Crystallographic Analysis of Martensite in 0.2C-2.0Mn-1.5Si-0.6Cr Steel by EBSD

The crystallography of martensite formed in 0.2C-2.0Mn-1.5Si-0.6Cr steel was studied using the EBSDtechnique. The results showed that the observed orientation relationship was closer to the Nishiyama-Wassermann (N-W) than to the Kurdjumov-Sachs (K-S) orientation relationship (OR). The microstructure ofmartensite consisted of parallel laths forming morphological packet-like structures. Typically, there were threedifferent lath orientations in a morphological packet consisting of three specific N-W OR variants sharing thesame {111} austenite plane. A packet of martensite laths with common {111} austenite plane was termed as acrystallographic packet. Generally, the crystallographic packet size corresponded to the morphological packetsize, but occasionally the morphological packet was found to consist of two or more crystallographic packets.Therefore, the crystallographic packet size appeared to be finer than the morphological packet size. Therelative orientation between the variants in crystallographic packets was found to be near 60°/<110>. Thisappears to explain the strong peak observed near 60° in the grain boundary misorientation distribution.Martensite also contained a high fraction of boundaries with their misorientation in the range 2.5-8°.Typically these boundaries were found to be located inside the martensite laths forming lath-like sub-grains,whose long axes were parallel with the long axis of the martensite laths

Phase Heritage: Deciphering Evidence of Pre-Existing Phases via Inherited Crystallographic Orientations

The concept of 'phase heritage' (e.g., Timms et al., 2017a) involves microstructural recognition of the former presence of a phase that has since transformed to another via evidence encoded in crystallographic orientations. Phase heritage relies on the phenomenon that newly grown (daughter) phases nucleate with particular crystallographic orientation relationships with the preceding (parent) phase. This phenomenon is common for displacive (i.e., shear or martensitic) transformations, well documented in the metals and ceramics literature, but is relatively uncommon in geosciences. This presentation outlines the concepts behind this approach, showcases results from software for automated analysis of EBSD data, and illustrates examples of polymorphic and dissociation phase transformations in the ZrSiO4-ZrO2-SiO2 system, which has particularly useful applications for 'extreme thermobarometry' in impact environments (Timms et al., 2017a)

Pancreatic cancer intrinsic PI3Kα activity accelerates metastasis and rewires macrophage component.

Pancreatic ductal adenocarcinoma (PDAC) patients frequently suffer from undetected micro-metastatic disease. This clinical situation would greatly benefit from additional investigation. Therefore, we set out to identify key signalling events that drive metastatic evolution from the pancreas. We searched for a gene signature that discriminate localised PDAC from confirmed metastatic PDAC and devised a preclinical protocol using circulating cell-free DNA (cfDNA) as an early biomarker of micro-metastatic disease to validate the identification of key signalling events. An unbiased approach identified, amongst actionable markers of disease progression, the PI3K pathway and a distinctive PI3Kα activation signature as predictive of PDAC aggressiveness and prognosis. Pharmacological or tumour-restricted genetic PI3Kα-selective inhibition prevented macro-metastatic evolution by hindering tumoural cell migratory behaviour independently of genetic alterations. We found that PI3Kα inhibition altered the quantity and the species composition of the produced lipid second messenger PIP3 , with a selective decrease of C36:2 PI-3,4,5-P3 . Tumoural PI3Kα inactivation prevented the accumulation of pro-tumoural CD206-positive macrophages in the tumour-adjacent tissue. Tumour cell-intrinsic PI3Kα promotes pro-metastatic features that could be pharmacologically targeted to delay macro-metastatic evolution

La Famille royale et l'opposition, par J.-B.-L. Cayron

Avec mode text

A la Raison : ode dédiée à M. Bouillier, professeur de philosophie à la Faculté des lettres de Lyon / par M. J.-L.-B. Cayron

Appartient à l’ensemble documentaire : LangRous1Avec mode text

Evidence of extensive lunar crust formation in impact melt sheets 4,330 Myr ago

Accurately constraining the formation and evolution of the lunar magnesian suite is key to understanding the earliest periods of magmatic crustal building that followed accretion and primordial differentiation of the Moon. However, the origin and evolution of these unique rocks is highly debated. Here, we report on the microstructural characterization of a large (~250-μm) baddeleyite (monoclinic-ZrO2) grain in Apollo troctolite 76535 that preserves quantifiable crystallographic relationships indicative of reversion from a precursor cubic-ZrO2 phase. This observation places important constraints on the formation temperature of the grain (>2,300 °C), which endogenic processes alone fail to reconcile. We conclude that the troctolite crystallized directly from a large, differentiated impact melt sheet 4,328 ± 8 Myr ago. These results suggest that impact bombardment would have played a critical role in the evolution of the earliest planetary crusts