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

A Proposal to Perform High Contrast Imaging of Human Palatine Tonsil with Cross Polarized Optical Coherence Tomography

The palatine tonsils provide the first line of immune defense against foreign pathogens inhaled or ingested. However, a disruption in the epithelial layer within the tonsil crypts can lead to recurrent acute tonsillitis (RAT). Current imaging techniques suffer from poor resolution and contrast and do not allow a classification of the severity of RAT. We have developed a cross-polarized optical coherence tomography system. The system can detect a change in the polarization of the light after the light-tissue interaction. We demonstrate improved resolution and contrast in tonsil imaging with the developed method. Intensity, as well as retardance images of the excised tonsil tissue, were acquired. Features such as crypt epithelium, lymphoid follicles, and dense connective tissue were observed with improved contrast. Cross polarized optical coherence tomography can be a valuable tool in the clinic to evaluate palatine tonsils as it would allow visualizing common tonsil features without the need for any external contrast agent

Resolving the L/T transition binary SDSS J2052-1609 AB

Binaries provide empirical key constraints for star formation theories, like the overall binary fraction, mass ratio distribution and the separation distribution. They play a crucial role to calibrate the output of theoretical models, like absolute magnitudes, colors and effective temperature depending on mass, metallicity and age. We present first results of our on-going high-resolution imaging survey of late type brown dwarfs. The survey aims at resolving tight brown dwarf binary systems to better constrain the T dwarf binary fraction. We intent to follow-up the individual binaries to determine orbital parameters. Using NACO at the VLT we performed AO-assisted near-infrared observations of SDSS J2052-1609. High-spatial resolution images of the T1 dwarf were obtained in H and Ks filters. We resolved SDSS J2052-1609 into a binary system with a separation of 0.101" \pm 0.001". Archival data from HST/NICMOS taken one year previous to our observations proves the components to be co-moving. Using the flux ratio between the components we infer J, H and Ks magnitudes for the resolved system. From the near-IR colors we estimate spectral types of T1 +1 -4 and T2.5 \pm 1 for component A and B, respectively. A first estimate of the total system mass yields Mtot > 78 Mjup, assuming a circular orbit.Comment: 5 pages, 3 figures, 3 tables, accepted for publication by A&

A direct and differential imaging search for sub-stellar companions to epsilon Indi A

We have carried out a direct and differential imaging search for sub-stellar companions to eps Indi A using the adaptive optics system NACO at the ESO VLT. The observations were carried out in September 2004 with NACO/SDI as well as with NACO's S27 camera in the H and Ks filters. The SDI data cover an area of \~2.8" around eps Indi A. No detection was achieved in the inner neighbourhood down to 53 Mj (5 sigma confidence level) at a separation > 0.4" (1.45 AU) and down to 21 Mj for separations > 1.3" (4.7 AU). To cover a wider field of view, observations with the S27 camera and a coronagraphic mask were obtained. We detected a faint source at a separation of (7.3 +/- 0.1)" and a position angle of (302.9 +/- 0.8) degree. The photometry for the candidate companion yields m(H)=(16.45 +/- 0.04)mag and m(Ks) = (15.41 +/- 0.06)mag, respectively. Those magnitudes and the resulting color (H-Ks) = (1.04 +/- 0.07)mag fit best to a spectral type of L5 - L9.5 if it is bound. Observations done with HST/NICMOS by M. Endl have shown the source to be a background object.Comment: 6 pages, 5 figures, accepted by A&

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

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

Human Umbilical Cord Blood Cells Restore Brain Damage Induced Changes in Rat Somatosensory Cortex

Intraperitoneal transplantation of human umbilical cord blood (hUCB) cells has been shown to reduce sensorimotor deficits after hypoxic ischemic brain injury in neonatal rats. However, the neuronal correlate of the functional recovery and how such a treatment enforces plastic remodelling at the level of neural processing remains elusive. Here we show by in-vivo recordings that hUCB cells have the capability of ameliorating the injury-related impairment of neural processing in primary somatosensory cortex. Intact cortical processing depends on a delicate balance of inhibitory and excitatory transmission, which is disturbed after injury. We found that the dimensions of cortical maps and receptive fields, which are significantly altered after injury, were largely restored. Additionally, the lesion induced hyperexcitability was no longer observed in hUCB treated animals as indicated by a paired-pulse behaviour resembling that observed in control animals. The beneficial effects on cortical processing were reflected in an almost complete recovery of sensorimotor behaviour. Our results demonstrate that hUCB cells reinstall the way central neurons process information by normalizing inhibitory and excitatory processes. We propose that the intermediate level of cortical processing will become relevant as a new stage to investigate efficacy and mechanisms of cell therapy in the treatment of brain injury