Temporal evolution of magnetic molecular shocks II. Analytics of the steady state and semi-analytical construction of intermediate ages

In the first paper of this series (Paper I) we computed time dependent simulations of multifluid shocks with chemistry and a transverse magnetic field frozen in the ions, using an adaptive moving grid. In this paper, we present new analytical results on steady-state molecular shocks. Relationships between density and pressure in the neutral fluid are derived for the cold magnetic precursor, hot magnetic precursor, adiabatic shock front, and the following cooling layer. The compression ratio and temperature behind a fully dissociative adiabatic shock is also derived. To prove that these results may even hold for intermediate ages, we design a test to locally characterise the validity of the steady state equations in a time-dependent shock simulation. Applying this tool to the results of Paper I, we show that most of these shocks (all the stable ones) are indeed in a quasi-steady state at all times, i.e. : a given snapshot is composed of one or more truncated steady shock. Finally, we use this property to produce a construction method of any intermediate time of low velocity shocks (u < 20 km/s) with only a steady-state code. In particular, this method allows one to predict the occurrence of steady CJ-type shocks more accurately than previously proposed criteria.Comment: A&A in pres

Emerging Technology to Exclude Wildlife from Roads: Electrified Pavement and Deer Guards in Utah, USA

Wildlife-vehicle collisions (WVCs) are a persistent problem that threaten public safety and can negatively affect wildlife populations. Wildlife crossing structures in combination with wildlife exclusion fencing can significantly reduce WVC rates. However, these measures can become ineffective if access roads that bisect fencing to not include barriers to deter animals from entering the highway. My objectives were to: 1) evaluate the relative effectiveness of barriers currently used to exclude mule deer (Odocoileus hemionus) from highways, and 2) determine whether cattle guards augmented with segments of electrified pavement could reduce wildlife intrusions through fence openings. Currently, transportation departments are seeking innovative methods to cost-effectively upgrade, augment, or replace cattle guards with barriers capable of reducing wildlife access to transportation infrastructure. In chapter 2, I evaluated the effectiveness of existing wildlife barriers at access roads in Utah. I placed camera traps at 14 vehicle access points in wildlife fencing equipped with one of five different barrier designs. Double cattle guards (two adjoining cattle guards) and wildlife guards (steel grates) were \u3e 80% effective in excluding deer. In contrast, electrified mats (plastic planks with embedded electrodes), standard cattle guards, and cattle guards without excavations were80% effective in excluding deer and \u3e95% effective in excluding elk (Cervus canadensis) from wildlife exclosures constructed in a natural area. However, when installed in the road surface in front of an existing cattle guard, a segment of electrified pavement (0.91-m-wide) was 54% effective in preventing deer intrusions into the fenced highway corridor. Electrified pavement appears to have potential as an effective tool to reduce ungulate access to roadways and other protected areas. However, to fully assess the viability of this emerging technology for use in excluding wildlife from highways, results from ongoing long-term monitoring at replicated in-road installations are needed

Innate Immunity in Lobsters: Partial Purification and Characterization of a Panulirus cygnus Anti-A Lectin

A lectin detected in haemolymph from the Australian spiny lobster Panulirus cygnus agglutinated human ABO Group A cells to a higher titre than Group O or B. The lectin also agglutinated rat and sheep erythrocytes, with reactivity with rat erythrocytes strongly enhanced by treatment with the proteolytic enzyme papain, an observation consistent with reactivity via a glycolipid. The lectin, purified by affinity chromatography on fixed rat-erythrocyte stroma, was inhibited equally by N-acetylglucosamine and N-acetylgalactosamine. Comparison of data from gel filtration of haemolymph (behaving as a 1,800,000 Da macromolecule), and polyacrylamide gel electrophoresis of purified lectin (a single 67,000 Da band), suggested that in haemolymph the lecin was a multimer. The purified anti-A lectin autoprecipitated unless the storage solution contained chaotropic inhibitors (125 mmol/L sucrose: 500 mmol/L urea). The properties of this anti-A lectin and other similar lectins are consistent with a role in innate immunity in these invertebrates

Mutual Aid: The Other Law of the Jungle. Gauthier Chapelle and Pablo Servigne. Cambridge, Polity Press. 2022. 310 pp

In 1902, the anarchist Peter Kropotkin published Mutual Aid in which he promoted a radical perspective on evolution in which cooperation, as well as selfishness, drive the form, diversification and organization of life on earth. Despite initial recognition, Kropotkin’s contributions have been largely forgotten, even as modern evolutionary theory has recognized the central role of cooperation. In Mutual Aid: the other law of the jungle, Pablo Servigne and Gauthier Chappelle restore Kropotkin’s insights to their rightful place as foundational for our understanding of evolution. They further seek to overturn the pernicious misconception of the 20th century, that nature is only selfish, and highlight how understanding the mechanisms that have evolved to drive cooperation in non-human organisms are also manifest in humans, our society and political institutions. Building forward, they present models of societies that generate, or atrophy, cooperation and consider how our current state will consequently affect our ability to respond to global crises. Through their emphasis on cooperation and its ubiquity in life, Servigne and Chappelle end by broadening their argument to suggest that we question the very nature of the self and reinterpret our existence as a component of a broader cooperative environment. Yet despite the compelling empirical evidence presented, one wonders whether skepticism has been neglected as the authors follow a single cooperative narrative. Does modern evolutionary theory reject the selfish gene in entirety, does selfishness acquiesce to the good of the group within our societies always, and is the centrality of cooperation grounds for the dissolution of the self? While recognizing the exceptional contribution Mutual Aid: the other law of the jungle makes to, it is also necessary to rebalance the vivacity of their cooperative narrative

