Radio polarimetric imaging of the interstellar medium: magnetic field and diffuse ionized gas structure near the W3/W4/W5/HB3 complex

We have used polarimetric imaging to study the magneto-ionic medium of the Galaxy, obtaining 1420 MHz images with an angular resolution of 1' over more than 40 square-degrees of sky around the W3/W4/W5/HB3 HII region/SNR complex in the Perseus Arm. Features detected in polarization angle are imposed on the linearly polarized Galactic synchrotron background emission by Faraday rotation arising in foreground ionized gas having an emission measure as low as 1 cm^{-6} pc. Several new remarkable phenomena have been identified, including: mottled polarization arising from random fluctuations in a magneto-ionic screen that we identify with a medium in the Perseus Arm, probably in the vicinity of the HII regions themselves; depolarization arising from very high rotation measures (several times 10^3 rad m^{-2}) and rotation measure gradients due to the dense, turbulent environs of the HII regions; highly ordered features spanning up to several degrees; and an extended influence of the HII regions beyond the boundaries defined by earlier observations. In particular, the effects of an extended, low-density ionized halo around the HII region W4 are evident, probably an example of the extended HII envelopes postulated as the origin of weak recombination-line emission detected from the Galactic ridge. Our polarization observations can be understood if the uniform magnetic field component in this envelope scales with the square-root of electron density and is 20 microG at the edge of the depolarized region around W4, although this is probably an over-estimate since the random field component will have a significant effect.Comment: 18 pages, 8 figures (7 jpeg and 1 postscript), accepted for publication in the Astrophysical Journa

Spider silk protein structure analysis by FTIR and STXM spectromicroscopy techniques

Spider silk displays incredible strength and elas¬ticity for its size and weight.[1] These properties have sparked interest in determining the protein structures of the silk fibers allowing for the pro¬duction of synthetic silks.[2] This study compares the mid-infrared (Mid IR) spectra of silk from five different spider species to investigate the com-monalities between species and web type. The results demonstrate the Mid IR spectra from all types of spider silk to be similar, showing protein peaks in the Amide I and II regions. To study the environmental effects of the acid solution on the silk protein structure, two of the five species’ silk: Black & Yellow Orb Weaver (Argiope aurantia) and Black Widow (Latrodectus hesperus), were exposed to either rain water or 0.001 M sulphuric acid solution, similar to acid rain in pH. Spectra obtained at the Mid IR beamline and the data obtained from the X-ray Absorption Near Edge Spectroscopy (XANES) were compared for these samples to see the effect of the acid rain-like solu¬tion on the silk proteins. No conclusive evidence from the data is present to suggest that the acid rain solution had an effect on the protein structures of either type of spider silk.La soie d’araignée est à la fois robuste et flexible pour sa taille et son poids.[1] Ces propriétés ont piqué la curiosité de déterminer la structure des protéines des fibres de soie qui pourrait permettre éventuelle¬ment la production des soies synthétiques.[2] Cette étude compare les spectres mi- infrarouges (Mi IR) de soie de cinq espèces différentes d’araignée afin de trouver des similitudes entre les espèces et les genres de toiles. Les résultats démontrent que les spectres mi- infrarouges de tout type de soie d’araignée étudié sont similaires, présentant des apogées de protéines dans les régions de l’Amide I et II. Afin d’étudier les effets environnementaux d’une solution acide sur la structure de la proté¬ine de soie, la soie de deux des cinq espèces, le orbe tisserand noir et jaune (Argiope aurantia) et la veuve noire (Latrodectus Hesperus), ont été expo¬sé soit à la pluie naturelle soit à une solution d’acide sulfurique 0.001 M qui est proche au pH de la pluie acide. Les spectres obtenus à l’onde dirigée Mi IR et les données obtenues de l’absorption de la radi¬ographie près du seuil de la spectroscopie (ARSS) ont été comparés de ces échantillons afin de con¬stater l’effet de la solution d’acide sulfurique sur des protéines de soie. Il n’y avait aucune preuve probante des données suggérant que la solution d’acide sulfurique avait un effet sur la structure des protéines de soie des araignées étudié

