Optimal behavior of viscoelastic flow at resonant frequencies

The global entropy generation rate in the zero-mean oscillatory flow of a Maxwell fluid in a pipe is analyzed with the aim at determining its behavior at resonant flow conditions. This quantity is calculated explicitly using the analytic expression for the velocity field and assuming isothermal conditions. The global entropy generation rate shows well-defined peaks at the resonant frequencies where the flow displays maximum velocities. It was found that resonant frequencies can be considered optimal in the sense that they maximize the power transmitted to the pulsating flow at the expense of maximum dissipation.Comment: Paper accepted to be published in Phys. Rev.

EPIdemiology of Surgery-Associated Acute Kidney Injury (EPIS-AKI) : Study protocol for a multicentre, observational trial

More than 300 million surgical procedures are performed each year. Acute kidney injury (AKI) is a common complication after major surgery and is associated with adverse short-term and long-term outcomes. However, there is a large variation in the incidence of reported AKI rates. The establishment of an accurate epidemiology of surgery-associated AKI is important for healthcare policy, quality initiatives, clinical trials, as well as for improving guidelines. The objective of the Epidemiology of Surgery-associated Acute Kidney Injury (EPIS-AKI) trial is to prospectively evaluate the epidemiology of AKI after major surgery using the latest Kidney Disease: Improving Global Outcomes (KDIGO) consensus definition of AKI. EPIS-AKI is an international prospective, observational, multicentre cohort study including 10 000 patients undergoing major surgery who are subsequently admitted to the ICU or a similar high dependency unit. The primary endpoint is the incidence of AKI within 72 hours after surgery according to the KDIGO criteria. Secondary endpoints include use of renal replacement therapy (RRT), mortality during ICU and hospital stay, length of ICU and hospital stay and major adverse kidney events (combined endpoint consisting of persistent renal dysfunction, RRT and mortality) at day 90. Further, we will evaluate preoperative and intraoperative risk factors affecting the incidence of postoperative AKI. In an add-on analysis, we will assess urinary biomarkers for early detection of AKI. EPIS-AKI has been approved by the leading Ethics Committee of the Medical Council North Rhine-Westphalia, of the Westphalian Wilhelms-University Münster and the corresponding Ethics Committee at each participating site. Results will be disseminated widely and published in peer-reviewed journals, presented at conferences and used to design further AKI-related trials. Trial registration number NCT04165369

Investigation of Salt Diffusion in Soil by Using Radiotracing Technique

In this study, it is aimed to observe diffusion of sodium in soil samples by using radiotracing technique. To produce the radiotracer Na-24, sodium-carbonate compound was irradiated at ITU TRIGA Mark II Research reactor at Energy Institute of Istanbul Technical University. The irradiated sodium-carbonate samples were sprinkled to the surface of soil columns. Then soil was watered with representative amounts of water according to selected rain regimes in Istanbul. Radioactivity measurements were carried out by using high efficiency gamma-ray measurement system at the outside of the column for different soil depths in different times

Investigation for Remediation of Selenium Aqueous Environment with Using Organic Pillared Bentonite by Radiotracer Technique

In this study remediation of selenium ions from aqueous solutions was investigated using organic pillared bentonite as an adsorbent. Organic pillared bentonite was produced from Resadiye (Tokat, Turkey) bentonite using hexadecylpyridinium chloride and aluminum polyoxy-cations. All the experiments were carried out by tracing with selenium radioisotope. For the production of the radioactive selenium radioisotope, selenium dioxide was irradiated in the central thimble of ITU TRIGA Mark II Training and Research Reactor at Energy Institute of Istanbul Technical University. Radioactivity measurements carried out by the gamma-ray spectroscopy system were used to determine of selenium isotope. The relative importance of test parameters like concentration of adsorbate, pH of the solution and contact time on adsorption performance of organic pillared bentonite for selenium ion was studied. Evaluation of experiments for different parameters showed possibility of remediation of selenium from aqueous media by using organic pillared bentonite