Kondo resonance of a Co atom exchange coupled to a ferromagnetic tip

The Kondo effect of a Co atom on Cu(100) was investigated with a low-temperature scanning tunneling microscope using a monoatomically sharp nickel tip. Upon a tip-Co contact, the differential conductance spectra exhibit a spin-split asymmetric Kondo resonance. The computed ab initio value of the exchange coupling is too small to suppress the Kondo effect, but sufficiently large to produce the splitting observed. A quantitative analysis of the line shape using the numerical renormalization group technique indicates that the junction spin polarization is weak.Comment: 5 pages, 4 figure

Modifying the Cu(111) Shockley surface state by Au alloying

The deposition of submonolayer amounts of Au onto Cu(111) results in a Au-Cu surface alloy with temperature- and thickness-dependent stoichiometry. Upon alloying, the characteristic Shockley state of Cu(111) is modified, shifting to 0.53 eV binding energy for a particular surface Au2Cu concentration, which is a very high binding energy for a noble-metal surface. Based on a phase accumulation model analysis, we discuss how this unusually large shift is likely reflecting an effective increase in the topmost layer thickness of the order of, but smaller than, the value expected from the moiré undulation. © 2012 American Physical Society.This work was supported in part by the Spanish MINECO (Grants No. MAT2010-21156-C03-01 and No. MAT2010-21156-C03-03), and the Basque Government (Grant No. IT-257-07). The SRC is funded by the National Science Foundation (Award No. DMR-0084402).Peer Reviewe

Comparison Between the Material Improvement of the Megarok and San José Quarries, Applying the AASTHO Standards

Comparative analyzes were carried out between the materials of the Magarok and San José quarries, taking into account AASTHO standards with the objective of being used as a base / sub-base in the pavement structure. The asphalt emulsion material was stabilized to increase the strength and give the material sub-base and / or base characteristics, with a suitable mixing design, obtaining results with suitable characteristics to be used in the pavement structure composed of a 65 % Asphalt AC 20; 34.30% water and 0.70% ASFIER 121 emulsions, with good resistance to the stability of the materials

Ballast Treated with Asphalt Emulsion, Megarok and San Jose. AASTHO Standards

In the research work, the results obtained at the laboratory level of the lending material (ballast) treated with asphalt emulsion from the quarries "Megarok and San José" are compared, applying the AASTHO standards. The quarries are located in the Picoazá-La Sequita parish of the Portoviejo canton. Samples from both quarries were evaluated in the laboratory and it was possible to carry out tests of natural humidity, Atterberg, granulometric, compaction, and soil bearing capacity (CBR). Based on the results obtained, they were compared by disclosing which of the quarries meets the appropriate conditions within the construction standards and techniques, in order to stabilize the material with asphalt emulsion; in addition to comparing it with the specifications of the AASTHO standards and the MTOP standard. The result was that the materials extracted from the quarries do not meet the technical specifications; but when mixed with the asphalt emulsion, the Megarok material fulfills as type A base

Modern pollen-vegetation relationships along a steep temperature gradient in the Tropical Andes of Ecuador

This is the author accepted manuscript. The final version is available from Cambridge University Press via the DOI in this record.The characterization of modern pollen rain assemblages along environmental gradients is an essential prerequisite for reliable interpretations of fossil pollen records. In this study, we identify pollen-vegetation relationships using modern pollen rain assemblages in moss polsters (n = 13) and lake sediment surface samples (n = 11) along a steep temperature gradient of 7°C (3100–4200 m above sea level) on the western Andean Cordillera, Ecuador. The pollen rain is correlated to vascular plant abundance data recorded in vegetation relevées (n = 13). Results show that pollen spectra from both moss polsters and sediment surface samples reflect changes in species composition along the temperature gradient, despite overrepresentation of upper montane forest taxa in the latter. Estimated pollen transport distance for a lake (Laguna Llaviucu) situated in a steep upper montane forest valley is 1–2 km, while a lake (Laguna Pallcacocha) in the páramo captures pollen input from a distance of up to 10–40 km. Weinmannia spp., Podocarpus spp., and Hedyosmum sp. are indicators of local upper montane forest vegetation, while Phlegmariurus spp. and Plantago spp. are indicators for local páramo vegetation.Earth and Life Science council (ALW) of the Netherlands Organisation of Scientific Researc

