Burn-Resistant, Strong Metal-Matrix Composites

Ceramic particulate fillers increase the specific strengths and burn resistances of metals: This is the conclusion drawn by researchers at Johnson Space Center's White Sands Test Facility. The researchers had theorized that the inclusion of ceramic particles in metal tools and other metal objects used in oxygen-rich atmospheres (e.g., in hyperbaric chambers and spacecraft) could reduce the risk of fire and the consequent injury or death of personnel. In such atmospheres, metal objects act as ignition sources, creating fire hazards. However, not all metals are equally hazardous: some are more burn-resistant than others are. It was the researchers purpose to identify a burn-resistant, high-specific-strength ceramic-particle/metal-matrix composite that could be used in oxygen-rich atmospheres. The researchers studied several metals. Nickel and cobalt alloys exhibit high burn resistances and are dense. The researchers next turned to ceramics, which they knew do not act as ignition sources. Unlike metals, ceramics are naturally burn-resistant. Unfortunately, they also exhibit low fracture toughnesses

Effect of dopants on thermal stability and self-diffusion in iron nitride thin films

We studied the effect of dopants (Al, Ti, Zr) on the thermal stability of iron nitride thin films prepared using a dc magnetron sputtering technique. Structure and magnetic characterization of deposited samples reveal that the thermal stability together with soft magnetic properties of iron nitride thin films get significantly improved with doping. To understand the observed results, detailed Fe and N self-diffusion measurements were performed. It was observed that N self-diffusion gets suppressed with Al doping whereas Ti or Zr doping results in somewhat faster N diffusion. On the other hand Fe self-diffusion seems to get suppressed with any dopant of which heat of nitride formation is significantly smaller than that of iron nitride. Importantly, it was observed that N self-diffusion plays only a trivial role, as compared to Fe self-diffusion, in affecting the thermal stability of iron nitride thin films. Based on the obtained results effect of dopants on self-diffusion process is discussed.Comment: 10 pages, 9 fig

Formation of iron nitride thin films with Al and Ti additives

In this work we investigate the process of iron nitride (Fe-N) phase formation using 2 at.% Al or 2 at.% Ti as additives. The samples were prepared with a magnetron sputtering technique using different amount of nitrogen during the deposition process. The nitrogen partial pressure (\pn) was varied between 0-50% (rest Argon) and the targets of pure Fe, [Fe+Ti] and [Fe+Al] were sputtered. The addition of small amount of Ti or Al results in improved soft-magnetic properties when sputtered using \pn $\leq$ 10\p. When \pn is increased to 50\p non-magnetic Fe-N phases are formed. We found that iron mononitride (FeN) phases (N at% $\sim$50) are formed with Al or Ti addition at \pn =50% whereas in absence of such addition \eFeN phases (N\pat$\sim$30) are formed. It was found that the overall nitrogen content can be increased significantly with Al or Ti additions. On the basis of obtained result we propose a mechanism describing formation of Fe-N phases Al and Ti additives.Comment: 9 Pages, 7 Figure

Fe and N self-diffusion in non-magnetic Fe:N

Fe and N self-diffusion in non-magnetic FeN has been studied using neutron reflectivity. The isotope labelled multilayers, FeN/57Fe:N and Fe:N/Fe:15N were prepared using magnetron sputtering. It was remarkable to observe that N diffusion was slower compared to Fe while the atomic size of Fe is larger compared to N. An attempt has been made to understand the diffusion of Fe and N in non-magnetic Fe:N

Integrating precipitation forecasts and climate prediction with basin scale hydroclimatic modelling in the Himalayas: report of scientific workshop May 2018

The India-UK Water Centre (IUKWC) promotes cooperation and collaboration between the complementary priorities of NERC-MoES water security research. This report represents an overview of the participation, activities and conclusions at a Science Workshop held at the Wildlife Institute of India, Dehradun, Uttarakhand, India, between the 2nd and 4th of May 2018. It was convened by the India UK Water Centre and led by Dr Martin Widmann of the University of Birmingham, UK and Dr Shresth Tayal of The Energy and Resource Institute (TERI), India. This inter-disciplinary workshop aimed to foster the integration of weather forecast and climate models with glacio-hydrological models for the Himalayas, which is crucial for the improvement of short-, medium-, and long-term hydrological predictions for Himalayan basins. By bringing together scientist from India and the UK it led to a detailed understanding of the key challenges related to data scarcity, process understanding, development and validation of meteorological and hydrological models, and to downscaling and bias adjustment methods. Based on this, a number of specific steps forward were suggested, which partly can be implemented in the near future using inter-disciplinary and inter-institutional synergies, and partly require additional resources and longer implementation periods. The report is intended for the workshop participants, IUKWC Open Network members and stakeholders

Hemodynamic determinants of left atrial strain in patients with hypertrophic cardiomyopathy:A combined echocardiography and CMR study

BackgroundLeft atrial (LA) strain is associated with symptomatic status and atrial fibrillation in patients with hypertrophic cardiomyopathy (HCM). However, hemodynamic determinants of LA reservoir (LARS), conduit, and pump strains have not been examined and data are needed on the relation of LA strain with exercise tolerance in HCM.MethodsFifty HCM patients with echocardiographic and CMR imaging within 30 days were included. Left ventricular (LV) volumes, mass, EF, scar extent, extracellular volume fraction (ECV), and LA maximum volume were measured by CMR. Echo studies were analyzed for mitral inflow, pulmonary vein flow, mitral annulus tissue Doppler velocities, LV global longitudinal strain, and LA strain. Twenty six patients able and willing to exercise underwent cardiopulmonary stress testing for peak oxygen consumption (MVO2), and VE/VCO2 slope. Patients were followed for clinical events.FindingsLARS was significantly associated with indices of LA systolic function, LV GLS, and LV filling pressures (PConclusionsLV structure, systolic and diastolic function, and LA systolic function determine the 3 components of LA strain. LA strain is associated with exercise tolerance and clinical events in patients with HCM

Radiative transition rates and collision strengths for Si II

Aims. This work reports radiative transition rates and electron impact excitation collision strengths for levels of the 3s23p, 3s3p2, 3s24s, and 3s23d configurations of Siii. Methods. The radiative data were computed using the Thomas-Fermi-Dirac-Amaldi central potential, but with the modifications introduced by Bautista (2008) that account for the effects of electron-electron interactions. We also introduce new schemes for the optimization of the variational parameters of the potential. Additional calculations were carried out with the Relativistic Hartree-Fock and the multiconfiguration Dirac-Fock methods. Collision strengths in LS-coupling were calculated in the close coupling approximation with the R-matrix method. Then, fine structure collision strengths were obtained by means of the intermediate-coupling frame transformation (ICFT) method which accounts for spin-orbit coupling effects. Results. We present extensive comparisons between the results of different approximations and with the most recent calculations and experiment available in the literature. From these comparisons we derive a recommended set of gf- values and radiative transition rates with their corresponding estimated uncertainties. We also study the effects of different approximations in the representation of the target ion on the electron-impact collision strengths. Our most accurate set of collision strengths were integrated over a Maxwellian distribution of electron energies and the resulting effective collision strengths are given for a wide range of temperatures. Our results present significant differences from recent calculations with the B-spline non-orthogonal R-matrix method. We discuss the sources of the differences.Comment: 6 figures, 5 tables within text, 2 electronic table