3,627 research outputs found
Wearing a bike helmet leads to less cognitive control, revealed by lower frontal midline theta power and risk indifference
A recent study claims that participants wearing a bike helmet behave riskier in a computer-based risk task compared to control participants without a bike helmet. We hypothesized that wearing a bike helmet reduces cognitive control over risky behavior. To test our hypothesis, we recorded participants' EEG brain responses while they played a risk game developed in our laboratory. Previously, we found that, in this risk game, anxious participants showed greater levels of cognitive control as revealed by greater frontal midline theta power, which was associated with less risky decisions. Here, we predicted that cognitive control would be reduced in the helmet group, indicated by reduced frontal midline theta power, and that this group would prefer riskier options in the risk game. In line with our hypothesis, we found that participants in the helmet group showed significantly lower frontal midline theta power than participants in the control group, indicating less cognitive control. We did not replicate the finding of generally riskier behavior in the helmet group. Instead, we found that participants chose the riskier option in about half of trials, no matter how risky the other option was. Our results suggest that wearing a bike helmet reduces cognitive control, as revealed by reduced frontal midline theta power, leading to risk indifference when evaluating potential behaviors
What you give is what you get : payment of one randomly selected trial induces risk-aversion and decreases brain responses to monetary feedback
In economic studies, it is standard practice to pay out the reward of only one randomly selected trial (pay-one) instead of the total reward accumulated across trials (pay-all), assuming that both methods are equivalent. We tested this assumption by recording electrophysiological activity to reward feedback from participants engaged in a decision-making task under both a pay-one and a pay-all condition. We show that participants are approximately 12% more risk averse in the pay-one condition than in the pay-all condition. Furthermore, we observed that the electrophysiological response to monetary rewards, the reward positivity, is significantly reduced in the pay-one condition relative to the pay-all condition. The difference of brain responses is associated with the difference in risky behavior across conditions. We concluded that the two payment methods lead to significantly different results and are therefore not equivalent
Dynamics of multi-cored magnetic structures in the quiet Sun
We report on the dynamical interaction of quiet-Sun magnetic fields and
granular convection in the solar photosphere as seen by \textsc{Sunrise}. We
use high spatial resolution (0\farcs 15--0\farcs 18) and temporal cadence (33
s) spectropolarimetric Imaging Magnetograph eXperiment data, together with
simultaneous CN and Ca\,\textsc{ii}\,H filtergrams from \textsc{Sunrise} Filter
Imager. We apply the SIR inversion code to the polarimetric data in order to
infer the line of sight velocity and vector magnetic field in the photosphere.
The analysis reveals bundles of individual flux tubes evolving as a single
entity during the entire 23 minute data set. The group shares a common canopy
in the upper photospheric layers, while the individual tubes continually
intensify, fragment and merge in the same way that chains of bright points in
photometric observations have been reported to do. The evolution of the tube
cores are driven by the local granular convection flows. They intensify when
they are "compressed" by surrounding granules and split when they are
"squeezed" between two moving granules. The resulting fragments are usually
later regrouped in intergranular lanes by the granular flows. The continual
intensification, fragmentation and coalescence of flux results in magnetic
field oscillations of the global entity. From the observations we conclude that
the magnetic field oscillations first reported by \citet{2011ApJ...730L..37M}
correspond to the forcing by granular motions and not to characteristic
oscillatory modes of thin flux tubes.Comment: 12 pages, 7 figures. Accepted in ApJ. Animation 1 can be downloaded
from: http://spg.iaa.es/download
The history of a quiet-Sun magnetic element revealed by IMaX/SUNRISE
Isolated flux tubes are considered to be fundamental magnetic building blocks
of the solar photosphere. Their formation is usually attributed to the
concentration of magnetic field to kG strengths by the convective collapse
mechanism. However, the small size of the magnetic elements in quiet-Sun areas
has prevented this scenario from being studied in fully resolved structures.
Here we report on the formation and subsequent evolution of one such
photospheric magnetic flux tube, observed in the quiet Sun with unprecedented
spatial resolution (0\farcs 15 - 0\farcs 18) and high temporal cadence (33 s).
The observations were acquired by the Imaging Magnetograph Experiment (IMaX)
aboard the \textsc{Sunrise} balloon-borne solar observatory. The equipartition
field strength magnetic element is the result of the merging of several same
polarity magnetic flux patches, including a footpoint of a previously emerged
loop. The magnetic structure is then further intensified to kG field strengths
by convective collapse. The fine structure found within the flux concentration
reveals that the scenario is more complex than can be described by a thin flux
tube model with bright points and downflow plumes being established near the
edges of the kG magnetic feature. We also observe a daisy-like alignment of
surrounding granules and a long-lived inflow towards the magnetic feature.
After a subsequent weakening process, the field is again intensified to kG
strengths. The area of the magnetic feature is seen to change in anti-phase
with the field strength, while the brightness of the bright points and the
speed of the downflows varies in phase. We also find a relation between the
brightness of the bright point and the presence of upflows within it.Comment: 13 pages. Accepted in ApJ. Animation 1 can be viewed and downloaded
from: http://spg.iaa.es/downloads.as
Inverse-Tunable Red Luminescence and Electronic Properties of Nitridoberylloaluminates Sr2-xBax[BeAl3N5]:Eu2+ (x=0-2)
The nitridoberylloaluminate Ba-2[BeAl3N5]:Eu2+ and solid solutions Sr2-xBax[BeAl3N5]:Eu2+ (x=0.5, 1.0, 1.5) were synthesized in a hot isostatic press (HIP) under 50 MPa N-2 atmosphere at 1200 degrees C. Ba-2[BeAl3N5]:Eu2+ crystallizes in tri-clinic space group P (1) over bar (no. 2) (Z=2, a=6.1869(10), b= 7.1736(13), c= 8.0391(14) angstrom, alpha = 102.754(8), beta = 112.032(6), gamma = 104.765(7)degrees), which was determined from single-crystal X-ray diffraction data. The lattice parameters of the solid solution series have been obtained from Rietveld refinements and show a nearly linear dependence on the atomic ratio Sr:Ba. The electronic properties and the band gaps of M-2[BeAl3N5](M=Sr, Ba) have been investigated by a combination of soft X-ray spectroscopy and density functional theory (DFT) calculations. Upon irradiation with blue light (440-450 nm), the nitridoberylloaluminates exhibit intense orange to red luminescence, which can be tuned between 610 and 656 nm (fwhm =1922-2025 cm(-1) (72-87 nm)). In contrast to the usual trend, the substitution of the smaller Sr2+= by larger Ba leads to an inverse-tunable luminescence to higher wavelengths. Low-temperature luminescence measurements have been performed to exclude anomalous emission
Excitation of Large Transverse Beam Oscillations without Emittance Blow-up using the AC-Dipole Principle
The so-called "AC-Dipole" principle allows the excitation of transverse oscillations to large (several sigma) excursions without emittance blow-up. The idea was originally proposed and tested at BNL for resonance crossing with polarized beams, using an orbit corrector dipole with an excitation frequency close to the betatron tune, hence "AC-Dipole". This method of beam excitation has several potential applications in teh LHC, such as phase advance and beta-measurements, dynamic aperture studies and the investigation of resonance strengths. The technique was recently tested in the CERN SPS using the transverse damper as an "AC-Dipole" providing the fixed frequency excitation. Results from this experiment are presented, along with an explanation of the underlying principle
Grain Structure Evolution of Al−Cu Alloys in Powder Bed Fusion with Laser Beam for Excellent Mechanical Properties
Powder Bed Fusion with Laser Beam of Metals (PBF-LB/M) is one of the fastest growing technology branches. More and more metallic alloys are being qualified, but processing of aluminum wrought alloys without cracks and defects is still challenging. It has already been shown that small parts with low residual porosity can be produced. However, suffering from microscopic hot cracks, the fracture behavior has been rather brittle. In this paper different combinations of temperature gradients and solidification rates are used to achieve specific solidification conditions in order to influence the resulting microstructure, as well as internal stresses. By this approach it could be shown that EN AW-2024, an aluminum-copper wrought alloy, is processable via PBF-LB/M fully dense and crack-free with outstanding material properties, exceeding those reported for commonly manufactured EN AW-2024 after T4 heat treatment
NGC 346 in the Small Magellanic Cloud. III. Recent Star Formation and Stellar Clustering Properties in the Bright HII Region N 66
In the third part of our photometric study of the star-forming region NGC
346/N~66 and its surrounding field in the Small Magellanic Cloud (SMC), we
focus on the large number of low-mass pre-main sequence (PMS) stars revealed by
the Hubble Space Telescope Observations with the Advanced Camera for Surveys.
We investigate the origin of the observed broadening of the pre-main sequence
population in the , CMD. The most likely explanations are either the
presence of differential reddening or an age spread among the young stars.
Assuming the latter, simulations indicate that we cannot exclude the
possibility that stars in NGC 346 might have formed in two distinct events
occurring about 10 and 5 Myr ago, respectively. We find that the PMS stars are
not homogeneously distributed across NGC 346, but instead are grouped in at
least five different clusters. On spatial scales from 0.8 to 8 (0.24 to
2.4 pc at the distance of the SMC) the clustering of the PMS stars as computed
by a two-point angular correlation function is self-similar with a power law
slope . The clustering properties are quite similar to
Milky Way star forming regions like Orion OB or Oph. Thus molecular
cloud fragmentation in the SMC seems to proceed on the same spatial scales as
in the Milky Way. This is remarkable given the differences in metallicity and
hence dust content between SMC and Milky Way star forming regions.Comment: Accepted for publication in ApJ. 16 pages, 13 (low-resolution)
figures, emulateapj.cls LaTeX styl
The Janthinobacterium sp. HH01 genome encodes a homologue of the V. cholerae CqsA and L. pneumophila LqsA autoinducer synthases
Janthinobacteria commonly form biofilms on eukaryotic hosts and are known to synthesize antibacterial and antifungal compounds. Janthinobacterium sp. HH01 was recently isolated from an aquatic environment and its genome sequence was established. The genome consists of a single chromosome and reveals a size of 7.10 Mb, being the largest janthinobacterial genome so far known. Approximately 80% of the 5,980 coding sequences (CDSs) present in the HH01 genome could be assigned putative functions. The genome encodes a wealth of secretory functions and several large clusters for polyketide biosynthesis. HH01 also encodes a remarkable number of proteins involved in resistance to drugs or heavy metals. Interestingly, the genome of HH01 apparently lacks the N-acylhomoserine lactone (AHL)-dependent signaling system and the AI-2-dependent quorum sensing regulatory circuit. Instead it encodes a homologue of the Legionella- and Vibrio-like autoinducer (lqsA/cqsA) synthase gene which we designated jqsA. The jqsA gene is linked to a cognate sensor kinase (jqsS) which is flanked by the response regulator jqsR. Here we show that a jqsA deletion has strong impact on the violacein biosynthesis in Janthinobacterium sp. HH01 and that a jqsA deletion mutant can be functionally complemented with the V. cholerae cqsA and the L. pneumophila lqsA genes
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