413 research outputs found

    Epitaxial Co2Cr0.6Fe0.4Al thin films and magnetic tunneling junctions

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    Epitaxial thin films of the theoretically predicted half metal Co2Cr0.6Fe0.4Al were deposited by dc magnetron sputtering on different substrates and buffer layers. The samples were characterized by x-ray and electron beam diffraction (RHEED) demonstrating the B2 order of the Heusler compound with only a small partition of disorder on the Co sites. Magnetic tunneling junctions with Co2Cr0.6Fe0.4Al electrode, AlOx barrier and Co counter electrode were prepared. From the Julliere model a spin polarisation of Co2Cr0.6Fe0.4Al of 54% at T=4K is deduced. The relation between the annealing temperature of the Heusler electrodes and the magnitude of the tunneling magnetoresistance effect was investigated and the results are discussed in the framework of morphology and surface order based of in situ STM and RHEED investigations.Comment: accepted by J. Phys. D: Appl. Phy

    Powers of componentwise linear ideals

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    We give criteria for graded ideals to have the property that all their powers are componentwise linear. Typical examples to which our criteria can be applied include the vertex cover ideals of certain finite graphs

    Koszul binomial edge ideals

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    It is shown that if the binomial edge ideal of a graph GG defines a Koszul algebra, then GG must be chordal and claw free. A converse of this statement is proved for a class of chordal and claw free graphs

    Pragmatic

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    A npresentation of Pragmatic 2014

    Brillouin light scattering study of Co2_{2}Cr0.6_{0.6}Fe0.4_{0.4}Al and Co2_{2}FeAl Heusler compounds

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    The thermal magnonic spectra of Co2_{2}Cr0.6_{0.6}Fe0.4_{0.4}Al (CCFA) and Co2_2FeAl were investigated using Brillouin light scattering spectroscopy (BLS). For CCFA, the exchange constant A (exchange stiffness D) is found to be 0.48 ÎĽ\muerg/cm (203 meV A2^2), while for Co2_2FeAl the corresponding values of 1.55 ÎĽ\muerg/cm (370 meV A2^2) were found. The observed asymmetry in the BLS spectra between the Stokes and anti-Stokes frequencies was assigned to an interplay between the asymmetrical profiles of hybridized Damon-Esbach and perpendicular standing spin-wave modes, combined with the optical sensitivity of the BLS signal to the upper side of the CCFA or Co2_2FeAl film

    The environmental security debate and its significance for climate change

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    Policymakers, military strategists and academics all increasingly hail climate change as a security issue. This article revisits the (comparatively) long-standing “environmental security debate” and asks what lessons that earlier debate holds for the push towards making climate change a security issue. Two important claims are made. First, the emerging climate security debate is in many ways a re-run of the earlier dispute. It features many of the same proponents and many of the same disagreements. These disagreements concern, amongst other things, the nature of the threat, the referent object of security and the appropriate policy responses. Second, given its many different interpretations, from an environmentalist perspective, securitisation of the climate is not necessarily a positive development

    In and out and out again: The travails of Brazil as a security provider in Africa

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    The story of Brazil as a contemporary security actor in Africa can prove a peculiar one. Marked by quick gains and an equally quick recognition over a short period of time, it has also been followed by an equally quick turnaround which has led, as of 2020, to a visible disengagement on the ground. We explore the main travails in this domain, which have compromised much of the gains previously obtained throughout the continent. The chapter begins with a general balance of the progress achieved between 2003 and 2016, followed by the highlights of the recent downturn. We then analyze a specific sub-area, namely, the inroads carried out at the defence industry level, in order to showcase the promises and contradictions often associated to what the country has offered across the Atlantic. We conclude by presenting some opportunities for a new pickup of Brazilian interest in the middle and long run

    For richer or poorer in sickness for wealth: what price consumerism?

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    Affluence and material goods of varying types are portents of a millennium age consumer culture that encourages the masses to voluntarily participate in the need to buy, buy and buy! This trend to spend creates a purchasing fervour that preoccupies many consumers with the ongoing yearning to shop until they drop. Clever marketing tactics such as enticing smells, catchy jingles, prize-draw entries, lucrative sales, discounts and the recruitment of celebrities to advertise a range of different wares are just some of the ploys adopted by vendors and retailers to maintain the sustainability of this cycle of consumer spending. This scenario promotes what could be perceived as a never-ending desire to procure yet more products and merchandise, which can create social dilemmas such as personal debt due to, for example, impulse buying, excessive spending and unnecessary borrowing. Retailers and manufacturers are driven by a quest to sell so constantly tout their goods to tempt consumers including those with a need for personal and social respect, to take the bait in order to encourage them to keep buying. This, coupled with the rapid advances in technology over recent decades, has made it easier for consumers to shop, order, obtain and pay for their goods from the comfort of an armchair or via handheld devices, and all at a tap of a button. In essence, technology has added to, or even exacerbated, the materialistic consumer trend as witnessed across many global societies today – from the east and the west to the north and the south. But what impact does consumerism have on the well-being of humankind and, in turn, the environment? This chapter adopts a comparative approach to answer this question by exploring the implications of consumerism as a means for broadening the topic’s framework and to contribute to debates regarding consumerism, well-being, social dilemma, sustainability and techno-economics
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