Among topological solitons, magnetic skyrmions are two-dimensional particle-like objects with a continuous winding of the magnetization, and magnetic Hopfions are three-dimensional objects that can ...be formed from a closed loop of twisted skyrmion strings. Theoretical models suggest that magnetic Hopfions can be stabilized in frustrated or chiral magnetic systems, and target skymions can be transformed into Hopfions by adapting their perpendicular magnetic anisotropy, but their experimental verification has been elusive so far. Here, we present an experimental study of magnetic Hopfions that are created in Ir/Co/Pt multilayers shaped into nanoscale disks, known to host target skyrmions. To characterize three-dimensional spin textures that distinguish Hopfions from target skyrmions magnetic images are recorded with surface-sensitive X-ray photoemission electron microscopy and bulk-sensitive soft X-ray transmission microscopy using element-specific X-ray magnetic circular dichroism effects as magnetic contrast. These results could stimulate further investigations of Hopfions and their potential application in three-dimensional spintronics devices.
Purpose - The purpose of this paper is to provide a personalised view by the Editors of the Rapid Prototyping Journal.Design methodology approach - It collects their years of experience in a series ...of observations and experiences that can be considered as a snapshot of where this technology is today.Findings - Development of these technologies has progressed according to application, materials and how the designers have applied their creativity to such a unique manufacturing tool.Originality value - The paper predicts how the future of additive manufacturing will look from the perspective of three key elements: applications, materials and design.
Ian Campbell's poem series about an age-old jacaranda tree in a university courtyard is an artistic venture across three languages: French, Indonesian and English. The series initiated with a French ...poem composed in 1989, followed by an Indonesian rendition published in the literary section of a newspaper in Bandung, West Java, in 2004, and concluded with an English version. Campbell's trilingual poetic exploration demonstrates how a single 'concept,' or the essence of a poem transfigures when articulated in the languages he is conversant with. His approach is reflective of his work in an earlier issue of PORTAL-Vol. 14, No 1, April 2017-which displayed thematic unity across poems in English, Spanish and Indonesian.
InKnowledge and the Ends of Empire, Ian W. Campbell investigates the connections between knowledge production and policy formation on the Kazak steppes of the Russian Empire. Hoping to better govern ...the region, tsarist officials were desperate to obtain reliable information about an unfamiliar environment and population. This thirst for knowledge created opportunities for Kazak intermediaries to represent themselves and their landscape to the tsarist state. Because tsarist officials were uncertain of what the steppe was, and disagreed on what could be made of it, Kazaks were able to be part of these debates, at times influencing the policies that were pursued.
Drawing on archival materials from Russia and Kazakhstan and a wide range of nineteenth-century periodicals in Russian and Kazak, Campbell tells a story that highlights the contingencies of and opportunities for cooperation with imperial rule. Kazak intermediaries were at first able to put forward their own idiosyncratic views on whether the steppe was to be Muslim or secular, whether it should be a center of stock-raising or of agriculture, and the extent to which local institutions needed to give way to imperial institutions. It was when the tsarist state was most confident in its knowledge of the steppe that it committed its gravest errors by alienating Kazak intermediaries and placing unbearable stresses on pastoral nomads. From the 1890s on, when the dominant visions in St. Petersburg were of large-scale peasant colonization of the steppe and its transformation into a hearth of sedentary agriculture, the same local knowledge that Kazaks had used to negotiate tsarist rule was transformed into a language of resistance.
Highlights • Postzygotic mutation is a common occurrence. • The developmental stage and timing of new mutations influence their phenotypic effects and likelihood of transmission. • All major classes ...of mutations are observed in the mosaic state. • Mathematical modeling of mosaicism can inform estimates of recurrence risk for new mutations.
It is now recognized that extensive maturational changes take place in the human brain during adolescence, and that the trajectories of these changes are best studied longitudinally. We report the ...first longitudinal study of the adolescent decline in non-rapid eye movement (NREM) delta (1-4 Hz) and theta (4-8 Hz) EEG. Delta and theta are the homeostatic frequencies of human sleep. We recorded sleep EEG in 9- and 12-year-old cohorts twice yearly over a 5-year period. Delta power density (PD) was unchanged between age 9 and 11 years and then fell precipitously, decreasing by 66% between age 11 and 16.5 years (P < .000001). The decline in theta PD began significantly earlier than that in delta PD and also was very steep (by 60%) between age 11 and 16.5 years (P < .000001). These data suggest that age 11-16.5 years is a critically important maturational period for the brain processes that underlie homeostatic NREM EEG, a finding not suggested in previous cross-sectional data. We hypothesize that these EEG changes reflect synaptic pruning. Comparing our data with published longitudinal declines in MRI-estimated cortical thickness suggests the theta age curve parallels the earlier maturational thinning in 3-layer cortex, whereas the delta curve tracks the later changes in 5-layer cortex. This comparison also reveals that adolescent declines in NREM delta and theta are substantially larger than decreases in cortical thickness (>60% vs. <20%). The magnitude, interindividual difference, and tight link to age of these EEG changes indicate that they provide excellent noninvasive tools for investigating neurobehavioral correlates of adolescent brain maturation.
SUR - otros puntos de vista Campbell, Ian
Portal (Sydney, N.S.W.),
03/2022, Letnik:
18, Številka:
1/2
Journal Article
Recenzirano
Odprti dostop
This suite of short poems with Latin American references draws from original versions written in Spanish in 2008 and early 2011. It follows on from other poems with Latin American references written ...by the poet in languages other than Spanish as part of the poet's interest in 'trilingual poetics.' Spanish is not the first language of the writer nor is the poet of Latin American heritage. It is part of a corpus of poems which aims to explore the potentialities of multiple language perspectives associated with or derived from a single poetic theme or set of themes. It is also part of the poet's explorations of what can be derived from some identification as a poet 'of the south.'
The shape of chondrite normalized zircon rare earth element (REE) patterns, including the magnitude of the Cerium (Ce) and Europium (Eu) anomalies, provide valuable insights into the magmatic ...conditions under which a zircon formed. However, lanthanum (La) and praseodymium (Pr), which are essential for the calculation of Ce anomalies, are often present at concentrations close to or below the detection limit of most analytical methods. We propose two new methods to calculate missing REE, based on Onuma diagrams (Chondrite-Onuma) and the lattice strain theory (Chondrite-Lattice), but using chondrite normalized values instead of partition coefficients. We compiled a dataset of ~ 1500 zircons with known REE + Y concentrations and used it to test and calibrate these methods and demonstrate that they are more accurate than other previously published models, with the Chondrite-Onuma method performing better than the Chondrite-Lattice method. These methods require analyses of as few as five REEs to impute the missing REE data or to estimate La and Pr concentrations or Ce anomalies in magmatic zircons, which allows a reduction in the number of REE analysed, where desirable, or to impute missing REEs in legacy data. The imputeREE package for the R programming language was written with a set of tools to apply these methods. A companion app is available to calculate missing REE and Ce and Eu anomalies.
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