Hierarchical Structure of Magnetohydrodynamic Turbulence In Position-Position-Velocity Space

Magnetohydrodynamic turbulence is able to create hierarchical structures in the interstellar medium that are correlated on a wide range of scales via the energy cascade. We use hierarchical tree diagrams known as dendrograms to characterize structures in synthetic Position-Position-Velocity (PPV) emission cubes of optically thin isothermal magnetohydrodynamic turbulence. We show that the structures and degree of hierarchy observed in PPV space are related to the physics of the gas, i.e. self-gravity and the global sonic and Alfvenic Mach number. Simulations with higher Alfvenic Mach number, self-gravity and supersonic flows display enhanced hierarchical structure. We observed a strong sonic and Alfvenic dependency when we apply the the statistical moments (i.e. mean, variance, skewness, kurtosis) to the dendrogram distribution. Larger magnetic field and sonic Mach number correspond to larger values of the moments. Application of the dendrogram to 3D density cubes, also known as Position-Position-Position cubes (PPP), reveals that the dominant emission contours in PPP and PPV are related for supersonic gas but not for subsonic. We also explore the effects of smoothing, thermal broadening and velocity resolution on the dendrograms in order to make our study more applicable to observational data. These results all point to hierarchical tree diagrams as being a promising additional tool for studying ISM turbulence and star forming regions in the direction of obtaining information on the degree of self-gravity, the Mach numbers and the complicated relationship between PPV and PPP.Comment: submitted to Ap

A systematic review of randomized trials for engaging socially disadvantaged groups in health research: A distillation approach

A systematic distallation of randomized community engagement interventions targeted at increasing research participation in social disadvantaged group

A systematic review of randomized trials for engaging socially disadvantaged groups in health research: A distillation approach

Research that fails to include sufficient representation from socially disadvantaged groups cannot make strong inferences about those groups. This relative lack of knowledge poses theoretical and clinical problems for health research. More effective community engagement with socially disadvantaged groups is often proposed as a way to increase research engagement. However, community engagement is a heterogeneous construct, including everything from how participants are contacted to whether researchers work with an organization within the community. Further, community engagement efforts vary widely in their effectiveness in recruiting and retaining participants from socially disadvantaged groups. Therefore, some types of community engagement may be more effective than others. We conducted a systematic review of randomized controlled trials attempting to increase recruitment or retention of socially disadvantaged groups. We then applied systematic distillation procedures to examine which components of community engagement interventions were associated with successful recruitment or retention outcomes. Generally, we found research process related variables (e.g. having a systematic contact plan) most frequently differentiated effective vs. ineffective recruitment or retention outcomes. Partial associations between components in effective interventions, including negative associations, were descriptively stronger than partial associations in the ineffective interventions, indicating targeted interventions may be more effective than more generalized interventions. The literature was also relatively sparse and at unclear-to-high-risk for bias. Future pre-registered, research process-oriented, and targeted recruitment and retention interventions may increase the research participation of socially disadvantaged groups in health research

Perfusion Assessment in Left-Sided/Low Anterior Resection (PILLAR III): A Randomized, Controlled, Parallel, Multicenter Study Assessing Perfusion Outcomes With PINPOINT Near-Infrared Fluorescence Imaging in Low Anterior Resection.

