3,012 research outputs found
A new contribution to the nuclear modification factor of non-photonic electrons in Au+Au collisions at sqrt(s) = 200 GeV
We investigate the effect of the so-called anomalous baryon/meson enhancement
to the nuclear modification factor of non-photonic electrons in Au+Au
collisions at sqrt(s) = 200 GeV. It is demonstrated that an enhancement of the
charm baryon/meson ratio, as it is observed for non-strange and strange
hadrons, can be responsible for part of the amplitude of the nuclear
modification factor of non-photonic electrons. About half of the measured
suppression of non-photonic electrons in the 2-4 pt range can be explained by a
charm baryon/meson enhancement of 5. This contribution to the non-photonic
electron nuclear modification factor has nothing to do with heavy quark energy
loss.Comment: 14 pages, 3 figure
The cortical states of wakefulness
Cortical neurons process information on a background of spontaneous, ongoing activity with distinct spatiotemporal profiles defining different cortical states. During wakefulness, cortical states alter constantly in relation to behavioral context, attentional level or general motor activity. In this review article, we will discuss our current understanding of cortical states in awake rodents, how they are controlled, their impact on sensory processing, and highlight areas for future research. A common observation in awake rodents is the rapid change in spontaneous cortical activity from high-amplitude, low-frequency (LF) fluctuations, when animals are quiet, to faster and smaller fluctuations when animals are active. This transition is typically thought of as a change in global brain state but recent work has shown variation in cortical states across regions, indicating the presence of a fine spatial scale control system. In sensory areas, the cortical state change is mediated by at least two convergent inputs, one from the thalamus and the other from cholinergic inputs in the basal forebrain. Cortical states have a major impact on the balance of activity between specific subtypes of neurons, on the synchronization between nearby neurons, as well as the functional coupling between distant cortical areas. This reorganization of the activity of cortical networks strongly affects sensory processing. Thus cortical states provide a dynamic control system for the moment-by-moment regulation of cortical processing
The role of environmental feedback in a brain state switch from passive to active sensing
No description supplie
Cis-Dioxido-molybdenum(VI) complexes of tridentate ONO hydrazone Schiff base: Synthesis, characterization, X-ray crystal structure, DFT calculation and catalytic activity
Two new cis-MoO₂ [MoO₂(L)(EtOH)] (1), [MoO₂(L) (Py)] (2) [L: (3-methoxy-2oxidobenzylidene)benzohydrazidato], complexes have been synthesized and fully characterized on the basis of elemental analysis, FT-IR, molar conductivity, ¹H NMR, ¹³C NMR and electronic spectra. The structure of complexes has been accomplished by single crystal X-ray diffraction. All experimental results confirmed that both complexes have an octahedral geometry around the Mo(VI) central atom, which is coordinated by the donor atoms of the dianionic hydrazone ligand, two oxido groups and oxygen/nitrogen atoms of solvent molecules. Computational studies were also performed using DFT calculations at B3LYP/DGDZVP level of theory. Furthermore, their catalytic activities were investigated on the electrophilic reaction of indole with aldehydes in molten tetrabutyl ammonium bromide (TBAB) to obtain bis(indolyl)methane derivatives
Event Anisotropy in High Energy Nucleus-Nucleus Collisions
The predictions of event anisotropy parameters from transport model RQMD are
compared with the recent experimental measurements for 158 GeV Pb+Pb
collisions. Using the same model, we study the time evolution of event
anisotropy at 2 GeV and 158 GeV for several colliding systems. For the
first time, both momentum and configuration space information are studied using
the Fourier analysis of the azimuthal angular distribution. We find that, in
the model, the initial geometry of the collision plays a dominant role in
determining the anisotropy parameters.Comment: 18 pages, 7 figures, 2 table
Flow angle from intermediate mass fragment measurements
Directed sideward flow of light charged particles and intermediate mass
fragments was measured in different symmetric reactions at bombarding energies
from 90 to 800 AMeV. The flow parameter is found to increase with the charge of
the detected fragment up to Z = 3-4 and then turns into saturation for heavier
fragments. Guided by simple simulations of an anisotropic expanding thermal
source, we show that the value at saturation can provide a good estimate of the
flow angle, , in the participant region. It is found that
depends strongly on the impact parameter. The excitation
function of reveals striking deviations from the ideal
hydrodynamical scaling. The data exhibit a steep rise of \Theta_{\flow} to a
maximum at around 250-400 AMeV, followed by a moderate decrease as the
bombarding energy increases further.Comment: 28 pages Revtex, 6 figures (ps files), to appear in Nucl.Phys.
