Weak localization in ferromagnetic (Ga,Mn)As nanostructures

We report on the observation of weak localization in arrays of (Ga,Mn)As nanowires at millikelvin temperatures. The corresponding phase coherence length is typically between 100 nm and 200 nm at 20 mK. Strong spin-orbit interaction in the material is manifested by a weak anti-localization correction around zero magnetic field.Comment: 5 pages, 3 figure

Towards precise ages and masses of free floating planetary mass brown dwarfs

© 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical SocietyMeasurement of the substellar initial mass function (IMF) in very young clusters is hampered by the possibility of the age spread of clustermembers. This is particularly serious for candidate planetary mass objects (PMOs), which have a very similar location to older and more massive brown dwarfs on the Hertzsprung-Russell Diagram (HRD). This degeneracy can be lifted by the measurement of gravity-sensitive spectral features. To this end we have obtained mediumresolution (R ~ 5000) Near-infrared Integral Field Spectrometer (NIFS) K-band spectra of a sample of late M-/early L-type dwarfs. The sample comprises old field dwarfs and very young brown dwarfs in the Taurus association and in the σ Orionis cluster. We demonstrate a positive correlation between the strengths of the 2.21 μm Na I doublet and the objects' ages. We demonstrate a further correlation between these objects' ages and the shape of their K-band spectra. We have quantified this correlation in the form of a new index, the H2(K) index. This index appears to be more gravity-sensitive than the Na I doublet and has the advantage that it can be computed for spectra where gravity-sensitive spectral lines are unresolved, while it is also more sensitive to surface gravity at very young ages (<10 Myr) than the triangular H-band peak. Both correlations differentiate young objects from field dwarfs, while the H2(K) index can distinguish, at least statistically, populations of ~1Myr objects from populations of ~10 Myr objects. We applied the H2(K) index to NIFS data for one Orion nebula cluster (ONC) PMO and to previously published low-resolution spectra for several other ONC PMOs where the 2.21 μm Na I doublet was unresolved and concluded that the average age of the PMOs is ~1Myr.Peer reviewe

Evaluation of a ferrozine based autonomous in situ lab-on-chip analyzer for dissolved iron species in coastal waters

The trace metal iron (Fe) is an essential micronutrient for phytoplankton growth and limits, or co-limits primary production across much of the world's surface ocean. Iron is a redox sensitive element, with Fe(II) and Fe(III) co-existing in natural waters. Whilst Fe(II) is the most soluble form, it is also transient with rapid oxidation rates in oxic seawater. Measurements of Fe(II) are therefore preferably undertaken in situ. For this purpose an autonomous wet chemical analyzer based on lab-on-chip technology was developed for the in situ determination of the concentration of dissolved (<0.45 μm) Fe species (Fe(II) and labile Fe) suitable for deployments in a wide range of aquatic environments. The spectrophotometric approach utilizes a buffered ferrozine solution and a ferrozine/ascorbic acid mixture for Fe(II) and labile Fe(III) analyses, respectively. Diffusive mixing, color development and spectrophotometric detection take place in three separate flow cells with different lengths such that the analyzer can measure a broad concentration range from low nM to several μM of Fe, depending on the desired application. A detection limit of 1.9 nM Fe was found. The microfluidic analyzer was tested in situ for nine days in shallow waters in the Kiel Fjord (Germany) along with other sensors as a part of the SenseOCEAN EU-project. The analyzer's performance under natural conditions was assessed with discrete samples collected and processed according to GEOTRACES protocol [acidified to pH < 2 and analyzed via inductively coupled plasma mass spectrometry (ICP-MS)]. The mechanical performance of the analyzer over the nine day period was good (consistent high precision of Fe(II) and Fe(III) standards with a standard deviation of 2.7% (n = 214) and 1.9% (n = 217), respectively, and successful completion of every programmed data point). However, total dissolved Fe was consistently low compared to ICP-MS data. Recoveries between 16 and 75% were observed, indicating that the analyzer does not measure a significant fraction of natural dissolved Fe species in coastal seawater. It is suggested that an acidification step would be necessary in order to ensure that the analyzer derived total dissolved Fe concentration is reproducible and consistent with discrete values

Economic predictors of differences in interview faking between countries : economic inequality matters, not the state of economy

