1,150 research outputs found
Comparison of Proxy and Multimodel Ensemble Means
Proxyâmodel comparisons show large discrepancies in the impact of volcanic aerosols on the hydrology of the Asian monsoon region (AMR). This was mostly imputed to uncertainties arising from the use of a single model in previous studies. Here we compare two groups of CMIP5 multimodel ensemble mean (MMEM) with the treeâringâbased reconstruction Monsoon Asia Drought Atlas (MADA PDSI), to examine their reliability in reproducing the hydrological effects of the volcanic eruptions in 1300â1850 CE. Time series plots indicate that the MADA PDSI and the MMEMs agree on the significant drying effect of volcanic perturbation over the monsoonâdominated subregion, while disparities exist over the westerliesâdominated subregion. Comparisons of the spatial patterns suggest that the MADA PDSI and the MMEMs show better agreement 1 year after the volcanic eruption than in the eruption year and in subregions where more treeâring chronologies are available. The MADA PDSI and the CMIP5 MMEMs agree on the drying effect of volcanic eruptions in westernâEast Asia, South Asian summer monsoon, and northern East Asian summer monsoon (EASM) regions. Model results suggest significant wetting effect in southern EASM and westernâSouth Asia, which agrees with the observed hydrological response to the 1991 Mount Pinatubo eruption. Analysis on model output from the Last Millennium Ensemble project shows similar hydrological responses. These results suggest that the CMIP5 MMEM is able to reproduce the impact of volcanic eruptions on the hydrology of the southern AMR
Impact of natural climate change and historical land use on landscape development in the Atlantic Forest of Rio de Janeiro, Brazil.
Climate variations and historical land use had a major impact on landscape development in the Brazilian Atlantic Forest (Mata AtlĂąntica). In southeast Brazil, rainforest expanded under warm-humid climate conditions in the late Holocene, but have been dramatically reduced in historical times. Nevertheless, the numerous remaining forest fragments are of outstanding biological richness. In our research in the Atlantic Forest of Rio de Janeiro we aim at the reconstruction of the late Quaternary landscape evolution and an assessment of human impact on landscapes and rainforests. In this context, special focus is given on (a) effects of climate variations on vegetation cover, soil development, and geomorphological processes, and (b) spatial and temporal land use and landscape degradation patterns. In this paper we present some new results of our interdisciplinary research in the Serra dos ĂrgĂŁos mountain range, state of Rio de Janeiro
Development of a thermal ionizer as ion catcher
An effective ion catcher is an important part of a radioactive beam facility
that is based on in-flight production. The catcher stops fast radioactive
products and emits them as singly charged slow ions. Current ion catchers are
based on stopping in He and H gas. However, with increasing intensity of
the secondary beam the amount of ion-electron pairs created eventually prevents
the electromagnetic extraction of the radioactive ions from the gas cell. In
contrast, such limitations are not present in thermal ionizers used with the
ISOL production technique. Therefore, at least for alkaline and alkaline earth
elements, a thermal ionizer should then be preferred. An important use of the
TRIP facility will be for precision measurements using atom traps. Atom
trapping is particularly possible for alkaline and alkaline earth isotopes. The
facility can produce up to 10 s of various Na isotopes with the
in-flight method. Therefore, we have built and tested a thermal ionizer. An
overview of the operation, design, construction, and commissioning of the
thermal ionizer for TRIP will be presented along with first results for
Na and Na.Comment: 10 pages, 4 figures, XVth International Conference on Electromagnetic
Isotope Separators and Techniques Related to their Applications (EMIS 2007
sedFlow â a tool for simulating fractional bedload transport and longitudinal profile evolution in mountain streams
Especially in
mountainous environments, the prediction of sediment
dynamics is important for managing natural hazards, assessing
in-stream habitats and understanding geomorphic evolution. We
present the new modelling tool {sedFlow} for simulating
fractional bedload transport dynamics in mountain streams. sedFlow is a one-dimensional model that aims
to realistically reproduce the total transport volumes and overall
morphodynamic changes resulting from sediment transport events such as major
floods. The model is intended for temporal scales from the individual event (several hours to few days)
up to longer-term evolution of stream channels (several years). The envisaged spatial scale covers complete
catchments at a spatial discretisation of several tens of metres to a few hundreds of metres. sedFlow
can deal with the effects of streambeds that slope uphill in a downstream direction and uses recently proposed and
tested approaches for quantifying macro-roughness effects in steep
channels. sedFlow offers different options for bedload transport equations, flow-resistance
relationships
and other elements which can be selected to fit the current application in a particular catchment. Local grain-size distributions are dynamically adjusted
according to the transport dynamics of each grain-size fraction. sedFlow features fast calculations and straightforward
pre- and postprocessing of simulation data. The high simulation speed allows for simulations of several
years, which can be used, e.g., to assess the long-term impact of river engineering works or climate change
effects. In combination with the straightforward pre- and postprocessing, the fast calculations facilitate
efficient workflows for the simulation of individual flood events, because the modeller gets the immediate
results as direct feedback to the selected parameter inputs.
The model is provided
together with its complete source code free of charge under the
terms of the GNU General Public License (GPL)
(www.wsl.ch/sedFlow). Examples of the application of
sedFlow are given in a companion article by
Heimann et al. (2015)
Evidence for a Kondo destroying quantum critical point in YbRh2Si2
The heavy-fermion metal YbRhSi is a weak antiferromagnet below
K. Application of a low magnetic field T () is sufficient to continuously suppress the antiferromagnetic (AF) order.
Below K, the Sommerfeld coefficient of the electronic specific
heat exhibits a logarithmic divergence. At K, (), while the electrical resistivity
(: residual resistivity). Upon
extrapolating finite- data of transport and thermodynamic quantities to , one observes (i) a vanishing of the "Fermi surface crossover" scale
, (ii) an abrupt jump of the initial Hall coefficient and
(iii) a violation of the Wiedemann Franz law at , the field-induced
quantum critical point (QCP). These observations are interpreted as evidence of
a critical destruction of the heavy quasiparticles, i.e., propagating Kondo
singlets, at the QCP of this material.Comment: 20 pages, 8 figures, SCES 201
Optimization of drift gases for accuracy in pressurized drift tubes
Modern detectors such as ATLAS use pressurized drift tubes to minimize diffusion and achieve high coordinate accuracy. However, the coordinate accuracy depends on the exact knowledge of converting measured times into coordinates. Linear space-time relationships are best for reconstruction, but difficult to achieve in the field. Previous mixtures, which contained methane or other organic quenchers, are disfavored because of ageing problems. From our studies of nitrogen and carbon dioxide, two mixtures with only small deviations from linearity were determined and measured. Scaling laws for different pressures and magnetic fields are also given
Challenges and Opportunities for Spark Plasma Sintering: A Key Technology for a New Generation of Materials
This is an open access article distributed under the terms of the Creative Commons Attribution License.-- et al.Peer reviewe
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