Identification of Birds through DNA Barcodes
Short DNA sequences from a standardized region of the genome provide a DNA barcode for identifying species. Compiling a public library of DNA barcodes linked to named specimens could provide a new master key for identifying species, one whose power will rise with increased taxon coverage and with faster, cheaper sequencing. Recent work suggests that sequence diversity in a 648-bp region of the mitochondrial gene, cytochrome c oxidase I (COI), might serve as a DNA barcode for the identification of animal species. This study tested the effectiveness of a COI barcode in discriminating bird species, one of the largest and best-studied vertebrate groups. We determined COI barcodes for 260 species of North American birds and found that distinguishing species was generally straightforward. All species had a different COI barcode(s), and the differences between closely related species were, on average, 18 times higher than the differences within species. Our results identified four probable new species of North American birds, suggesting that a global survey will lead to the recognition of many additional bird species. The finding of large COI sequence differences between, as compared to small differences within, species confirms the effectiveness of COI barcodes for the identification of bird species. This result plus those from other groups of animals imply that a standard screening threshold of sequence difference (10× average intraspecific difference) could speed the discovery of new animal species. The growing evidence for the effectiveness of DNA barcodes as a basis for species identification supports an international exercise that has recently begun to assemble a comprehensive library of COI sequences linked to named specimens
The value of multiple data set calibration versus model complexity for improving the performance of hydrological models in mountain catchments
The assessment of snow, glacier, and rainfall runoff contribution to discharge in mountain streams is of major importance for an adequate water resource management. Such contributions can be estimated via hydrological models, provided that the modeling adequately accounts for snow and glacier melt, as well as rainfall runoff. We present a multiple data set calibration approach to estimate runoff composition using hydrological models with three levels of complexity. For this purpose, the code of the conceptual runoff model HBV-light was enhanced to allow calibration and validation of simulations against glacier mass balances, satellite-derived snow cover area and measured discharge. Three levels of complexity of the model were applied to glacierized catchments in Switzerland, ranging from 39 to 103 km2. The results indicate that all three observational data sets are reproduced adequately by the model, allowing an accurate estimation of the runoff composition in the three mountain streams. However, calibration against only runoff leads to unrealistic snow and glacier melt rates. Based on these results, we recommend using all three observational data sets in order to constrain model parameters and compute snow, glacier, and rain contributions. Finally, based on the comparison of model performance of different complexities, we postulate that the availability and use of different data sets to calibrate hydrological models might be more important than model complexity to achieve realistic estimations of runoff composition
Strangeness dynamics and transverse pressure in relativistic nucleus-nucleus collisions
We investigate hadron production as well as transverse hadron spectra from
proton-proton, proton-nucleus and nucleus-nucleus collisions from 2 GeV
to 21.3 TeV within two independent transport approaches (HSD and UrQMD)
that are based on quark, diquark, string and hadronic degrees of freedom. The
comparison to experimental data on transverse mass spectra from , and
C+C (or Si+Si) reactions shows the reliability of the transport models for
light systems. For central Au+Au (Pb+Pb) collisions at bombarding energies
above 5 AGeV, furthermore, the measured transverse mass
spectra have a larger inverse slope parameter than expected from the default
calculations. We investigate various scenarios to explore their potential
effects on the spectra. In particular the initial state Cronin effect
is found to play a substantial role at top SPS and RHIC energies. However, the
maximum in the ratio at 20 to 30 AGeV is missed by ~40% and
the approximately constant slope of the spectra at SPS energies is not
reproduced either. Our systematic analysis suggests that the additional
pressure - as expected from lattice QCD calculations at finite quark chemical
potential and temperature - should be generated by strong
interactions in the early pre-hadronic/partonic phase of central Au+Au (Pb+Pb)
collisions.Comment: 20 pages, 15 figures, Phys. Rev. C, in pres
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