Astrophysical bow shocks: An analytical solution for the hypersonic blunt body problem in the intergalactic medium

Aims: Bow shock waves are a common feature of groups and clusters of galaxies since they are generated as a result of supersonic motion of galaxies through the intergalactic medium. The goal of this work is to present an analytical solution technique for such astrophysical hypersonic blunt body problems. Methods: A method, developed by Schneider (1968, JFM, 31, 397) in the context of aeronautics, allows calculation of the galaxy's shape as long as the shape of the bow shock wave is known (so-called inverse method). In contrast to other analytical models, the solution is valid in the whole flow region (from the stagnation point up to the bow shock wings) and in particular takes into account velocity gradients along the streamlines. We compare our analytical results with two-dimensional hydrodynamical simulations carried out with an extended version of the VH-1 hydrocode which is based on the piecewise parabolic method with a Lagrangian remap. Results: It is shown that the applied method accurately predicts the galaxy's shape and the fluid variables in the post-shock flow, thus saving a tremendous amount of computing time for future interpretations of similar objects. We also find that the method can be applied to arbitrary angles between the direction of the incoming flow and the axis of symmetry of the body. We emphasize that it is general enough to be applied to other astrophysical bow shocks, such as those on stellar and galactic scales.Comment: 11 pages, 7 figures, accepted for publication in A&

A mosaic of conserved and novel modes of gene expression and morphogenesis in mesoderm and muscle formation of a larval bivalve

The mesoderm gives rise to several key morphological features of bilaterian animals including endoskeletal elements and the musculature. A number of regulatory genes involved in mesoderm and/or muscle formation (e.g., Brachyury (Bra), even-skipped (eve), Mox, myosin II heavy chain (mhc)) have been identified chiefly from chordates and the ecdysozoans Drosophila and Caenorhabditis elegans, but data for non-model protostomes, especially those belonging to the ecdysozoan sister clade, Lophotrochozoa (e.g., flatworms, annelids, mollusks), are only beginning to emerge. Within the lophotrochozoans, Mollusca constitutes the most speciose and diverse phylum. Interestingly, however, information on the morphological and molecular underpinnings of key ontogenetic processes such as mesoderm formation and myogenesis remains scarce even for prominent molluscan sublineages such as the bivalves. Here, we investigated myogenesis and developmental expression of Bra, eve, Mox, and mhc in the quagga mussel Dreissena rostriformis, an invasive freshwater bivalve and an emerging model in invertebrate evodevo. We found that all four genes are expressed during mesoderm formation, but some show additional, individual sites of expression during ontogeny. While Mox and mhc are involved in early myogenesis, eve is also expressed in the embryonic shell field and Bra is additionally present in the foregut. Comparative analysis suggests that Mox has an ancestral role in mesoderm and possibly muscle formation in bilaterians, while Bra and eve are conserved regulators of mesoderm development of nephrozoans (protostomes and deuterostomes). The fully developed Dreissena veliger larva shows a highly complex muscular architecture, supporting a muscular ground pattern of autobranch bivalve larvae that includes at least a velum muscle ring, three or four pairs of velum retractors, one or two pairs of larval retractors, two pairs of foot retractors, a pedal plexus, possibly two pairs of mantle retractors, and the muscles of the pallial line, as well as an anterior and a posterior adductor. As is typical for their molluscan kin, remodelling and loss of prominent larval features such as the velum musculature and various retractor systems appear to be also common in bivalves

Addressing climate change with behavioral science: a global intervention tournament in 63 countries

