Turbulent kinetic energy production in the vane of a low-pressure linear turbine cascade with incoming wakes

Copyright © 2015 V. Michelassi and J. G. Wissink. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Incompressible large eddy simulation and direct numerical simulation of a low-pressure turbine at R e = 5.18 × 10 4 and 1.48 × 10 5 with discrete incoming wakes are analyzed to identify the turbulent kinetic energy generation mechanism outside of the blade boundary layer. The results highlight the growth of turbulent kinetic energy at the bow apex of the wake and correlate it to the stress-strain tensors relative orientation. The production rate is analytically split according to the principal axes, and then terms are computed by using the simulation results. The analysis of the turbulent kinetic energy is followed both along the discrete incoming wakes and in the stationary frame of reference. Both direct numerical and large eddy simulation concur in identifying the same production mechanism that is driven by both a growth of strain rate in the wake, first, followed by the growth of turbulent shear stress after. The peak of turbulent kinetic energy diffuses and can eventually reach the suction side boundary layer for the largest Reynolds number investigated here with higher incidence angle. As a consequence, the local turbulence intensity outside the boundary layer can grow significantly above the free-stream level with a potential impact on the suction side boundary layer transition mechanism.The German Research Foundation (DFG) within the joint Project “Periodic Unsteady Flow in Turbomachinery.

RANS Turbulence Model Development using CFD-Driven Machine Learning

This paper presents a novel CFD-driven machine learning framework to develop Reynolds-averaged Navier-Stokes (RANS) models. The CFD-driven training is an extension of the gene expression programming method (Weatheritt and Sandberg, 2016), but crucially the fitness of candidate models is now evaluated by running RANS calculations in an integrated way, rather than using an algebraic function. Unlike other data-driven methods that fit the Reynolds stresses of trained models to high-fidelity data, the cost function for the CFD-driven training can be defined based on any flow feature from the CFD results. This extends the applicability of the method especially when the training data is limited. Furthermore, the resulting model, which is the one providing the most accurate CFD results at the end of the training, inherently shows good performance in RANS calculations. To demonstrate the potential of this new method, the CFD-driven machine learning approach is applied to model development for wake mixing in turbomachines. A new model is trained based on a high-pressure turbine case and then tested for three additional cases, all representative of modern turbine nozzles. Despite the geometric configurations and operating conditions being different among the cases, the predicted wake mixing profiles are significantly improved in all of these a posteriori tests. Moreover, the model equation is explicitly given and available for analysis, thus it could be deduced that the enhanced wake prediction is predominantly due to the extra diffusion introduced by the CFD-driven model.Comment: Accepted by Journal of Computational Physic

Religiosity Associated with Prolonged Survival in Liver Transplant Recipients

We tested the hypothesis that religiosity (ie, seeking God\u27s help, having faith in God, trusting in God, and trying to perceive God\u27s will in the disease) is associated with improved survival in patients with end-stage liver disease who have undergone orthotopic liver transplantation. We studied a group of 179 candidates for liver transplantation who responded to a questionnaire on religiosity during the pretransplant psychological evaluation and underwent transplantation between 2004 and 2007. The demographic data, educational level, employment status, clinical data, and results of the questionnaire were compared with the survival of patients during follow-up, regardless of the cause of any deaths. Factorial analysis of responses to the questionnaire revealed 3 main factors: searching for God (active), waiting for God (passive), and fatalism. The consistency of the matrix was very high (consistency index ? 0.92). Eighteen patients died during follow-up (median time ? 21 months). In multivariate analysis, only the searching for God factor [hazard ratio (HR) ? 2.95, 95% confidence interval (CI) ? 1.05-8.32, v2 ? 4.205, P ? 0.040] and the posttransplant length of stay in the intensive care unit (HR ? 1.05, 95% CI ? 1.01-1.08, v2 ? 8.506, P ? 0.035) were independently associated with survival, even after adjustments for the waiting for God factor, fatalism, age, sex, marital status, employment, educational level, viral etiology, Child-Pugh score, serum creatinine level, time from the questionnaire to transplantation, donor age, and intraoperative bleeding. Patients who did not present the searching for God factor were younger than those who did, but they had shorter survival times (P ? 0.037) and a 3-fold increased relative risk of dying (HR ? 3.01, 95% CI ? 1.07-8.45). In conclusion, religiosity is associated with prolonged survival in patients undergoing liver transplantation. Liver Transpl 16:1158-1163, 2010. VC 2010 AASLD

Chapter Didascalia comica

The first part of this paper consists of a theatre play written specifically for the international congress El teatro Español en Europa and performed on that occasion by the Segugi theatre company. The play stages the generational and poetic conflict between two seventeenth-century Florentine playwrights: the tragedian Girolamo Bartolommei (1584-1662) and his son, the comedian Mattias Maria (1640-1695). Girolamo, contrary to the innovations of modern comedy and the mixture of tragic and comic, dedicated in 1658 a treatise entitled Didascalia comica to Mattias in which he sought to bring his son to traditional positions; nevertheless, Mattias became a leading exponent of that new Spanish imitation comic theatre that, since the times of Giacinto Andrea Cicognini (1606-1649), had found in Florence a fertile place of reworking and diffusion. The second part offers a critical note on the historical issues illustrated in the pièce

