189 research outputs found
Detrimental adsorbate fields in experiments with cold Rydberg gases near surfaces
We observe the shift of Rydberg levels of rubidium close to a copper surface
when atomic clouds are repeatedly deposited on it. We measure transition
frequencies of rubidium to S and D Rydberg states with principal quantum
numbers n between 31 and 48 using the technique of electromagnetically induced
transparency. The spectroscopic measurement shows a strong increase of electric
fields towards the surface that evolves with the deposition of atoms. Starting
with a clean surface, we measure the evolution of electrostatic fields in the
range between 30 and 300 \mum from the surface. We find that after the
deposition of a few hundred atomic clouds, each containing ~10^6 atoms, the
field of adsorbates reaches 1 V/cm for a distance of 30 \mum from the surface.
This evolution of the electrostatic field sets serious limitations on cavity
QED experiments proposed for Rydberg atoms on atom chips.Comment: 4 pages, 3 figures Submitted to Phys. Rev.
Integrated analysis of water quality in a mesoscale lowland basin
This article describes a modelling study on nitrogen transport from diffuse sources in the Nuthe catchment, representing a typical lowland region in the north-eastern Germany. Building on a hydrological validation performed in advance using the ecohydrological model SWIM, the nitrogen flows were simulated over a 20-year period (1981-2000). The relatively good quality of the input data, particularly for the years from 1993 to 2000, enabled the nitrogen flows to be reproduced sufficiently well, although modelling nutrient flows is always associated with a great deal of uncertainty. Subsequently, scenario calculations were carried out in order to investigate how nitrogen transport from the catchment could be further reduced. The selected scenario results with the greatest reduction of nitrogen washoff will briefly be presented in the paper
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Integrated analysis of water quality in a mesoscale lowland basin
This article describes a modelling study on nitrogen transport from diffuse sources in the Nuthe catchment, representing a typical lowland region in the north-eastern Germany. Building on a hydrological validation performed in advance using the ecohydrological model SWIM, the nitrogen flows were simulated over a 20-year period (1981-2000). The relatively good quality of the input data, particularly for the years from 1993 to 2000, enabled the nitrogen flows to be reproduced sufficiently well, although modelling nutrient flows is always associated with a great deal of uncertainty. Subsequently, scenario calculations were carried out in order to investigate how nitrogen transport from the catchment could be further reduced. The selected scenario results with the greatest reduction of nitrogen washoff will briefly be presented in the paper
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Discharge alterations of the Mures River, Romania under ensembles of future climate projections and sequential threats to aquatic ecosystem by the end of the century
Measurement of absolute transition frequencies of 87Rb to nS and nD Rydberg states by means of electromagnetically induced transparency
We report the measurement of absolute excitation frequencies of 87Rb to nS
and nD Rydberg states. The Rydberg transition frequencies are obtained by
observing electromagnetically induced transparency on a rubidium vapor cell.
The accuracy of the measurement of each state is < 1 MHz, which is achieved by
frequency stabilizing the two diode lasers employed for the spectroscopy to a
frequency comb and a frequency comb calibrated wavelength meter, respectively.
Based on the spectroscopic data we determine the quantum defects of 87Rb, and
compare it with previous measurements on 85Rb. We determine the ionization
frequency from the 5S1/2(F=1) ground state of 87Rb to 1010.0291646(3) THz,
providing the binding energy of the ground state with an accuracy improved by
two orders of magnitude
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Impacts of global change on water-related sectors and society in a trans-boundary central European river basin – Part 2: From eco-hydrology to water demand management
This second part of the paper presents the details of the eco-hydrological model SWIM simulating the natural water supply and its coupling to WBalMo, a water management model.
Based on the climate scenarios of the STAR model, SWIM simulates the natural water and matter fluxes for the entire Elbe River area. All relevant processes are modelled for hydrotopes and the resulting discharges are accumulated in subbasins. The output data are input for the water management model WBalMo and the quality models Moneris and QSim.
WBalMo takes storage management, inputs and withdrawals into account and analyses how demands by industry, power plants and households will be met at changing natural supply conditions. Some of the first results shall be presented here
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Large-scale hydrological modelling and the Water Framework Directive and Floods Directive of the European Union - 10th Workshop on Large-Scale Hydrological Modelling
In December 2000, the Water Framework Directive (WFD) of the European Union (EU) was enforced (EC, 2000) to provide
a new legislative basis for water management in Europe. The main goal of the WFD is the implementation of river basin water management plans in which comprehensive
studies of the current status of the surface and ground water bodies must be reported and management programs must be enforced with cost-effective measures with which a good
ecological condition of the water bodies can be attained and sustained
Impacts of global change on water-related sectors and society in a trans-boundary central European river basin – Part 1: Project framework and impacts on agriculture
Central Europe, the focus region of this study, is a region in transition, climatically from maritime to continental and politically from formerly more planning-oriented to more market-oriented management regimes, and in terms of climate change from regions of increasing precipitation in the west and north of Europe to regions of decreasing precipitation in central and southern Europe. The Elbe basin, a trans-boundary catchment flowing from the Czech Republic through Germany into the North Sea, was selected to investigate the possible impacts of global change on crop yields and water resources in this region.
For technical reasons, the paper has been split into two parts, the first showing the overall model concept, the model set-up for the agricultural sector, and first results linking eco-hydrological and agro-economic tools for the German part of the basin. The second part describes the model set-up for simulating water supply and demand linking eco-hydrological and water management tools for the entire basin including the Czech part
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