraphic units based on geologic relationships and paleomagnetic observations may be distinguished on Pinzon Island. The oldest unit is a broad shield which forms the main body of the island and was erupted during a period of reversed magnetic polarity from an area now occupied by a caldera. Subsequent activity was centered about 1.5 km to the north-northwest from vents later engulfed by the collapse of a younger caldera. The lower portion of this sequence was erupted during a period of transitional pole positions and is overlain by flows of normal polarity. Pinzon has the most diverse suite of differentiated tholeiitic rocks found in the Galapagos Archipelago. Products of eruptive cycles are preserved as sequences of tuffs and flows that have decreasing degrees of differentiation and increasing phenocryst abundance upsection. The sequences may be a consequence of tapping successively deeper levels of compositionally zoned magma chambers. Such a model is consistent with computer calculations utilizing major and trace element data for Pinzon rocks, which suggest that lavas of the island may be related by shallow-level crystal fractionation of observed phenocryst minerals.     

The nature of the luminous X-ray emission of NGC 6240

We briefly review and extend our discussion of the ROSAT detectionof the extraordinarily luminous (>10⁴² erg/s) partly extended(>30 kpc diameter) X-ray emission from the ultraluminous infrared galaxy NGC 6240.The `standard'-model of starburst outflow is contrasted with alternatives and a comparison with the X-ray properties of ellipticals is performed.     

A data model for moving regions of fixed shape in databases

Moving object databases are designed to store and process spatial and temporal object data. An especially useful moving object type is a moving region, which consists of one or more moving polygons suitable for modeling the spread of forest fires, the movement of clouds, spread of diseases and many other real-world phenomena. Previous implementations usually allow a changing shape of the region during the movement; however, the necessary restrictions on this model result in an inaccurate interpolation of rotating objects. In this paper, we present an alternative approach for moving and rotating regions of fixed shape, called Fixed Moving Regions, which provide a significantly better model for a wide range of applications like modeling the movement of oil tankers, icebergs and other rigid structures. Furthermore, we describe and implement several useful operations on this new object type to enable a database system to solve many real-world problems, as for example collision tests, projections and intersections, much more accurate than with other models. Based on this research, we also implemented a library for easy integration into moving objects database systems, as for example the DBMS Secondo (1) (2) developed at the FernUniversität in Hagen.