671 research outputs found
Gravitational Collapse of a Homogeneous Scalar Field in Deformed Phase Space
We study the gravitational collapse of a homogeneous scalar field, minimally
coupled to gravity, in the presence of a particular type of dynamical
deformation between the canonical momenta of the scale factor and of the scalar
field. In the absence of such a deformation, a class of solutions can be found
in the literature [R. Goswami and P. S. Joshi, arXiv:gr-qc/0410144],
%\cite{JG04}, whereby a curvature singularity occurs at the collapse end state,
which can be either hidden behind a horizon or be visible to external
observers. However, when the phase-space is deformed, as implemented herein
this paper, we find that the singularity may be either removed or instead,
attained faster. More precisely, for negative values of the deformation
parameter, we identify the emergence of a negative pressure term, which slows
down the collapse so that the singularity is replaced with a bounce. In this
respect, the formation of a dynamical horizon can be avoided depending on the
suitable choice of the boundary surface of the star. Whereas for positive
values, the pressure that originates from the deformation effects assists the
collapse toward the singularity formation. In this case, since the collapse
speed is unbounded, the condition on the horizon formation is always satisfied
and furthermore the dynamical horizon develops earlier than when the
phase-space deformations are absent. These results are obtained by means of a
thoroughly numerical discussion.Comment: 17 pages, 17 figure
Loop quantum effect and the fate of tachyon field collapse
We study the fate of gravitational collapse of a tachyon field matter. In
presence of an inverse square potential a black hole forms. Loop quantum
corrections lead to the avoidance of classical singularities, which is followed
by an outward flux of energy.Comment: Contribution to the conference of Loops'11, Madri
A Unified Approach to Attractor Reconstruction
In the analysis of complex, nonlinear time series, scientists in a variety of
disciplines have relied on a time delayed embedding of their data, i.e.
attractor reconstruction. The process has focused primarily on heuristic and
empirical arguments for selection of the key embedding parameters, delay and
embedding dimension. This approach has left several long-standing, but common
problems unresolved in which the standard approaches produce inferior results
or give no guidance at all. We view the current reconstruction process as
unnecessarily broken into separate problems. We propose an alternative approach
that views the problem of choosing all embedding parameters as being one and
the same problem addressable using a single statistical test formulated
directly from the reconstruction theorems. This allows for varying time delays
appropriate to the data and simultaneously helps decide on embedding dimension.
A second new statistic, undersampling, acts as a check against overly long time
delays and overly large embedding dimension. Our approach is more flexible than
those currently used, but is more directly connected with the mathematical
requirements of embedding. In addition, the statistics developed guide the user
by allowing optimization and warning when embedding parameters are chosen
beyond what the data can support. We demonstrate our approach on uni- and
multivariate data, data possessing multiple time scales, and chaotic data. This
unified approach resolves all the main issues in attractor reconstruction.Comment: 22 pages, revised version as submitted to CHAOS. Manuscript is
currently under review. 4 Figures, 31 reference
Prosodic exercises for children with ASD via virtual therapy
which means that there is a wide degree of variation in the way it affects people. It is known that, even though it has a huge spectrum, the characterization of the speech of autistic children has been consensual in the literature as devoid of wealth prosodic parameters manifested by healthy children, such as the emotional aspects that are reflected in communicative interaction. The use of technology as a teaching tool has been growing and the presentation of educational exercises through electronic devices reveals itself as more attractive and captivating for children when compared with traditional methods. In this project, we developed prosodic exercises for intonation assessment in an imitation task, where the main focus is the development and enrichment of prosodic abilities of children with autism spectrum disorders, as a complement to therapy sessions.We evaluated the intonation assessment method, achieving accuracy values between 70%and 83.3%, depending on the feature set adapted (pitch, energy, Mel-Frequency Cepstral features, and pseudo-syllable information), and also by making a fusion of all features. Although the original intention was to integrate these exercises in an existing platform for children diagnosed with ASD, the current implementation is a stand-alone mobile application.info:eu-repo/semantics/publishedVersio
Population-level factors associated with maternal mortality in the United States, 1997–2012
Abstract
Background
In contrast to peer nations, the United States is experiencing rapid increases in maternal mortality. Trends in individual and population-level demographic factors and health trends may play a role in this change.
Methods
We analyzed state-level maternal mortality for the years 1997–2012 using multilevel mixed-effects regression grouped by state, using publicly available data including whether a state had adopted the 2003 U.S. Standard Certificate of Death, designed to simplify identification of pregnant and recently pregnant decedents. We calculated the proportion of the increase in maternal mortality attributable to specific factors during the study period.