BackgroundIndocyanine green fluoroscopy has been shown to improve anastomotic leak rates in early phase trials.ObjectiveWe hypothesized that the use of fluoroscopy to ensure anastomotic perfusion may decrease anastomotic leak after low anterior resection.DesignWe performed a 1:1 randomized controlled parallel study. Recruitment of 450 to 1000 patients was planned over 2 years.SettingsThis was a multicenter trial.PatientsIncluded patients were those undergoing resection defined as anastomosis within 10 cm of the anal verge.InterventionPatients underwent standard evaluation of tissue perfusion versus standard in conjunction with perfusion evaluation using indocyanine green fluoroscopy.Main outcome measuresPrimary outcome was anastomotic leak, with secondary outcomes of perfusion assessment and the rate of postoperative abscess requiring intervention.ResultsThis study was concluded early because of decreasing accrual rates. A total of 25 centers recruited 347 patients, of whom 178 were randomly assigned to perfusion and 169 to standard. The groups had comparable tumor-specific and patient-specific demographics. Neoadjuvant chemoradiation was performed in 63.5% of perfusion and 65.7% of standard (p > 0.05). Mean level of anastomosis was 5.2 ± 3.1 cm in perfusion compared with 5.2 ± 3.3 cm in standard (p > 0.05). Sufficient visualization of perfusion was reported in 95.4% of patients in the perfusion group. Postoperative abscess requiring surgical management was reported in 5.7% of perfusion and 4.2% of standard (p = 0.75). Anastomotic leak was reported in 9.0% of perfusion compared with 9.6% of standard (p = 0.37). On multivariate regression analysis, there was no difference in anastomotic leak rates between perfusion and standard (OR = 0.845 (95% CI, 0.375-1.905); p = 0.34).LimitationsThe predetermined sample size to adequately reduce the risk of type II error was not achieved.ConclusionsSuccessful visualization of perfusion can be achieved with indocyanine green fluoroscopy. However, no difference in anastomotic leak rates was observed between patients who underwent perfusion assessment versus standard surgical technique. In experienced hands, the addition of routine indocyanine green fluoroscopy to standard practice adds no evident clinical benefit. See Video Abstract at http://links.lww.com/DCR/B560.Valoracin de la irrigacin de lado izquierdo/reseccin anterior baja pilar iii un estudio aleatorizado, controlado, paralelo y multicntrico que evala los resultados de la irrigacin con pinpoint imgenes de fluorescencia cercana al infrarrojo en la reseccin anterior bajaANTECEDENTES:Se ha demostrado que la fluoroscopia con verde de indocianina mejora las tasas de fuga anastomótica en ensayos en fases iniciales.OBJETIVO:Nuestra hipótesis es que la utilización de fluoroscopia para asegurar la irrigación anastomótica puede disminuir la fuga anastomótica luego de una resección anterior baja.DISEÑO:Realizamos un estudio paralelo, controlado, aleatorizado 1:1. Se planificó el reclutamiento de 450-1000 pacientes durante 2 años.AMBITO:Multicéntrico.PACIENTES:Pacientes sometidos a resección definida como una anastomosis dentro de los 10cm del margen anal.INTERVENCIÓN:Pacientes que se sometieron a la evaluación estándar de la irrigación tisular contra la estándar en conjunto con la valoración de la irrigación mediante fluoroscopia con verde indocianina.PRINCIPALES VARIABLES EVALUADAS:El principal resultado fue la fuga anastomótica, y los resultados secundarios fueron la evaluación de la perfusión y la tasa de absceso posoperatorio que requirió intervención.RESULTADOS:Este estudio se cerró anticipadamente debido a la disminución de las tasas de acumulación. Un total de 25 centros reclutaron a 347 pacientes, de los cuales 178 fueron, de manera aleatoria, asignados a perfusión y 169 a estándar. Los grupos tenían datos demográficos específicos del tumor y del paciente similares. Recibieron quimio-radioterapia neoadyuvante el 63,5% de la perfusión y el 65,7% del estándar (p> 0,05). La anastomosis estuvo en un nivel promedio de 5,2 + 3,1 cm en perfusión en comparación con 5,2 + 3,3 cm en estándar (p> 0,05). Se reportó una visualización suficiente de la perfusión en el 95,4% de los pacientes del grupo de perfusión. El absceso posoperatorio que requirió tratamiento quirúrgico fue de 5,7% de los perfusion y en el 4,2% del estándar (p = 0,75). Se informó fuga anastomótica en el 9,0% de la perfusión en comparación con el 9,6% del estándar (p = 0,37). En el análisis de regresión multivariante, no hubo diferencias en las tasas de fuga anastomótica entre la perfusión y el estándar (OR 0,845; IC del 95% (0,375; 1,905); p = 0,34).LIMITACIONES:No se logró el tamaño de muestra predeterminado para reducir satisfactoriamente el riesgo de error tipo II.CONCLUSIÓN:Se puede obtener una visualización adecuada de la perfusión con ICG-F. Sin embargo, no se observaron diferencias en las tasas de fuga anastomótica entre los pacientes que se sometieron a evaluación de la perfusión versus la técnica quirúrgica estándar. En manos expertas, agregar ICG-F a la rutina de la práctica estándar no agrega ningún beneficio clínico evidente. Consulte Video Resumen en http://links.lww.com/DCR/B560. (Traducción-Dr Juan Antonio Villanueva-Herrero)