Spin-Torque-Induced Rotational Dynamics of a Magnetic Vortex Dipole

We study, both experimentally and by numerical modeling, the magnetic dynamics that can be excited in a magnetic thin-film nanopillar device using the spin torque from a spatially localized current injected via a 10s-of-nm-diameter aperture. The current-driven magnetic dynamics can produce large amplitude microwave emission at zero magnetic field, with a frequency well below that of the uniform ferromagnetic resonance mode. Micromagnetic simulations indicate that the physical origin of this efficient microwave nano-oscillator is the nucleation and subsequent steady-state rotational dynamics of a magnetic vortex dipole driven by the localized spin torque. These results show this novel implementation of a spintronic nano-oscillator is a promising candidate for microwave technology applications.Comment: 19 pages, 4 figures

Discovery of an OB Runaway Star Inside SNR S147

We present first results of a long term study: Searching for OB--type runaway stars inside supernova remnants (SNRs). We identified spectral types and measured radial velocities (RV) by optical spectroscopic observations and we found an early type runaway star inside SNR S147. HD 37424 is a B0.5V type star with a peculiar velocity of 74$\pm$8 km s$^{-1}$. Tracing back the past trajectories via Monte Carlo simulations, we found that HD 37424 was located at the same position as the central compact object, PSR J0538+2817, $30\!\pm\!4$ kyr ago. This position is only $\sim$4 arcmin away from the geometrical center of the SNR. So, we suggest that HD 37424 was the pre--supernova binary companion to the progenitor of the pulsar and the SNR. We found a distance of 1333$^{+103}_{-112}$ pc to the SNR. The zero age main sequence progenitor mass should be greater than 13 $M_\odot$. The age is $30\pm4$ kyr and the total visual absorption towards the center is 1.28$\pm$0.06 mag. For different progenitor masses, we calculated the pre--supernova binary parameters. The Roche Lobe radii suggest that it was an interacting binary in the late stages of the progenitor.Comment: Accepted to be published in MNRAS, 10 pages, 5 figure

Cheese in Chijnaya: Communal Entrepreneurship in Rural Peru

Individual entrepreneurship and social entrepreneurship may be more common both in daily life and in the research literature, but community- based entrepreneurship also plays an important role in economic development. We present a case study of community entrepreneurship in a rural area of the Andes, where the community of Chijnaya operates a successful cheese production business. Buying milk from its farmer members in the community, the business produces cheeses that are sold in regional urban markets and beyond. This account draws on decades of ethnographic research and collaboration with the community. Here, we discuss the history of the community in general and of the cheese enterprise in particular. The organizational structure of the business is outlined along with a description of the production processes. We end with an analysis of problems faced by the community in moving the enterprise forward toward a more profitable future and a discussion of the relevance of this case to entrepreneurship studies

Tuning the Kondo effect with a mechanically controllable break junction

We study electron transport through C60 molecules in the Kondo regime using a mechanically controllable break junction. By varying the electrode spacing, we are able to change both the width and height of the Kondo resonance, indicating modification of the Kondo temperature and the relative strength of coupling to the two electrodes. The linear conductance as a function of T/T_K agrees with the scaling function expected for the spin-1/2 Kondo problem. We are also able to tune finite-bias Kondo features which appear at the energy of the first C60 intracage vibrational mode.Comment: 4 pages with 4 figure

Space QUEST mission proposal: experimentally testing decoherence due to gravity

Models of quantum systems on curved space-times lack sufficient experimental verification. Some speculative theories suggest that quantum correlations, such as entanglement, may exhibit different behavior to purely classical correlations in curved space. By measuring this effect or lack thereof, we can test the hypotheses behind several such models. For instance, as predicted by Ralph et al [5] and Ralph and Pienaar [1], a bipartite entangled system could decohere if each particle traversed through a different gravitational field gradient. We propose to study this effect in a ground to space uplink scenario. We extend the above theoretical predictions of Ralph and coworkers and discuss the scientific consequences of detecting/failing to detect the predicted gravitational decoherence. We present a detailed mission design of the European Space Agency's Space QUEST (Space—Quantum Entanglement Space Test) mission, and study the feasibility of the mission scheme.Peer ReviewedPostprint (published version

The Effects of Cuento Therapy on Reading Achievement and Psychological Outcomes of Mexican-American Students

This investigation evaluated the effects of cuento therapy (an intervention using Spanish-language tales) on children’s self-esteem, affect, and reading test performance. The sample was composed of 58 third-grade Mexican-American students who were randomly assigned to the treatment and control groups. The results showed a mean self-esteem gain score difference between groups in favor of the treatment group for Global, Academic, and General self-esteem scores. Following intervention, the treatment group reported less physiological anxiety than did the control group. The results also showed mean increases in the pre- and post-standardized high-stakes reading test scores for both groups. Other significant findings regarding selfesteem and anxiety are reported

Identification of additional young nearby runaway stars based on Gaia data release 2 observations and the lithium test

Runaway stars are characterized by their remarkably high space velocities, and the study of their formation mechanisms has attracted considerable interest. Young, nearby runaway stars are the most favorable for identifying their place of origin, and for searching for possible associated objects such as neutron stars. Usually, the research field of runaway stars focuses on O‐ and B‐type stars, because these objects are better detectable at larger distances than late‐type stars. Early‐type runaway stars have the advantage that they evolve faster and can therefore better be confirmed to be young. In contrast to this, the catalog of Young runaway stars within 3 kpc by Tetzlaff, N., Neuhäuser, R., & Hohle, M. M. (2011, MNRAS, 410(1), 190–200) contains also stars of spectral type A and later. The objects in this catalog were originally classified as young ( ≤ 50 Myr) runaway stars by using Hipparcos data to estimate the ages from their location in the Hertzsprung‐Russell diagram and evolutionary models. In this article, we redetermine and/or constrain their ages not only by using the more precise second data release of the Gaia mission, but also by measuring the equivalent width of the lithium (6,708 Å) line, which is a youth indicator. Therefore, we searched for lithium absorption in the spectra of 51 target stars, taken at the University Observatory Jena between March and September 2020 with the Échelle spectrograph FLECHAS, and within additional TRES‐spectra from the Fred L. Whipple Observatory. The main part of this campaign with its 308 reduced spectra, accessible at VizieR , was already published. In this work, which is the continuation and completion of the in 2015 initiated observing campaign, we found three additional young runaway star candidates

Surface anisotropy and magnetic freezing of MnO nanoparticles

Nanoparticles of bulk antiferromagnets often exhibit ferromagnetic behavior due to uncompensated surface spins. The peak temperature in the zero-field-cooled magnetization of MnO—in contrast to other antiferromagnetic nanoparticles—has anomalous behavior, shifting to higher temperatures with decreasing nanoparticle size. We attribute this behavior to surface anisotropy enhanced by the specific occupancy of 3d levels in Mn, which produces a high-spin–low-spin transition not present in NiO nanoparticles