The Astrophysical Multipurpose Software Environment

We present the open source Astrophysical Multi-purpose Software Environment (AMUSE, www.amusecode.org), a component library for performing astrophysical simulations involving different physical domains and scales. It couples existing codes within a Python framework based on a communication layer using MPI. The interfaces are standardized for each domain and their implementation based on MPI guarantees that the whole framework is well-suited for distributed computation. It includes facilities for unit handling and data storage. Currently it includes codes for gravitational dynamics, stellar evolution, hydrodynamics and radiative transfer. Within each domain the interfaces to the codes are as similar as possible. We describe the design and implementation of AMUSE, as well as the main components and community codes currently supported and we discuss the code interactions facilitated by the framework. Additionally, we demonstrate how AMUSE can be used to resolve complex astrophysical problems by presenting example applications.Comment: 23 pages, 25 figures, accepted for A&

Intensifying agricultural sustainability: an analysis of impacts and drivers in the development of ‘bright spots’

Food security / Farming systems / Sustainable agriculture / Productivity / Investment / Thailand / Palestine / Latin America / Africa

Investigating the interstellar dust through the Fe K-edge

The chemical and physical properties of interstellar dust in the densest regions of the Galaxy are still not well understood. X-rays provide a powerful probe since they can penetrate gas and dust over a wide range of column densities (up to $10^{24}\ \rm{cm}^{-2}$). The interaction (scattering and absorption) with the medium imprints spectral signatures that reflect the individual atoms which constitute the gas, molecule, or solid. In this work we investigate the ability of high resolution X-ray spectroscopy to probe the properties of cosmic grains containing iron. Although iron is heavily depleted into interstellar dust, the nature of the Fe-bearing grains is still largely uncertain. In our analysis we use iron K-edge synchrotron data of minerals likely present in the ISM dust taken at the European Synchrotron Radiation Facility. We explore the prospects of determining the chemical composition and the size of astrophysical dust in the Galactic centre and in molecular clouds with future X-ray missions. The energy resolution and the effective area of the present X-ray telescopes are not sufficient to detect and study the Fe K-edge, even for bright X-ray sources. From the analysis of the extinction cross sections of our dust models implemented in the spectral fitting program SPEX, the Fe K-edge is promising for investigating both the chemistry and the size distribution of the interstellar dust. We find that the chemical composition regulates the X-ray absorption fine structures in the post edge region, whereas the scattering feature in the pre-edge is sensitive to the mean grain size. Finally, we note that the Fe K-edge is insensitive to other dust properties, such as the porosity and the geometry of the dust.Comment: 11 pages, 10 figures. Accepted for publication in Astronomy and Astrophysic

Global assessment of nitrogen deposition effects on terrestrial plant diversity : a synthesis

Atmospheric nitrogen (N) deposition is it recognized threat to plant diversity ill temperate and northern parts of Europe and North America. This paper assesses evidence from field experiments for N deposition effects and thresholds for terrestrial plant diversity protection across a latitudinal range of main categories of ecosystems. from arctic and boreal systems to tropical forests. Current thinking on the mechanisms of N deposition effects on plant diversity, the global distribution of G200 ecoregions, and current and future (2030) estimates of atmospheric N-deposition rates are then used to identify the risks to plant diversity in all major ecosystem types now and in the future. This synthesis paper clearly shows that N accumulation is the main driver of changes to species composition across the whole range of different ecosystem types by driving the competitive interactions that lead to composition change and/or making conditions unfavorable for some species. Other effects such its direct toxicity of nitrogen gases and aerosols long-term negative effects of increased ammonium and ammonia availability, soil-mediated effects of acidification, and secondary stress and disturbance are more ecosystem, and site-specific and often play a supporting role. N deposition effects in mediterranean ecosystems have now been identified, leading to a first estimate of an effect threshold. Importantly, ecosystems thought of as not N limited, such as tropical and subtropical systems, may be more vulnerable in the regeneration phase. in situations where heterogeneity in N availability is reduced by atmospheric N deposition, on sandy soils, or in montane areas. Critical loads are effect thresholds for N deposition. and the critical load concept has helped European governments make progress toward reducing N loads on sensitive ecosystems. More needs to be done in Europe and North America. especially for the more sensitive ecosystem types. including several ecosystems of high conservation importance. The results of this assessment Show that the Vulnerable regions outside Europe and North America which have not received enough attention are ecoregions in eastern and Southern Asia (China, India), an important part of the mediterranean ecoregion (California, southern Europe). and in the coming decades several subtropical and tropical parts of Latin America and Africa. Reductions in plant diversity by increased atmospheric N deposition may be more widespread than first thought, and more targeted Studies are required in low background areas, especially in the G200 ecoregions

