Building Neural Network Models for Time Series: A Statistical Approach

This paper is concerned with modelling time series by single hidden layer feedforward neural network models. A coherent modelling strategy based on statistical inference is presented. Variable selection is carried out using existing techniques. The problem of selecting the number of hidden units is solved by sequentially applying Lagrange multiplier type tests, with the aim of avoiding the estimation of unidentified models. Misspecification tests are derived for evaluating an estimated neural network model. A small-sample simulation experiment is carried out to show how the proposed modelling strategy works and how the misspecification tests behave in small samples. Two applications to real time series, one univariate and the other multivariate, are considered as well. Sets of one-step-ahead forecasts are constructed and forecast accuracy is compared with that of other nonlinear models applied to the same series.

Implante de marcapasso cardíaco definitivo em paciente com síndrome bradicardia-taquicardia, transplantado renal e com persistência de veia cava superior esquerda

A persistência da veia cava superior esquerda é rara, principalmente quando associada a ausência da veia cava superior direita, e mais ainda quando associada a síndrome bradicardia-taquicardia. Relata-se o caso em que o diagnóstico dessa anomalia venosa foi feito durante o implante de marcapasso cardíaco artificial definitivo para tratamento de síndrome bradicardia-taquicardia. O paciente havia sido submetido a transplante renal e apresentava funçao renal limítrofe, razao pela qual se optou por nao utilizar contraste para realizaçao de venografia, dando preferência à análise do trajeto do fio guia

Implante de marcapasso cardíaco definitivo em paciente com síndrome bradicardia-taquicardia, transplantado renal e com persistência de veia cava superior esquerda

A persistência da veia cava superior esquerda é rara, principalmente quando associada a ausência da veia cava superior direita, e mais ainda quando associada a síndrome bradicardia-taquicardia. Relata-se o caso em que o diagnóstico dessa anomalia venosa foi feito durante o implante de marcapasso cardíaco artificial definitivo para tratamento de síndrome bradicardia-taquicardia. O paciente havia sido submetido a transplante renal e apresentava funçao renal limítrofe, razao pela qual se optou por nao utilizar contraste para realizaçao de venografia, dando preferência à análise do trajeto do fio guia

Balanço energético de um incinerador de leito fixo para incineração de resíduos sólidos da indústria coureiro-calçadista

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Reduced Precision DWC: an Efficient Hardening Strategy for Mixed-Precision Architectures

Duplication with Comparison (DWC) is an effective software-level solution to improve the reliability of computing devices. However, it introduces performance and energy consumption overheads that could be unsuitable for high-performance computing or real-time safety-critical applications. In this work, we present Reduced-Precision Duplication with Comparison (RP-DWC) as a means to lower the overhead of DWC by executing the redundant copy in reduced precision. RP-DWC is particularly suitable for modern mixed-precision architectures, such as NVIDIA GPUs, that feature dedicated functional units for computing with programmable accuracy. We discuss the benefits and challenges associated with RP-DWC and show that the intrinsic difference between the mixed-precision copies allows for detecting most, but not all, errors. However, as the undetected faults are the ones that fall into the difference between precisions, they are the ones that produce a much smaller impact on the application output and, thus, might be tolerated. We investigate RP-DWC impact into fault detection, performance, and energy consumption on Volta GPUs. Through fault injection and beam experiment, using three microbenchmarks and four real applications, we show that RP-DWC achieves an excellent coverage (up to 86%) with minimal overheads (as low as 0.1% time and 24% energy consumption overhead

Diagnostic accuracy of multiorgan point-of-care ultrasound compared with pulmonary computed tomographic angiogram in critically ill patients with suspected pulmonary embolism

Background: Critically ill patients have a higher incidence of pulmonary embolism (PE) than non-critically ill patients, yet no diagnostic algorithm has been validated in this population, leading to the overuse of pulmonary artery computed tomographic angiogram (CTA). This study aimed to comparatively evaluate the diagnostic accuracy of point-of-care ultrasound (POCUS) combined with laboratory data versus CTA in predicting PE in critically ill patients. Methods: A prospective diagnostic accuracy study. Critically ill patients with suspected acute PE undergoing CTA were prospectively enrolled. Demographic and clinical data were collected from electronic medical records. Blood samples were collected, and the Wells and revised Geneva scores were calculated. Standardized multiorgan POCUS and CTA were performed. The discriminatory power of multiorgan POCUS combined with biochemical markers was tested using ROC curves, and multivariate analysis was performed. Results: A total of 88 patients were included, and 37 (42%) had PE. Multivariate analysis showed a relative risk (RR) of PE of 2.79 (95% CI, 1.61-4.84) for the presence of right ventricular (RV) dysfunction, of 2.54 (95% CI, 0.89-7.20) for D-dimer levels >1000 ng/mL, and of 1.69 (95% CI, 1.12-2.63) for the absence of an alternative diagnosis to PE on lung POCUS or chest radiograph. The combination with the highest diagnostic accuracy for PE included the following variables: 1- POCUS transthoracic echocardiography with evidence of RV dysfunction; 2- lung POCUS or chest radiograph without an alternative diagnosis to PE; and 3- plasma D-dimer levels >1000 ng/mL. Combining these three findings resulted in an area under the curve of 0.85 (95% CI, 0.77-0.94), with 50% sensitivity and 96% specificity. Conclusions: Multiorgan POCUS combined with laboratory data has acceptable diagnostic accuracy for PE compared with CTA. The combined use of these methods might reduce CTA overuse in critically ill patients

Association between prolonged corticosteroids use in COVID-19 and increased mortality in hospitalized patients : a retrospective study with inverse probability of treatment weighting analysis