Effectively reducing climate change requires marked, global behavior change. However, it is unclear which strategies are most likely to motivate people to change their climate beliefs and behaviors. Here, we tested 11 expert-crowdsourced interventions on four climate mitigation outcomes: beliefs, policy support, information sharing intention, and an effortful tree-planting behavioral task. Across 59,440 participants from 63 countries, the interventions’ effectiveness was small, largely limited to nonclimate skeptics, and differed across outcomes: Beliefs were strengthened mostly by decreasing psychological distance (by 2.3%), policy support by writing a letter to a future-generation member (2.6%), information sharing by negative emotion induction (12.1%), and no intervention increased the more effortful behavior—several interventions even reduced tree planting. Last, the effects of each intervention differed depending on people’s initial climate beliefs. These findings suggest that the impact of behavioral climate interventions varies across audiences and target behaviors

Numerical studies on the link between radioisotopic signatures on Earth and the formation of the Local Bubble

Context. Measurements of long-lived radioisotopes, which have grown rapidly in quantity and sensitivity over the last few years, provide a means, completely independent of other observational channels, to draw conclusions about near-Earth supernovae (SNe) and thus the origin of the Local Bubble (LB), our Galactic habitat. First and foremost in this context is 60Fe, which has already been detected across the Earth and on the Moon. Aims. The present study constitutes a significant step in further refining the coherent picture of the formation of the LB, constrained by radioisotopic anomalies, that we have drawn earlier and is based on the most sophisticated initial conditions determined to date. Methods. Using Gaìa EDR3, we identified 14 SN explosions, with 13 occurring in Upper Centaurus-Lupus and Lower Centaurus-Crux, and one in V1062 Sco, all being subgroups of the Scorpius-Centaurus OB association. The timing of these explosions was obtained by us through interpolation of modern rotating stellar evolution tracks via the initial masses of the already exploded massive stars. We further developed a new Monte Carlo-type approach for deriving the trajectories of the SN progenitors, utilising a plethora of test-particle simulations in a realistic Milky Way potential and selecting explosion sites based on maximum values in six-dimensional phase-space probability distributions constructed from the simulations. We then performed high-resolution three-dimensional hydrodynamic simulations based on these initial conditions to explore the evolution of the LB in an inhomogeneous local interstellar medium and the transport of radioisotopes to Earth. The simulations include the effects of age- and initial mass-dependent stellar winds from the SN progenitors and additional radioisotopes (26Al, 53Mn, and 244Pu) besides 60Fe using wind-derived and explosive yields from rotating models. Results. From our modelling of the LB, we find for our main results that (i) our simulations are consistent with measurements of 60Fe, in particular, a peak 2–3 Myr before present, as well as 26Al, 53Mn, and 244Pu data; (ii) stellar winds contribute to the distribution of radioisotopes and also to the dynamics of the LB; (iii) the Solar System (SS) entered the LB about 4.6 Myr ago; and (iv) the recent influx of 60Fe, discovered in Antarctic snow and deep-sea sediments, can be naturally explained by turbulent radioisotopic transport (in dust grains) mainly originating from the SN explosions and from the shock waves reflected at the LB shell. Conclusions. Our simulations not only support the recent hypothesis that the LB triggered star formation in the solar vicinity through its expansion, but they also suggest that the second, separate 60Fe peak measured at 6–9 Myr ago was generated by the passage of the SS through a neighbouring superbubble (SB), possibly the Orion-Eridanus SB, prior to its current residence in the LB

The DFPase from Loligo Vulgaris in sugar surfactant based bicontinuous microemulsions

Wellert S, Tiersch B, Koetz J, et al. The DFPase from Loligo Vulgaris in sugar surfactant based bicontinuous microemulsions. Euro. Biophysics J. 2011;40(6):761-774

The Link Between the Local Bubble and Radioisotopic Signatures on Earth

Traces of 2-3 Myr old 60Fe were recently discovered in a manganese crust and in lunar samples. We have found that this signal is extended in time and is present in globally distributed deep-sea archives. A second 6.5-8.7 Myr old signature was revealed in a manganese crust. The existence of the Local Bubble hints to a recent nearby supernova-activity starting 13 Myr ago. With analytical and numerical models generating the Local Bubble, we explain the younger 60Fe-signature and thus link the evolution of the solar neighborhood to terrestrial anomalies