Magnetophononics: ultrafast spin control through the lattice

Using a combination of first-principles and magnetization-dynamics calculations, we study the effect of the intense optical excitation of phonons on the magnetic behavior in insulating magnetic materials. Taking the prototypical magnetoelectric \CrO\ as our model system, we show that excitation of a polar mode at 17 THz causes a pronounced modification of the magnetic exchange interactions through a change in the average Cr-Cr distance. In particular, the quasi-static deformation induced by nonlinear phononic coupling yields a structure with a modified magnetic state, which persists for the duration of the phonon excitation. In addition, our time-dependent magnetization dynamics computations show that systematic modulation of the magnetic exchange interaction by the phonon excitation modifies the magnetization dynamics. This temporal modulation of the magnetic exchange interaction strengths using phonons provides a new route to creating non-equilibrium magnetic states and suggests new avenues for fast manipulation of spin arrangements and dynamics.Comment: 11 pages with 7 figure

“The Golden Door”: Does Business Hold the Key?

“The New Colossus,” Emma Lazarus’ poem, although a later addition to Liberty Island, has now become synonymous with the Statue of Liberty itself. Its words, however, are not without controversy. Was Lazarus arguing that the United States is morally obligated to open her door to the poor and the oppressed? If so, what role does/should business play in granting immigrants entry? The poem frames this discussion of a contemporary understanding of what it means to be human in a global society and, building on this concept, the paper evaluates current US employment-based immigration law and suggests a paradigm to assess future policy

Additive manufacturing of Oxide Dispersion Strengthened (ODS) alloys

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High temperature isothermal oxidation behaviour of an oxide dispersion strengthened derivative of IN625

Gas atomised IN625 powder was mechanically alloyed with <1·0 Wt.% nano-yttria and consolidated by spark plasma sintering (SPS) to produce an oxide dispersion strengthened (ODS) alloy. The isothermal oxidation rate constant of the ODS alloy, and wrought IN625, was determined by thermogravimetric analysis. This was performed at 900 °C in static laboratory air for exposure times of up to 1000 h. It was found that the ODS alloy oxidised ~40x slower than wrought IN625, which is attributed to the reactive element effect. It is further proposed that the improvement in oxidation resistance of the ODS alloy, and the superior morphology of the oxide scale formed on the ODS alloy, may be related to the presence of Nb carbide, rather than δ-phase, in the ODS alloy

Microstructure and oxide particle stability in a novel ODS γ-TiAl alloy processed by spark plasma sintering and laser additive manufacturing

In this work, a novel oxide dispersion strengthened titanium aluminide alloy (Ti-45Al-3Nb-<0.2Y2O3 at.%) was developed for powder-based processing technologies with a focus on spark plasma sintering and additive manufacturing. Titanium aluminides are promising structural intermetallics for weight reduction and an increased performance of high temperature components. The alloy design and selection process was supported by computational thermodynamics based on the CALPHAD approach, taking into account requirements for processing as well as long term alloy behavior under service conditions. Processing trials using spark plasma sintering, direct metal deposition and selective laser melting were conducted to study the alloy behavior, microstructure formation and introduction as well as stability of the ODS particles. Additionally, thermal annealing on the sintered and laser consolidated material was performed. Conventional dual phase α2-Ti3Al and γ-TiAl duplex and near-lamellar microstructures were obtained from the processed material. The ODS particles were homogeneously distributed in the alloy matrix after processing in the liquid state. For the direct metal deposition process, the novel alloy was compared to the established GE48-2-2 alloy (Ti-48Al-2Cr-2Nb) in terms of phases, microstructure and texture after processing. A significantly reduced texture formation was observed with the novel alloy. The hardness of the consolidated material shows superior properties for ODS-containing TiAl compared to ODS-free material. This work provides a first step towards tailored alloys for AM and the production of ODS TiAl alloys

THE CONCEPT OF MORTALITY IN ERNEST BECKER: A FOUNDATION FOR A CONTEMPORARY THEOLOGY

This dissertation is a work of fundamental theology which utilizes Ernest Becker\u27s analysis of the human experience of mortality and the biblical passages dealing with death as sources. As such, it studies and evaluates Becker\u27s concept of mortality and correlates it with biblical reflections on death in the fashion suggested by David Tracy. Although the value of Becker\u27s analysis of the human condition is often noted, to date no major study of his thought has been undertaken. In view of this lack, this dissertation critically examines Becker\u27s concept of mortality from the perspectives of psychology, social theory and theology. Moreover, these perspectives are not only studied separately, but are integrated into a model of the human person which is characterized by a dialectic between immortality and mortality. This model of the human person indicates that mortality constitutes a central human experience of religious significance. Its religious value lies in the fact that awareness of mortality urges people to acknowledge their creatureliness. Once mortality is established as a religious concept, it is brought into dialogue with the biblical passages dealing with death. Although it would be possible to utilize these sources in a variety of ways, this dissertation focuses on their theistic components. Correlating the experiential and scriptural concepts of mortality gives rise to a notion of God as a living, compassionate, saving Creator. Based on Becker\u27s analysis of mortality, the author contends that existentialism provides the philosophical framework in which such a concept of God can be understood. More specifically, the ontology of Paul Tillich is utilized for this task. Although Becker\u27s concept of mortality demands that Tillich\u27s system be revised to admit that the situation not only gives rise to the question of God but also points to the answer, with this modification it is judged to provide a framework for understanding God that is in keeping with the exigencies of both the experiential and biblical sources