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[en] The distribution of hydrogen from the corrosion of iron in a radioactive waste repository is investigated. From the derived balance equation it follows that the hydrogen inventory depends on the pressure in the gas cushion which develops in the crown of the disposal room. As the excavation damaged zone has an increased permeability, this zone can be expected to assist the dissipation of hydrogen. A convenient way of determining the permeability of the excavation damaged zone is by use of the vacuum permeability method. The method is based on measuring the pneumatic response to evacuation behind the rock face in a test borehole. The data can be evaluated analytically and numerically. The method has been employed under a wide range of geomechanical conditions. In the course of our measurements we established characteristic patterns of permeability distribution in the excavation damaged zone which can be used to evaluate the dissipation of gases from an underground repository. 9 refs., 6 figs., 2 tabs
[en] Due to the COVID-19 outbreak, several planned training missions to the Himalayan and Andes region on the use of cosmic-ray neutron sensor technology were changed to a novel online teaching format, as part of the interregional project INT5156 on Building Capacity and Generating Evidence for Climate Change Impacts on Soil, Sediments and Water Resources in Mountainous Regions. In total 15 scientists from Bolivia, Chile, Peru and Ecuador participated on 17-19 August 2020, and 25 scientists from China, Nepal, Pakistan and Afghanistan participated on 13-15 October 2020. They learned how to install, calibrate and use the innovative cosmic-ray neutron sensor technology for better managing water resources in highlands.
[en] To further improve the application of cosmic-ray neutron sensor technology, the SWMCN Laboratory during the summer validated the footprint, effective depth and accuracy of the mobile or “backpack” version of the sensor. Through sixteen different calibrations for five research sites in Austria, located between 300 and 1700 m a.s.l., a comparison was made between the volumetric water content measured by the backpack and gravimetric measurements for different radii of influence. Results indicated similar outcomes based on a 0-75-meter footprint as compared to a 0-200 meter study suggesting that measurements by the mobile cosmic-ray neutron sensor have a footprint with a 200-meter radius (i.e. 20 hectares). The same data were also used to determine the effective depth, results showed that the effective depth is about 10 cm for volumetric water contents ranging between 30 and 60%.
[en] The SWMCNL team has finalized the first stage of the development of new soil moisture monitoring techniques using the cosmic-ray neutron sensor (CRNS) backpack. For this purpose, a series of field measurements were conducted at the National Park Neusiedler See Seewinkel, Austria, in close collaboration with the University of Nebraska-Lincoln. The tests consisted of seven measurements from September 2017 to April 2018 to capture the entire dry-wet cycle in this area. The selected study area is suitable for this kind of tests, as the difference between the lowest and highest soil moisture contents is large and soil texture changes at short distance.
[en] We present a depletion imaging technique to map out the spatial and temporal dependency of the density distribution of an ultracold gas of Rydberg atoms. Locally resolved absorption depletion, observed through differential ground state absorption imaging of a 87Rb cloud in presence and absence of pre-excited Rydberg atoms, reveals their projected two-dimensional distribution. By employing a closed two-level optical transition uncoupled from the Rydberg state, the highly excited atoms are preserved during imaging. We measure the excitation dynamics of the state of 87Rb, observing a saturation of the two-dimensional Rydberg density. Such outcome can be explained by the Rydberg blockade effect which prevents resonant excitation of close-by Rydberg atoms due to strong dipolar interactions. By combining the superatom description, where atoms within a blockade radius are represented as collective excitations, with a Monte Carlo sampling, we can quantitatively model the observed excitation dynamics and infer the full three-dimensional distribution of Rydberg atoms, that can serve as a starting point for quantum simulation of many-body dynamics involving Rydberg spin systems. (paper)
[en] The Cosmic-Ray Neutron Sensor (CRNS) technique for estimating area-average soil water content (SWC) is now a decade old and has established practical methodology for measurements, detection area, detection depth, installation, calibration, and validation of stationary and mobile applications (see TECDOC 1809 & 1845 and Figure 1). However, the relevance and practical uses of the CRNS technique to estimate both water flux (i.e. rainfall, deep percolation, evapotranspiration) and root zone storage changes require supporting products which need to be developed for further utilization of the technique in hydrology, ecology, and agronomy. In particular, simple methods to estimate daily SWC values at mean areal scales for decision makers and stakeholders interested in utilizing this technique. Moreover, estimating mean areal values are necessary for more comparable comparisons with remote sensing products and further refinement of their algorithms. While remote sensing has made significant progress in recent years, significant gaps in space and time observations still exist (McCabe et al. 2017). In particular, estimates of daily rainfall and root zone soil moisture at 1 to 10 ha field scale remain elusive and impractical with current and planned satellite missions. With the limitation of satellites to directly estimate root zone water storage, indirect methods using a combination of satellites, ground sensors like CRNS, and models are needed for the practical use of their data products.
[en] We examined six patients with isolated venous thrombosis (n = 2), or venous thrombosis combined with sinus thrombosis (n = 4) (CVT). The clinical symptoms were non-specific (acute cephalea, paresis, epileptic seizure, progressive speech disorder). All examinations were performed on a 1.5 T system (Magnetom Symphony, Siemens, Erlangen, Germany), maximum gradient field strength 30 mT/m, minimal gradient rise time 450 μs, according to the following protocol: Transverse T2-weighted turbo spin-echo (TSE), fluid attenuated inversion recovery (FLAIR), T1-weighted spin-echo (SE), before and after administration of contrast medium, T2*-weighted conventional gradient-echo (GRE), T2*-weighted spin-echo echo planar imaging (SE EPI), both without and with diffusion weighting as well as two-dimensional (2D) venous time-of-flight (TOF) MRA. The venous thromboses were best detectable in the T2*-weighted conventional GRE sequence in all patients. In two patients, the CVT was discernible only in this sequence. The sinus thrombosis was well discernible only in the T2*-weighted GRE sequence in only one case; in the remaining cases it was detectable only with difficulty. For these cases, other sequences such as SE, diffusion-weighted, or 2D-TOF-MRA sequence were superior. The T2*-weighted conventional GRE sequence was superior to the T2*-weighted SE EPI sequence in all patients. To sum up, it can be concluded, that T2*-weighted conventional GRE sequences are possibly the best method of detection of acute cortical vein thromboses. Therefore, it seems to be of benefit to integrate a T2*-weighted conventional GRE sequence into the MR-protocol for the diagnosis of isolated cortical vein thrombosis