635 research outputs found

    Spin-orbit-coupled Bose-Einstein-condensed atoms confined in annular potentials

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    A spin-orbit-coupled Bose-Einstein-condensed cloud of atoms confined in an annular trapping potential shows a variety of phases that we investigate in the present study. Starting with the non-interacting problem, the homogeneous phase that is present in an untrapped system is replaced by a sinusoidal density variation in the limit of a very narrow annulus. In the case of an untrapped system there is another phase with a striped-like density distribution, and its counterpart is also found in the limit of a very narrow annulus. As the width of the annulus increases, this picture persists qualitatively. Depending on the relative strength between the inter- and the intra-components, interactions either favor the striped phase, or suppress it, in which case either a homogeneous, or a sinusoidal-like phase appears. Interactions also give rise to novel solutions with a nonzero circulation.Comment: Final, slightly revised versio

    Magnetic field dependence of hole levels in self-assembled InAs quantum dots

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    Recent magneto-transport experiments of holes in InGaAs quantum dots [D. Reuter, P. Kailuweit, A.D. Wieck, U. Zeitler, O. Wibbelhoff, C. Meier, A. Lorke, and J.C. Maan, Phys. Rev. Lett. 94, 026808 (2005)] are interpreted by employing a multi-band kp Hamiltonian, which considers the interaction between heavy hole and light hole subbands explicitely. No need of invoking an incomplete energy shell filling is required within this model. The crucial role we ascribe to the heavy hole-light hole interaction is further supported by one-band local-spin-density functional calculations, which show that Coulomb interactions do not induce any incomplete hole shell filling and therefore cannot account for the experimental magnetic field dispersion.Comment: 5 pages with 3 figures and one table. The paper has been submitted to Phys.Rev.

    Spin-orbit-enhanced Wigner localization in quantum dots

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    We investigate quantum dots with Rashba spin-orbit coupling in the strongly-correlated regime. We show that the presence of the Rashba interaction enhances the Wigner localization in these systems, making it achievable for higher densities than those at which it is observed in Rashba-free quantum dots. Recurring shapes in the pair-correlated densities of the yrast spectrum, which might be associated with rotational and vibrational modes, are also reported.Comment: 5 pages, 4 figure

    ‘There was no freedom to leave’: Global South international students in Portugal during the COVID-19 Pandemic

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    This article looks at the impact of the COVID-19 pandemic on international students, focusing on Portuguese-speaking African and Brazilian students during the lockdown of spring 2020. Using evidence from interviews conducted with 27 students domiciled in Portugal, we illustrate some of the challenges faced by students when coping with the pandemic, including difficulties in meeting the cost of tertiary education and the centrality of working to sustain their stays abroad, alongside the emotional impact of prolonged domestic confinement and separation from families. We also consider the paradoxes of online teaching, which have made visible the digital gap between local and international Global South students in the context of their stays. In this sense, pre-existing inequalities are more at the centre of students’ concerns than new issues raised by COVID-19, a pandemic that served to reveal former injustice in the context of global capitalism. In our conclusion, we argue that there is a need for greater recognition of the vulnerabilities facing certain African and Brazilian students at Global North universities in the context of contemporary neoliberalism, including their dependence upon precarious work. Policy responses include the need for a more serious involvement and responsibility by both home and host higher education institutions in the lives of their students abroad.info:eu-repo/semantics/acceptedVersio

    Lisbon, the Portuguese Erasmus city? Mis-match between representation in urban policies and international student experiences

