Photon-photon interaction in axial channeling

We investigate the possibility that high-energy photons are channeled, when passing through an oriented single crystal, due to Delbrück scattering. For this purpose the exact electron propagator for the single-string model is constructed. Starting from a separation of variables, we solve the Dirac equation for a cylindrical electrostatic potential. The propagator for such external fields is constructed from solutions of the radial Dirac equation. This propagator is applied to a calculation of the S matrix for Delbrück scattering. We specify the conditions under which photon channeling takes place. Unfortunately these conditions are only matched for a very small fraction of those photons being produced by channeled electrons

Detection of phosphates originating from Enceladus’s ocean

Saturn’s moon Enceladus harbours a global1 ice-covered water ocean2,3. The Cassini spacecraft investigated the composition of the ocean by analysis of material ejected into space by the moon’s cryovolcanic plume4,5,6,7,8,9. The analysis of salt-rich ice grains by Cassini’s Cosmic Dust Analyzer10 enabled inference of major solutes in the ocean water (Na+, K+, Cl–, HCO3–, CO32–) and its alkaline pH3,11. Phosphorus, the least abundant of the bio-essential elements12,13,14, has not yet been detected in an ocean beyond Earth. Earlier geochemical modelling studies suggest that phosphate might be scarce in the ocean of Enceladus and other icy ocean worlds15,16. However, more recent modelling of mineral solubilities in Enceladus’s ocean indicates that phosphate could be relatively abundant17. Here we present Cassini’s Cosmic Dust Analyzer mass spectra of ice grains emitted by Enceladus that show the presence of sodium phosphates. Our observational results, together with laboratory analogue experiments, suggest that phosphorus is readily available in Enceladus’s ocean in the form of orthophosphates, with phosphorus concentrations at least 100-fold higher in the moon’s plume-forming ocean waters than in Earth’s oceans. Furthermore, geochemical experiments and modelling demonstrate that such high phosphate abundances could be achieved in Enceladus and possibly in other icy ocean worlds beyond the primordial CO2 snowline, either at the cold seafloor or in hydrothermal environments with moderate temperatures. In both cases the main driver is probably the higher solubility of calcium phosphate minerals compared with calcium carbonate in moderately alkaline solutions rich in carbonate or bicarbonate ions

Real-life data on Selexipag for the treatment of pulmonary hypertension

Selexipag is an orally available selective IP prostacyclin-receptor agonist licensed since 2016 for the therapy of pulmonary arterial hypertension (PAH). We aimed to describe real-life data of patients with pulmonary hypertension (PH) treated with selexipag. We analyzed all patients initiated with selexipag from July 2016 to April 2018 at the Department of Internal Medicine V, University of Munich. Non-invasive and invasive parameters corresponding to the risk assessment were collected at baseline and follow-up (FU). Furthermore, we recorded tolerability. Twenty-six patients were treated with selexipag, of whom 23 had PAH and three had chronic thromboembolic PH. At baseline, most patients were in function class (FC) II or III (42% and 54%, respectively). All patients were under medical treatment for PH, mostly dual therapy (92%). One or more side effects were noted in 19 patients, while seven reported no side-effects. FU assessment was available in 20 patients after 149 +/- 80 days of treatment. Nt-proBNP (median, baseline 1641 pg/mL, FU 1185 pg/mL, P = 0.05) and PVR (mean +/- SD, baseline 8.5 +/- 4.3 WU, FU 5.6 +/- 1.1 WU;P < 0.05) improved significantly. At FU, at least one risk assessment parameter improved in nine patients (45%), all parameters remained in the same risk group in seven patients (35%), and at least one parameter deteriorated in four patients (20%). Interestingly, patients with any side effect throughout the dose titration had a better treatment response than those without any side effects. In our real-life cohort, the majority of patients with PH treated with selexipag showed a stable or improved risk assessment at FU

Macromolecular organic compounds from the depths of Enceladus

Abstract Saturn’s moon Enceladus harbours a global water ocean¹, which lies under an ice crust and above a rocky core². Through warm cracks in the crust³ a cryo-volcanic plume ejects ice grains and vapour into space⁴–⁷ that contain materials originating from the ocean⁸,⁹. Hydrothermal activity is suspected to occur deep inside the porous core¹⁰–¹², powered by tidal dissipation¹³. So far, only simple organic compounds with molecular masses mostly below 50 atomic mass units have been observed in plume material⁶,¹⁴,¹⁵. Here we report observations of emitted ice grains containing concentrated and complex macromolecular organic material with molecular masses above 200 atomic mass units. The data constrain the macromolecular structure of organics detected in the ice grains and suggest the presence of a thin organic-rich film on top of the oceanic water table, where organic nucleation cores generated by the bursting of bubbles allow the probing of Enceladus’ organic inventory in enhanced concentrations