53 research outputs found
Suppressed superconductivity in ultrathin Mo2N films due to pair-breaking at the interface
A strong disorder characterized by a small product of the Fermi vector kF and
the electron mean free l drives superconductors towards insulating state. Such
disorder can be introduced by making the films very thin. Here, we present 3-nm
Mo2N film with k_F*l ~ 2 with a resistive superconducting transition
temperature Tc = 2 K heavily suppressed in comparison with the bulk Tc.
Superconducting density of states (DOS) with smeared gap-like peaks and in-gap
states, so called Dynes DOS, is observed by the low temperature tunneling
spectroscopy despite a sharp resistive transition. By scanning tunneling
microscope the spectral maps are obtained and related to the surface
topography. The maps show a spatial variation of the superconducting energy gap
on the order of 20 % which is not accidental but well correlates with the
surface corrugation: protrusions reveal larger gap, smaller spectral smearing
and smaller in-gap states. In agreement with our previous measurements on
ultrathin MoC films we suggest that the film-substrate interface introducing
the local pair-breaking is responsible for the observed effects and generally
for the suppression of the superconductivity in these ultrathin films.Comment: Manuscript with 3 Figure
Disorder- and magnetic field-tuned fermionic superconductor-insulator transition in MoN thin films. Transport and STM studies
Superconductor-insulator transition (SIT) driven by disorder and transverse
magnetic field has been investigated in ultrathin MoN films by means of
transport measurements and scanning tunneling microscopy and spectroscopy. Upon
decreasing thickness, the homogeneously disordered films show increasing sheet
resistance Rs, shift of the superconducting transition Tc to lower temperatures
with the 3 nm MoN being the last superconducting film and thinner films already
insulating. Fermionic scenario of SIT is evidenced by applicability of the
Finkelsteins model, by the fact that Tc and the superconducting gap are coupled
with a constant ratio, and by the spatial homogeneity of the superconducting
and electronic characteristics. The logarithmic anomaly found in the tunneling
spectra of the non-superconducting films is further enhanced in increased
magnetic field due to the Zeeman spin effects driving the system deeper into
the insulating state and pointing also to fermionic SIT.Comment: Manuscript (6 Figures) including Supplemental Materials (7 Figures
First Principles Calculations of Fe on GaAs (100)
We have calculated from first principles the electronic structure of 0.5
monolayer upto 5 monolayer thick Fe layers on top of a GaAs (100) surface. We
find the Fe magnetic moment to be determined by the Fe-As distance. As
segregates to the top of the Fe film, whereas Ga most likely is found within
the Fe film. Moreover, we find an asymmetric in-plane contraction of our
unit-cell along with an expansion perpendicular to the surface. We predict the
number of Fe 3d-holes to increase with increasing Fe thickness on -doped
GaAs.Comment: 9 pages, 14 figures, submitted to PR
Analysis of Microplastics in Food Samples
This chapter presents a compilation of the analytical techniques used to detect and analyze microplastics in food. A detailed description of microplastics found in different samples is provided as well as an estimate of the annual intake of these particles. A total of 22–37 milligrams of microplastics per year was found. The factors that can influence the presence of particles in food, especially table salt, are discussed, showing that a background presence of microplastics in the environment can explain a large amount of experimental data.Support for this work was provided by the CTQ2016-76608-R project from the Ministry of Economy, Industry and Competitiveness (Spain) and by the University of Alicante under the project UAUSTI18-06
Phenomenology After Conceptual Art
The reception of phenomenology in art criticism reached its apex in the mid-1960s in its application to Minimalism in the United States. The focus was on the embodied, direct perceptual experience of Minimalist sculpture, but in light of Conceptual art’s ‘dematerialised’ practices, which developed as the decade progressed, the interest in phenomenology waned. This essay looks at the history of this reception and presents Merleau-Ponty’s late ontological work as a corrective to an inadequate understanding of phenomenology in critical discourses on art at the time. It argues that the late Merleau-Ponty offers tools for an effective critique of early conceptualism’s idealism, as well as a basis on which the ‘dematerialised’ and dispersed ontology of the art work shared by both Conceptual and more recent Post-Conceptual practices can be investigated
Variação espacial de cátions, ânions e variáveis físico-químicas no rio Solimões-Amazonas entre Manaus e Jutaí, bacia amazônica
Cátions e ânions majoritários são espécies químicas de grande importância nos diversos compartimentos aquáticos, porém, pouco abordados de forma exclusiva na bacia amazônica. Neste sentido, o objetivo deste estudo foi avaliar a dinâmica espacial de Na+, Ca2+, K+, Mg2+, Cl- e SO4 2- em um trecho do rio Solimões-Amazonas, levando-se em consideração a alcalinidade, potencial hidrogeniônico (pH), condutividade elétrica (CE), sólidos totais em suspensão (STS) e carbono orgânico total (COT). As coletas foram realizadas em maio, julho e setembro de 2012 em sete pontos na calha principal do rio Solimões-Amazonas e na foz de alguns dos principais tributários: rios Jutaí, Juruá, Japurá e Purus. Os cátions e ânions foram analisados por cromatografia de íons, STS por gravimetria, pH por potenciometria, alcalinidade por titulação potenciométrica, CE por condutimetria e o COT por oxidação catalítica por combustão. As concentrações médias dos cátions seguiram esta ordem Ca2+>Na+>Mg2+>K+ e dos ânions SO4 2->Cl-. De montante à jusante a tendência foi diminuição nas concentrações de cátions e ânions, das variáveis pH, CE, STS e alcalinidade, além do aumento das concentrações de COT. O presente estudo evidenciou mudanças nas características químicas sofridas pelo rio Solimões em seu curso. O aporte dos tributários pode ser apontado como um dos fatores responsáveis por essas modificações
Origem e dinâmica da deposição dos sedimentos superficiais na Várzea do Lago Grande de Curuai, Pará, Brasil
Biodiversity inventories in high gear: DNA barcoding facilitates a rapid biotic survey of a temperate nature reserve
Comprehensive biotic surveys, or ‘all taxon biodiversity inventories’ (ATBI), have traditionally been limited in scale or scope due to the complications surrounding specimen sorting and species identification. To circumvent these issues, several ATBI projects have successfully integrated DNA barcoding into their identification procedures and witnessed acceleration in their surveys and subsequent increase in project scope and scale. The Biodiversity Institute of Ontario partnered with the rare Charitable Research Reserve and delegates of the 6th International Barcode of Life Conference to complete its own rapid, barcode-assisted ATBI of an established land trust in Cambridge, Ontario, Canada
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