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    This article looks at the mis-match between official discursive representations aimed at promoting Lisbon, the Portuguese capital city, as an international student hub and international students’ experiences. At a theoretical level, our work builds on the idea that re-branding a city’s image in terms of creativity, innovation and new technologies with a view to attract international students can foster less positive urban changes linked to gentrification, pushing overseas students away rather than attracting greater numbers. Discussion includes consideration of the success of policies at the municipal level that have aimed to use international students as a means to re-brand the city as a center for creativity and innovation, a part of the wider strategy of putting Lisbon on the map as a global learning destination. Analysis includes assessment of publicity materials advertising the city’s appeal to international students, juxtaposed with findings from interviews conducted with incoming students at the city’s universities during 2020. This material illustrates some of the most prominent contradictions, and arguably, a number of shortcomings, in the city’s imagological strategy, particularly in regard to concerns with Lisbon’s housing market.info:eu-repo/semantics/acceptedVersio

    Conclusion: Youth migration in the age of pandemic immobility

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    This concluding chapter takes account of recent developments in the field of public health. Had it not been for the global spread of Covid-19 in 2020, youth mobility might well have continued along its decades long course of global expansion and diversification, spreading into different forms of education, work and training, with the dividing line between mobility for these purposes and tourism continuing to blur. These concerns are no longer as pressing as they once were, and may not return to being high priorities for a very long time. Right now, writing in the middle of what has come to feel like an open-ended pandemic, all we can do is look at what has happened in the last few months and attempt to grasp some of the main consequences for young people who still wish or need to be mobile, in addition to engaging with the pressing problem of how to re-orient mobility practices that have stalled or never got off the ground, literally and figuratively. Additional concerns are evident in regard to how to maintain mobility systems at a time when institutions have closed their doors, again literally and figuratively, and are struggling to re-open in any meaningful sense of the word.info:eu-repo/semantics/acceptedVersio

    The tris formulation of Fluorouracil is more cardiotoxic than the sodium-salt formulations

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    The cardiotoxicity of 5-fluorouracil (FU) was attributed to degradation compounds present in the injected vials, fluoroacetaldehyde (Facet) and fluoromalonaldehydic acid (FMald). FU-NaOH vials were much less cardiotoxic than FU-Tris vials on the isolated perfused rabbit heart model since Facet and FMald are stored in stable depot forms in FU-Tris vials whereas, in FU-NaOH vials, they are extensively transformed. Cardiotoxic fluoroacetate (FAG), coming from Facet metabolization, was found in urine of patients, with a ratio FAC /FU catabolites 10-30 fold lower in patients treated with FU-NaOH than in those treated with FU-Tris

    Isospin phases of vertically coupled double quantum rings under the influence of perpendicular magnetic fields

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    Vertically coupled double quantum rings submitted to a perpendicular magnetic field BB are addressed within the local spin-density functional theory. We describe the structure of quantum ring molecules containing up to 40 electrons considering different inter-ring distances and intensities of the applied magnetic field. When the rings are quantum mechanically strongly coupled, only bonding states are occupied and the addition spectrum of the artificial molecules resembles that of a single quantum ring, with some small differences appearing as an effect of the magnetic field. Despite the latter has the tendency to flatten the spectra, in the strong coupling limit some clear peaks are still found even when B≠0B\neq 0 that can be interpretated from the single-particle energy levels analogously as at zero applied field, namely in terms of closed-shell and Hund's-rule configurations. Increasing the inter-ring distance, the occupation of the first antibonding orbitals washes out such structures and the addition spectra become flatter and irregular. In the weak coupling regime, numerous isospin oscillations are found as a function of BB.Comment: 27 pages, 11 figures. To be published in Phys. Rev.

    Cardiotoxicity of commercial 5-fluorouracil vials stems from the alkaline hydrolysis of this drug.

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    The cardiotoxicity of 5-fluorouracil (FU) was attributed to impurities present in the injected vials. One of these impurities was identified as fluoroacetaldehyde which is metabolised by isolated perfused rabbit hearts into fluoroacetate (FAC), a highly cardiotoxic compound. FAC was also detected in the urine of patients treated with FU. These impurities were found to be degradation products of FU that are formed in the basic medium employed to dissolve this compound. To avoid chemical degradation of this antineoplastic drug, the solution of FU that will be injected should be prepared immediately before use
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