On the Fe Enrichment during Anodic Polarization of Mg and Its Impact on Hydrogen Evolution

Iron (Fe) is an unintentional impurity present in pure magnesium (Mg) and Mg alloys, albeit nominally in low and innocuous concentrations (\u3c 100 ppmw). Since Fe, like most metals, is more noble than Mg, the presence of Fe impurities can serve as cathodic sites within the Mg matrix. During anodic polarization of Mg, incongruent dissolution can lead to undissolved Fe impurities accumulating upon the Mg surface, permitting an increase in the overall rate of hydrogen evolution. The experimental manifestation of the incongruent dissolution of Mg, has not yet been clarified, wherein, the extent and efficiency of Fe enrichment during anodic polarization is not known, and also the increase in the hydrogen evolution rate due to Fe enrichment has not been quantified. In this work, Mg specimens with Fe concentration between 40 to 13,000 ppmw were examined in 0.1 M NaCl to obtain a quantitative relation between the Fe concentration and the rate of cathodic hydrogen evolution. These base-line alloys were then anodically polarized to facilitate surface Fe enrichment, and subsequently again cathodically polarized to determine the impact of prior dissolution and Fe enrichment on the subsequent hydrogen evolution. A simple model to predict Fe enrichment was used to analyze the electrochemical data and predict the extent and efficiency of Fe enrichment

Intrinsic and Atomic Layer Etching Enhanced Area-Selective Atomic Layer Deposition of Molybdenum Disulfide Thin Films

For continual scaling in microelectronics, new processes for precise high volume fabrication are required. Area-selective atomic layer deposition (ASALD) can provide an avenue for self-aligned material patterning and offers an approach to correct edge placement errors commonly found in top-down patterning processes. Two-dimensional transition metal dichalcogenides also offer great potential in scaled microelectronic devices due to their high mobilities and few-atom thickness. In this work, we report ASALD of MoS2 thin films by deposition with MoF6 and H2S precursor reactants. The inherent selectivity of the MoS2 atomic layer deposition (ALD) process is demonstrated by growth on common dielectric materials in contrast to thermal oxide/ nitride substrates. The selective deposition produced few layer MoS2 films on patterned growth regions as measured by Raman spectroscopy and time-of-flight secondary ion mass spectrometry. We additionally demonstrate that the selectivity can be enhanced by implementing atomic layer etching (ALE) steps at regular intervals during MoS2 growth. This area-selective ALD process provides an approach for integrating 2D films into next-generation devices by leveraging the inherent differences in surface chemistries and providing insight into the effectiveness of a supercycle ALD and ALE process

Detection of Topological Spin Textures via Nonlinear Magnetic Responses

Topologically nontrivial spin textures, such as skyrmions and dislocations, display emergent electrodynamics and can be moved by spin currents over macroscopic distances. These unique properties and their nanoscale size make them excellent candidates for the development of next-generation race-track memory and unconventional computing. A major challenge for these applications and the investigation of nanoscale magnetic structures in general is the realization of suitable detection schemes. We study magnetic disclinations, dislocations, and domain walls in FeGe and reveal pronounced responses that distinguish them from the helimagnetic background. A combination of magnetic force microscopy (MFM) and micromagnetic simulations links the response to the local magnetic susceptibility, that is, characteristic changes in the spin texture driven by the MFM tip. On the basis of the findings, which we explain using nonlinear response theory, we propose a read-out scheme using superconducting microcoils, presenting an innovative approach for detecting topological spin textures and domain walls in device-relevant geometries

A review of freshwater gastropod conservation: challenges and opportunities

North American freshwater gastropods remain an understudied, yet critically imperiled, fauna. As part of a larger discussion on freshwater mollusks in this special issue, we review 4 specific areas of concern regarding freshwater gastropods and discuss how best to address those concerns in the context of conservation. Areas of concern include freshwater gastropod conservation strategies, taxonomy and systematics, ecological research, and conservation challenges. We illustrate how each of these topics relates to conservation efforts and discuss opportunities to improve our baseline knowledge of freshwater gastropod taxonomy, ecology, and conservation. We emphasize throughout that effective conservation strategies require the participation of as many affected and interested groups, from local communities to governmental agencies, as possible for successful implementation and management. We offer suggestions for the direction of cooperative conservation with regard to freshwater gastropods. The freshwater gastropod fauna of the USA and Canada consists of 842 nominal taxa (NatureServe 2007). This fauna is increasingly imperiled by river regulation, habitat loss, poor water quality, reduced water quantity, and invasive species. Estimates suggest that .40% of freshwater snail species are negatively affected by anthropogenic factors (Neves et al. 1997), resulting in many extinctions in North America (Master et al. 2000). More than 60% of the total nominal freshwater snail fauna have global ranks of G1 (critically imperiled), G2 (imperiled), or GH–GX (presumed or possibly extinct; Fig. 1), and recent extinctions support these rankings (Sada and Vinyard 2002, Hershler et al. 2007). Less than ¼ of all North American taxa are thought to be secure (G5) or apparently secure (G4; NatureServe 2007). The US Fish and Wildlife Service lists 23 species of snails as endangered or threatened (Table 1). Our objectives are to summarize what is known about freshwater gastropod conservation needs in North America (Brown et al. 2008, Perez and Minton 2008), highlight critical knowledge gaps that negative-ly affect conservation efforts, and suggest a logical path for future work

When assessment defines the content—understanding goals in between teachers and policy

© 2020 The Authors. The Curriculum Journal published by John Wiley & Sons Ltd on behalf of British Educational Research Association.Education policy development internationally reflect a widespread expansion of learning outcome orientation in policy, curricula and assessment. In this paper, teachers’ perceptions about their work are explored, as goals and assessment play a more prominent role driven by the introduction of a learning outcomes‐oriented system. This is investigated through interviews of Norwegian teachers and extensive policy analysis of Norwegian policy documents. The findings indicate that the teachers are finding ways to negotiate and adjust to the language in the policies investigated in this study. Furthermore, the findings show that the teachers have developed their professional language according to the policies. The teachers referred to their self‐made criteria and goal sheets as central tools in explicating what is to be learned. In many ways, the tools for assessment, thus determine the content of education as well as what is valued in the educational system.publishedVersio