Carta t2 con base en estimadores robustos de los parámetros

En la primera etapa de implementación de un sistema de control multivariado, usando la carta T ² de Hotelling con n observaciones históricas individuales, la presencia de outliers distorsiona la estimación de los parámetros del proceso y del límite de control debido al efecto de enmascaramiento. En este trabajo proponemos el uso de estimadores robustos para la construcción del estadístico T ² en esta primera etapa. Se prueba con estimadores MVE (elipsoide de mínimo volumen) y estimadores S biponderados, para el caso p = 2. Los resultados de simulaciones señalan que estos dos procedimientos resultan consistentes en la detección de outliers provenientes de perturbaciones en el vector de medias y de la matriz de varianzas covarianzas, consideradas individual y conjuntamente, con diferentes niveles de contaminación.In Phase I, Stage 1 of a multivariate process control, the implementation of a Hotelling's T ² chart with n individual observation, outliers cause difficulties with the estimation of process parameters and control limits due to masking effects. We propose procedures to construct robust estimators based upon the MVE (Minimum Volume Ellipsoide) and the biweighted S estimator, for case p = 2 (Bivariate Process). Simulation results show the good performance of these estimators before outliers presence, avoiding masking effects, when we are estimating the mean vector and varianza covarianza matrix, both individually and jointly. We make the investigation with different levels of contamination affecting the mean vector and varianza covarianza matrix

Comparación entre riesgos competitivos vía el estimador cópula-gráfico

En riesgos competitivos, el problema de identificabilidad asociado a la dependencia entre los modos de falla, se puede resolver utilizando el estimador cópula-gráfico que asume la forma de la cópula conocida. En este trabajo se compara, mediante simulación, este estimador para un modelo de riesgos competitivos dependientes con el estimador tradicional que asume independencia. Se muestra que ignorar la dependencia puede causar subestimación significativa de la función de confiabilidad. Se ilustra la temática con un ejemplo y se visualiza a futuro la posible utilidad del estimador cópulagráfico en confiabilidad industrial para predecir en experimentos acelerados.The identifiability problem in competing risks associated to the dependence measure between the failure modes, can be solved by means of the copula-graphic estimator which assumes the copula function known. This paper compares, through a simulation study, the copula-graphic estimator for a dependent competing risks model with the traditional one under the assumption of independence. It is shown that a significant subestimation of the reliability function can be made when the dependence is not taken into account. An example ilustrates this point and as a future work it is seen the possibility of using copula-graphic in industrial reliability to predict in accelerated life tests

Comparative study of the dependence effect on competing risks models with three modes of failure via estimators copula based

Resumen En un modelo de riesgos competitivos dependientes es imposible determinar las distribuciones marginales a partir solamente de los datos de riesgos competitivos. Esta situación se conoce como el problema de identificabilidad. Zheng y Klein (1995) proponen el estimador cópula gráfico como solución al problema de identificabilidad para dos riesgos competitivos. Para ello asumen una estructura de dependencia usando una cópula para la distribución conjunta entre los tiempos de falla y su parámetro de dependencia conocido. En el caso de un modelo con más de dos riesgos competitivos, Lo y Wilke (2010) proponen el método de combinación de riesgo (“risk pooling method”) como una extensión del estimador cópula gráfico cuando la cópula es Arquimediana. En este trabajo para el caso trivariado, se compara la función de sobrevivencia conjunta verdadera, con la función de sobrevivencia conjunta estimada asumiendo independencia entre los tiempos de falla y la función de sobrevivencia estimada mediante el método de combinación de riesgos. Estas comparaciones se realizan vía simulación teniendo en cuenta tiempos de falla asociados a una distribución Weibull y lognormal multivariada y diferentes niveles de dependencia entre los tiempos de falla. Se concluye que el estimador asumiendo independencia es menos eficiente que el estimador de la función de sobrevivencia utilizando el método de combinación de riesgos. Se ilustra la metodología con datos de la confiabilidad de interruptores tipo FL245 en Interconexión Eléctrica S.A. E.S.P. (ISA), que muestran la utilidad de la temática en confiabilidad industrial. Abstract In a dependent competing risks model is impossible to determine the marginal distributions from the competing risks data alone. This is known as the identifiability problem. Zheng and Klein (1995) propose the copula graphic estimator as a solution to the identifiability problem for two competing risks. For that, they assume a dependence structure using a copula for the joint distribution of failure times and its dependence parameter known. Lo and Wilke (2010) propose the risk pooling method as an extension of the copula graphic estimator when the copula is Archimedean. This research for the trivariate case, is compared the true joint survival function, with joint survival function estimated assuming independence among failure times and the survival function estimated by the risk pooling method. These comparisons are performed via simulation considering failure times associated with multivariate Weibull and lognormal distributions and different levels of dependence between failure times. We conclude that the estimator assuming independence is less efficient than the estimator of the survival function using the risk pooling method. The methodology is illustrated with reliability data of FL245 switches in Interconexión Eléctrica S.A. E.S.P. (ISA), which show the usefulness of this topic in industrial reliability