Dust in Hot Environments: Giant Dusty Galactic Halos

I review some of the evidences for dust in the Local Bubble and in galactic halos and show that a general mechanism based on radiation pressure is capable of evacuating dust grains from regions dominated by massive star energy input and thus originate huge dusty halos. A Monte Carlo/particle model has been developed to study the dust dynamics above HII chimneys and the results, among other findings, show that dust can travel several kpc away from the plane of the parent galaxy. The cosmological implications of extragalactic dust are briefly outlined.Comment: 10 pages, LaTeX (lamuphys.sty), 3 figures, IAU166, The Local Bubble and Beyond, Highlight Tal

Bedforms and sedimentary structures related to supercritical flows in glacigenic settings

Upper-flow-regime bedforms, including upper-stage-plane beds, antidunes, chutes-and-pools and cyclic steps, are ubiquitous in glacigenic depositional environments characterized by abundant meltwater discharge and sediment supply. In this study, the depositional record of Froude near-critical and supercritical flows in glacigenic settings is reviewed, and similarities and differences between different depositional environments are discussed. Upper-flow-regime bedforms may occur in subglacial, subaerial and subaqueous environments, recording deposition by free-surface flows and submerged density flows. Although individual bedform types are generally not indicative of any specific depositional environment, some observed trends are similar to those documented in non-glacigenic settings. Important parameters for bedform evolution that differ between depositional environments include flow confinement, bed slope, aggradation rate and grain size. Cyclic-step deposits are more common in confined settings, like channels or incised valleys, or steep slopes of coarse-grained deltas. Antidune deposits prevail in unconfined settings and on more gentle slopes, like glacifluvial fans, sand-rich delta slopes or subaqueous (ice-contact) fans. At low aggradation rates, only the basal portions of bedforms are preserved, such as scour fills related to the hydraulic-jump zone of cyclic steps or antidune-wave breaking, which are common in glacifluvial systems and during glacial lake-outburst floods and (related) lake-level falls. Higher aggradation rates result in increased preservation potential, possibly leading to the preservation of complete bedforms. Such conditions are met in sediment-laden jökulhlaups and subaqueous proglacial environments characterized by expanding density flows. Coarser-grained sediment leads to steeper bedform profiles and highly scoured facies architectures, while finer-grained deposits display less steep bedform architectures. Such differences are in part related to stronger flows, faster settling of coarse clasts, and more rapid breaking of antidune waves or hydraulic-jump formation over hydraulically rough beds. © 2020 The Authors. Sedimentology published by John Wiley & Sons Ltd on behalf of International Association of Sedimentologist

Slip pulse and resonance of the Kathmandu basin during the 2015 Gorkha earthquake, Nepal.