Many companies recruit employees from different parts of the globe, and faking behavior by potential employees is a ubiquitous phenomenon. It seems that applicants from some countries are more prone to faking compared to others, but the reasons for these differences are largely unexplored. This study relates country-level economic variables to faking behavior in hiring processes. In a cross-national study across 20 countries, participants (N = 3839) reported their faking behavior in their last job interview. This study used the random response technique (RRT) to ensure participants anonymity and to foster honest answers regarding faking behavior. Results indicate that general economic indicators (gross domestic product per capita [GDP] and unemployment rate) show negligible correlations with faking across the countries, whereas economic inequality is positively related to the extent of applicant faking to a substantial extent. These findings imply that people are sensitive to inequality within countries and that inequality relates to faking, because inequality might actuate other psychological processes (e.g., envy) which in turn increase the probability for unethical behavior in many forms

Concepts of health and well-being in managers: An organizational study

Global changes and new managerial challenges require new concepts of health and well-being in organizational contexts. In the South African context, health and well-being of managers have gained relevance in organizations and in management sciences. International organizations, in particular, attempt to address the increasing demand for health care and the delivery of health services to their managers. Careful and appropriate health management requires research to evaluate context-specific health concepts and strategies. The purpose and aim of this article is to assess managerial concepts on health and well-being that could be used by the organization to contribute to managerial well-being by implementing health promotion according to managerial needs. At the same time, this article contributes to salutogenetic health research that is very rare with regard to the South African organizational management research

Discovery of an Unusually Red L-type Brown Dwarf

We report the discovery of an unusually red brown dwarf found in a search for high proper motion objects using WISE and 2MASS data. WISEP J004701.06+680352.1 is moving at 0.44$ arcsec/yr and lies relatively close to the Galactic Plane (b=5.2 degrees). Near-infrared photometry and spectroscopy reveals that this is one of the reddest (2MASS J-K_s = 2.55 +/- 0.08 mag) field L dwarfs yet detected, making this object an important member of the class of unusually red L dwarfs. We discuss evidence for thick condensate clouds and speculate on the age of the object. Although models by different research groups agree that thick clouds can explain the red spectrum, they predict dramatically different effective temperatures, ranging from 1100K to 1600K. This brown dwarf is well suited for additional studies of extremely dusty substellar atmospheres because it is relatively bright (K_s = 13.05 +/- 0.03 mag), which should also contribute to an improved understanding of young gas-giant planets and the transition between L and T brown dwarfs.Comment: Accepted to Astronomical Journal (AJ

The Hyperactive L Dwarf 2MASS J13153094-2649513: Continued Emission and a Brown Dwarf Companion

We report new observations of the unusually active, high proper motion L5e dwarf 2MASS J13153094-2649513. Optical spectroscopy with Magellan/MagE reveals persistent nonthermal emission, with narrow H I Balmer, Na I and K I lines all observed in emission. Low-resolution near-infrared spectroscopy with IRTF/SpeX indicates the presence of a low-temperature companion, which is resolved through multi-epoch laser guide star adaptive optics imaging at Keck. The comoving companion is separated by 338 \pm 4 mas, and its relative brightness (\Delta K_s = 5.09 \pm 0.10) makes this system the second most extreme flux ratio very low-mass binary identified to date. Resolved near-infrared spectroscopy with Keck/OSIRIS identifies this companion as a T7 dwarf. The absence of Li I absorption in combined-light optical spectroscopy constrains the system age to >~0.8-1.0 Gyr, while the system's kinematics and unusually low mass ratio (M_2/M_1 = 0.3-0.6) suggests that it is even older. A coevality test of the components also indicates an older age, but reveals discrepancies between evolutionary and atmosphere model fits of the secondary which are likely attributable to poor reproduction of its near-infrared spectrum. With a projected separation of 6.6 \pm 0.9 AU, the 2MASS J13153094-2649513 system is too widely separated for mass exchange or magnetospheric interactions to be powering its persistent nonthermal emission. Rather, the emission is probably chromospheric in nature, signaling an inversion in the age-activity relation in which strong magnetic fields are maintained by relatively old and massive ultracool dwarfs.Comment: 15 pages, accepted for publication in Astrophysical Journa