137 research outputs found
Metabasites from the KTB Oberpfalz target area, Bavaria - geochemical characteristics and examples of mobile behaviour of "immobile" elements
No abstract availabl
Geochemistry of metabasites and gabbroic rocks from the Tepla-Domazlice zone.
Various amphibolites, metagabbros and eclogitic relics of the Mariimske Lazne complex, and amphibolites from the Cerna Hora Massif exhibit an uniform geochemical character which compares well with modern mid-ocean ridge basalts. Geochemically these metabasites are similar to the amphibolites of the My to area and to schistose. partly striped amphibolites of the neighbouring Tirschenreuth-Mahring Zone and the Erbendorf-Vohenstrauss Zone (Bavaria). Greenschists and amphibolites from the Domailice metamorphic complex show an alkaline-basaltic tendency conforming to modern within-plate basalts or basalts from anomalous midocean ridge segments. In their chemical character, these metabasites compare well with the flaseramphibolites of the Erbendorf-Vohenstrauss Zone. Fine-grained amphibolites in the Warzenrieth area and gabbroic amphiboltes in the Blatterberg-Hoher Bogen area show normal MORB character. The metamorphosed gabbroic rocks in the southern part of the Neukirchen-Kdyne (meta-) igneous complex are subalkaline-tholeiitic and exhibit a magmatic differentiation trend. They differ from the neighbouring amphibolites by generally lower contents of incompatible elements
Electron Microprobe Analysis and X-ray Diffraction Methods in Archaeometry: Investigations on Pre-Islamic Beads from the Sultanate of Oman
Beads from graves of the Samad Assemblage, Sultanate of Oman and from an ancient crafts quarter of the old kingdom of Ruhana, in Sri Lanka, were investigated using electron analysis and X-ray powder diffraction. Both experimental methods were optimized toward non-destructive analysis
On the measurement of the proton-air cross section using air shower data
The analysis of high-energy air shower data allows one to study the
proton-air cross section at energies beyond the reach of fixed target and
collider experiments. The mean depth of the first interaction point and its
fluctuations are a measure of the proton-air particle production cross section.
Since the first interaction point in air cannot be measured directly, various
methods have been developed in the past to estimate the depth of the first
interaction from air shower observables in combination with simulations. As the
simulations depend on assumptions made for hadronic particle production at
energies and phase space regions not accessible in accelerator experiments, the
derived cross sections are subject to significant systematic uncertainties. The
focus of this work is the development of an improved analysis technique that
allows a significant reduction of the model dependence of the derived cross
section at very high energy. Performing a detailed Monte Carlo study of the
potential and the limitations of different measurement methods, we quantify the
dependence of the measured cross section on the used hadronic interaction
model. Based on these results, a general improvement to the analysis methods is
proposed by introducing the actually derived cross section already in the
simulation of reference showers. The reduction of the model dependence is
demonstrated for one of the measurement methods.Comment: Accepted by NJP. To appear in the Focus Issue "High Energy Cosmic
Rays
On the measurement of the proton-air cross section using longitudinal shower profiles
In this paper, we will discuss the prospects of deducing the proton-air cross
section from fluorescence telescope measurements of extensive air showers. As
it is not possible to observe the point of first interaction
directly, other observables closely linked to must be inferred from
the longitudinal profiles. This introduces a dependence on the models used to
describe the shower development. The most straightforward candidate for a good
correlation to is the depth of shower maximum . We
will discuss the sensitivity of an -based analysis on and quantify the systematic uncertainties arising from the model
dependence, parameters of the reconstruction method itself and a possible
non-proton contamination of the selected shower sample.Comment: 4 pages, Proceedings for ISVHECRI Weihei 200
Large-scale horizontal flows in the solar photosphere II: Long-term behaviour and magnetic activity response
Recently, we have developed a method useful for mapping large-scale
horizontal velocity fields in the solar photosphere. The method was developed,
tuned and calibrated using the synthetic data. Now, we applied the method to
the series of Michelson Doppler Imager (MDI) dopplergrams covering almost one
solar cycle in order to get the information about the long-term behaviour of
surface flows. We have found that our method clearly reproduces the widely
accepted properties of mean flow field components, such as torsional
oscillations and a pattern of meridional circulation. We also performed a
periodic analysis, however due to the data series length and large gaps we did
not detect any significant periods. The relation between the magnetic activity
influencing the mean zonal motion is studied. We found an evidence that the
emergence of compact magnetic regions locally accelerates the rotation of
supergranular pattern in their vicinity and that the presence of magnetic
fields generally decelerates the rotation in the equatorial region. Our results
show that active regions in the equatorial region emerge exhibiting a constant
velocity (faster by 60 +/- 9 m/s than Carrington rate) suggesting that they
emerge from the base of the surface radial shear at 0.95 R_sun, disconnect from
their magnetic roots, and slow down during their evolution.Comment: 9 pages, 8 figures, accepted for publication in Astronomy &
Astrophysic
Large-scale horizontal flows in the solar photosphere V: Possible evidence for the disconnection of bi-polar sunspot groups from their magnetic roots
In a recent paper (Svanda et al., 2008, A&A 477, 285) we pointed out that,
based on the tracking of Doppler features in the full-disc MDI Dopplergrams,
the active regions display two dynamically different regimes. We speculated
that this could be a manifestation of the sudden change in the active regions
dynamics, caused by the dynamic disconnection of sunspots from their magnetic
roots as proposed by Schuessler & Rempel (2005, A&A 441, 337). Here we
investigate the dynamic behaviour of the active regions recorded in the
high-cadence MDI data over the last solar cycle in order to confirm the
predictions in the Schuessler's & Rempel's paper. We find that, after drastic
reduction of the sample, which is done to avoid disturbing effects, a large
fraction of active regions displays a sudden decrease in the rotation speed,
which is compatible with the mechanism of the dynamic disconnection of sunspots
from their parental magnetic structures.Comment: 11 pages, 9 figures, 1 table; accepted in Astronomy & Astrophysic
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