This is the author accepted manuscript. The final version is available from AAAS via http://dx.doi.org/10.1126/science.aac6383Detailed geodetic imaging of earthquake ruptures enhances our understanding of earthquake physics and associated ground shaking. The 25 April 2015 moment magnitude 7.8 earthquake in Gorkha, Nepal was the first large continental megathrust rupture to have occurred beneath a high-rate (5-hertz) Global Positioning System (GPS) network. We used GPS and interferometric synthetic aperture radar data to model the earthquake rupture as a slip pulse ~20 kilometers in width, ~6 seconds in duration, and with a peak sliding velocity of 1.1 meters per second, which propagated toward the Kathmandu basin at ~3.3 kilometers per second over ~140 kilometers. The smooth slip onset, indicating a large (~5-meter) slip-weakening distance, caused moderate ground shaking at high frequencies (>1 hertz; peak ground acceleration, ~16% of Earth's gravity) and minimized damage to vernacular dwellings. Whole-basin resonance at a period of 4 to 5 seconds caused the collapse of tall structures, including cultural artifacts.The Nepal Geodetic Array was funded by internal funding to JPA from Caltech and DASE and by the Gordon and Betty Moore Foundation, through Grant GBMF 423.01 to the Caltech Tectonics Observatory and was maintained thanks to NSF Grant EAR 13-5136. Andrew Miner and the PAcific Northwest Geodetic Array (PANGA) at Central Washington University are thanked for technical assistance with the construction and operation of the Tribhuvan University-CWU network. Additional funding for the TU-CWU network came from United Nations Development Programme and Nepal Academy for Science and Technology. The high rate data were recovered thanks to a rapid intervention funded by NASA (US) and the Department of Foreign International Development (UK). We thank Trimble Navigation Ltd and the Vaidya family for supporting the rapid response as well. The accelerometer record at KATNP was provided by USGS. Research at UC Berkeley was funded by the Gordon and Betty Moore Foundation through grant GBMF 3024. A portion of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The GPS data were processed by ARIA (JPL) and the Scripps Orbit and Permanent Array Center. The effort at the Scripps Institution of Oceanography was funded by NASA grants NNX14AQ53G and NNX14AT33G. ALOS-2 data were provided under JAXA (Japan) PI Investigations 1148 and 1413. JPA thanks the Royal Society for support. We thank Susan Hough, Doug Given, Irving Flores and Jim Luetgert for contribution to the installation of this station

Combined impacts of elevated CO2 and anthropogenic noise on European sea bass

There is another record in ORE for this publication: http://hdl.handle.net/10871/32962Ocean acidification (OA) and anthropogenic noise are both known to cause stress and induce physiological and behavioural changes in fish, with consequences for fitness. OA is also predicted to reduce the ocean's capacity to absorb low-frequency sounds produced by human activity. Consequently, anthropogenic noise could propagate further under an increasingly acidic ocean. For the first time, this study investigated the independent and combined impacts of elevated carbon dioxide (CO2) and anthropogenic noise on the behaviour of a marine fish, the European sea bass (Dicentrarchus labrax). In a fully factorial experiment crossing two CO2 levels (current day and elevated) with two noise conditions (ambient and pile driving), D. labrax were exposed to four CO2/noise treatment combinations: 400 µatm/ambient, 1000 µatm/ambient, 400 µatm/pile-driving, and 1000 µatm/pile-driving. Pile-driving noise increased ventilation rate (indicating stress) compared with ambient noise conditions. Elevated CO2 did not alter the ventilation rate response to noise. Furthermore, there was no interaction effect between elevated CO2 and pile-driving noise, suggesting that OA is unlikely to influence startle or ventilatory responses of fish to anthropogenic noise. However, effective management of anthropogenic noise could reduce fish stress, which may improve resilience to future stressors.Natural Environment Research Counci

A consistent global approach for morphometric characterisation of subaqueous landslides

Landslides are common in aquatic settings worldwide, from lakes and coastal environments to the deep sea. Fast-moving, large-volume landslides can potentially trigger destructive tsunamis. Landslides damage and disrupt global communication links and other critical marine infrastructure. Landslide deposits act as foci for localized, but important, deep-seafloor biological communities. Under burial, landslide deposits play an important role in a successful petroleum system. While the broad importance of understanding subaqueous landslide processes is evident, a number of important scientific questions have yet to receive the needed attention. Collecting quantitative data is a critical step to addressing questions surrounding subaqueous landslides. Quantitative metrics of subaqueous landslides are routinely recorded, but which ones, and how they are defined, depends on the end-user focus. Differences in focus can inhibit communication of knowledge between communities, and complicate comparative analysis. This study outlines an approach specifically for consistent measurement of subaqueous landslide morphometrics to be used in the design of a broader, global open-source, peer-curated database. Examples from different settings illustrate how the approach can be applied, as well as the difficulties encountered when analysing different landslides and data types. Standardizing data collection for subaqueous landslides should result in more accurate geohazard predictions and resource estimation