Results
Maternal mortality was associated with higher population prevalence of obesity and high school non-completion among women of childbearing age; these factors explained 31.0% and 5.3% of the attributable increase in maternal mortality during the study period, respectively. Among delivering mothers, prevalence of diabetes (17.0%), attending fewer than 10 prenatal visits (4.9%), and African American race (2.0%) were also associated with higher maternal mortality, as was time-varying state adoption of the 2003 death certificate (31.1%).
Conclusions
Our findings indicate that, in addition to better case ascertainment of maternal deaths, adverse changes in chronic diseases, insufficient healthcare access, and social determinants of health represent identifiable risks for maternal mortality that merit prompt attention in population-directed interventions and health policies.https://deepblue.lib.umich.edu/bitstream/2027.42/145432/1/12889_2018_Article_5935.pd
Speech features for discriminating stress using branch and bound wrapper search
Stress detection from speech is a less explored field than Automatic Emotion Recognition and it is still not clear which features are
better stress discriminants. VOCE aims at doing speech classification
as stressed or not-stressed in real-time, using acoustic-prosodic features
only. We therefore look for the best discriminating feature subsets from
a set of 6285 features – 6125 features extracted with openSMILE toolkit
and 160 Teager Energy Operator (TEO) features. We use a mutual information filter and a branch and bound wrapper heuristic with an SVM
classifier to perform feature selection. Since many feature sets are selected, we analyse them in terms of chosen features and classifier performance concerning also true positive and false positive rates. The results
show that the best feature types for our application case are Audio Spectral, MFCC, PCM and TEO. We reached results as high as 70.36% for
generalisation accuracyinfo:eu-repo/semantics/acceptedVersio
Correlation Effects in Nuclear Transparency
The Glauber approximation is used to calculate the contribution of nucleon
correlations in high-energy reactions. When the excitation energy of
the residual nucleus is small, the increase of the nuclear transparency due to
correlations between the struck nucleon and the other nucleons is mostly
compensated by a decrease of the transparency due to the correlations between
non detected nucleons. We derive Glauber model predictions for nuclear
transparency for the differential cross section when nuclear shell level
excitations are measured. The role of correlations in color transparency is
briefly discussed.Comment: 24 pages revtex, 4 uuencoded PostScript Figures as separate fil
Rabdomiólise como manifestação de uma doença metabólica: relato de caso
Rhabdomyolysis is a process of muscle destruction that can present with varying clinical manifestations. In pediatric patients, its main etiology is infectious diseases. We present a previously healthy adolescent who was admitted to our emergency department with a four-day history of myalgia, muscle weakness and dark urine. At presentation, she was dehydrated. Blood analysis revealed acute renal failure and increased muscular enzymes. She was transferred to our pediatric intensive care unit. Medical therapies for correction of dehydration and the ionic and metabolic consequences of renal failure were performed. Due to oliguria, renal replacement therapy was initiated. An etiological investigation revealed a beta-oxidation defect. Metabolic diseases are a known cause of rhabdomyolysis. Muscular destruction should be diagnosed early in order to avoid its potential consequences. Generally, the treatment of rhabdomyolysis is conservative, although in some situations, a more invasive approach is needed.info:eu-repo/semantics/publishedVersio
H1N1 disseminated infection in a 3-month-old boy
Earlier this year a new influenza virus emerged. In children, the clinical manifestations of H1N1 infection are similar to those reported during periods of seasonal influenza. We report on a 3-month-old boy with an upper respiratory tract infection who presented enteropathy, coagulopathy and encephalitis related to H1N1. The infection was confirmed in nasopharyngeal aspirate, stools and cerebrospinal fluid by real-time PCR. Treatment with oseltamivir was started.info:eu-repo/semantics/publishedVersio
Supersymmetric Quantization of Anisotropic Scalar-Tensor Cosmologies
In this paper we show that the spatially homogeneous Bianchi type I and
Kantowski-Sachs cosmologies derived from the Brans-Dicke theory of gravity
admit a supersymmetric extension at the quantum level. Global symmetries in the
effective one-dimensional actions characterize both classical and quantum
solutions. A wide family of exact wavefunctions satisfying the supersymmetric
constraints are found. A connection with quantum wormholes is briefly
discussed.Comment: In Press, Class. Quantum Grav. 20 pages, Late
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