10,657 research outputs found
Interferometric Mapping of Magnetic fields: NGC2071IR
We present polarization maps of NGC2071IR from thermal dust emission at 1.3
mm and from CO J= line emission. The observations were obtained using
the Berkeley-Illinois-Maryland Association array in the period 2002-2004. We
detected dust and line polarized emission from NGC2071IR that we used to
constrain the morphology of the magnetic field. From CO J= polarized
emission we found evidence for a magnetic field in the powerful bipolar outflow
present in this region. We calculated a visual extinction mag from our dust observations. This result, when compared with early
single dish work, seems to show that dust grains emit polarized radiation
efficiently at higher densities than previously thought. Mechanical alignment
by the outflow is proposed to explain the polarization pattern observed in
NGC2071IR, which is consistent with the observed flattening in this source.Comment: 17 pages, 4 Figures, Accepted for publication in Ap
Dynamical Synapses Enhance Neural Information Processing: Gracefulness, Accuracy and Mobility
Experimental data have revealed that neuronal connection efficacy exhibits
two forms of short-term plasticity, namely, short-term depression (STD) and
short-term facilitation (STF). They have time constants residing between fast
neural signaling and rapid learning, and may serve as substrates for neural
systems manipulating temporal information on relevant time scales. The present
study investigates the impact of STD and STF on the dynamics of continuous
attractor neural networks (CANNs) and their potential roles in neural
information processing. We find that STD endows the network with slow-decaying
plateau behaviors-the network that is initially being stimulated to an active
state decays to a silent state very slowly on the time scale of STD rather than
on the time scale of neural signaling. This provides a mechanism for neural
systems to hold sensory memory easily and shut off persistent activities
gracefully. With STF, we find that the network can hold a memory trace of
external inputs in the facilitated neuronal interactions, which provides a way
to stabilize the network response to noisy inputs, leading to improved accuracy
in population decoding. Furthermore, we find that STD increases the mobility of
the network states. The increased mobility enhances the tracking performance of
the network in response to time-varying stimuli, leading to anticipative neural
responses. In general, we find that STD and STP tend to have opposite effects
on network dynamics and complementary computational advantages, suggesting that
the brain may employ a strategy of weighting them differentially depending on
the computational purpose.Comment: 40 pages, 17 figure
Quantificação das mudanças hormonais promovidas por produtos quÃmicos e microorganismos em arroz (Oryza sativa L.).
utilização de microorganismos em arroz com dupla ação, promoção do crescimento e proteção contra doenças vem sendo extensivamente estudada. Objetivou-se quantificar as mudanças hormonais promovidas por produtos quÃmicos comerciais, duas bactérias e um fungo na cultura do arroz, isolados e em combinação um com o outro
Learning Based on Problems (ABP), Impact of RAEE: A Case Study
Using a case of research as a methodological tool, applied in the research lab with students of the ninth semester of the academic program of chemical engineering (IQ) of the Faculty of chemical sciences and engineering (FCQeI) of the Autonomous University of the State of Morelos (UAEM), analyzed competition to students include scientific concepts acquired, where education is a human process more than verify that cognitive skills according to the approach [1], are developed during the resolution of the case. The results showed that students managed to explain the concepts involved, reflected on his own work and realized what had to be improved. For that, students employed higher order cognitive skills, such as explain, investigate, conclude, argue, make decisions and cognitive skills of low order, such as describing, enunciating, memorize and reproduce
Kinematics of a globular cluster with an extended profile: NGC5694
We present a study of the kinematics of the remote globular cluster NGC5694
based on GIRAFFE@VLT medium resolution spectra. A sample of 165 individual
stars selected to lie on the Red Giant Branch in the cluster Color Magnitude
Diagram was considered. Using radial velocity and metallicity from Calcium
triplet, we were able to select 83 bona-fide cluster members. The addition of
six previously known members leads to a total sample of 89 cluster giants with
typical uncertainties <1.0 km/s in their radial velocity estimates. The sample
covers a wide range of projected distances from the cluster center, from ~0.2
arcmin to 6.5 arcmin = 23 half-light radii (r_h). We find only very weak
rotation, as typical of metal-poor globular clusters. The velocity dispersion
gently declines from a central value of sigma=6.1 km/s to sigma = 2.5 km/s at
~2 arcmin = 7.1= r_h, then it remainins flat out to the next (and last)
measured point of the dispersion profile, at ~4 arcmin = 14.0 r_h, at odds with
the predictions of isotropic King models. We show that both isotropic
single-mass non-collisional models and multi-mass anisotropic models can
reproduce the observed surface brightness and velocity dispersion profiles.Comment: Accepted for publication by MNRAS. Pdflatex, 10 pages, 10 figure
The effect of neural adaptation of population coding accuracy
Most neurons in the primary visual cortex initially respond vigorously when a
preferred stimulus is presented, but adapt as stimulation continues. The
functional consequences of adaptation are unclear. Typically a reduction of
firing rate would reduce single neuron accuracy as less spikes are available
for decoding, but it has been suggested that on the population level,
adaptation increases coding accuracy. This question requires careful analysis
as adaptation not only changes the firing rates of neurons, but also the neural
variability and correlations between neurons, which affect coding accuracy as
well. We calculate the coding accuracy using a computational model that
implements two forms of adaptation: spike frequency adaptation and synaptic
adaptation in the form of short-term synaptic plasticity. We find that the net
effect of adaptation is subtle and heterogeneous. Depending on adaptation
mechanism and test stimulus, adaptation can either increase or decrease coding
accuracy. We discuss the neurophysiological and psychophysical implications of
the findings and relate it to published experimental data.Comment: 35 pages, 8 figure
- …