Un procedimiento para obtener clusters utilizando la D.V.S. de una matriz. Comparaciones con el biplot y con el modelo Q-factorial

Durante las últimas décadas, el análisis de un conjunto de n individuos medidos en p variables, proporcionando una matriz de datos Xn,p, mediante técnicas de representación que utilizan la Descomposición en Valores Singulares de la matriz Xn,p (o alguna derivada), han permitido resumir la información que aportan los datos en alguna forma óptima, siendo muy útil para indicar la presencia de clusters entre los n individuos y/o para prevenir ante posibles clasificaciones erróneas producidas por técnicas de agrupamiento más complejas. En este artículo estudiaremos un procedimiento que puede utilizarse en ocasiones para obtener clasificaciones naturales de un conjunto de datos, basado en la representación biplot y en el modelo Q-factorial que puede obtenerse a partir de la DVS

Un modelo Poissoniano para predecir la matriculación de vehículos en países europeos

En este artículo presentamos una modelización para la matriculación de vehículos en países de Europa mediante un proceso de Poisson Doblemente Estocástico con media aleatoria Normal truncada. Apoyándonos en trabajos previos acerca de este proceso, se amplía el estudio de características de éste. Asímismo, se hace una predicción de este proceso para los años 2000 y 2001

Estudio coprológico de infecciones intestinales en los estudiantes marroquíes de la Universidad de Granada

Se ha realizado un estudio coprológico de las muestras fecales de 145 estudiantes marroquíes (varones y hembras) matriculados en la Universidad de Granada durante el curso académico 1985-86. Se ha obtenido un I.P .S. de 42'75%, con un 37,24% de Protozoos y un 9'65% de Helmintos. La prevalencia de los mismos es la siguiente: E. coli: 18'62%; E. hartmanni: 2'75%; E. nana: 15'55%; D.fragilis: 1'37%; J. butschlii: 6'89%; G. lamblia: 4'82%; T. trichiura: 5'51 %; A. lumbricoides: 1'37%; H. nana: 1'37%; S. stercoralis: 1'37%. El trabajo se completa con un estudio estadístico, cuyos resultados se discuten

Aspectos operativos del movimiento browniano y del proceso de ruido blanco

El presente trabajo tiene por objeto describir la forma en que puede descomponerse un proceso estocástico como suma numerable de componentes ortogonales, y aplicar dicho desarrollo a los procesos de movimiento browniano y de ruido blanco.The aim of the present paper is the description of the way in which a stochastic process can be decomposed as a countable sum of orthogonal terms, and the application of such expansion to the brownian movement and to the white noise

Estimación óptima de señales en presencia de ruido

In the present paper we precise the mathematical notion of a realizable filter, and we procede to construct the optimal filter for signal estimation under a noise perturbation, analyzing in detail the case in which the noise is white. Likewise we introduce a suboptimal filter to carry out such estimation.En el presente trabajo precisamos la noción matemática de filtro realizable, y procedemos a construir el filtro óptimo para estimación de sefiales perturbadas por un ruido, analizando detalladamente el caso en que el ruido sea blanco. Asimismo, introducimos un filtro subóptimo para llevar a cabo tal estimación

Estimación optima de señales en presencia de ruido

In the present paper we precise the mathematical notion of a realizable filter, and we procede to construct the optimal filter for signal estimation under a noise perturbation, analyzing in detail the case in which the noise is white. Likewise we introduce a suboptimal filter to carry out such estimation.En el presente trabajo precisamos la noción matemática de filtro realizable, y procedemos a construir el filtro óptimo para estimación de señales perturbadas por un ruido, analizando detalladamente el caso en que el ruido sea blanco. Asimismo, introducimos un filtro subóptimo para llevar a cabo tal estimación

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic