395 research outputs found
The influence of tDCS on perceived bouncing/streaming
Processing ambiguous situations is a constant challenge in everyday life and sensory input from different modalities needs to be integrated to form a coherent mental representation on the environment. The bouncing/streaming illusion can be studied to provide insights into the ambiguous perception and processing of multi-modal environments. In short, the likelihood of reporting bouncing rather than streaming impressions increases when a sound coincides with the moment of overlap between two moving disks. Neuroimaging studies revealed that the right posterior parietal cortex is crucial in cross-modal integration and is active during the bouncing/streaming illusion. Consequently, in the present study, we used transcranial direct current stimulation to stimulate this brain area. In the active stimulation conditions, a 9 cm2 electrode was positioned over the P4-EEG position and the 35 cm2 reference positioned over the left upper arm. The stimulation lasted 15 min. Each participant did the bouncing/streaming task three times: before, during and after anodal or sham stimulation. In a sample of N = 60 healthy, young adults, we found no influence of anodal tDCS. Bayesian analysis showed strong evidence against tDCS effects. There are two possible explanations for the finding that anodal tDCS over perceptual areas did not modulate multimodal integration. First, upregulation of multimodal integration is not possible using tDCS over the PPC as the integration process already functions at maximum capacity. Second, prefrontal decision-making areas may have overruled any modulated input from the PPC as it may not have matched their decision-making criterion and compensated for the modulation
Forcing mechanisms of the terdiurnal tide
Using a nonlinear mechanistic global circulation model we analyze the
migrating terdiurnal tide in the middle atmosphere with respect to its
possible forcing mechanisms, i.e., the absorption of solar radiation in the
water vapor and ozone band, nonlinear tidal interactions, and gravity
wave–tide interactions. In comparison to the forcing mechanisms of diurnal
and semidiurnal tides, these terdiurnal forcings are less well understood and
there are contradictory opinions about their respective relevance. In our
simulations we remove the wave number 3 pattern for each forcing individually
and analyze the remaining tidal wind and temperature fields. We find that the
direct solar forcing is dominant and explains most of the migrating
terdiurnal tide's amplitude. Nonlinear interactions due to other tides or
gravity waves are most important during local winter. Further analyses show
that the nonlinear forcings are locally counteracting the solar forcing due
to destructive interferences. Therefore, tidal amplitudes can become even
larger for simulations with removed nonlinear forcings.</p
Quarterdiurnal signature in sporadic E occurrence rates and comparison with neutral wind shear
The GPS radio occultation (RO) technique is used to study
sporadic E (Es) layer plasma irregularities of the Earth's ionosphere on a
global scale using GPS signal-to-noise ratio (SNR) profiles from the
COSMIC/FORMOSAT-3 satellite. The maximum deviation from the mean SNR can be
attributed to the height of the Es layer. Es are generally accepted to be
produced by ion convergence due to vertical wind shear in the presence of a
horizontal component of the Earth's magnetic field, while the wind shear is
provided mainly by the solar tides. Here we present analyses of
quarterdiurnal tide (QDT) signatures in Es occurrence rates. From a local
comparison with mesosphere/lower thermosphere wind shear obtained with a
meteor radar at Collm (51.3∘ N, 13.0∘ E), we find that the
phases of the QDT in Es agree well with those of negative vertical shear of
the zonal wind for all seasons except for summer, when the QDT amplitudes are
small. We also compare the global QDT Es signal with numerical model results.