SGLT2 inhibitors: suggestions from the amphibian world

Sodium-glucose cotransporter 2 inhibitors are a class of antidiabetic drugs that inhibit glucose reabsorption in the proximal renal tubules. In many trials these drugs have shown unpredictable major cardio- and nephroprotective properties. Multiple hypotheses have been raised to elucidate the mechanisms underlying the last effects. Some authors suggest they may be due to the contemporary urinary loss of energy (as glucose) and water (by osmotic diuresis). This particular condition could induce metabolic changes resulting in more efficient energetics at cardiac and renal levels and in less oxidative stress. These changes might really be part of a series of evolutionarily conserved metabolic switches that allow organisms to survive in arid habitats with restricted nutrients and water availability, well studied in amphibians and collectively named "estivation"

Trends of Increasing Medical Radiation Exposure in a Population Hospitalized for Cardiovascular Disease (1970-2009)

Abstract Background: High radiation doses employed in cardiac imaging may increase cancer frequency in exposed patients after decades. The aim of this study was to evaluate the relative trends in medical radiation exposure in a population hospitalized for cardiovascular disease. Methods and Results: An observational single-center study was conducted to examine 16,431 consecutive patients with heart disease admitted to the Italian National Research Council Institute of Clinical Physiology between January 1970 and December 2009. In all patients, the cumulative estimated effective dose was obtained from data mining of electronic records of hospital admissions, adopting the effective dose typical values of the American Heart Association 2009 statement and Mettler\u27s 2008 catalog of doses. Cumulative estimated effective dose per patient in the last 5 years was 22 (12-42) mSv (median, 25th-75th percentiles), with higher values in ischemic heart disease (IHD), 37 (20-59) vs non-IHD, 13 (8-22) mSv, p,0.001. Trends in radiation exposure showed a steady increase in IHD and a flat trend in non-IHD patients, with variation from 1970-74 to 2005-2009 of +155% for IHD (p,0.001) and 21% in non-IHD (NS). The relative contribution of different imaging techniques was remodeled over time, with nuclear cardiology dominating in 1970s (23% of individual exposure) and invasive fluoroscopy in the last decade (90% of individual exposure). Conclusion: A progressive increase in cumulative estimated effective dose is observed in hospitalized IHD patients. The growing medical radiation exposure may encourage a more careful justification policy regarding ionizing imaging in cardiology patients applying the two main principles of radiation protection: appropriate justification for ordering and performing each procedure, and careful optimization of the radiation dose used during each procedure

È possibile una gestione "ideale" della pandemia da malattia renale cronica?

Chronic Kidney Disease (CKD) is recognized as one of the major categories of noncommunicable epidemic diseases and in the last decades it has been largely growing in incidence and prevalence all over the world. Ideal management of CKD pandemic should be comprehensive of measures of tertiary, secondary, primary and primordial prevention. So, it should include prompt diagnosis and treatment of traditional and non-traditional risk factors for CKD, optimal conservative treatment for non-dialysis dependent CKD patients and appropriated dialysis therapy or renal transplantation for patients with end-stage renal disease. However, these goals are not easy to obtain on a global scale. It would be possible only by a broad and holistic approach, ranging from good governance to achievement of the sustainable development goals (SDGs)

Interpretation of the "obesity paradox": A 30-year study in patients with cardiovascular disease

Background: Several epidemiological reports indicate that the body mass index (BMI) is inversely related with mortality, in spite of the notion that obesity is a recognized cardio-metabolic risk factor. The aim of the study was to evaluate the independent impact of overweight and obesity on long-term mortality in a large cohort of patients with heart disease (HD). Methods: The study included 10,446 patients hospitalized in the last three decades for ischemic (60%) or nonischemic HD and followed-up for 10 years. The relationship between BMI and total or cardiovascular mortality was analyzed in the whole cohort, and in age-stratified categories (≤65 and >65 years). Considering that survival in HD patients has improved after the introduction of revascularization, beta-blockers, ACE inhibitors, and statins, the relationship was re-examined separately in patients hospitalized before and after 1990. Results: Diabetes, hyperuricemia, hypertension, glycaemia, and triglyceridemia increased across BMI groups. During follow-up (73?59 months) there were 1707 all-cause deaths (47% cardiac). Any relationship between BMI and mortality was lost in the ≤65 age category and in patients hospitalized before 1990, but it persisted in old patients hospitalized after 1990. Most significant independent predictors of mortality in all groups were hyperuricemia, diabetes and impaired ejection fraction. Conclusions: No independent relationship was found between BMI and mortality in subjects ≤65 years of age. This neutral relationship seems to be partly counteracted by treatment, particularly in old patients. A different effect of obesity onset in old vs. young age cannot be ruled out