Desarrollo de alumnos talentosos en la educación superior técnica tecnológica de Ecuador. Caso de estudio: Integración a un concurso académico externo (Experiencias)

The effects of the memories of the integration of a talented student of the Ecuadorian technological technical higher education in an external academic contest are described. The methodological process is based on the achievement of three phases: the first for the selection and preparation of the student, the second for the development of the contest, and phase three to evaluate the skills acquired by the student after their participation. The experience and learning of the successful participation in the event falls mainly on the strengthening of behavioral competencies related to perseverance to achieve and complete the goals set, effective performance during collaborative work, the development of relationships, effective social and self-recognition as an individual who contributes to a certain social niche and to the productive sector for which he has been trained. The results established the linking of talented students to external competitions as a valid strategy for developing competencies, mainly behavioral, which, for reasons and conditions specific to this type of student, have not been able to be potentiated in the classroom.En este artículo se describen las memorias de la integración de una estudiante talentosa de la formación superior técnica tecnológica ecuatoriana en un concurso académico externo. El proceso metodológico se basa en la consecución de tres fases: la primera, para la selección y preparación de la estudiante; la segunda, para el desarrollo del concurso; y la tercera, para evaluar las competencias adquiridas por la estudiante tras su participación. La experiencia y los aprendizajes de la participación exitosa en el evento recaen principalmente sobre el fortalecimiento de las competencias de tipo conductuales, relacionadas con la perseverancia para alcanzar y concluir las metas trazadas, el desempeño eficaz durante el trabajo colaborativo, el desarrollo de relaciones sociales efectivas y el autorreconocimiento como individuo que aporta a un determinado nicho social y al sector productivo para el cual se ha formado. Los resultados alcanzados posesionan a la vinculación de alumnos talentosos a los concursos externos como una estrategia válida para el desarrollo de competencias, principalmente conductuales, que por razones y condiciones propias de este tipo de estudiantes no se han podido potencializar en las aulas

Vibron-assisted spin excitation in a magnetically anisotropic nickelocene complex

The ability to electrically-drive spin excitations in molecules with magnetic anisotropy is key for high-density storage and quantum-information technology. Electrons, however, also tunnel via the vibrational excitations unique to a molecule. The interplay of spin and vibrational excitations offers novel routes to study and, ultimately, electrically manipulate molecular magnetism. Here we use a scanning tunneling microscope to electrically induce spin and vibrational excitations in a single molecule consisting of a nickelocene magnetically coupled to a Ni atom. We evidence a vibron-assisted spin excitation at an energy one order of magnitude higher compared to the usual spin excitations of nickelocene and explain it using first-principles calculations that include electron correlations. Furthermore, we observe that spin excitations can be quenched by modifying the Ni-nickelocene coupling. Our study suggests that nickelocene-based complexes constitute a model playground for exploring the interaction of spin and vibrations in the electron transport through single magnetic molecules

Vibron-assisted spin excitation in a magnetically anisotropic molecule

The electrical control and readout of molecular spin states are key for high-density storage. Expectations are that electrically-driven spin and vibrational excitations in a molecule should give rise to new conductance features in the presence of magnetic anisotropy, offering alternative routes to study and, ultimately, manipulate molecular magnetism. Here, we use inelastic electron tunneling spectroscopy to promote and detect the excited spin states of a prototypical molecule with magnetic anisotropy. We demonstrate the existence of a vibron-assisted spin excitation that can exceed in energy and in amplitude a simple excitation among spin states. This excitation, which can be quenched by structural changes in the magnetic molecule, is explained using first-principles calculations that include dynamical electroniccorrelations.We thank M. Ternes for providing his fitting program. This work was supported by the Agence Nationale de la Recherche (grants No. ANR-13-BS10-0016, ANR-11-LABX-0058 NIE and ANR-10-LABX-0026 CSC) and by the Agencia Española de Investigación (grants Nos. MAT2016-78293-C6-1-R and MDM-2016-0618). D.-J.C. and N.L. thank the MICINN (project RTI2018-097895-B-C44). M.-L.B. thanks the national computational center CINES and TGCC (GENCI project: A0030807364)