Background: Previous studies have demonstrated a beneficial effect of early use of corticosteroids in patients with COVID-19. This study aimed to compare hospitalized patients with COVID-19 who received short-course corticosteroid treatment with those who received prolonged-course corticosteroid treatment to determine whether prolonged use of corticosteroids improves clinical outcomes, including mortality. Methods: This is a retrospective cohort study including adult patients with positive testing for Sars-CoV-2 hospitalized for more than 10 days. Data were obtained from electronic medical records. Patients were divided into two groups, according to the duration of treatment with corticosteroids: a short-course (10 days) and a prolonged-course (longer than 10 days) group. Inverse probability treatment weighting (IPTW) analysis was used to evaluate whether prolonged use of corticosteroids improved outcomes. The primary outcome was in-hospital mortality. Secondary outcomes were hospital infection and the association of different doses of corticosteroids with hospital mortality. Restricted cubic splines were used to assess the nonlinear association between mortality and dose and duration of corticosteroids use. Results: We enrolled 1,539 patients with COVID-19. Among them, 1127 received corticosteroids for more than 10 days (prolonged-course group). The in-hospital mortality was higher in patients that received prolonged course corticosteroids (39.5% vs. 26%, p < 0.001). The IPTW revealed that prolonged use of corticosteroids significantly increased mortality [relative risk (RR) = 1.52, 95% confidence interval (95% CI): 1.24-1.89]. In comparison to short course treatment, the cubic spline analysis showed an inverted U-shaped curve for mortality, with the highest risk associated with the prolonged use at 30 days (RR = 1.50, 95% CI 1.21-1.78). Conclusions: Prolonged course of treatment with corticosteroids in hospitalized patients with COVID-19 was associated with higher mortality

Dinâmicas contemporâneas das mobilizações sociais

O objetivo deste dossiê é promover a discussão em torno de processos contemporâneos de organização e mobilização social em diferentes contextos e que busquem o diálogo com as diversas perspectivas teóricas sobre os processos de associação, contestação e engajamento

Processos de geocodificação em estudos de coorte: métodos aplicados no EpiFloripa Idoso

OBJECTIVE: To describe the process and epidemiological implications of georeferencing in EpiFloripa Aging samples (2009–2019). METHOD: The EpiFloripa Aging Cohort Study sought to investigate and monitor the living and health conditions of the older adult population (≥ 60) of Florianópolis in three study waves (2009/2010, 2013/2014, 2017/2019). With an automatic geocoding tool, the residential addresses were spatialized, allowing to investigate the effect of the georeferencing sample losses regarding 19 variables, evaluated in the three waves. The influence of different neighborhood definitions (census tracts, Euclidean buffers, and buffers across the street network) was examined in the results of seven variables: area, income, residential density, mixed land use, connectivity, health unit count, and public open space count. Pearson’s correlation coefficients were calculated to evaluate the differences between neighborhood definitions according to three variables: contextual income, residential density, and land use diversity. RESULT: The losses imposed by geocoding (6%, n = 240) caused no statistically significant difference between the total sample and the geocoded sample. The analysis of the study variables suggests that the geocoding process may have included a higher proportion of participants with better income, education, and living conditions. The correlation coefficients showed little correspondence between measures calculated by the three neighborhood definitions (r = 0.37–0.54). The statistical difference between the variables calculated by buffers and census tracts highlights limitations in their use in the description of geospatial attributes. CONCLUSION: Despite the challenges related to geocoding, such as inconsistencies in addresses, adequate correction and verification mechanisms provided a high rate of assignment of geographic coordinates, the findings suggest that adopting buffers, favored by geocoding, represents a potential for spatial epidemiological analyses by improving the representation of environmental attributes and the understanding of health outcomes.OBJETIVO: Descrever o processo e as implicações epidemiológicas do georreferenciamento nas amostras do EpiFloripa Idoso (2009–2019). MÉTODO: O estudo de coorte EpiFloripa Idoso buscou investigar e acompanhar as condições de vida e saúde da população idosa (≥ 60) de Florianópolis em três ondas de estudo (2009/2010, 2013/2014, 2017/2019). Com uma ferramenta de geocodificação automática, os endereços residenciais foram espacializados, permitindo a investigação do efeito das perdas amostrais do georreferenciamento em relação a 19 variáveis, avaliadas nas três ondas. A influência de diferentes definições de vizinhança (setores censitários, buffers euclidianos e buffers pela rede de ruas) foi examinada nos resultados de sete variáveis: área, renda, densidade residencial, uso misto do solo, conectividade, contagem de unidades de saúde, e contagem de espaços livres públicos. Coeficientes de correlação de Pearson foram calculados para avaliar as diferenças entre as definições de vizinhança de acordo com três variáveis: renda contextual, densidade residencial e diversidade de uso do solo. RESULTADO: As perdas impostas pela geocodificação (6%, n = 240) não ocasionaram diferença estatística significativa entre a amostra total e a georreferenciada. A análise das variáveis do estudo sugere que o processo de geocodificação pode ter incluído uma maior proporção de participantes com melhor nível de renda, escolaridade e condições de vida. Os coeficientes de correlação evidenciaram pouca correspondência entre medidas calculadas pelas três definições de vizinhança (r = 0,37–0,54). A diferença estatística entre as variáveis calculadas por buffers e setores censitários ressalta limitações no uso destes na descrição dos atributos geoespaciais. CONCLUSÃO: Apesar dos desafios relacionados à geocodificação, como inconsistências nos endereços, adequados mecanismos de correção e verificação propiciaram elevada taxa de atribuição de coordenadas geográficas. Os achados sugerem que a adoção de buffers, favorecida pela geocodificação, representa uma potencialidade para análises epidemiológicas espaciais ao aprimorar a representação dos atributos do ambiente e a compreensão dos desfechos de saúde