Shock effects in plagioclase feldspar from the Mistastin Lake impact structure, Canada

Shock metamorphism, caused by hypervelocity impact, is a poorly understood process in feldspar due to the complexity of the crystal structure, the relative ease of weathering, and chemical variations, making optical studies of shocked feldspars challenging. Understanding shock metamorphism in feldspars, and plagioclase in particular, is vital for understanding the history of Earth's moon, Mars, and many other planetary bodies. We present here a comprehensive study of shock effects in andesine and labradorite from the Mistastin Lake impact structure, Labrador, Canada. Samples from a range of different settings were studied, from in situ central uplift materials to clasts from various breccias and impact melt rocks. Evidence of shock metamorphism includes undulose extinction, offset twins, kinked twins, alternate twin deformation, and partial to complete transformation to diaplectic plagioclase glass. In some cases, isotropization of alternating twin lamellae was observed. Planar deformation features (PDFs) are notably absent in the plagioclase, even when present in neighboring quartz grains. It is notable that various microlites, twin planes, and compositionally different lamellae could easily be mistaken for PDFs and so care must be taken. A pseudomorphous zeolite phase (levyne-Ca) was identified as a replacement mineral of diaplectic feldspar glass in some samples, which could, in some instances, also be potentially mistaken for PDFs. We suggest that the lack of PDFs in plagioclase could be due to a combination of structural controls relating to the crystal structure of different feldspars and/or the presence of existing planes of weakness in the form of twin and cleavage planes

Ultra high energy muons in extensive air showers

The design of the modification required to increase the angular resolution of the Haverah Park Magnet Spectrograph is described. It is shown that the reduction in uncertainty of angular measurement achieved by the modification is characterised by a standard deviation of 0.l6 , corresponding to a limit of momentum resolution of 120 GeV/c. The momentum spectra, of muons in EAS derired from the data available at the conclusion of the period of operation of the original spectrograph are presented. These spectra relate to muons falling between 150 m and 600 m from the cores of showers of primary energy within the approximate range 10(^-16) eV to 18(^-18) eV. The preliminary results from the modified spectrograph are also presented but they are shown to be statistically insufficient to be considered as evidence, for or against, the validity of the earlier data. An investigation of the dependence of the momentum spectra on primary energy and shower zenith angle, originally undertaken using data available prior to the end of the period of operation of the Original spectrograph, has been repeated in the light of the improved statistics and revised EAS data. In addition, other checks have been undertaken: (a) on the effect of the accuracy of core location on the momentum spectra, and (b) on the method of deriving the spectra from the data. The data available at the conclusion of the original experiment have also been used, in conjunction with a new theoretical study of the distortion of the muon charge ratio produced by the geomagnetic field, to estimate the height of origin of muons in EAS. It is shown that measurement of this distortion cannot be used to give sufficiently accurate assessment of the height of muon production, to allow comment to be made on the nature of the primary particle or the ultra high energy interactions. Finally, an improved analytical model of EAS is described and the results are compared with those of other workers and observation

Toward quantification of strain-related mosaicity in shocked lunar and terrestrial plagioclase by in situ micro-X-ray diffraction

Studies of shock metamorphism of feldspar typically rely on qualitative petrographic observations, which, while providing invaluable information, can be difficult to interpret. Shocked feldspars, therefore, are now being studied in greater detail by various groups using a variety of modern techniques. We apply in situ micro-X-ray diffraction (μXRD) to shocked lunar and terrestrial plagioclase feldspar to contribute to the development of a quantitative scale of shock deformation for the feldspar group. Andesine and labradorite from the Mistastin Lake impact structure, Labrador, Canada, and anorthite from Earth's Moon, returned during the Apollo program, were examined using optical petrography and assigned to subgroups of the optical shock level classification system of Stöffler (1971). Two-dimensional μXRD patterns from the same samples revealed increased peak broadening in the chi dimension (χ), due to strain-related mosaicity, with increased optical signs of deformation. Measurement of the full width at half maximum along χ (FWHMχ) of these peaks provides a quantitative way to measure strain-related mosaicity in plagioclase feldspar as a proxy for shock level

Responsible research and innovation: A manifesto for empirical ethics?

