9,083 research outputs found
Twin Peaks: A possible signal in the production of resonances beyond special relativity
It is usually expected that quantum gravity corrections will modify somehow
the symmetries of special relativity. In this paper we point out that the
possibility of very low-energy (with respect to the Planck energy)
modifications to special relativity in the framework of a deformed relativistic
theory is not ruled out, and that, depending on the value of that scale, such a
possibility could be tested in accelerator physics. In particular, we take a
simple example of a relativistic kinematics beyond special relativity from the
literature, and obtain a remarkable effect: two correlated peaks ("twin peaks")
associated to a single resonance. We analyze this phenomenology in detail, use
LEP data to put constraints of the order of TeV on the scale of corrections to
special relativity, and note that such an effect might be observable in a
future very high-energy proton collider.Comment: 17 pages, accepted for publication in Symmetr
Identification of redundant and synergetic circuits in triplets of electrophysiological data
Neural systems are comprised of interacting units, and relevant information
regarding their function or malfunction can be inferred by analyzing the
statistical dependencies between the activity of each unit. Whilst correlations
and mutual information are commonly used to characterize these dependencies,
our objective here is to extend interactions to triplets of variables to better
detect and characterize dynamic information transfer. Our approach relies on
the measure of interaction information (II). The sign of II provides
information as to the extent to which the interaction of variables in triplets
is redundant (R) or synergetic (S). Here, based on this approach, we calculated
the R and S status for triplets of electrophysiological data recorded from
drug-resistant patients with mesial temporal lobe epilepsy in order to study
the spatial organization and dynamics of R and S close to the epileptogenic
zone (the area responsible for seizure propagation). In terms of spatial
organization, our results show that R matched the epileptogenic zone while S
was distributed more in the surrounding area. In relation to dynamics, R made
the largest contribution to high frequency bands (14-100Hz), whilst S was
expressed more strongly at lower frequencies (1-7Hz). Thus, applying
interaction information to such clinical data reveals new aspects of
epileptogenic structure in terms of the nature (redundancy vs. synergy) and
dynamics (fast vs. slow rhythms) of the interactions. We expect this
methodology, robust and simple, can reveal new aspects beyond pair-interactions
in networks of interacting units in other setups with multi-recording data sets
(and thus, not necessarily in epilepsy, the pathology we have approached here).Comment: 31 pages, 6 figures, 3 supplementary figures. To appear in the
Journal of Neural Engineering in its current for
Exploring Food Detection using CNNs
One of the most common critical factors directly related to the cause of a
chronic disease is unhealthy diet consumption. In this sense, building an
automatic system for food analysis could allow a better understanding of the
nutritional information with respect to the food eaten and thus it could help
in taking corrective actions in order to consume a better diet. The Computer
Vision community has focused its efforts on several areas involved in the
visual food analysis such as: food detection, food recognition, food
localization, portion estimation, among others. For food detection, the best
results evidenced in the state of the art were obtained using Convolutional
Neural Network. However, the results of all these different approaches were
gotten on different datasets and therefore are not directly comparable. This
article proposes an overview of the last advances on food detection and an
optimal model based on GoogLeNet Convolutional Neural Network method, principal
component analysis, and a support vector machine that outperforms the state of
the art on two public food/non-food datasets
The molecular clump towards the eastern border of SNR G18.8+0.3
The eastern border of the SNR G18.8+0.3, close to an HII regions complex, is
a very interesting region to study the molecular gas that it is probably in
contact with the SNR shock front. We observed the aforementioned region using
the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO J=3-2, 13CO
J=3-2, HCO+ J=4-3, and CS J=7-6 lines with an angular resolution of 22". To
complement these observations, we analyzed IR, submillimeter and radio
continuum archival data. In this work, we clearly show that the radio continuum
"protrusion" that was early thought to belong to the SNR is an HII regions
complex deeply embedded in a molecular clump. The new molecular observations
reveal that this dense clump, belonging to an extended molecular cloud that
surrounds the SNR southeast border, is not physically in contact with SNR
G18.8+0.3, suggesting that the SNR shock front have not yet reached it or maybe
they are located at different distances. We found some young stellar objects
embedded in the molecular clump, suggesting that their formation should be
approximately coeval with the SN explosion.Comment: Accepted for publication in A&A (Sept. 7, 2012
Some properties of local weighted second-order statistics for spatio-temporal point processes
Diagnostics of goodness-of-fit in the theory of point processes are often considered through the transformation of data into residuals as a result of a thinning or a rescaling procedure. We alternatively consider here second-order statistics coming from weighted measures. Motivated by Adelfio and Schoenberg (2009) for the temporal and spatial cases, we consider an extension to the spatio-temporal context in addition to focussing on local characteristics. In particular, our proposed method assesses goodness-of-fit of spatio-temporal models by using local weighted secondorder statistics, computed after weighting the contribution of each observed point by the inverse of the conditional intensity function that identifies the process. Weighted second-order statistics directly apply to data without assuming homogeneity nor transforming the data into residuals, eliminating thus the sampling variability due to the use of a transforming procedure. We provide some characterisations and show a number of simulation studies
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
Analysis of the tautomeric equilibrium of two red monoazo dyes by UV–Visible, Raman and SERS spectroscopies
Acid Red 26 and Acid Red 18 are two early synthetic dyes belonging to the monazo dye class. The molecular structure of this class of dyes is characterized by the chromophoric azo group (N[dbnd]N) generally attached to benzene or naphthalene derivatives containing electron withdrawing and/or donating groups as substituents. As both red dyes have an OH group in ortho- position respect to the azo group, they undergo an azo-hydrazone tautomerism. In this work, UV–Vis, Raman and SERS spectroscopic analysis of the red dye solutions were carried out at different pH conditions, in order to evaluate the preponderance of one tautomer over the other as a function of the pH. Different experimental conditions were tested in order to find the best ones for the detection of both dyes. Thus, Raman spectra of the powder and aqueous solutions of AR26 and AR18 were obtained at the natural pH of the solutions, and above and below that value. The SERS analysis of the dye solutions were carried out at various pH values between 2 and 10, and with excitation at 442, 532 and 633 nm. The molecular structure and the theoretical Raman spectra of the two tautomers of both red dyes were calculated by DFT methods. The obtained results were used for the assignment of the Acid Red 26 and Acid Red 18 vibrational modes. Finally, a textile sample dyed with AR18 was analyzed by SERS
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