Soft proton flux on <Emphasis Type="Italic">ATHENA</Emphasis> focal plane and its impact on the magnetic diverter design

The experience gained with the current generation of X-ray telescopes like Chandra and XMM-Newton has shown that low energy “soft” protons can pose a severe threat to the possibility to exploit scientific data, reducing the available exposure times by up to 50% and introducing a poorly reproducible background component. These soft protons are present in orbits outside the radiation belts and enter the mirrors, being concentrated towards the focal plane instruments, losing energy along their path and finally depositing their remaining energy in the detectors. Their contribution to the residual background will be even higher for ATHENA with respect to previous missions, given the much higher collecting area of the mirrors, even if the instruments will likely suffer no significant radiation damage from this particles flux. As a consequence this soft proton flux shall be damped with the use of a magnetic diverter to avoid excess background loading on the WFI or X-IFU instruments. We present here a first complete evaluation of this background component for the two focal plane instruments of the ATHENA mission in absence of a magnetic diverter, and derive the requirements for such device to reduce the soft protons induced background below the level required to enable the mission science. We estimate the soft proton flux expected in L2 for the interplanetary component and for the component generated locally by acceleration processes in the magnetotail. We produce a proton response matrix for each of the two instruments of ATHENA focal plane, exploiting two independent Monte Carlo simulations to estimate the optics concentration efficiency, and Geant4 simulations to evaluate the energy loss inside the radiation filters and deposited in the detector. With this modular approach we derive the expected fluxes and spectra for the soft protons component of the background. Finally, we calculate the specifics of a magnetic diverter able to reduce such flux below the required level for both X-IFU and WFI.     

Grazing Management Plans improve pasture selection by cattle and forage quality in sub-alpine and alpine grasslands

Over the last decades, the reduction of manpower for herd management has led to an increase of continuous grazing systems(CGS) in the Italian Alps, which allow cattle to roam freely. Under CGS, due to high selectivity, livestock exploit grasslands unevenly, over-and under-using specific areas at the same time with negative effects on their conservation. To counteract these effects, a specific policy and management tool(i.e. Grazing Management Plan) has been implemented by Piedmont Region since 2010. The Grazing Management Plans are based on the implementation of rotational grazing systems(RGS), with animal stocking rate adjusted to balance it with grassland carrying capacity. A case study was conducted on alpine summer pastures to test the 5-year effects produced by the implementation of a Grazing Management Plan in grasslands formerly managed under several years of CGS on 1) the selection for different vegetation communities by cattle, 2) the abundance of oligo-, meso-, and eutrophic plant species(defined according to Landolt N indicator value), and 3) forage yield, quality, and palatability. A total of 193 vegetation surveys were carried out in 2011 and repeated in 2016. Cows were tracked yearly with Global Positioning System collars to assess their grazing selectivity, and forage Pastoral Value(PV) was computed to evaluate forage yield, quality, and palatability. Five years after RGS implementation, cow selectivity significantly decreased and the preference for the different vegetation communities was more balanced than under CGS. The abundance of meso-and eutrophic species increased, whereas oligotrophic ones decreased. Moreover, the abundance of moderately to highly palatable plant species increased, whereas non-palatable plant species decreased, with a consequent significant enhancement of the PV. Our findings indicate that the implementation of Grazing Management Plans can be considered a sustainable and effective management tool for improving pasture selection by cattle and forage quality in mountain pastures.     

Phytoplankton abundance, biomass and diversity within and between Pantanal wetland habitats

During the high water season, the flooding reduces environmental heterogeneity in aquatic ecosystems of the Pantanal wetland. When the water level recedes, lakes and channels are formed as individual systems. Therefore, we expected the spatial heterogeneity during the low water phase resulting in changes on biological communities leading to high phytoplankton abundance, biomass and diversity within and between habitats. To test this hypothesis, we analyzed eight freshwater systems (five oxbow lakes, two channels, and the river) during the low water period. Phytoplankton biomass, abundance, diversity (alpha, beta, gamma) and diversity metrics as richness (species per sample), Shannon diversity (H′) and evenness were measured in all systems along with nutrient concentrations, zooplankton and bacteria abundances. We found 97 species as gamma diversity. The alpha diversity was unexpectedly low in comparison to most other South American floodplain systems (38 species in river, 24 in channels and 29 in lakes). Also, the systems are relatively similar in composition (beta diversity, 28%). Connectivity differences between systems highlighted differences in phytoplankton abundance and biomass (fresh weight) ranging from 1428 ind mL⁻¹ (river) to 3710 ind mL⁻¹ (lakes) and from 0.71 mg L⁻¹ (river) to 2.9 mg L⁻¹ (lakes), respectively. However, our results did not indicate significant differences in phytoplankton species richness between the systems during the low water. Our main conclusions are that local factors may be responsible for changes on phytoplankton community and the time of isolation during the low water phase was not sufficient to promote changes in phytoplankton diversity between the habitats.     