In 2013 the Nuffield Council on Bioethics launched their report Novel Neurotechnologies: Intervening in the Brain. The report, which adopts the European Commission's notion of Responsible Research and Innovation, puts forward a set of priorities to guide ethical research into, and the development of, new therapeutic neurotechnologies. In this paper, we critically engage with these priorities. We argue that the Nuffield Council's priorities, and the Responsible Research and Innovation initiative as a whole, are laudable and should guide research and innovation in all areas of healthcare. However, we argue that operationalising Responsible Research and Innovation requires an in-depth understanding of the research and clinical contexts. Providing such an understanding is an important task for empirical ethics. Drawing on examples from sociology, science and technology studies, and related disciplines, we propose four avenues of social science research which can provide such an understanding. We suggest that these avenues can provide a manifesto for empirical ethics.The paper derives from a project that was funded by Wellcome Trust (Wellcome Trust Biomedical Strategic Award 086034)

‘It just opens up their world’: autism, empathy, and the therapeutic effects of equine interactions

Experiences of autism-spectrum disorder are now increasingly studied by social scientists. Human–animal relations have also become a major focus of social inquiry in recent years. Examining horse-assisted therapy for autistic spectrum disorders, this is the first paper that brings these fields together. Drawing on participant observation and interviews at a UK horse therapy Centre, this article examines how staff and the parents of riders account for the successes and limitations of equine therapy. To the respondents, horses ‘open up’ autistic children and make possible interactions that seemed impossible before. Horses were regarded as facilitating the emergence of apparently social behaviours, which included eye contact, pointing, and speech. Three key explanations emerged for therapeutic success: the sensorial, embodied experience of riding the horse; the specific movements and rhythms of the horse; and, the ‘personality’ of the horse. Equine therapy can be regarded as enabling a form of multispecies intersubjectivity, with the resonance between rider and horse seeming to make possible a new attunement between humans. Practices of equine therapy, and perceptions of its efficacy, serve in turn to attune social scientists to a version of empathy constituted through lively and sensorial interactions, as opposed to one that is restricted to particular kinds of humans

The Stac Fada “impact ejecta” layer: not what it seems

The Stac Fada Member (SFM) forms part of the Stoer Group of the Torridonian of NW Scotland. The SFM is unique in the Torridonian, being characterized by the presence of greenish altered glass clasts. Its origin has been debated for decades with several hypotheses being proposed but all invoking some connection with volcanic activity in the region. More recently, Amor et al. suggested that the SFM represents “a chord section through the continuous ejecta blanket surrounding an impact crater”. Here, we confirm the presence of shocked material within the SFM and then discuss its origin

Advanced Methods for Spatial Analysis of Bioaerosol Long-Range Transport Processes

Research on bioaerosol is still in its infancy. The dynamics and, therefore, the effects on atmospheric processes and the biosphere are often underestimated, or have not yet been sufficiently investigated. Atmospheric models such as FLEXPART and HYSPLIT enable researchers to simulate the transport of particles in the atmosphere and provide information on where air-parcels originate from. In the following, we present two methods for combining results of these models with spatial information, e.g., about vegetation. The first method shows how spatial CORINE land cover distribution can be analyzed within the boundaries of HYSPLIT trajectories. In a second method, FLEXPART simulations are used in combination with COSMO rain data and tree maps to generate maps that indicate the potential origin of bioaerosol for selected periods of time

The role of intrinsic disorder and dynamics in the assembly and function of the type II secretion system

International audienceMany Gram-negative commensal and pathogenic bacteria use a type II secretion system (T2SS) to transport proteins out of the cell. These exported proteins or substrates play a major role in toxin delivery, maintaining biofilms, replication in the host and subversion of host immune responses to infection. We review the current structural and functional work on this system and argue that intrinsically disordered regions and protein dynamics are central for assembly, exo-protein recognition, and secretion competence of the T2SS. The central role of intrinsic disorder-order transitions in these processes may be a particular feature of type secretion

Shock metamorphism in plagioclase and selective amorphization

Plagioclase feldspar is one of the most common rock‐forming minerals on the surfaces of the Earth and other terrestrial planetary bodies, where it has been exposed to the ubiquitous process of hypervelocity impact. However, the response of plagioclase to shock metamorphism remains poorly understood. In particular, constraining the initiation and progression of shock‐induced amorphization in plagioclase (i.e., conversion to diaplectic glass) would improve our knowledge of how shock progressively deforms plagioclase. In turn, this information would enable plagioclase to be used to evaluate the shock stage of meteorites and terrestrial impactites, whenever they lack traditionally used shock indicator minerals, such as olivine and quartz. Here, we report on an electron backscatter diffraction (EBSD) study of shocked plagioclase grains in a metagranite shatter cone from the central uplift of the Manicouagan impact structure, Canada. Our study suggests that, in plagioclase, shock amorphization is initially localized either within pre‐existing twins or along lamellae, with similar characteristics to planar deformation features (PDFs) but that resemble twins in their periodicity. These lamellae likely represent specific crystallographic planes that undergo preferential structural failure under shock conditions. The orientation of preexisting twin sets that are preferentially amorphized and that of amorphous lamellae is likely favorable with respect to scattering of the local shock wave and corresponds to the “weakest” orientation for a specific shock pressure value. This observation supports a universal formation mechanism for PDFs in silicate minerals