Oxygen clamps in gold nanowires

We investigate how the insertion of an oxygen atom in an atomically thin gold nanowire can affect its rupture. We find, using ab initio total energy density functional theory calculations, that O atoms when inserted in gold nanowires form not only stable but also very strong bonds, in such a way that they can extract atoms from a stable tip, serving in this way as a clamp that could be used to pull a string of gold atoms.Comment: 4 pages; 4 figure

Followup Observations of SDSS and CRTS Candidate Cataclysmic Variables

We present photometry of 11 and spectroscopy of 35 potential cataclysmic variables from the Sloan Digital Sky Survey, the Catalina Real-Time Transient Survey and vsnet-alerts. The photometry results include quasi-periodic oscillations during the decline of V1363 Cyg, nightly accretion changes in the likely Polar (AM Herculis binary) SDSS J1344+20, eclipses in SDSS J2141+05 with an orbital period of 76+/-2 min, and possible eclipses in SDSS J2158+09 at an orbital period near 100 min. Time-resolved spectra reveal short orbital periods near 80 min for SDSS J0206+20, 85 min for SDSS J1502+33, and near 100 min for CSS J0015+26, RXS J0150+37, SDSS J1132+62, SDSS J2154+15 and SDSS J2158+09. The prominent HeII line and velocity amplitude of SDSS J2154+15 are consistent with a Polar nature for this object, while the lack of this line and a low velocity amplitude argue against this classification for RXS J0150+37. Single spectra of 10 objects were obtained near outburst and the rest near quiescence, confirming the dwarf novae nature of these objects.Comment: 34 pages, 14 figures, in press at A

Potencial de solubilização de fósforo in vitro por isolados fúngicos do solo.

FertBio 2010

Prospecção de comunidades bacterianas do solo para o aproveitamento agrícola de fosfatos de rocha.

FertBio 2010

Adiabatic dynamics in open quantum critical many-body systems

The purpose of this work is to understand the effect of an external environment on the adiabatic dynamics of a quantum critical system. By means of scaling arguments we derive a general expression for the density of excitations produced in the quench as a function of its velocity and of the temperature of the bath. We corroborate the scaling analysis by explicitly solving the case of a one-dimensional quantum Ising model coupled to an Ohmic bath.Comment: 4 pages, 4 figures; revised version to be published in Phys. Rev. Let

The Virtual Environments and Platforms in the Teaching of English

Abstract The research aims to highlight the significance of virtual learning environments and platforms in promoting cognitive competencies through interactive learning. The objective is to create effective learning environments by utilizing Virtual Learning Environments and implementing platforms to enhance communicative competencies. The methodology employed for this study includes quantitative and qualitative, descriptive, and predictive approaches, using technological innovation through the implementation of the Schoology platform based on the TPACK model. The results of the study indicate that students exhibit high levels of motivation and discernment toward virtual environments, particularly in English classes. Therefore, selecting appropriate didactic resources and incorporating pedagogical mediation is crucial for optimizing learning outcomes. It is essential to educate students on the significance of learning a foreign language and how it can impact the neural structure of the bilingual brain. Virtual environments facilitate interaction between team members, leading to the creation of new networks and learning environments for the development of language and communicative competencies in another language. Keywords: virtual environments, English teaching, technological innovation, TPACK model. Resumen La investigación se enfoca en la importancia de los entornos y plataformas virtuales de aprendizaje porque permiten la interacción para desarrollar competencias cognitivas, para ello el objetivo consiste en generar ambientes de aprendizaje basados en los Entornos Virtuales de Aprendizaje, mediante la implementación de plataformas y fortalecer las competencias comunicativas, con este fin la metodología tiene un enfoque cuantitativo – cualitativo, de naturaleza descriptiva y predictiva desde la innovación tecnológica con la implementación de plataforma Schoology basados en el modelo TPACK. De acuerdo a los resultados, se evidencia que existe un alto discernimiento y motivación de los estudiantes a la implementación de los entornos virtuales, en particular a las clases de inglés. Para lo cual la necesidad de una mediación pedagógica en la selección de los recursos didácticos podría potencializar aún más el aprendizaje, para ello es fundamental hacer comprender a los estudiantes la relevancia de aprender un idioma extranjero y como este cambia en la estructura neuronal y su trascendencia en un cerebro bilingüe. Por tanto, los entornos virtuales promueven la interacción entre equipos de trabajo con la finalidad de generar nuevas redes y ambientes de aprendizaje, para el desarrollo de competencias lingüísticas y comunicativas en otro idioma. Palabras Clave: entornos virtuales, enseñanza inglesa, innovación tecnológica, modelo TPACK

Temperature dependence of antiferromagnetic susceptibility in ferritin

We show that antiferromagnetic susceptibility in ferritin increases with temperature between 4.2 K and 180 K (i. e. below the N\'{e}el temperature) when taken as the derivative of the magnetization at high fields ($30\times10^4$ Oe). This behavior contrasts with the decrease in temperature previously found, where the susceptibility was determined at lower fields ($5\times10^4$ Oe). At high fields (up to $50 \times10^4$ Oe) the temperature dependence of the antiferromagnetic susceptibility in ferritin nanoparticles approaches the normal behavior of bulk antiferromagnets and nanoparticles considering superantiferromagnetism, this latter leading to a better agreement at high field and low temperature. The contrast with the previous results is due to the insufficient field range used ($< 5 \times10^4$ Oe), not enough to saturate the ferritin uncompensated moment.Comment: 7 pages, 7 figures, accepted in Phys. Rev.

Adiabatic dynamics of a quantum critical system coupled to an environment: Scaling and kinetic equation approaches

We study the dynamics of open quantum many-body systems driven across a critical point by quenching an Hamiltonian parameter at a certain velocity. General scaling laws are derived for the density of excitations and energy produced during the quench as a function of quench velocity and bath temperature. The scaling laws and their regimes of validity are verified for the XY spin chain locally coupled to bosonic baths. A detailed derivation and analysis of the kinetic equation of the problem is presented.Comment: 15 pages, 13 figure