Crystal structure, thermodynamics, magnetics and disorder properties of Be-Fe-Al intermetallics

The elastic and magnetic properties, thermodynamical stability, deviation from stoichiometry and order/disorder transformations of phases that are relevant to Be alloys were investigated using density functional theory simulations coupled with phonon density of states calculations to capture temperature effects. A novel structure and composition were identified for the Be-Fe binary {\epsilon} phase. In absence of Al, FeBe_5 is predicted to form at equilibrium above ~ 1250 K, while the {\epsilon} phase is stable only below ~ 1650 K, and FeBe_2 is stable at all temperatures below melting. Small additions of Al are found to stabilise FeBe_5 over FeBe_2 and {\epsilon}, while at high Al content, AlFeBe_4 is predicted to form. Deviations from stoichiometric compositions are also considered and found to be important in the case of FeBe_5 and {\epsilon}. The propensity for disordered vs ordered structures is also important for AlFeBe_4 (which exhibits complete Al-Fe disordered at all temperatures) and FeBe_5 (which exhibits an order-disorder transition at ~ 950 K).Comment: 14 pages, 10 figures, accepted for publication in J. Alloy Compd. on 14 March 201

Mitochondrial DNA Heteroplasmy and Purifying Selection in the Mammalian Female Germ Line.

Inherited mutations in the mitochondrial (mt)DNA are a major cause of human disease, with approximately 1 in 5000 people affected by one of the hundreds of identified pathogenic mtDNA point mutations or deletions. Due to the severe, and often untreatable, symptoms of many mitochondrial diseases, identifying how these mutations are inherited from one generation to the next has been an area of intense research in recent years. Despite large advances in our understanding of this complex process, many questions remain unanswered, with one of the most hotly debated being whether or not purifying selection acts against pathogenic mutations during germline development

Order, disorder and stability in Be intermetallics for fusion applications

Be intermetallics are a promising family of materials for the first wall and neutron multiplying applications in future nuclear fusion reactors, owing to their low atomic number, still high beryllium content but improved thermo-mechanical properties over pure beryllium. Due to the difficulties of working with Be, however, they are often poorly characterized. Thus, the crystallography, elastic and magnetic properties, thermodynamical stability, deviation from stoichiometry and order/disorder transformations of intermetallics, which are relevant to Be alloys have been investigated using computer simulation [1,2,3]. These include Be-Fe-Al ternary phases as well as a series of Be-transition metal binaries. Throughout the density functional code CASTEP was employed, coupled with phonon density of states calculations to capture temperature effects. The propensity for intermetallics to act as impurity sinks was also considered. Please click Additional Files below to see the full abstract

Hydrogen trapping mechanisms of TiC and (Ti,Mo)C precipitates in steels

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Its About TIME: A Rigorous New Process for Selecting Instructional Materials for Science

California counties and school districts are implementing a critically needed change in how they evaluate science instructional materials before investing in local adoption. Past adoptions were often too superficial in nature, focusing on candidate materials' overall look and feel, use of graphical elements, and availability of ancillary materials while insufficiently attending to the substance of the materials for high-quality teaching and learning. In contrast, the California NGSS Toolkit for Instructional Materials Evaluation (hereafter referred to as TIME) process enables participants to use evidence-based measures to choose materials aligned to the Next Generation Science Standards (NGSS) that meet their district's needs.This 11th report in the NGSS Early Implementers Initiative evaluation series is intended for school and district administrators, leaders of science professional learning, and state policymakers. It provides an overview of the full TIME process, including participants' perceptions, a detailed description of the statewide TIME trainings of 2018-19, and a vignette that illustrates a portion of the TIME process

Submission 238 to: Australia's Science and Research Priorities - Conversation Starter

Australia plans to obtain, build, and operate nuclear propelled submarines. The immense challenges brought about by this change in national defence strategy, along with the ambition to create a 20,000 strong nuclear science and engineering capable workforce, must be reflected in the National Science and Research Priorities, and the National Science Statement. We therefore recommend the inclusion of Nuclear Technology as a contemporary National Science and Research Priority, for consideration by the Science Strategy and Priorities Taskforce

Structural and phase evolution in U₃Si₂ during steam corrosion

U₃Si₂ nuclear fuel is corroded in deuterated steam with in situ neutron diffraction. Density functional theory is coupled with rigorous thermodynamic description of the hydride including gas/solid entropy contributions. H absorbs in the 2b interstitial site of U₃Si₂Hx and moves to 8j for x ≥ 0.5. Hydriding forces lattice expansion and change in a/c ratio linked to site preference. Rietveld refinement tracks the corrosion reactions at 350-500 °C and preference for the 8j site. Above 375 °C, formation of UO₂, U₃Si₅ and USi₃ take place in the grain boundaries and bulk. Hydriding occurs in bulk and precedes other reactions

Hydrogen trapping and embrittlement in metals – a review

Hydrogen embrittlement in metals (HE) is a serious challenge for the use of high strength materials in engineering practice and a major barrier to the use of hydrogen for global decarbonization. Here we describe the factors and variables that determine HE susceptibility and provide an overview of the latest understanding of HE mechanisms. We discuss hydrogen uptake and how it can be managed. We summarize hydrogen trapping and the techniques used for its characterization. We also review literature that argues that hydrogen trapping can be used to decrease HE susceptibility. We discuss the future research that is required to advance the understanding of HE and hydrogen trapping and to develop HE-resistant alloys

A Forward Genetic Screen Reveals Novel Independent Regulators of Ulbp1, an Activating Ligand for Natural Killer Cells

Recognition and elimination of tumor cells by the immune system is crucial for limiting tumor growth. Natural killer (NK) cells become activated when the receptor NKG2D is engaged by ligands that are frequently upregulated in primary tumors and on cancer cell lines. However, the molecular mechanisms driving NKG2D ligand expression on tumor cells are not well defined. Using a forward genetic screen in a tumor-derived human cell line, we identified several novel factors supporting expression of the NKG2D ligand ULBP1. Our results show stepwise contributions of independent pathways working at multiple stages of ULBP1 biogenesis. Deeper investigation of selected hits from the screen showed that the transcription factor ATF4 drives ULBP1 gene expression in cancer cell lines, while the RNA-binding protein RBM4 supports ULBP1 expression by suppressing a novel alternatively spliced isoform of ULBP1 mRNA. These findings offer insight into the stress pathways that alert the immune system to danger