Advances in Electron Beam Melting of Aluminum Alloys

The high thermal conductivity and melt pool optical reflectivity associated with aluminum alloys can pose significant challenges for direct-metal SFF processes. The use of SFF processes to produce aluminum parts is often not cost effective relative to CNC machining for simple geometries. However, the use of SFF techniques for aluminum alloys is justified for some applications such as aerospace forgings or high surface area heat exchangers. This paper describes recent progress in processing aluminum alloys using the Electron Beam Melting process. Structure and properties will be discussed, as well challenges associated with high vapor pressure alloying elements such as zinc and magnesium.Mechanical Engineerin

Pronouns, agreement and classifiers: What sign languages can tell us about linguistic diversity and linguistic universals

The search for linguistic universals (and understanding universals in the face of diversity) is one of the key issues in linguistics today. Yet the vast majority of the linguistic research has focused only on spoken languages. Sign languages constitute an important test case for theories on universals and diversity, since a language “universal” only deserves this name if it holds both for signed and spoken languages, and languages in a different modality surely have much to teach us about the full range of diversity within human language. In this paper I consider three morphosyntactic phenomena found in sign languages that have traditionally been assumed to be the same as spoken languages but which, on closer inspection, reveal some fundamental differences relating to particular affordances of the visual-spatial modality. In order to understand these differences in more detail, linguists must consider the multimodal nature of human language (including gesture) rather than just the classic linguistic characteristics which are the exclusive focus of much work in mainstream approaches to the study of language

Accent or not? Language attitudes towards regional variation in British Sign Language

British Sign Language (BSL) has been shown to have a high degree of regional variation especially at the lexical level. This study explores awareness and attitudes of the British deaf community towards this regional variation. We studied interview data from the BSL Corpus (http://bslcorpusproject.org/data) from 121 deaf, BSL signers from six regions across the UK including Belfast, Birmingham, Bristol, Glasgow, London and Manchester, focusing on responses to five questions in relation to regional variation in BSL. Responses were analysed using thematic analysis, following (Braun, V. & V. Clark. 2006. Using thematic analysis in psychology. Qualitative Research in Psychology 3(2). 77–101. https://doi.org/10.1191/1478088706qp063oa). Findings reveal that BSL signers exhibited overall high levels of meta-linguistic awareness, as many of their attitudes and beliefs were in line with what has been reported in relation to linguistic behaviour with BSL such as mouthing, fingerspelling and accommodation. In addition, BSL signers seem to place enormous value on regional variation in BSL, believing that such variation contributes to the richness of BSL as a language and puts it on equal footing with the surrounding majority language, i.e. English. We explore the implications of these attitudes towards a broader understanding of language ideologies, including the concept of accent

Unsolved problems in the lowermost mantle

Many characteristics of D '' layer may be attributed to the recently discovered MgSiO3 post-perovskite phase without chemical heterogeneities. They include a sharp discontinuity at the top of D '', regional variation in seismic anisotropy, and a steep Clapeyron slope. However, some features remain unexplained. The seismically inferred velocity jump is too large in comparison to first principles calculations, and the sharpness of the discontinuity may require a chemical boundary. Chemical heterogeneity may play an important role in addition to the phase transformation from perovskite to post-perovskite. Phase transformation and chemical heterogeneity and the attendant changes in physical properties, such as rheology and thermal conductivity, are likely to play competing roles in defining the dynamical stability of the D '' layer. Revealing the relative roles between phase transition and chemical anomalies is an outstanding challenge in the study of the role of D '' in thermal-chemical evolution of the Earth

WE\u27RE STILL EMERGING: A POETIC INQUIRY EXPLORING THE TENSIONS BETWEEN INCLUSIVE MINDSETS, TEACHER IDENTITY AND DISABILITY STIGMA