The global distribution of the Es occurrence rates qualitatively agrees with
the modeled zonal wind shears. The results indicate that zonal wind shear is
indeed an important driving mechanism for the QDT seen in Es.</p
Influence of nanoparticle encapsulation and encoding on the surface chemistry of polymer carrier beads
Surface-functionalized polymer beads encoded with molecular luminophores and nanocrystalline emitters such as semiconductor nanocrystals, often referred to as quantum dots (QDs), or magnetic nanoparticles are broadly used in the life sciences as reporters and carrier beads. Many of these applications require a profound knowledge of the chemical nature and total number of their surface functional groups (FGs), that control bead charge, colloidal stability, hydrophobicity, and the interaction with the environment and biological systems. For bioanalytical applications, also the number of groups accessible for the subsequent functionalization with, e.g., biomolecules or targeting ligands is relevant. In this study, we explore the influence of QD encoding on the amount of carboxylic acid (COOH) surface FGs of 2 µm polystyrene microparticles (PSMPs). This is done for frequently employed oleic acid and oleylamine stabilized, luminescent core/shell CdSe QDs and two commonly used encoding procedures. This included QD addition during bead formation by a thermally induced polymerization reaction and a post synthetic swelling procedure. The accessible number of COOH groups on the surface of QD-encoded and pristine beads was quantified by two colorimetric assays, utilizing differently sized reporters and electrostatic and covalent interactions. The results were compared to the total number of FGs obtained by a conductometric titration and Fourier transform infrared spectroscopy (FTIR). In addition, a comparison of the impact of QD and dye encoding on the bead surface chemistry was performed. Our results demonstrate the influence of QD encoding and the QD-encoding strategy on the number of surface FG that is ascribed to an interaction of the QDs with the carboxylic acid groups on the bead surface. These findings are of considerable relevance for applications of nanoparticle-encoded beads and safe-by-design concepts for nanomaterials
Differential functional benefits of ultra highfield MR systems within the language network
Several investigations have shown limitations of fMRI reliability with the current standard field strengths. Improvement is expected from ultra highfield systems but studies on possible benefits for cognitive networks are lacking. Here we provide an initial investigation on a prominent and clinically highly-relevant cognitive function: language processing in individual brains. 26 patients evaluated for presurgical language localization were investigated with a standardized overt language fMRI paradigm on both 3T and 7T MR scanners. During data acquisition and analysis we made particular efforts to minimize effects not related to static magnetic field strength differences. Six measures relevant for functional activation showed a large dissociation between essential language network nodes: although in Wernicke's area 5/6 measures indicated a benefit of ultra highfield, in Broca's area no comparison was significant. The most important reason for this discrepancy was identified as being an increase in susceptibility-related artifacts in inferior frontal brain areas at ultra high field. We conclude that functional UHF benefits are evident, however these depend crucially on the brain region investigated and the ability to control local artifacts
Planets Around Low-Mass Stars (PALMS). I. A Substellar Companion to the Young M Dwarf 1RXS J235133.3+312720
We report the discovery of a brown dwarf companion to the young M dwarf 1RXS
J235133.3+312720 as part of a high contrast imaging search for planets around
nearby young low-mass stars with Keck-II/NIRC2 and Subaru/HiCIAO. The 2.4"
(~120 AU) pair is confirmed to be comoving from two epochs of high resolution
imaging. Follow-up low- and moderate-resolution near-infrared spectroscopy of
1RXS J2351+3127 B with IRTF/SpeX and Keck-II/OSIRIS reveals a spectral type of
L0. The M2 primary star 1RXS J2351+3127 A exhibits X-ray and UV
activity levels comparable to young moving group members with ages of ~10-100
Myr. UVW kinematics based the measured radial velocity of the primary and the
system's photometric distance (50 +/- 10 pc) indicate it is likely a member of
the ~50-150 Myr AB Dor moving group. The near-infrared spectrum of 1RXS
J2351+3127 B does not exhibit obvious signs of youth, but its H-band morphology
shows subtle hints of intermediate surface gravity. The spectrum is also an
excellent match to the ~200 Myr M9 brown dwarf LP 944-20. Assuming an age of
50-150 Myr, evolutionary models imply a mass of 32 +/- 6 Mjup for the
companion, making 1RXS J2351+3127 B the second lowest-mass member of the AB Dor
moving group after the L4 companion CD-35 2722 B and one of the few benchmark
brown dwarfs known at young ages.Comment: Accepted for publication in ApJ. 24 pages, 12 figures, 4 table
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
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
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
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
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