1,279 research outputs found
Archaeological dating of colluvial and lacustrine deposits in a GIS environment investigating the multi-period site Gortz 1 on Oberer Beetzsee, Brandenburg
From the mid-14th century CE onwards, extensive soil erosion, caused by intensive agricultural practices, has led to the destruction of landscape structures in Central Europe. In 2016, the University of Applied Sciences in Berlin investigated the colluvial deposits at the site of Gortz in western Brandenburg (Germany), which had accumulated on the lower slopes and were caused by the processes just mentioned.
The mapping of each individual archaeological find made it possible to project all finds onto one profile running along the slope. Transformation of the finds' coordinates from profile view to plan view enabled the visualization in a Geographical Information System (GIS). The combination of adjacent strata into larger units using a pedological and sedimentological approach enabled an improved dating of colluvial deposits. In addition, the method facilitated the dating of historical water levels in the Beetzsee chain of lakes, which are part of the Havel river system.
As a result, it could be demonstrated that substantial anthropogenic activity, such as clay quarrying and bank straightening, took place during the Late Slavic Period. An interlocking horizon of colluvial and lacustrine deposits indicates that the water level of the lake Oberer Beetzsee rose from a value under 29.4âm above sea level (a.s.l.) in the 11th/12th century CE to approximately 29.8âmâa.s.l. in the 13th century CE. However, isolated flooding events during the 13th century CE can be recorded up to a height of 30.5âmâa.s.l. A modern colluvial deposit of 1âm in thickness indicates an acute endangerment of the archaeological site by modern agriculture.FlĂ€chenhafte Bodenerosion, ausgelöst durch intensive landwirtschaftliche Nutzung, fĂŒhrte ab Mitte des 14. Jahrhunderts u.Z. zur Zerstörung von Landschaftsstrukturen und in Mitteleuropa. Kolluvien, welche durch diese Prozesse entstanden und am Unterhang akkumulierten, wurden auf dem Fundplatz Gortz (westliches Brandenburg, Deutschland) durch die Hochschule fĂŒr Technik und Wirtschaft Berlin im Jahr 2016 untersucht.
Konsequente Einzelfundeinmessung ermöglichte die Projizierung aller Funde auf eines der lÀngs zum Hang verlaufenden Profile. Koordinatentransformation der Funde von der Profilansicht in die Draufsicht, ermöglichte die Visualisierung in einem GIS. Die Zusammenfassung benachbarter Schichten auf Basis der bodenkundlich-sedimentologischen Ansprache ermöglichte eine verbesserte Datierung der Kolluvien. ZusÀtzlich ermöglichte diese Methode die Datierung historischer PegelstÀnde der Beetzseekette, eines Teils des Flusssystems der Havel.
Im Ergebnis lieĂen sich fĂŒr die spĂ€tslawische Zeit starke anthropogene AktivitĂ€ten wie Mergelabbau und eine Uferbegradigung nachweisen. Ăber einen Verzahnungshorizont limnischer und kolluvialer Sedimente. lieĂ sich ein Pegelanstieg des Oberen Beetzsees von einem Wert unterhalb von 29.4âm Normalhöhennull (NHN) im 11./12. Jahrhundert u.Z. auf etwa 29.8âm NHN im 13. Jahrhundert u.Z. feststellen. Es lassen sich fĂŒr das 13. Jahrhundert u.Z. jedoch auch vereinzelte Ăberschwemmungsereignisse bis in eine Höhe von 30.5âm NHN fassen.
