Olivine in CV chondrite matrices: Structure, size-distribution, and morphology

Accepted versio

A rock fabric in chondrite matrix.

Accepted versio

Fabric analysis of allende matrix using EBSD

Accepted versio

Fayalitic olivine in Allende matrix: Evidence for a secondary origin

Published versio

Parasitic pneumonia in roe deer (Capreolus capreolus) in Cornwall, Great Britain, caused by Varestrongylus capreoli (Protostrongylidae)

Abstract Background Roe deer (Capreolus capreolus) became extinct over large areas of Britain during the post mediaeval period but following re-introductions from Europe during the 1800s and early 1900s the population started to recover and in recent decades there has been a spectacular increase. Many roe deer are shot in Britain each year but despite this there is little published information on the diseases and causes of mortality of roe deer in Great Britain. Case presentation The lungs of two hunter-shot roe deer in Cornwall showed multiple, raised, nodular lesions associated with numerous protostrongylid-type nematode eggs and first stage larvae. There was a pronounced inflammatory cell response (mostly macrophages, eosinophils and multinucleate giant cells) and smooth muscle hypertrophy of the smaller bronchioles. The morphology of the larvae was consistent with that of a Varestrongylus species and sequencing of an internal transcribed spacer-2 fragment confirmed 100% identity with a published Norwegian Varestrongylus cf. capreoli sequence. To the best of the authors’ knowledge this is the first confirmed record of V. capreoli in Great Britain. Co-infection with an adult protostrongylid, identified by DNA sequencing as Varestrongylus sagittatus, was also demonstrated in one case. Conclusions Parasitic pneumonia is regarded as a common cause of mortality in roe deer and is typically attributed to infection with Dictyocaulus sp. This study has shown that Varestrongylus capreoli also has the capability to cause significant lung pathology in roe deer and heavy infection could be of clinical significance

Insights into anisotropy development and weakening of ice from in situ P wave velocity monitoring during laboratory creep

Polycrystalline ice weakens significantly after a few percent strain, during high homologous temperature deformation. Weakening is correlated broadly with the development of a crystallographic preferred orientation (CPO). We deformed synthetic polycrystalline ice at -5°C under uniaxial compression, while measuring ultrasonic P wave velocities along several raypaths through the sample. Changes in measured P wave velocities (V p ) and in the velocities calculated from microstructural measurements of CPO (by cryo-electron backscatter diffraction) both show that velocities along trajectories parallel and perpendicular to shortening decrease with increasing strain, while velocities on diagonal trajectories increase. Thus, in these experiments, velocity data provide a continuous measurement of CPO evolution in creeping ice. Samples reach peak stresses after 1% shortening. Weakening corresponds to the start of CPO development, as indicated by divergence of P wave velocity changes for different raypaths, and initiates at ≈3% shortening. Selective growth by strain-induced grain boundary migration (GBM) of grains favorably oriented for basal slip may initiate weakening through the formation of an interconnected network of these grains by 3% shortening. After weakening initiates, CPO continues to develop by GBM and nucleation processes. The resultant CPO has an open cone (small circle) configuration, with the cone axis parallel to shortening. The development of this CPO causes significant weakening under uniaxial compression, where the shear stresses resolved on the basal planes (Schmid factors) are high

Redox-freezing and nucleation of diamond via magnetite formation in the Earth’s mantle

Diamonds and their inclusions are unique probes into the deep Earth, tracking the deep carbon cycle to >800 km. Understanding the mechanisms of carbon mobilization and freezing is a prerequisite for quantifying the fluxes of carbon in the deep Earth. Here we show direct evidence for the formation of diamond by redox reactions involving FeNi sulfides. Transmission Kikuchi Diffraction identifies an arrested redox reaction from pyrrhotite to magnetite included in diamond. The magnetite corona shows coherent epitaxy with relict pyrrhotite and diamond, indicating that diamond nucleated on magnetite. Furthermore, structures inherited from h-Fe3O4 define a phase transformation at depths of 320–330 km, the base of the Kaapvaal lithosphere. The oxidation of pyrrhotite to magnetite is an important trigger of diamond precipitation in the upper mantle, explaining the presence of these phases in diamonds