51 research outputs found
Índice de Massa Corporal, Idade, Maturação Sexual e a Incidência de Hiperlordose Lombar em crianças e adolescentes
Introduction: Hyperlordosis can cause several degenerative spinal pathologies in children and adolescents.
Objective: Determine whether body mass index, age and sexual maturation predict the occurrence of hyperlordosis in children and adolescents. Method: The study analyzed 380 students aged between 10 and 18 years. Body mass index was evaluated using the reference values suggested by the Fitnessgram test battery, and sexual maturation through Tanner’s scale of self-assessed pubic hair growth. Postural assessment was conducted using the DIPA photogrammetry method, version 3.1. (Digital Image Based Postural Assessment) The SPSS 24.0 program was used to analyze the data, and the following statistical tests were applied: chi squared, Mann-Whitney, Fisher’s exact and binary logistic regression. Results: There was statistical significance between hyperlordosis, girls’ age and puberty in boys (p 0.05). Conclusion: The girls’ age and boys’ stage of puberty were associated with the occurrence of hyperlordosis.Introdução: A Hiperlordose lombar pode ocasionar diversas patologias degenerativas na coluna vertebral de crianças e adolescentes. Objetivo: Identificar se o Índice de Massa Corporal, a Idade e a Maturação Sexual são previsores da ocorrência da hiperlordose lombar em crianças e adolescentes. Método: O estudo analisou 380 estudantes entre 10 e 18 anos. O Índice de Massa Corporal foi avaliado por meio dos valores de referência sugeridos pela bateria de testes Fitnessgram e a maturação sexual por meio da auto-avaliação da pilosidade pubiana de Tanner. A avaliação postural foi realizada pelo método de fotogrametria DIPA versão 3.1. (Avaliação Postural Baseada em Imagem Digital). Para análise dos dados foi utilizado o programa SPSS 24.0, tendo sido aplicados os testes estatísticos: Qui-Quadrado, Mann Whitney, Exato de Fisher e Regressão Logística Binária. Resultados: Observou-se que houve significância estatística entre a Hiperlordose lombar e a idade das meninas e a puberdade dos meninos (p0,05). Conclusão: A idade das meninas e a puberdade dos meninos foi associada à ocorrência da hiperlordose lombar.This study was funded by CIEC (Center for
Investigations in Childhood Studies), Strategic Project
UID/CED/00317/2013, via National FCT (Science and
Technology Foundation) funds and co-funded by the
European Regional Development Fund (FEDER), via
COMPETE 2020 – Competitivity and Internalization
Operational Program (POCI) under reference number
POCI-01-0145-FEDER-007562
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Detection of cosmic structures using the bispectrum phase. II. First results from application to cosmic reionization using the Hydrogen Epoch of Reionization Array
Characterizing the epoch of reionization (EoR) at via the
redshifted 21 cm line of neutral Hydrogen (HI) is critical to modern
astrophysics and cosmology, and thus a key science goal of many current and planned low-frequency radio telescopes. The primary challenge to detecting this signal is the overwhelmingly bright foreground emission at these frequencies, placing stringent requirements on the knowledge of the instruments and inaccuracies in analyses. Results from these experiments have largely been limited not by thermal sensitivity but by systematics, particularly caused by the inability to calibrate the instrument to high accuracy. The interferometric bispectrum phase is immune to antenna-based calibration and errors therein, and presents an independent alternative to detect the EoR HI fluctuations while largely avoiding calibration systematics. Here, we provide a demonstration of this technique on a subset of data from the Hydrogen Epoch of Reionization Array (HERA) to place approximate constraints on the IGM brightness temperature. From this limited data, at we infer "" upper limits on the IGM brightness temperature to be "pseudo" mK at Mpc (data-limited) and
"pseudo" mK at
Mpc (noise-limited). The "pseudo" units denote only an approximate and not an exact correspondence to the actual distance scales and brightness temperatures. By propagating models in parallel to the data analysis, we confirm that the dynamic range required to separate the cosmic HI signal from the foregrounds is similar to that in standard approaches, and the power spectrum of the bispectrum phase is still data-limited (at dynamic range) indicating scope for further improvement in sensitivity as the array build-out continues
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Detection of cosmic structures using the bispectrum phase. II. First results from application to cosmic reionization using the Hydrogen Epoch of Reionization Array
Characterizing the epoch of reionization (EoR) at via the
redshifted 21 cm line of neutral Hydrogen (HI) is critical to modern
astrophysics and cosmology, and thus a key science goal of many current and planned low-frequency radio telescopes. The primary challenge to detecting this signal is the overwhelmingly bright foreground emission at these frequencies, placing stringent requirements on the knowledge of the instruments and inaccuracies in analyses. Results from these experiments have largely been limited not by thermal sensitivity but by systematics, particularly caused by the inability to calibrate the instrument to high accuracy. The interferometric bispectrum phase is immune to antenna-based calibration and errors therein, and presents an independent alternative to detect the EoR HI fluctuations while largely avoiding calibration systematics. Here, we provide a demonstration of this technique on a subset of data from the Hydrogen Epoch of Reionization Array (HERA) to place approximate constraints on the IGM brightness temperature. From this limited data, at we infer "" upper limits on the IGM brightness temperature to be "pseudo" mK at Mpc (data-limited) and
"pseudo" mK at
Mpc (noise-limited). The "pseudo" units denote only an approximate and not an exact correspondence to the actual distance scales and brightness temperatures. By propagating models in parallel to the data analysis, we confirm that the dynamic range required to separate the cosmic HI signal from the foregrounds is similar to that in standard approaches, and the power spectrum of the bispectrum phase is still data-limited (at dynamic range) indicating scope for further improvement in sensitivity as the array build-out continues
Imaging and Modeling Data from the Hydrogen Epoch of Reionization Array
We analyze data from the Hydrogen Epoch of Reionization Array. This is the
