2,667 research outputs found
Land use dynamics in favorable and unfavorable areas of southwest Germany
Since the “Neolithic Revolution” and the beginning of agriculture in central Europe about 7.500 a ago human influence on the environment is increasing. Human activities led to quasi-natural relief formation and created in many places a cultural landscape. Colluvial deposits are the correlate sediments of human induced soil erosion on slopes and depict an excellent archive for land use and landscape history. The present study combines pedological, archaeological and palynological analyses and knowledge with AMS 14C and luminescence datings to build up a stratigraphy of colluvial deposits, thereby allowing the reconstruction of past land use dynamics southwest Germany.
Compared with Black Forest and the Swabian Jura, the Baar is a favorable area for agricultural land use, where seven main phases of colluvial deposition could be detected. Increased colluviation, and thus land use intensity, took place during the younger Neolithic, the early to middle Bronze Age, the Iron Age, the Roman Empire, and in three phases from the High Middle Ages onwards. The southeastern Black Forest low mountain range is an unfavorable area characterized by low temperatures, high precipitation and steep slopes. Nevertheless, human influence dates back to the Neolithic. Minor colluvial deposition phases were detected before the Middle Ages and increased formation of colluvial deposits during the High Middle Ages and the Modern Times. The colluvial stratigraphy shows an intense land use of the Black Forest area from the Middle Ages onwards. In the western Swabian Jura the pattern of colluvial deposition indicates land use from the Bronze Age onwards and for one site even since the Neolithic.
The different land use dynamics in the Baar area compared to the Black Forest and Swabian Jura will be discussed against the paleoenvironmental conditions reconstructed from different archives. It is to analyze whether climate was the main determining factor for the settlement pattern in time and space or if there were other factors responsible, such as: different human motivations to settle the land depending on natural or cultural resources, conflicts in neighboring areas or trading relations. Feedback mechanisms of the anthropogenically modified landscape might also interact and determine settlement and land use dynamics
Anharmonic Decay of Vibrational States in Amorphous Silicon
Anharmonic decay rates are calculated for a realistic atomic model of
amorphous silicon. The results show that the vibrational states decay on
picosecond timescales and follow the two-mode density of states, similar to
crystalline silicon, but somewhat faster. Surprisingly little change occurs for
localized states. These results disagree with a recent experiment.Comment: 10 pages, 4 Postscript figure
An Introduction to Nuclear Supersymmetry: a Unification Scheme for Nuclei
The main ideas behind nuclear supersymmetry are presented, starting from the
basic concepts of symmetry and the methods of group theory in physics. We
propose new, more stringent experimental tests that probe the supersymmetry
classification in nuclei and point out that specific correlations should exist
for particle transfer intensities among supersymmetric partners. We also
discuss possible ways to generalize these ideas to cases where no dynamical
symmetries are present. The combination of these theoretical and experimental
studies may play a unifying role in nuclear phenomena.Comment: 40 pages, 11 figures, lecture notes `VIII Hispalensis International
Summer School: Exotic Nuclear Physics', Oromana, Sevilla, Spain, June 9-21,
200
Polarized radio emission from extensive air showers measured with LOFAR
We present LOFAR measurements of radio emission from extensive air showers.
We find that this emission is strongly polarized, with a median degree of
polarization of nearly , and that the angle between the polarization
direction of the electric field and the Lorentz force acting on the particles,
depends on the observer location in the shower plane. This can be understood as
a superposition of the radially polarized charge-excess emission mechanism,
first proposed by Askaryan and the geomagnetic emission mechanism proposed by
Kahn and Lerche. We calculate the relative strengths of both contributions, as
quantified by the charge-excess fraction, for individual air showers. We
find that the measured charge-excess fraction is higher for air showers
arriving from closer to the zenith. Furthermore, the measured charge-excess
fraction also increases with increasing observer distance from the air shower
symmetry axis. The measured values range from for very
inclined air showers at to for almost
vertical showers at . Both dependencies are in qualitative
agreement with theoretical predictions.Comment: 22 pages, 14 figures, accepted for publication in JCA
The radio emission pattern of air showers as measured with LOFAR - a tool for the reconstruction of the energy and the shower maximum
The pattern of the radio emission of air showers is finely sampled with the
Low-Frequency ARray (LOFAR). A set of 382 measured air showers is used to test
a fast, analytic parameterization of the distribution of pulse powers. Using
this parameterization we are able to reconstruct the shower axis and give
estimators for the energy of the air shower as well as the distance to the
shower maximum.Comment: 15 pages, 10 figures, accepted for publication in JCA
A method for high precision reconstruction of air shower Xmax using two-dimensional radio intensity profiles
The mass composition of cosmic rays contains important clues about their
origin. Accurate measurements are needed to resolve long-standing issues such
as the transition from Galactic to extragalactic origin, and the nature of the
cutoff observed at the highest energies. Composition can be studied by
measuring the atmospheric depth of the shower maximum Xmax of air showers
generated by high-energy cosmic rays hitting the Earth's atmosphere. We present
a new method to reconstruct Xmax based on radio measurements. The radio
emission mechanism of air showers is a complex process that creates an
asymmetric intensity pattern on the ground. The shape of this pattern strongly
depends on the longitudinal development of the shower. We reconstruct Xmax by
fitting two-dimensional intensity profiles, simulated with CoREAS, to data from
the LOFAR radio telescope. In the dense LOFAR core, air showers are detected by
hundreds of antennas simultaneously. The simulations fit the data very well,
indicating that the radiation mechanism is now well-understood. The typical
uncertainty on the reconstruction of Xmax for LOFAR showers is 17 g/cm^2.Comment: 12 pages, 10 figures, submitted to Phys. Rev.
Realtime processing of LOFAR data for the detection of nano-second pulses from the Moon
The low flux of the ultra-high energy cosmic rays (UHECR) at the highest
energies provides a challenge to answer the long standing question about their
origin and nature. Even lower fluxes of neutrinos with energies above
eV are predicted in certain Grand-Unifying-Theories (GUTs) and e.g.\ models for
super-heavy dark matter (SHDM). The significant increase in detector volume
required to detect these particles can be achieved by searching for the
nano-second radio pulses that are emitted when a particle interacts in Earth's
moon with current and future radio telescopes.
In this contribution we present the design of an online analysis and trigger
pipeline for the detection of nano-second pulses with the LOFAR radio
telescope. The most important steps of the processing pipeline are digital
focusing of the antennas towards the Moon, correction of the signal for
ionospheric dispersion, and synthesis of the time-domain signal from the
polyphased-filtered signal in frequency domain. The implementation of the
pipeline on a GPU/CPU cluster will be discussed together with the computing
performance of the prototype.Comment: Proceedings of the 22nd International Conference on Computing in High
Energy and Nuclear Physics (CHEP2016), US
Boson-conserving one-nucleon transfer operator in the interacting boson model
The boson-conserving one-nucleon transfer operator in the interacting boson
model (IBA) is reanalyzed. Extra terms are added to the usual form used for
that operator. These new terms change generalized seniority by one unit, as the
ones considered up to now. The results obtained using the new form for the
transfer operator are compared with those obtained with the traditional form in
a simple case involving the pseudo-spin Bose-Fermi symmetry in its limit. Sizeable differences are
found. These results are of relevance in the study of transfer reactions to
check nuclear supersymmetry and in the description of (\beta)-decay within IBA.Comment: 13 pages, 1 table, 0 figures. To be published in Phys. Rev.
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