Isolation and characterization of two crude oil-degrading yeast strains, Yarrowia lipolytica PG-20 and PG-32, from the Persian Gulf

Among six crude oil-degrading yeasts that were isolated from an oil-polluted area in the Persian Gulf, two yeast strains showed high degradation activity of aliphatic hydrocarbons. From an analysis of 18S rRNA sequences and biochemical characteristics, these strains were identified as Yarrowia lipolytica strains PG-20 and PG-32. Gas Chromatography (GC) analysis of the crude oil remaining in the culture medium after 1 week at 30°C showed that the strains PG-20 and PG-32 degraded 68% and 58% of crude oil, respectively. The optimal growth condition and biodegradation of hydrocarbons was in ONR medium with an acidic pH (pH5). These two strains may degrade aliphatic hydrocarbons more efficiently than aromatic hydrocarbons, although strain PG-20 had better degradation than strain PG-32. The two Y. lipolytica strains reduce surface tension when cultured on hydrocarbon substrates (1% v/v). These strains showed a cell surface hydrophobicity higher than 70%. These results suggested that Y. lipolytica strains PG-20 and PG-32 have high crude oil degrading activity due to their high emulsifying activity and cell hydrophobicity. In conclusion, these yeast strains can be useful for the bioremediation process in the Persian Gulf and decreasing oil pollution in this marine ecosystem.     

X-ray Spectromicroscopy of Mineral Intergrowths in the Santa Catharina Meteorite

This work describes the application of microfocus X-ray absorption spectroscopy (XAS) and X-ray photo-emission electron microscopy (XPEEM) to the study of the complex mineralogical intergrowths within the Santa Catharina meteorite. The Santa Catharina meteorite of this study (BM52283 from the meteorite collection of the Natural History Museum, London, UK) primarily comprises a taenite bulk host phase (Fe:Ni ratio = 70.9 ± 0.8%:29.1 ± 0.8%) with a set of oxide-bearing cloudy zone textured regions (Fe:Ni:O ratio = 40.4 ± 0.3%:49.0 ± 0.7%:10.6 ± 0.8% at the core and Fe:Ni:O ratio = 34.4 ± 1.5%:42.7 ± 0.6%:22.9 ± 1.8% towards the rims) and numerous schreibersite (Fe:Ni:P ratio = 38.6 ± 1.6%:38.4 ± 0.9%:23.0 ± 0.5%) inclusions. Between the schreibersite and the taenite are rims up to 50 μm across of Ni-rich kamacite (Fe:Ni ratio = 93.4 ± 0.4%:6.6 ± 0.5%). No chemical zoning or spatial variations in the Fe and Ni speciation was observed within either the schreibersite or the kamacite phases. The oxide-bearing cloudy zone textured regions mostly comprise metallic Fe–Ni alloy, predominantly tetrataenite. Within the oxide phases, the Fe is predominantly, but not entirely, tetrahedrally co-ordinated Fe³⁺ and the Ni is octahedrally co-ordinated Ni²⁺. Structural analysis supports the suggestion that non-stoichiometric Fe₂NiO₄ trevorite is the oxide phase. The trevorite:tetrataenite ratio increases at the edges of the oxide-bearing cloudy zone textured regions indicating increased oxidation at the edges of these zones. The spatial resolution of the XPEEM achieved was between 110 and 150 nm, which precluded the study of either the previously reported ∼ 10 nm precipitates of tetrataenite within the bulk taenite or any antitaenite.     

Sensitivity of HF radar-derived surface current self-organizing maps to various processing procedures and mesoscale wind forcing

We performed a number of sensitivity experiments by applying a mapping technique, self-organizing maps (SOM) method, to the surface current data measured by high-frequency (HF) radars in the northern Adriatic and surface winds modelled by two state-of-the-art mesoscale meteorological models, the Aladin (Aire Limitée Adaptation Dynamique Développement InterNational) and the Weather and Research Forecasting models. Surface current data used for the SOM training were collected during a period in which radar coverage was the highest: between February and November 2008. Different pre-processing techniques, such as removal of tides and low-pass filtering, were applied to the data in order to test the sensitivity of characteristic patterns and the connectivity between different SOM solutions. Topographic error did not exceed 15 %, indicating the applicability of the SOM method to the data. The largest difference has been obtained when comparing SOM patterns originating from unprocessed and low-pass filtered data. Introduction of modelled winds in joint SOM analyses stabilized the solutions, while sensitivity to wind forcing coming from the two different meteorological models was found to be small. Such a low sensitivity is considered to be favourable for creation of an operational ocean forecasting system based on neural networks, HF radar measurements and numerical weather prediction mesoscale models.     

Are metal-induced hypersensitivities in harbor seals associated with liver function?

Environmental exposure to metals is believed to affect marine mammal health adversely including immunosuppression or acute as well as chronic inflammatory processes leading to hypersensitivities or autoimmune diseases. Metal-specific hypersensitivities were found in several pinnipeds of the North Sea. However, hypersensitivity is a complex phenomenon whose characteristics are still not completely understood; in particular, effects on health are not well established. In the present study, we compared basic hematological and biochemical parameters of seals with and without metal-specific hypersensitivities. We found altered hematological parameters and liver enzyme patterns in seals with a metal-induced hypersensitivity, including a reduction in macrophages, an increase in lymphocytes, and elevated levels of lactate dehydrogenase. These findings support the suggestion of a chronic influence of metal pollutants on the health of marine mammals of the North Sea.