third in a series of papers on the closure phase delay-spectrum technique
designed to detect the HI 21cm emission from cosmic reionization. We present
the details of the data and models employed in the power spectral analysis, and
discuss limitations to the process. We compare images and visibility spectra
made with HERA data, to parallel quantities generated from sky models based on
the GLEAM survey, incorporating the HERA telescope model. We find reasonable
agreement between images made from HERA data, with those generated from the
models, down to the confusion level. For the visibility spectra, there is broad
agreement between model and data across the full band of MHz. However,
models with only GLEAM sources do not reproduce a roughly sinusoidal spectral
structure at the tens of percent level seen in the observed visibility spectra
on scales MHz on 29 m baselines. We find that this structure is
likely due to diffuse Galactic emission, predominantly the Galactic plane,
filling the far sidelobes of the antenna primary beam. We show that our current
knowledge of the frequency dependence of the diffuse sky radio emission, and
the primary beam at large zenith angles, is inadequate to provide an accurate
reproduction of the diffuse structure in the models. We discuss implications
due to this missing structure in the models, including calibration, and in the
search for the HI 21cm signal, as well as possible mitigation techniques
Understanding the HERA Phase i receiver system with simulations and its impact on the detectability of the EoR delay power spectrum
The detection of the Epoch of Reionization (EoR) delay power spectrum using a
"foreground avoidance method" highly depends on the instrument chromaticity.
The systematic effects induced by the radio-telescope spread the foreground
signal in the delay domain, which contaminates the EoR window theoretically
observable. Applied to the Hydrogen Epoch of Reionization Array (HERA), this
paper combines detailed electromagnetic and electrical simulations in order to
model the chromatic effects of the instrument, and quantify its frequency and
time responses. In particular, the effects of the analogue receiver,
transmission cables, and mutual coupling are included. These simulations are
able to accurately predict the intensity of the reflections occurring in the
150-m cable which links the antenna to the back-end. They also show that
electromagnetic waves can propagate from one dish to another one through large
sections of the array due to mutual coupling. The simulated system time
response is attenuated by a factor after a characteristic delay which
depends on the size of the array and on the antenna position. Ultimately, the
system response is attenuated by a factor after 1400 ns because of the
reflections in the cable, which corresponds to characterizable
-modes above 0.7 at 150 MHz. Thus, this new
study shows that the detection of the EoR signal with HERA Phase I will be more
challenging than expected. On the other hand, it improves our understanding of
the telescope, which is essential to mitigate the instrument chromaticity
Automated Detection of Antenna Malfunctions in Large-N Interferometers: A case study With the Hydrogen Epoch of Reionization Array
We present a framework for identifying and flagging malfunctioning antennas in large radio
interferometers. We outline two distinct categories of metrics designed to detect outliers along known failure
modes of large arrays: cross-correlation metrics, based on all antenna pairs, and auto-correlation metrics, based
solely on individual antennas. We define and motivate the statistical framework for all metrics used, and present
tailored visualizations that aid us in clearly identifying new and existing systematics. We implement these
techniques using data from 105 antennas in the Hydrogen Epoch of Reionization Array (HERA) as a case study.
Finally, we provide a detailed algorithm for implementing these metrics as flagging tools on real data sets
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Foreground modelling via Gaussian process regression: An application to HERA data
The key challenge in the observation of the redshifted 21-cm signal from
cosmic reionization is its separation from the much brighter foreground
emission. Such separation relies on the different spectral properties of the
two components, although, in real life, the foreground intrinsic spectrum is
often corrupted by the instrumental response, inducing systematic effects that
can further jeopardize the measurement of the 21-cm signal. In this paper, we
use Gaussian Process Regression to model both foreground emission and
instrumental systematics in hours of data from the Hydrogen Epoch of
Reionization Array. We find that a simple co-variance model with three
components matches the data well, giving a residual power spectrum with white
noise properties. These consist of an "intrinsic" and instrumentally corrupted
component with a coherence-scale of 20 MHz and 2.4 MHz respectively (dominating
the line of sight power spectrum over scales h
cMpc) and a baseline dependent periodic signal with a period of
MHz (dominating over h cMpc) which should
be distinguishable from the 21-cm EoR signal whose typical coherence-scales is
MHz
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Foreground modelling via Gaussian process regression: An application to HERA data
The key challenge in the observation of the redshifted 21-cm signal from
cosmic reionization is its separation from the much brighter foreground
emission. Such separation relies on the different spectral properties of the
two components, although, in real life, the foreground intrinsic spectrum is
often corrupted by the instrumental response, inducing systematic effects that
can further jeopardize the measurement of the 21-cm signal. In this paper, we
use Gaussian Process Regression to model both foreground emission and
instrumental systematics in hours of data from the Hydrogen Epoch of
Reionization Array. We find that a simple co-variance model with three
components matches the data well, giving a residual power spectrum with white
noise properties. These consist of an "intrinsic" and instrumentally corrupted
component with a coherence-scale of 20 MHz and 2.4 MHz respectively (dominating
the line of sight power spectrum over scales h
cMpc) and a baseline dependent periodic signal with a period of
MHz (dominating over h cMpc) which should
be distinguishable from the 21-cm EoR signal whose typical coherence-scales is
MHz
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