This poetic inquiry sought to understand the tensions, perspectives and experiences of teachers as they work to create more inclusive mindsets and identities despite working in a system that allows for ability profiling and disability stigma in schools. This work fills a gap in the literature in that not much is known about the journeys teachers take as they come to identify as inclusive educators. The conceptual framework drew from scholarship in the fields of Disability Studies in Education, Studies in Ableism, critical pedagogy, and teacher identity. Conducted in a professional development school, I worked as the university\u27s professor-in-residence to provide professional development for teachers that centered a disability memoir and critical reflection. Qualitative data was gathered through interviews and book club discussions. Lines from these transcripts were then used to construct transcription poems. After creating these initial poems, threshold poems were then created that juxtaposed a transcript poem with a found poem from each of the four key areas of the conceptual framework. These poems brought theory and praxis into dialogue, supplemented by my own analytical thinking inspired by the theorists\u27 and participants\u27 words. Significant findings indicate that: (1) ableism is deeply embedded in schools, policy and practice, with teachers inadvertently working from a place of dysconscious ableism; (2) inclusion must be presented as both an ideological commitment and actionable process; (3) teachers\u27 stories to live by must be reframed so that inclusive mindsets are magnified among the school community; and (4) PDSs partnerships can be a driving vehicle to develop inclusive cultures among schools

In or out? Spatial scale and enactment in narratives of native and nonnative signing deaf children acquiring British Sign Language

In this study we investigate the use of spatial scale and enactment (via constructed action, or CA) in British Sign Language (BSL) narratives of deaf native and nonnative signing children aged eight to ten. We find that the two types of prototypically aligned uses of spatial scale and enactment as described in the sign language literature (i.e. use of character scale with CA, and use of observer scale without CA) occur in both the native and nonnative signing children. We find that observer scale with CA is used by the non-native signing children but not the native signing children, and the opposite pattern with character scale without CA. These findings suggest that cognitive abilities such as perspective taking and the use of spatial scale should be considered along with linguistic abilities when looking at age of acquisition effects

Interference effects in two-photon ATI by multiple orders high harmonics with random or locked phases

We numerically study 2-photon processes using a set of harmonics from a Ti:Sapphire laser and in particular interference effects in the Above Threshold Ionization spectra. We compare the situation where the harmonic phases are assumed locked to the case where they have a random distribution. Suggestions for possible experiments, using realistic parameters are discussed.Comment: 11 pages, 13 figures, LaTe

Probing Catalyst Degradation in Metathesis of Internal Olefins: Expanding Access to Amine-Tagged ROMP Polymers

Ruthenium-promoted ring-opening metathesis polymerization (ROMP) offers potentially powerful routes to amine-functionalized polymers with antimicrobial, adhesive, and self-healing properties. However, amines readily degrade the methylidene and unsubstituted ruthenacyclobutane intermediates formed in metathesis of terminal olefins. Examined herein is the relevance of these decomposition pathways to ROMP (i.e., metathesis of internal olefins) by the third-generation Grubbs catalyst. Primary alkylamines rapidly quench polymerization via fast adduct formation, followed by nucleophilic abstraction of the propagating alkylidene. Bulkier, Brønsted-basic amines are less aggressive: attack competes only for slow polymerization or strong bases (e.g., DBU). Added HCl limits degradation, as demonstrated by the successful ROMP of an otherwise intractable methylamine monomer.publishedVersio

On the gravitational production of superheavy dark matter

The dark matter in the universe can be in the form of a superheavy matter species (WIMPZILLA). Several mechanisms have been proposed for the production of WIMPZILLA particles during or immediately following the inflationary epoch. Perhaps the most attractive mechanism is through gravitational particle production, where particles are produced simply as a result of the expansion of the universe. In this paper we present a detailed numerical calculation of WIMPZILLA gravitational production in hybrid-inflation models and natural-inflation models. Generalizing these findings, we also explore the dependence of the gravitational production mechanism on various models of inflation. We show that superheavy dark matter production seems to be robust, with Omega_X h^2 ~ (M_X / (10^11 GeV))^2 (T_RH / (10^9 GeV)), so long as M_X < H_I, where M_X is the WIMPZILLA mass, T_RH is the reheat temperature, and H_I is the expansion rate of the universe during inflation.Comment: 26 pages, 7 figures; LaTeX; submitted to Physical Review D; minor typographical error correcte