Ein modernes Kolluvium von einem Meter MÀchtigkeit zeigt die akute GefÀhrdung des Bodendenkmals durch die moderne Landwirtschaft
Spin self-rephasing and very long coherence times in a trapped atomic ensemble
We perform Ramsey spectroscopy on the ground state of ultra-cold 87Rb atoms
magnetically trapped on a chip in the Knudsen regime. Field inhomogeneities
over the sample should limit the 1/e contrast decay time to about 3 s, while
decay times of 58 s are actually observed. We explain this surprising result by
a spin self-rephasing mechanism induced by the identical spin rotation effect
originating from particle indistinguishability. We propose a theory of this
synchronization mechanism and obtain good agreement with the experimental
observations. The effect is general and susceptible to appear in other physical
systems.Comment: Revised version; improved description of the theoretical treatmen
A comparison of parameter choice rules for âp - âq minimization
Images that have been contaminated by various kinds of blur and noise can be restored by the minimization of an âp-âq functional. The quality of the reconstruction depends on the choice of a regularization parameter. Several approaches to determine this parameter have been described in the literature. This work presents a numerical comparison of known approaches as well as of a new one
Fractal time random walk and subrecoil laser cooling considered as renewal processes with infinite mean waiting times
There exist important stochastic physical processes involving infinite mean
waiting times. The mean divergence has dramatic consequences on the process
dynamics. Fractal time random walks, a diffusion process, and subrecoil laser
cooling, a concentration process, are two such processes that look
qualitatively dissimilar. Yet, a unifying treatment of these two processes,
which is the topic of this pedagogic paper, can be developed by combining
renewal theory with the generalized central limit theorem. This approach
enables to derive without technical difficulties the key physical properties
and it emphasizes the role of the behaviour of sums with infinite means.Comment: 9 pages, 7 figures, to appear in the Proceedings of Cargese Summer
School on "Chaotic dynamics and transport in classical and quantum systems
An Efficient Implementation of the Gauss-Newton Method Via Generalized Krylov Subspaces
The solution of nonlinear inverse problems is a challenging task in numerical analysis. In most cases, this kind of problems is solved by iterative procedures that, at each iteration, linearize the problem in a neighborhood of the currently available approximation of the solution. The linearized problem is then solved by a direct or iterative method. Among this class of solution methods, the Gauss-Newton method is one of the most popular ones. We propose an efficient implementation of this method for large-scale problems. Our implementation is based on projecting the nonlinear problem into a sequence of nested subspaces, referred to as Generalized Krylov Subspaces, whose dimension increases with the number of iterations, except for when restarts are carried out. When the computation of the Jacobian matrix is expensive, we combine our iterative method with secant (Broyden) updates to further reduce the computational cost. We show convergence of the proposed solution methods and provide a few numerical examples that illustrate their performance
Theoretical analysis of the implementation of a quantum phase gate with neutral atoms on atom chips
We present a detailed, realistic analysis of the implementation of a proposal
for a quantum phase gate based on atomic vibrational states, specializing it to
neutral rubidium atoms on atom chips. We show how to create a double--well
potential with static currents on the atom chips, using for all relevant
parameters values that are achieved with present technology. The potential
barrier between the two wells can be modified by varying the currents in order
to realize a quantum phase gate for qubit states encoded in the atomic external
degree of freedom. The gate performance is analyzed through numerical
simulations; the operation time is ~10 ms with a performance fidelity above
99.9%. For storage of the state between the operations the qubit state can be
transferred efficiently via Raman transitions to two hyperfine states, where
its decoherence is strongly inhibited. In addition we discuss the limits
imposed by the proximity of the surface to the gate fidelity.Comment: 9 pages, 5 color figure
Enhanced production of propionic acid through acidic hydrolysis by choice of inoculum
BACKGROUND
In this study, the enhancement of propionic acid production from a model feedstock mimicking kitchen waste was investigated. For that purpose, two operational runs of a semicontinuous anaerobic hydrolysis reactor were carried out at pH 6.0 ±â0.1 and mesophilic (30â°C) temperature. Two different types of inocula, a mixed microbial culture selected over 24âmonths for growth on cellulose and a culture contained in goat cheese were compared.
RESULTS
The results show that the goat cheese inoculum was significantly more efficient for propionic acid (PA) production. The highest propionic acid concentration achieved amounted to 139âmmolâLâ1 at a yield of 23.3 mgâgâ1 volatile solids (VS), which was 55% greater than what was achieved with the mixed culture. Furthermore, it was observed that propionic acid production was enhanced by a combination of high hydraulic retention time (HRT) with low organic loading rate (OLR), ensuring sufficient time for complete processing of the complex organic substrates. The fermentation could be kept in a stable process of propionic acid production at HRT of 20âdays and a rather low OLR of 11.1 gâLâ1 dayâ1 VS.
CONCLUSION
Our results give a better understanding of PA production in semicontinuous mode, applying optimized process parameters and selecting the adequate microbial community for inoculation. This study provides important information for the improvement of PA production from complex substrates for future industrial application. © 2020 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI)
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