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

CARTA T2 CON BASE EN ESTIMADORES ROBUSTOS DE LOS PARÁMETROS CARTA T2 CON BASE EN ESTIMADORES ROBUSTOS DE LOS PARÁMETROS

In Phase I, Stage 1 of a multivariate process control, the implementation of a Hotelling's T ² chart with n individual observation, outliers cause difficulties with the estimation of process parameters and control limits due to masking effects. We propose procedures to construct robust estimators based upon the MVE (Minimum Volume Ellipsoide) and the biweighted S estimator, for case p = 2 (Bivariate Process). Simulation results show the good performance of these estimators before outliers presence, avoiding masking effects, when we are estimating the mean vector and varianza covarianza matrix, both individually and jointly. We make the investigation with different levels of contamination affecting the mean vector and varianza covarianza matrix.En la primera etapa de implementación de un sistema de control multivariado, usando la carta T ² de Hotelling con n observaciones históricas individuales, la presencia de outliers distorsiona la estimación de los parámetros del proceso y del límite de control debido al efecto de enmascaramiento. En este trabajo proponemos el uso de estimadores robustos para la construcción del estadístico T ² en esta primera etapa. Se prueba con estimadores MVE (elipsoide de mínimo volumen) y estimadores S biponderados, para el caso p = 2. Los resultados de simulaciones señalan que estos dos procedimientos resultan consistentes en la detección de outliers provenientes de perturbaciones en el vector de medias y de la matriz de varianzas covarianzas, consideradas individual y conjuntamente, con diferentes niveles de contaminación

Comparación entre riesgos competitivos vía el estimador cópula-gráfico Comparison between Competing Risks via the Copula-Graphic Estimator

En riesgos competitivos, el problema de identificabilidad asociado a la dependencia entre los modos de falla, se puede resolver utilizando el estimador cópula-gráfico que asume la forma de la cópula conocida. En este trabajo se compara, mediante simulación, este estimador para un modelo de riesgos competitivos dependientes con el estimador tradicional que asume independencia. Se muestra que ignorar la dependencia puede causar subestimación significativa de la función de confiabilidad. Se ilustra la temática con un ejemplo y se visualiza a futuro la posible utilidad del estimador cópula-gráfico en confiabilidad industrial para predecir en experimentos acelerados.The identifiability problem in competing risks associated to the dependence measure between the failure modes, can be solved by means of the copula-graphic estimator which assumes the copula function known. This paper compares, through a simulation study, the copula-graphic estimator for a dependent competing risks model with the traditional one under the assumption of independence. It is shown that a significant subestimation of the reliability function can be made when the dependence is not taken into account. An example ilustrates this point and as a future work it is seen the possibility of using copula-graphic in industrial reliability to predict in accelerated life tests

Estudio comparativo del efecto de la dependencia en modelos de riesgos competitivos con tres modos de falla vía estimadores basados en cópulas

In a dependent competing risks model is impossible to determine the marginal distributions from the competing risks data alone. This is known as the identifiability problem. &nbsp;Zheng and Klein (1995) propose the copula graphic estimator as a solution to the identifiability problem for two competing risks. For that, they assume a dependence structure using a copula for the joint distribution of failure times and its dependence parameter known. Lo and Wilke (2010) propose the risk pooling method as an extension of the copula graphic estimator when the copula is &nbsp;Archimedean. &nbsp;This &nbsp;research &nbsp;for &nbsp;the &nbsp;trivariate &nbsp;case, &nbsp;is &nbsp;compared &nbsp;the &nbsp;true &nbsp;joint &nbsp;survival &nbsp;function, &nbsp;with &nbsp;joint &nbsp;survival function estimated assuming independence among failure times and the survival function estimated by the risk pooling method. These comparisons are performed via simulation considering failure times associated with &nbsp;multivariate &nbsp;Weibull &nbsp;and &nbsp;lognormal &nbsp;distributions &nbsp;and &nbsp;different &nbsp;levels &nbsp;of &nbsp;dependence &nbsp;between &nbsp;failure &nbsp;times. We conclude that the estimator assuming independence is less efficient than the estimator of the survival function using the risk pooling method. The methodology is illustrated with reliability data of FL245 switches in Interconexión Eléctrica S.A. E.S.P. (ISA), which show the usefulness of this topic in industrial reliability.En un modelo de riesgos competitivos dependientes es imposible determinar las distribuciones marginales a partir solamente de los datos de riesgos competitivos. Esta situación se conoce como el problema de identificabilidad. Zheng y Klein (1995) proponen el estimador cópula gráfico como solución al problema de identificabilidad para dos riesgos competitivos. Para ello asumen una estructura de dependencia usando una cópula para la distribución conjunta entre los tiempos de falla y su parámetro de dependencia conocido. En el caso de un modelo con más de dos riesgos competitivos, Lo y Wilke (2010) proponen el método de combinación de riesgo (“risk pooling method”) como una extensión del estimador cópula gráfico cuando la cópula es Arquimediana. En este trabajo para el caso trivariado, se compara la función de sobrevivencia conjunta verdadera, con la función de sobrevivencia conjunta estimada asumiendo independencia entre los tiempos de falla y la función de sobrevivencia estimada mediante el método de combinación de riesgos. Estas comparaciones se realizan vía simulación teniendo en cuenta tiempos de falla asociados a una distribución Weibull y lognormal multivariada y diferentes niveles de dependencia entre los tiempos de falla. Se concluye que el estimador asumiendo independencia es menos eficiente que el estimador de la función de sobrevivencia utilizando el método de combinación de riesgos. Se ilustra la metodología con datos de la confiabilidad de interruptores tipo FL245 en Interconexión Eléctrica S.A. E.S.P. (ISA), que muestran la utilidad de la temática en confiabilidad industrial