ALBERT

Beschreibung: Well defined productivity-precipitation relationships of ecosystems are needed as benchmarks for the validation of land-models used for future projections. The productivity-precipitation relationship may be studied in two ways: the spatial approach relates differences in productivity to those in precipitation among sites along a precipitation gradient (the spatial fit, with a steeper slope); the temporal approach relates inter-annual productivity changes to variation in precipitation within sites (the temporal fits, with flatter slopes). Precipitation-reduction experiments in natural ecosystems represent a complement to the fits, because they can reduce precipitation below the natural range and are thus well suited to study potential effects of climate drying. Here, we analyze the effects of dry treatments in eleven multi-year precipitation-manipulation experiments, focusing on changes in the temporal fit. We expected that structural changes in the dry treatments would occur in some experiments, thereby reducing the intercept of the temporal fit and displacing the productivity-precipitation relationship downward the spatial fit. The majority of experiments (72%) showed that dry treatments did not alter the temporal fit. This implies that current temporal fits are to be preferred over the spatial fit to benchmark land-model projections of productivity under future climate within the precipitation ranges covered by the experiments. Moreover, in two experiments, the intercept of the temporal fit unexpectedly increased due to mechanisms that reduced either water- or nutrient losses. The expected decrease of the intercept was observed in only one experiment, and only when distinguishing between the late and the early phases of the experiment. This implies that we currently do not know at which precipitation-reduction level or at which experimental duration structural changes will start to alter ecosystem productivity. Our study highlights the need for experiments with multiple, including more extreme, dry treatments, to identify the precipitation boundaries within which the current temporal fits remain valid. This article is protected by copyright. All rights reserved.

Beschreibung: Article Helium is an atom of great scientific interest, yet much debate exists surrounding the shape its molecules form. Here Voigtsberger et al. present experimental results imaging the wavefuction of 4 He 3 and 3 He 4 He 2 trimer systems, which suggest that 4 He 3 is a random cloud while 3 He 4 He 2 is a quantum halo state. Nature Communications doi: 10.1038/ncomms6765 Authors: J. Voigtsberger, S. Zeller, J. Becht, N. Neumann, F. Sturm, H.-K. Kim, M. Waitz, F. Trinter, M. Kunitski, A. Kalinin, J. Wu, W. Schöllkopf, D. Bressanini, A. Czasch, J. B. Williams, K. Ullmann-Pfleger, L. Ph H. Schmidt, M. S. Schöffler, R. E. Grisenti, T. Jahnke, R. Dörner

Beschreibung: Ionization of the atmosphere due to precipitating solar energetic particles as well as magnetospheric particles is a major source of thermospheric electron density. In this paper we evaluate numerical simulations of the 3-D spatial and temporal electron densities produced by these particle populations through a comparison with incoherent scatter radar observations. The 3-D precipitation patterns are determined with the Atmospheric Ionization Module Osnabrück (AIMOS). We use a version of the general circulation and chemistry model Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA) enhanced by ion chemistry to calculate the impact of particle ionization on the electron density. These modeled data are compared to radar observations from European Incoherent Scatter Svalbard and Tromsø as well as the incoherent scatter radar stations at Millstone Hill and Sondrestrom. Particle precipitation is severely affected by geomagnetic disturbance and latitude. Therefore, different locations (inside the polar cap and at auroral latitudes) and geomagnetic conditions are included in the comparison. The main results of the paper can be summarized as follows: (1) as expected, particle forcing will significantly improve modeled electron density in comparison to results of the radar measurements; (2) in particular nighttime comparisons of the electron density are affected; here the particle forcing will account for a boost of 2 to 3 orders of magnitude.

Beschreibung: Probing the tunnelling site of electrons in strong field enhanced ionization of molecules Nature Communications 3, 1113 (2012). doi:10.1038/ncomms2130 Authors: J. Wu, M. Meckel, L.Ph.H. Schmidt, M. Kunitski, S. Voss, H. Sann, H. Kim, T. Jahnke, A. Czasch & R. Dörner

Beschreibung: Article Ultrafast laser pulses are useful to study electron dynamics in chemical bonds, but their influence on bond breaking is not fully understood. Wu et al. study H 2 bond breaking with coincidence techniques, and find a phase-dependent anisotropy of the H + fragmentation even for isotropic multicycle laser pulses. Nature Communications doi: 10.1038/ncomms3177 Authors: J. Wu, M. Magrakvelidze, L.P.H. Schmidt, M. Kunitski, T. Pfeifer, M. Schöffler, M. Pitzer, M. Richter, S. Voss, H. Sann, H. Kim, J. Lower, T. Jahnke, A. Czasch, U. Thumm, R. Dörner

Beschreibung: Neutrino interferometry for high-precision tests of Lorentz symmetry with IceCube Neutrino interferometry for high-precision tests of Lorentz symmetry with IceCube, Published online: 16 July 2018; doi:10.1038/s41567-018-0172-2 A violation of Lorentz symmetry would represent a fundamental departure from the physics of the standard model. Searching for anomalous neutrino oscillations, the IceCube collaboration reports no violation, and puts stringent bounds on its existence.

Beschreibung: The Mars Science laboratory (MSL) made a successful landing at Gale crater early August 2012. MSL has an environmental instrument package called the Rover Environmental Monitoring Station (REMS) as a part of its scientific payload. REMS comprises instrumentation for the observation of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements. We concentrate on describing the REMS-H measurement performance and initial observations during the first 100 MSL sols as well as constraining the REMS-H results by comparing them with earlier observations and modelling results. The REMS-H device is based on polymeric capacitive humidity sensors developed by Vaisala Inc. and it makes use of transducer electronics section placed in the vicinity of the three (3) humidity sensor heads. The humidity device is mounted on the REMS boom providing ventilation with the ambient atmosphere through a filter protecting the device from airborne dust. The final relative humidity results appear to be convincing and are aligned with earlier indirect observations of the total atmospheric precipitable water content. The water mixing ratio in the atmospheric surface layer appears to vary between 30 and 75 ppm. When assuming uniform mixing, the precipitable water content of the atmosphere is ranging from a few to 6 precipitable micrometers.