Ages of Extragalactic Intermediate-Age Star Clusters

A dating technique for faint, distant star clusters observable in the local group of galaxies with the space telescope is discussed. Color-magnitude diagrams of Magellanic Cloud clusters are mentioned along with the metallicity of star clusters

Physical disruption of intervertebral disc promotes cell clustering and a degenerative phenotype

© 2019, The Author(s). To test the hypothesis that physical disruption of an intervertebral disc disturbs cell-matrix binding, leading to cell clustering and increased expression of matrix degrading enzymes that contribute towards degenerative disc cell phenotype. Lumbar disc tissue was removed at surgery from 21 patients with disc herniation, 11 with disc degeneration, and 8 with adolescent scoliosis. 5 μm sections were examined with histology, and 30-µm sections by confocal microscopy. Antibodies were used against integrin α5beta1, matrix metalloproteinases (MMP) 1, MMP-3, caspase 3, and denatured collagen types I and II. Spatial associations were sought between cell clustering and various degenerative features. An additional, 11 non-herniated human discs were used to examine causality: half of each specimen was cultured in a manner that allowed free ‘unconstrained’ swelling (similar to a herniated disc in vivo), while the other half was cultured within a perspex ring that allowed ‘constrained’ swelling. Changes were monitored over 36 h using live-cell imaging. 1,9-Di-methyl methylene blue (DMMB) assay for glycosaminoglycan loss was carried out from tissue medium. Partially constrained specimens showed little swelling or cell movement in vitro. In contrast, unconstrained swelling significantly increased matrix distortion, glycosaminoglycan loss, exposure of integrin binding sites, expression of MMPs 1 and 3, and collagen denaturation. In the association studies, herniated disc specimens showed changes that resembled unconstrained swelling in vitro. In addition, they exhibited increased cell clustering, apoptosis, MMP expression, and collagen denaturation compared to ‘control’ discs. Results support our hypothesis. Further confirmation will require longitudinal animal experiments

Decomposition of NO studied by infrared emission and CO laser absorption

A diagnostic technique for monitoring the concentration of NO using absorption of CO laser radiation was developed and applied in a study of the decomposition kinetics of NO. Simultaneous measurements of infrared emission by NO at 5.3 microns were also made to validate the laser absorption technique. The data were obtained behind incident shocks in NO-N2O-Ar (or Kr) mixtures, with temperatures in the range 2400-4100 K. Rate constants for dominant reactions were inferred from comparisons with computer simulations of the reactive flow

Converts and Islamist Terrorism: An Introduction

Converts to Islam represent a small percentage of the Muslim community in Western countries. Yet when it comes to Islamist extremism and terrorism, research has suggested that converts are considerably overrepresented. This ICCT Policy Brief serves as an introduction to this topic by providing an overview of what is known about converts’ involvement in homegrown jihadism and the foreign fighter phenomenon. Notwithstanding considerable reservations about the quantity and quality of the available data, this Policy Brief finds support for the notion of convert overrepresentation in these activities. This is especially so in the case of foreign fighters. What little data was found on converts’ involvement in homegrown jihadism provided a more nuanced picture, emphasizing that overrepresentation may not be the norm in all Western countries and that it may be a relatively recent development. Numerous explanations for converts’ involvement in Islamist extremism and terrorism have been provided, running the gamut from structural-level explanations to distinctly personal motives. At present, however, a comprehensive, theoretically sound and empirically grounded understanding of how and why converts become involved in Islamist militancy is absent. The Policy Brief concludes by stressing the need to develop our understanding of this important yet under-researched topic.Security and Global Affair

Rotational quenching of CO due to H2_2 collisions

Rate coefficients for state-to-state rotational transitions in CO induced by both para- and ortho-H$_2$ collisions are presented. The results were obtained using the close-coupling method and the coupled-states approximation, with the CO-H$_2$ interaction potential of Jankowski & Szalewicz (2005). Rate coefficients are presented for temperatures between 1 and 3000 K, and for CO($v=0,j$) quenching from $j=1-40$ to all lower $j^\prime$ levels. Comparisons with previous calculations using an earlier potential show some discrepancies, especially at low temperatures and for rotational transitions involving large $|\Delta j|$. The differences in the well depths of the van der Waals interactions in the two potential surfaces lead to different resonance structures in the energy dependence of the cross sections which influence the low temperature rate coefficients. Applications to far infrared observations of astrophysical environments are briefly discussed.Comment: 28 pages, 10 figure

Nitrogen chemistry and depletion in starless cores

We investigated the chemistry of nitrogen--containing species, principally isotopomers of CN, HCN, and HNC, in a sample of pre-protostellar cores. We used the IRAM 30 m telescope to measure the emission in rotational and hyperfine transitions of CN, HCN, 13CN, H13CN, HN13C, and HC15N, in L 1544, L 183, Oph D, L 1517B, L 310. The observations were made along axial cuts through the dust emission peak, at a number of regularly--spaced offset positions. The observations were reduced and analyzed to obtain the column densities, using the measurements of the less abundant isotopic variants in order to minimize the consequences of finite optical depths in the lines. The observations were compared with the predictions of a free--fall gravitational collapse model, which incorporates a non-equilibrium treatment of the relevant chemistry. We found that CN, HCN, and HNC remain present in the gas phase at densities well above that at which CO depletes on to grains. The CN:HCN and the HNC:HCN abundance ratios are larger than unity in all the objects of our sample. Furthermore, there is no observational evidence for large variations of these ratios with increasing offset from the dust emission peak and hence with density. Whilst the differential freeze--out of CN and CO can be understood in terms of the current chemistry, the behaviour of the CN:HCN ratio is more difficult to explain. Models suggest that most nitrogen is not in the gas phase but may be locked in ices. Unambiguous conclusions require measurements of the rate coefficients of the key neutral--neutral reactions at low temperatures