A low-energy perspective on the minimal left-right symmetric model

We perform a global analysis of the low-energy phenomenology of the minimal left-right symmetric model (mLRSM) with parity symmetry. We match the mLRSM to the Standard Model Effective Field Theory Lagrangian at the left-right-symmetry breaking scale and perform a comprehensive fit to low-energy data including mesonic, neutron, and nuclear $\beta$-decay processes, $\Delta F=1$ and $\Delta F=2$ CP-even and -odd processes in the bottom and strange sectors, and electric dipole moments (EDMs) of nucleons, nuclei, and atoms. We fit the Cabibbo-Kobayashi-Maskawa and mLRSM parameters simultaneously and determine a lower bound on the mass of the right-handed $W_R$ boson. In models where a Peccei-Quinn mechanism provides a solution to the strong CP problem, we obtain $M_{W_R} \gtrsim 5.5$ TeV at $95\%$ C.L. which can be significantly improved with next-generation EDM experiments. In the $P$-symmetric mLRSM without a Peccei-Quinn mechanism we obtain a more stringent constraint $M_{W_R} \gtrsim 17$ TeV at $95\%$ C.L., which is difficult to improve with low-energy measurements alone. In all cases, the additional scalar fields of the mLRSM are required to be a few times heavier than the right-handed gauge bosons. We consider a recent discrepancy in tests of first-row unitarity of the CKM matrix. We find that, while TeV-scale $W_R$ bosons can alleviate some of the tension found in the $V_{ud,us}$ determinations, a solution to the discrepancy is disfavored when taking into account other low-energy observables within the mLRSM.Comment: 42 pages plus appendices. Published versio

Modelling long-term impacts of fertilization and liming on soil acidification at Rothamsted experimental station

Liming is widely used to reduce the impacts of soil acidification and optimize soil pH for agricultural production. Whether models can simulate the effect of liming on soil pH, and base saturation (BS), and thereby guide lime application, is still largely unknown. Long-term experimental data from a grassland (Park Grass, 1965–2012)and arable land (Sawyers Field, 1962–1972) at Rothamsted Research, UK, were thus used to assess the ability of the VSD+ model to simulate the effects of long-term fertilization and liming on soil acidification. The VSD+model was capable of simulating observed soil pHand BS changes over time in the long-termliming experiments, except for a treatment in which sulphur (S) was added. NormalizedMean Absolute Errors (NMAE) and Normalized Root Mean Square Errors (NRMSE) of simulated and observed pH values, averaged over the observation periods varied between 0.02 and 0.08 (NMAE) and 0.01–0.05 (NRMSE). The acidity budget results for Park Grass suggest that nitrogen (N) transformations contributed most to acidity production, causing predominantly aluminium (Al) exchange in the topsoil (0–23 cm) followed by base cation (BC) release, but in the treatment with S addition, BC uptake had a nearly similar effect on acidity production.However, in Sawyers Field, the acidity budget suggested that BC uptakewas the dominant cause of soil acidification,while the impacts of N transformations were limited. Liming was found to sufficiently replenish BC and decrease Al exchange in the topsoil layer. Overall, the VSD+ model can adequately reconstruct the impacts of fertilizer and liming applications on acid neutralizing processes and related soil pH and BC changes at the soil exchange complex

Direct Neutron Capture for Magic-Shell Nuclei

In neutron capture for magic--shell nuclei the direct reaction mechanism can be important and may even dominate. As an example we investigated the reaction $^{48}$Ca(n,$\gamma)^{49}$Ca for projectile energies below 250\,keV in a direct capture model using the folding procedure for optical and bound state potentials. The obtained theoretical cross sections are in agreement with the experimental data showing the dominance of the direct reaction mechanism in this case. The above method was also used to calculate the cross section for $^{50}$Ca(n,$\gamma)^{51}$Ca.Comment: REVTeX, 7 pages plus 3 uuencoded figures, the complete uuencoded postscript file is available at ftp://is1.kph.tuwien.ac.at/pub/ohu/calcium.u

Optical Spectroscopy of Galactic Cirrus Clouds: Extended Red Emission in the Diffuse Interstellar Medium

We present initial results from the first optical spectroscopic survey of high latitude Galactic cirrus clouds. The observed shape of the cirrus spectrum does not agree with that of scattered ambient Galactic starlight. This mismatch can be explained by the presence of Extended Red Emission (ERE) in the diffuse interstellar medium, as found in many other astronomical objects, probably caused by photoluminescence of hydrocarbons. The integrated ERE intensity, I_ERE \approx 1.2 x 10^{-5} erg s^{-1} cm^{-2} sr^{-1}, is roughly a third of the scattered light intensity, consistent with recent color measurements of diffuse Galactic light. The peak of the cirrus ERE (lambda_{0} \sim 6000 AA) is shifted towards short (bluer) wavelengths compared to the ERE in sources excited by intense ultraviolet radiation, such as HII regions (lambda_{0} sim 8000 AA); such a trend is seen in laboratory experiments on hydrogenated amorphous carbon films.Comment: 7 pages, 2 figures. Accepted for publication in ApJ Letter